inst240_sec1

INST 240 (Pressure and Level Measurement), section 1

Lab

Pressure measurement loop: Questions 91 and 92, completed objectives due by the end of day 4,section 2

Exam

Day 5 of next section – only a simple calculator may be used!

Specific objectives for the “mastery” exam:

• Build a circuit to energize an electromechanical relay (question 93)• Convert between different pressure units (PSI, ”W.C., bar, etc.)• Calculate pressure applied to a DP instrument in a realistic scenario• Calculate instrument input and output values given calibrated ranges• Solve for a specified variable in an algebraic formula• Determine the possibility of suggested faults in a series-parallel circuit given measured values (voltage,

current), a schematic diagram, and reported symptoms• INST231 Review: Sketch proper wire connections for sourcing or sinking PLC I/O points• INST251 Review: Determine the effect of a component fault or condition change in a single-loop

controlled process• INST260 Review: Convert between different numeration systems (decimal, binary, hexadecimal)

Recommended daily schedule

Day 1

Theory session topic: Concepts of pressure and pressure unit conversions

Questions 1 through 20; answer questions 1-10 in preparation for discussion (remainder for practice)

Day 2

Theory session topic: Pressure measurement technologies


Day 3

Theory session topic: Instrument calibration


Day 4

Theory session topic: Electronic pressure measurement


Feedback questions (81 through 90) are optional and may be submitted for review at the end of the day

Introduction to Fall Quarter

This quarter focuses on the subject of measurement. Ideas to keep in mind for special projects(alternatives to standard lab as well as extra-credit) include measuring and recording physical variablesin and around the college campus. For those who have studied programmable logic controllers (PLCs), therewill be application to use your PLCs again if equipped with analog inputs to receive the 4-20 mA signalsproduced by industrial transmitters.

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Course Syllabus

INSTRUCTOR CONTACT INFORMATION:Tony Kuphaldt(360)-752-8477 [office phone](360)-752-7277 [fax][email protected]

DEPT/COURSE #: INST 240

CREDITS: 6 Lecture Hours: 26 Lab Hours: 82 Work-based Hours: 0

COURSE TITLE: Pressure and Level Measurement

COURSE OUTCOMES: Commission, analyze, and efficiently diagnose instrumented systems measuringfluid pressure and liquid level.

COURSE DESCRIPTION: In this course you will learn how to precisely measure both fluid pressureand fluid/solids level in a variety of applications, as well as accurately calibrate and efficiently troubleshootpressure and level measurement systems. Pre/Corequisite course: INST 200 (Introduction toInstrumentation) Prerequisite course: MATH&141 (Precalculus 1)

COURSE OUTLINE: A course calendar in electronic format (Excel spreadsheet) resides on the Y:network drive, and also in printed paper format in classroom DMC130, for convenient student access. Thiscalendar is updated to reflect schedule changes resulting from employer recruiting visits, interviews, andother impromptu events. Course worksheets provide comprehensive lists of all course assignments andactivities, with the first page outlining the schedule and sequencing of topics and assignment due dates.These worksheets are available in PDF format at http://openbookproject.net/books/socratic/sinst

• INST240 Section 1 (Pressure and pressure instruments): 4 days theory and labwork• INST240 Section 2 (Pneumatic instrumentation): 4 days theory and labwork + 1 day for

mastery/proportional Exams• INST240 Section 3 (Hydrostatic, displacer, and interface level measurement): 4 days theory and labwork• INST240 Section 4 (Other level measurement technologies): 4 days theory and labwork + 1 day for

mastery/proportional Exams

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STUDENT PERFORMANCE OBJECTIVES:• Without references or notes, within a limited time (3 hours total for each exam session), independently

perform the following tasks. Multiple re-tries are allowed on mastery (100% accuracy) objectives, eachwith a different set of problems:→ Build a circuit to energize an electromechanical relay given a switch and relay both randomly selectedby the instructor, with 100% accuracy (mastery)→ Build a circuit to sense either pressure or vacuum using a DP transmitter randomly selected by theinstructor, with 100% accuracy (mastery)→ Convert between different pressure units (PSI, ”W.C., bar. etc.) with 100% accuracy (mastery)→ Determine suitability of different level-measuring technologies for a given process fluid type, with100% accuracy (mastery)→ Calculate pressure applied to a DP instrument given a pictorial diagram, with 100% accuracy(mastery)→ Calculate ranges for hydrostatic (DP) level-measuring instruments given physical dimensions andfluid densities, with 100% accuracy (mastery)→ Calculate buoyant force values for a displacer-type level-measuring instrument at different liquidlevels, with 100% accuracy (mastery)→ Calculate instrument input and output values given calibrated ranges, with 100% accuracy (mastery)→ Solve for specified variables in algebraic formulae, with 100% accuracy (mastery)→ Determine the possibility of suggested faults in series-parallel circuits and Wheatstone bridge circuitsgiven measured values (voltage, current), schematic diagrams, and reported symptoms, with 100%accuracy (mastery)→ Predict the response of automatic pressure and level control systems to component faults and changesin process conditions, given pictorial and/or schematic illustrations→ Sketch proper power and signal connections between individual instruments to fulfill specified controlsystem functions, given pictorial and/or schematic illustrations of those instruments

• In a team environment and with full access to references, notes, and instructor assistance, perform thefollowing tasks:→ Demonstrate proper use of safety equipment and application of safe procedures while using powertools, and working on live systems→ Communicate effectively with teammates to plan work, arrange for absences, and share responsibilitiesin completing all labwork→ Construct and commission a working pressure-measurement “loop” consisting of an electronicpressure transmitter, signal wiring, and indicator→ Construct and commission a working level-measurement “loop” consisting of a pneumatic leveltransmitter, signal tubing, and indicator→ Generate accurate loop diagrams compliant with ISA standards documenting your team’s systems

• Independently perform the following tasks with 100% accuracy (mastery). Multiple re-tries are allowedwith different specifications/conditions each time):→ Calibrate an electronic pressure transmitter to specified accuracy using industry-standard calibrationequipment→ Demonstrate the proper usage of a deadweight tester for generating precise pressures→ Calibrate a pneumatic level transmitter to specified accuracy using industry-standard calibrationequipment→ Demonstrate the proper usage of a manometer for measuring gas pressure→ Diagnose a random fault placed in another team’s pressure measurement system by the instructorwithin a limited time using no test equipment except a multimeter, logically justifying your steps in theinstructor’s direct presence→ Diagnose a random fault placed in another team’s level measurement system by the instructor withina limited time using no test equipment except a pressure gauge, logically justifying your steps in theinstructor’s direct presence

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METHODS OF INSTRUCTION: Course structure and methods are intentionally designed to developcritical-thinking and life-long learning abilities, continually placing the student in an active rather than apassive role.• Independent study: daily worksheet questions specify reading assignments, problems to solve, and

experiments to perform in preparation (before) classroom theory sessions. Open-note quizzes and workinspections ensure accountability for this essential preparatory work. The purpose of this is to conveyinformation and basic concepts, so valuable class time isn’t wasted transmitting bare facts, and also tofoster the independent research ability necessary for self-directed learning in your career.

• Classroom sessions: a combination of Socratic discussion, short lectures, small-group problem-solving,and hands-on demonstrations/experiments review and illuminate concepts covered in the preparatoryquestions. The purpose of this is to develop problem-solving skills, strengthen conceptual understanding,and practice both quantitative and qualitative analysis techniques.

• Lab activities: an emphasis on constructing and documenting working projects (real instrumentationand control systems) to illuminate theoretical knowledge with practical contexts. Special projectsoff-campus or in different areas of campus (e.g. BTC’s Fish Hatchery) are encouraged. Hands-ontroubleshooting exercises build diagnostic skills.

• Feedback questions: sets of practice problems at the end of each course section challenge yourknowledge and problem-solving ability in current as as well as first year (Electronics) subjects. Theseare optional assignments, counting neither for nor against your grade. Their purpose is to provide youand your instructor with direct feedback on what you have learned.

• Tours and guest speakers: quarterly tours of local industry and guest speakers on technical topicsadd breadth and additional context to the learning experience.

STUDENT ASSIGNMENTS/REQUIREMENTS: All assignments for this course are thoroughlydocumented in the following course worksheets located at:http://openbookproject.net/books/socratic/sinst/index.html

• INST240 sec1.pdf




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EVALUATION AND GRADING STANDARDS: (out of 100% for the course grade)• Mastery exams and mastery lab objectives = 50% of course grade• Proportional exams = 40% (2 exams at 20% each)• Lab questions = 10% (2 question sets at 5% each)• Quiz penalty = -1% per failed quiz• Tardiness penalty = -1% per incident (1 “free” tardy per course)• Attendance penalty = -1% per hour (12 hours “sick time” per quarter)• Extra credit = +5% per project

All grades are criterion-referenced (i.e. no grading on a “curve”)

100% ≥ A ≥ 95% 95% > A- ≥ 90%90% > B+ ≥ 86% 86% > B ≥ 83% 83% > B- ≥ 80%80% > C+ ≥ 76% 76% > C ≥ 73% 73% > C- ≥ 70% (minimum passing course grade)70% > D+ ≥ 66% 66% > D ≥ 63% 63% > D- ≥ 60% 60% > F

Graded quizzes at the start of each classroom session gauge your independent learning. If absent orlate, you may receive credit by passing a comparable quiz afterward or by having your preparatory work(reading outlines, work done answering questions) thoroughly reviewed prior to the absence.

Absence on a scheduled exam day will result in a 0% score for the proportional exam unless you providedocumented evidence of an unavoidable emergency.

If you fail a mastery exam, you must re-take a different version of that mastery exam on a differentday. Multiple re-tries are allowed, on a different version of the exam each re-try. There is no penalty leviedon your course grade for re-taking mastery exams, but failure to successfully pass a mastery exam by thedue date (i.e. by the date of the next exam in the course sequence) will result in a failing grade (F) for thecourse.

If any other “mastery” objectives are not completed by their specified deadlines, your overall gradefor the course will be capped at 70% (C- grade), and you will have one more school day to complete theunfinished objectives. Failure to complete those mastery objectives by the end of that extra day (except inthe case of documented, unavoidable emergencies) will result in a failing grade (F) for the course.

“Lab questions” are assessed by individual questioning, at any date after the respective lab objective(mastery) has been completed by your team. These questions serve to guide your completion of each labexercise and confirm participation of each individual student. Grading is as follows: full credit for thorough,correct answers; half credit for partially correct answers; and zero credit for major conceptual errors. Alllab questions must be answered by the due date of the lab exercise.

Extra credit opportunities exist for each course, and may be assigned to students upon request. Thestudent and the instructor will first review the student’s performance on feedback questions, homework,exams, and any other relevant indicators in order to identify areas of conceptual or practical weakness. Then,both will work together to select an appropriate extra credit activity focusing on those identified weaknesses,for the purpose of strengthening the student’s competence. A due date will be assigned (typically two weeksfollowing the request), which must be honored in order for any credit to be earned from the activity. Extracredit may be denied at the instructor’s discretion if the student has not invested the necessary preparatoryeffort to perform well (e.g. lack of preparation for daily class sessions, poor attendance, no feedback questionssubmitted, etc.).

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REQUIRED STUDENT SUPPLIES AND MATERIALS:• Course worksheets available for download in PDF format• Lessons in Industrial Instrumentation textbook, available for download in PDF format

→ Access worksheets and book at: http://openbookproject.net/books/socratic/sinst• Spiral-bound notebook for reading annotation, homework documentation, and note-taking.• Instrumentation reference CD-ROM (free, from instructor). This disk contains many tutorials and

datasheets in PDF format to supplement your textbook(s).• Tool kit (see detailed list)• Simple scientific calculator (non-programmable, non-graphing, no unit conversions, no numeration

system conversions), TI-30Xa or TI-30XIIS recommended

ADDITIONAL INSTRUCTIONAL RESOURCES:• The BTC Library hosts a substantial collection of textbooks and references on the subject of

Instrumentation, as well as links in its online catalog to free Instrumentation e-book resources availableon the Internet.

• “BTCInstrumentation” channel on YouTube (http://www.youtube.com/BTCInstrumentation), hostsa variety of short video tutorials and demonstrations on instrumentation.

• ISA Student Section at BTC meets regularly to set up industry tours, raise funds for scholarships,and serve as a general resource for Instrumentation students. Membership in the ISA is $10 per year,payable to the national ISA organization. Membership includes a complementary subscription to InTechmagazine.

• ISA website (http://www.isa.org) provides all of its standards in electronic format, many of whichare freely available to ISA members.

• Instrument Engineer’s Handbook, Volume 1: Process Measurement and Analysis, edited by Bela Liptak,published by CRC Press. 4th edition ISBN-10: 0849310830 ; ISBN-13: 978-0849310836.

• Purdy’s Instrument Handbook, by Ralph Dewey. ISBN-10: 1-880215-26-8. A pocket-sized field referenceon basic measurement and control.

• Cad Standard (CadStd) or similar AutoCAD-like drafting software (useful for sketching loop andwiring diagrams). Cad Standard is a simplified clone of AutoCAD, and is freely available at:http://www.cadstd.com

• To receive classroom accommodations, registration with Disability Support Services (DSS) is required.Call 360-752-8450, email [email protected], or visit the DSS office in the Counseling and CareerCenter (room 106, College Services building).

file INST240syllabus

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Sequence of second-year Instrumentation courses

INST 240 -- 6 crPressure/Level Measurement

INST 241 -- 6 crTemp./Flow Measurement

INST 242 -- 5 crAnalytical Measurement

INST 250 -- 5 cr

INST 251 -- 5 crPID Control

Final Control Elements

Loop TuningINST 252 -- 4 cr

Data Acquisition Systems

INST 262 -- 5 crDCS and Fieldbus

INST 263 -- 5 crControl Strategies

Fall quarter Winter quarter Spring quarterSummer quarter

INST 230 -- 3 crMotor Controls

INST 231 -- 3 crPLC Programming

INST 232 -- 3 crPLC Systems

Offered 1st week ofINST 200 -- 1 wkIntro. to Instrumentation

Job Prep I

Job Prep II

INST 205 -- 1 cr

INST 206 -- 1 cr

INST25x, and INST26x coursesPrerequisite for all INST24x, Fall, Winter, and

Spring quarters

Offered 1st week ofFall, Winter, andSpring quarters

INST 260 -- 4 cr

ENGT 122 -- 6 crCAD 1: Basics

including MATH 141 (Precalculus 1)Core Electronics -- 3 qtrs

Prerequisite for INST206

(Only if 4th quarter was Summer: INST23x)

All coursescompleted? No

Yes

Graduate!!!

PTEC 107 -- 5 crProcess Science

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The particular sequence of courses you take during the second year depends on when you complete allfirst-year courses and enter the second year. Since students enter the second year of Instrumentation at fourdifferent times (beginnings of Summer, Fall, Winter, and Spring quarters), the particular course sequencefor any student will likely be different from the course sequence of classmates.

Some second-year courses are only offered in particular quarters with those quarters not having to bein sequence, while others are offered three out of the four quarters and must be taken in sequence. Thefollowing layout shows four typical course sequences for second-year Instrumentation students, depending onwhen they first enter the second year of the program:

Summer quarter







Fall quarter

INST 200 -- 1 wkIntro. to Instrumentation

Winter quarter

Job Prep IINST 205 -- 1 cr

INST 250 -- 5 crFinal Control Elements



Job Prep IIINST 206 -- 1 cr

Spring quarter

Data Acquisition SystemsINST 260 -- 4 cr




Graduation!

Possible course schedules depending on date of entry into 2nd year

Summer quarter







Fall quarter


Winter quarter






Spring quarter





Graduation!

Summer quarter







Fall quarter

Winter quarter




Spring quarter





Graduation!

Summer quarter







Fall quarter

Winter quarter




Spring quarter





Graduation!







July

Aug.

Sept.

Dec.

Jan.

Mar.

April

June

July

Aug.

Sept.

Dec.

Jan.

Mar.

April

June

Jan.

Mar.

April

June

July

Aug.

Sept.

Dec.

April

June

July

Aug.

Sept.

Dec.

Jan.

Mar.

Beginning in Summer Beginning in Fall Beginning in Winter Beginning in Spring





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General student expectations

Your future employer expects you to: show up for work on time, prepared, every day; to work safely,efficiently, conscientiously, and with a clear mind; to be self-directed and take initiative; to follow throughon all commitments; and to take responsibility for all your actions and for the consequences of those actions.Instrument technicians work on highly complex, mission-critical measurement and control systems, whereincompetence and/or lack of integrity invites disaster. This is also why employers check legal records andsocial networking websites for signs of irresponsibility when considering a graduate for hire. Substance abuseis particularly noteworthy since it impairs reasoning, and this is first and foremost a “thinking” career.

(Mastery) You are expected to master the fundamentals of your chosen craft. Accordingly, you will bechallenged with “mastery” assessments ensuring 100% competence in specific knowledge and skill areas (withmultiple opportunities to re-try if necessary). Failure to pass any mastery assessment by the deadline resultsin your grade for that course being capped at a C-, with one more day given to demonstrate mastery. Failureto pass the mastery assessment during that extra day results in a failing grade for the course.

(Punctuality and Attendance) You are expected to arrive on time, every scheduled day, and attend allday, just as you would for a job. If a session begins at 12:00 noon, 12:00:01 is considered late. Each studenthas 12 “sick hours” per quarter applicable to absences not verifiably employment-related, school-related,weather-related, or required by law. Each student must confer with the instructor to apply “sick hours” toany missed time – this is not done automatically for the student. Students may donate unused “sick hours”to whomever they specifically choose. You must contact your instructor and team members immediately ifyou know you will be late or absent, and it is your responsibility to catch up on all missed activities. Absenceon an exam day will result in a zero score for that exam, unless due to a documented emergency.

(Independent study) Industry advisors and successful graduates have consistently identified the ability toindependently learn new concepts and technologies as the most important skill for this career. You will buildthis vital skill by studying new facts and concepts before class begins, and you will be held accountable everyday for this preparatory learning and for your problem-solving during class time. It is your responsibility tocheck the course schedule (given on the front page of every worksheet) to identify assignments and due dates.Most students find 2 hours per day the absolute minimum time commitment for adequate study. Question0 (included in every worksheet) lists practical tips for independent learning and problem-solving.

(Safety) You are expected to work safely in the lab just as you will be on the job. This includes wearingproper attire (safety glasses when working with tools producing chips or dust, no open-toed shoes in thelab), implementing lock-out/tag-out procedures when working on circuits over 24 volts, using ladders toreach high places rather than standing on tables or chairs, and maintaining an orderly work environment.

(Teamwork) You will work in instructor-assigned teams to complete lab assignments, just as you will workin teams to complete complex assignments on the job. As part of a team, you must keep your teammatesinformed of your whereabouts in the event you must step away from the lab or cannot attend for anyreason. Any student regularly compromising team performance through absence, tardiness, disrespect,unsafe work, or other disruptive behavior(s) will be expelled from their team and required to complete alllabwork independently for the remainder of the quarter.

(Responsibility for actions) If you lose or damage college property (e.g. lab equipment), you must find,repair, or help replace it. If your actions strain the relationship between the program and an employer (e.g.poor behavior during a tour or an internship), you must make amends. The general rule here is this: “Ifyou break it, you fix it!”

(Disciplinary action) The Student Code of Conduct (Washington Administrative Codes WAC 495B-

120) explicitly authorizes disciplinary action against misconduct including: academic dishonesty (e.g.cheating, plagiarism), dangerous or lewd behavior, theft, harassment, intoxication, destruction of property,or disruption of the learning environment.

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General student expectations (continued)

Formal learning is a partnership between instructor and student: both are responsible for maximizinglearning. Your instructors’ responsibilities include – but are not limited to – maintaining an environmentconducive to learning, providing necessary learning resources, continuously testing your comprehension,dispensing appropriate advice, and actively challenging you to think deeper than you would be inclined todo on your own (just like an athletic trainer will “push” their clients to go faster, farther, and work harderthan they would otherwise do on their own). Your responsibilities as a student include – but are not limitedto – prioritizing time for study, utilizing all learning resources offered to you, heeding your instructor’s advice,and above all taking your role as a learner seriously.

The single most important factor in any student’s education is that student’s dedication. The mosttalented instructor, at the most well-equipped institution, is worthless if the student doesn’t care to learn.Conversely, virtually no circumstance can prevent a dedicated student from learning whatever they want.

In order to clearly illustrate what dedication to learning looks like from a student’s perspective, thefollowing clarifications are given:

You are here to learn, not to receive a high grade, not to earn a degree, and not even to get a job. If youmake learning your first priority, you will attain all those other goals as a bonus. If, however, you attemptto achieve those secondary goals to the exclusion of learning, you will seriously compromise your long-termsuccess in this career, and you will have wasted your time here.

Memorization alone is not learning. Sadly, many students’ educational experiences lead them to believelearning is nothing more than an accumulation of facts and procedures, when in truth you will need to domuch more than memorize new things in order to be successful as an instrument technician. True learningis gaining the ability to think in new ways. The “gold standard” of learning is when you have grasped aconcept so well that you are able to apply it in creative ways to applications and contexts completely newto you. In fact, this is a simple way for you to test your own learning: see how well you are able to apply itto new scenarios.

Observation alone is not learning. Merely watching someone else perform a task, execute a procedure,or solve a problem does not mean you are proficient in the same, any more than watching an athlete play thegame means you now can play at the same skill level. Unless and until you can consistently and independentlyapply your knowledge, you haven’t learned.

The goal of any learning activity is to master the underlying principles, not merely to completethe activity. The instructor does not need your answers to homework problems. The instructor does notneed your completed lab project. What the instructor needs is a demonstration of your competence inapplying foundational concepts to real applications. The activity itself is nothing more than a means to anend – merely a tool for sharpening skills and demonstrating competence. As such, you should never mistakethe result of the activity (a finished product) for the goal of the activity (conceptual learning).

The most important question to ask “Why?” Ask yourself this question constantly as you learn newthings. Why does this new concept work the way it does? Why does this procedure produce results? Whyare we learning this skill? Why does the instructor keep referring me to the literature instead of just givingme the answer I need? “Why” is a catalyst for deeper understanding.

There are no shortcuts to learning. Relying on classmates for answers rather than figuring them out foryourself, skipping learning activities because you think they’re too challenging or take too long, and othersimilar “shortcuts” do nothing to help you learn. Let me be clear on this point: I am not advising youto avoid shortcuts in your learning; I’m telling you shortcuts to learning don’t actually exist at all. Anytime you think you’ve discovered a shortcut to learning, what you have actually done is find a way to avoidlearning. Learning is hard work – always! Accept this fact and do the hard work necessary to learn.

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General tool and supply list

Wrenches• Combination (box- and open-end) wrench set, 1/4” to 3/4” – the most important wrench sizes are 7/16”,

1/2”, 9/16”, and 5/8”; get these immediately!• Adjustable wrench, 6” handle (sometimes called “Crescent” wrench)• Hex wrench (“Allen” wrench) set, fractional – 1/16” to 3/8”• Optional: Hex wrench (“Allen” wrench) set, metric – 1.5 mm to 10 mm• Optional: Miniature combination wrench set, 3/32” to 1/4” (sometimes called an “ignition wrench” set)

Note: when turning a bolt, nut, or tube fitting with a hexagonal body, the preferred ranking of handtools to use (from first to last) is box-end wrench or socket, open-end wrench, and finally adjustable wrench.Pliers should never be used to turn the head of a fitting or fastener unless it is absolutely unavoidable!

Pliers• Needle-nose pliers• Tongue-and-groove pliers (sometimes called “Channel-lock” pliers)• Diagonal wire cutters (sometimes called “dikes”)

Screwdrivers• Slotted, 1/8” and 1/4” shaft• Phillips, #1 and #2• Jeweler’s screwdriver set• Optional: Magnetic multi-bit screwdriver (e.g. Klein Tools model 70035)

Measurement tools• Tape measure. 12 feet minimum• Optional: Vernier calipers• Optional: Bubble level

Electrical• Multimeter, Fluke model 87-IV or better• Wire strippers/terminal crimpers with a range including 10 AWG to 18 AWG wire• Soldering iron, 10 to 25 watt• Rosin-core solder• Package of compression-style fork terminals (e.g. Thomas & Betts “Sta-Kon” part number 14RB-10F,

14 to 18 AWG wire size, #10 stud size)

Safety• Safety glasses or goggles (available at BTC bookstore)• Earplugs (available at BTC bookstore)

Miscellaneous• Simple scientific calculator (non-programmable, non-graphing, no unit conversions, no numeration

system conversions), TI-30Xa or TI-30XIIS recommended. Required for some exams!• Teflon pipe tape• Utility knife• Optional: Flashlight

An inexpensive source of high-quality tools is your local pawn shop. Look for name-brand tools withunlimited lifetime guarantees (e.g. Sears “Craftsman” brand, Snap-On, etc.). Some local tool suppliers giveBTC student discounts as well!

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Methods of instruction

This course develops self-instructional and diagnostic skills by placing students in situations where theyare required to research and think independently. In all portions of the curriculum, the goal is to avoid apassive learning environment, favoring instead active engagement of the learner through reading, reflection,problem-solving, and experimental activities. The curriculum may be roughly divided into two portions:theory and practical.

TheoryIn the theory portion of each course, students independently research subjects prior to entering the

classroom for discussion. This means working through all the day’s assigned questions as completely aspossible. This usually requires a fair amount of technical reading, and may also require setting up andrunning simple experiments. At the start of the classroom session, the instructor will check each student’spreparation with a quiz. Students then spend the rest of the classroom time working in groups and directlywith the instructor to thoroughly answer all questions assigned for that day, articulate problem-solvingstrategies, and to approach the questions from multiple perspectives. To put it simply: fact-gatheringhappens outside of class and is the individual responsibility of each student, so that class time may bedevoted to the more complex tasks of critical thinking and problem solving where the instructor’s attentionis best applied.

Classroom theory sessions usually begin with either a brief Q&A discussion or with a “VirtualTroubleshooting” session where the instructor shows one of the day’s diagnostic question diagrams whilestudents propose diagnostic tests and the instructor tells those students what the test results would begiven some imagined (“virtual”) fault scenario, writing the test results on the board where all can see. Thestudents then attempt to identify the nature and location of the fault, based on the test results.

Each student is free to leave the classroom when they have completely worked through all problems andhave answered a “summary” quiz designed to gauge their learning during the theory session. If a studentfinishes ahead of time, they are free to leave, or may help tutor classmates who need extra help.

The express goal of this “inverted classroom” teaching methodology is to help each student cultivatecritical-thinking and problem-solving skills, and to sharpen their abilities as independent learners. Whilethis approach may be very new to you, it is more realistic and beneficial to the type of work done ininstrumentation, where critical thinking, problem-solving, and independent learning are “must-have” skills.

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LabIn the lab portion of each course, students work in teams to install, configure, document, calibrate, and

troubleshoot working instrument loop systems. Each lab exercise focuses on a different type of instrument,with a eight-day period typically allotted for completion. An ordinary lab session might look like this:

(1) Start of practical (lab) session: announcements and planning(a) The instructor makes general announcements to all students(b) The instructor works with team to plan that day’s goals, making sure each team member has a

clear idea of what they should accomplish(2) Teams work on lab unit completion according to recommended schedule:

(First day) Select and bench-test instrument(s)(One day) Connect instrument(s) into a complete loop(One day) Each team member drafts their own loop documentation, inspection done as a team (withinstructor)(One or two days) Each team member calibrates/configures the instrument(s)(Remaining days, up to last) Each team member troubleshoots the instrument loop

(3) End of practical (lab) session: debriefing where each team reports on their work to the whole class

Troubleshooting assessments must meet the following guidelines:

• Troubleshooting must be performed on a system the student did not build themselves. This forcesstudents to rely on another team’s documentation rather than their own memory of how the system wasbuilt.

• Each student must individually demonstrate proper troubleshooting technique.• Simply finding the fault is not good enough. Each student must consistently demonstrate sound

reasoning while troubleshooting.• If a student fails to properly diagnose the system fault, they must attempt (as many times as necessary)

with different scenarios until they do, reviewing any mistakes with the instructor after each failedattempt.

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Distance delivery methods

Sometimes the demands of life prevent students from attending college 6 hours per day. In such cases,there exist alternatives to the normal 8:00 AM to 3:00 PM class/lab schedule, allowing students to completecoursework in non-traditional ways, at a “distance” from the college campus proper.

For such “distance” students, the same worksheets, lab activities, exams, and academic standards stillapply. Instead of working in small groups and in teams to complete theory and lab sections, though, studentsparticipating in an alternative fashion must do all the work themselves. Participation via teleconferencing,video- or audio-recorded small-group sessions, and such is encouraged and supported.

There is no recording of hours attended or tardiness for students participating in this manner. The paceof the course is likewise determined by the “distance” student. Experience has shown that it is a benefit for“distance” students to maintain the same pace as their on-campus classmates whenever possible.

In lieu of small-group activities and class discussions, comprehension of the theory portion of each coursewill be ensured by completing and submitting detailed answers for all worksheet questions, not just passingdaily quizzes as is the standard for conventional students. The instructor will discuss any incomplete and/orincorrect worksheet answers with the student, and ask that those questions be re-answered by the studentto correct any misunderstandings before moving on.

Labwork is perhaps the most difficult portion of the curriculum for a “distance” student to complete,since the equipment used in Instrumentation is typically too large and expensive to leave the school labfacility. “Distance” students must find a way to complete the required lab activities, either by arrangingtime in the school lab facility and/or completing activities on equivalent equipment outside of school (e.g.at their place of employment, if applicable). Labwork completed outside of school must be validated by asupervisor and/or documented via photograph or videorecording.

Conventional students may opt to switch to “distance” mode at any time. This has proven to be abenefit to students whose lives are disrupted by catastrophic events. Likewise, “distance” students mayswitch back to conventional mode if and when their schedules permit. Although the existence of alternativemodes of student participation is a great benefit for students with challenging schedules, it requires a greaterinvestment of time and a greater level of self-discipline than the traditional mode where the student attendsschool for 6 hours every day. No student should consider the “distance” mode of learning a way to havemore free time to themselves, because they will actually spend more time engaged in the coursework thanif they attend school on a regular schedule. It exists merely for the sake of those who cannot attend duringregular school hours, as an alternative to course withdrawal.

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14

General advice for successful learning

Focus on principles, not procedures• Effective problem-solvers don’t bother trying to memorize procedures for problem-solving because

procedures are too specific to the type of problem. Rather, they internalize general principles applicableto a wide variety of problems.

• When asking questions about some new subject, concentrate on “why” rather than “how” or “what.”

Cultivate meta-cognitive skills (the ability to monitor your own thinking on a subject)!• Whenever you get “stuck” trying to understand a concept, clearly identify where you are getting stuck,

and where things stop making sense.• When you think you understand a concept, test your understanding by explaining it in your own words.

You can do this by trying to explain it to a willing classmate, or by imagining yourself trying to explainit to someone. If you cannot clearly explain a concept to someone else, you do not understand it wellenough yourself !

• The technique of trying to explain a concept also works well to identify where you are stuck. The pointat which you find yourself unable to clearly articulate the concept is very likely the exact point of yourmisconception or confusion.

Join or create a study group with like-minded classmates!• Read the textbook assignments together.• Solve assigned problems together.• Collectively identify difficult concepts and areas needing clarification, to bring up later during class.• Take turns trying to explain complicated concepts to each other, then critiquing those explanations.

Eliminate distractions in your life!• Time-wasting technologies: televisions, internet, video games, mobile phones, etc.• Unhelpful friends, unhealthy relationships, etc.

Make use of “wasted” time to study!• Carefully plan your lab sessions with your teammates to reserve a portion of each day’s lab time for

study.• Bring a meal to school every day and use your one-hour lunch break for study instead of eating out.

This will not just save you time, but also money!• Plan to arrive at school at least a half-hour early (the doors unlock at 7:00 AM) and use the time to

study as opposed to studying late at night. This also helps guard against tardiness in the event ofunexpected delays, and ensures you a better parking space!

Take responsibility for your learning and your life!• Do not procrastinate, waiting until the last minute to do something.• Obtain all the required books, and any supplementary study materials available to you. If the books

cost too much, look on the internet for used texts (www.amazon.com, www.half.com, etc.) and use themoney from the sale of your television and video games to buy them!

• Make an honest attempt to solve problems before asking someone else to help you. Being able toproblem-solve is a skill that will improve only if you continue to work at it.

• If you detect trouble understanding a basic concept, address it immediately. Never ignore an area ofconfusion, believing you will pick up on it later. Later may be too late!

• Do not wait for others to do things for you. No one is going to make extra effort purely on your behalf.

. . . And the number one tip for success . . .• Realize that there are no shortcuts to learning. Every time you seek a shortcut, you are actually cheating

yourself out of a learning opportunity!!

file studytips

15

Creative Commons License

This worksheet is licensed under the Creative Commons Attribution License, version 1.0. To viewa copy of this license, visit http://creativecommons.org/licenses/by/1.0/ or send a letter to CreativeCommons, 559 Nathan Abbott Way, Stanford, California 94305, USA. The terms and conditions of thislicense allow for free copying, distribution, and/or modification of all licensed works by the general public.

Simple explanation of Attribution License:

The licensor (Tony Kuphaldt) permits others to copy, distribute, display, and otherwise use thiswork. In return, licensees must give the original author(s) credit. For the full license text, please visithttp://creativecommons.org/licenses/by/1.0/ on the internet.

More detailed explanation of Attribution License:

Under the terms and conditions of the Creative Commons Attribution License, you may make freelyuse, make copies, and even modify these worksheets (and the individual “source” files comprising them)without having to ask me (the author and licensor) for permission. The one thing you must do is properlycredit my original authorship. Basically, this protects my efforts against plagiarism without hindering theend-user as would normally be the case under full copyright protection. This gives educators a great dealof freedom in how they might adapt my learning materials to their unique needs, removing all financial andlegal barriers which would normally hinder if not prevent creative use.

Nothing in the License prohibits the sale of original or adapted materials by others. You are free tocopy what I have created, modify them if you please (or not), and then sell them at any price. Once again,the only catch is that you must give proper credit to myself as the original author and licensor. Given thatthese worksheets will be continually made available on the internet for free download, though, few peoplewill pay for what you are selling unless you have somehow added value.

Nothing in the License prohibits the application of a more restrictive license (or no license at all) toderivative works. This means you can add your own content to that which I have made, and then exercisefull copyright restriction over the new (derivative) work, choosing not to release your additions under thesame free and open terms. An example of where you might wish to do this is if you are a teacher who desiresto add a detailed “answer key” for your own benefit but not to make this answer key available to anyoneelse (e.g. students).

Note: the text on this page is not a license. It is simply a handy reference for understanding the LegalCode (the full license) - it is a human-readable expression of some of its key terms. Think of it as theuser-friendly interface to the Legal Code beneath. This simple explanation itself has no legal value, and itscontents do not appear in the actual license.

file license

16

Metric prefixes and conversion constants

• Metric prefixes

• Yotta = 1024 Symbol: Y

• Zeta = 1021 Symbol: Z

• Exa = 1018 Symbol: E

• Peta = 1015 Symbol: P

• Tera = 1012 Symbol: T

• Giga = 109 Symbol: G

• Mega = 106 Symbol: M

• Kilo = 103 Symbol: k

• Hecto = 102 Symbol: h

• Deca = 101 Symbol: da

• Deci = 10−1 Symbol: d

• Centi = 10−2 Symbol: c

• Milli = 10−3 Symbol: m

• Micro = 10−6 Symbol: µ

• Nano = 10−9 Symbol: n

• Pico = 10−12 Symbol: p

• Femto = 10−15 Symbol: f

• Atto = 10−18 Symbol: a

• Zepto = 10−21 Symbol: z

• Yocto = 10−24 Symbol: y

1001031061091012 10-3 10-6 10-9 10-12(none)kilomegagigatera milli micro nano pico

kMGT m µ n p

10-210-1101102

deci centidecahectoh da d c

METRIC PREFIX SCALE

• Conversion formulae for temperature

• oF = (oC)(9/5) + 32

• oC = (oF - 32)(5/9)

• oR = oF + 459.67

• K = oC + 273.15

Conversion equivalencies for distance

1 inch (in) = 2.540000 centimeter (cm)

1 foot (ft) = 12 inches (in)

1 yard (yd) = 3 feet (ft)

1 mile (mi) = 5280 feet (ft)

17

Conversion equivalencies for volume

1 gallon (gal) = 231.0 cubic inches (in3) = 4 quarts (qt) = 8 pints (pt) = 128 fluid ounces (fl. oz.)= 3.7854 liters (l)

1 milliliter (ml) = 1 cubic centimeter (cm3)

Conversion equivalencies for velocity

1 mile per hour (mi/h) = 88 feet per minute (ft/m) = 1.46667 feet per second (ft/s) = 1.60934kilometer per hour (km/h) = 0.44704 meter per second (m/s) = 0.868976 knot (knot – international)

Conversion equivalencies for mass

1 pound (lbm) = 0.45359 kilogram (kg) = 0.031081 slugs

Conversion equivalencies for force

1 pound-force (lbf) = 4.44822 newton (N)

Conversion equivalencies for area

1 acre = 43560 square feet (ft2) = 4840 square yards (yd2) = 4046.86 square meters (m2)

Conversion equivalencies for common pressure units (either all gauge or all absolute)

1 pound per square inch (PSI) = 2.03602 inches of mercury (in. Hg) = 27.6799 inches of water (in.W.C.) = 6.894757 kilo-pascals (kPa) = 0.06894757 bar

1 bar = 100 kilo-pascals (kPa) = 14.504 pounds per square inch (PSI)

Conversion equivalencies for absolute pressure units (only)

1 atmosphere (Atm) = 14.7 pounds per square inch absolute (PSIA) = 101.325 kilo-pascals absolute(kPaA) = 1.01325 bar (bar) = 760 millimeters of mercury absolute (mmHgA) = 760 torr (torr)

Conversion equivalencies for energy or work

1 british thermal unit (Btu – “International Table”) = 251.996 calories (cal – “International Table”)= 1055.06 joules (J) = 1055.06 watt-seconds (W-s) = 0.293071 watt-hour (W-hr) = 1.05506 x 1010

ergs (erg) = 778.169 foot-pound-force (ft-lbf)

Conversion equivalencies for power

1 horsepower (hp – 550 ft-lbf/s) = 745.7 watts (W) = 2544.43 british thermal units per hour(Btu/hr) = 0.0760181 boiler horsepower (hp – boiler)

Acceleration of gravity (free fall), Earth standard

9.806650 meters per second per second (m/s2) = 32.1740 feet per second per second (ft/s2)

18

Physical constants

Speed of light in a vacuum (c) = 2.9979 × 108 meters per second (m/s) = 186,281 miles per second(mi/s)

Avogadro’s number (NA) = 6.022 × 1023 per mole (mol−1)

Electronic charge (e) = 1.602 × 10−19 Coulomb (C)

Boltzmann’s constant (k) = 1.38 × 10−23 Joules per Kelvin (J/K)

Stefan-Boltzmann constant (σ) = 5.67 × 10−8 Watts per square meter-Kelvin4 (W/m2·K4)

Molar gas constant (R) = 8.314 Joules per mole-Kelvin (J/mol-K)

Properties of Water

Freezing point at sea level = 32oF = 0oC

Boiling point at sea level = 212oF = 100oC

Density of water at 4oC = 1000 kg/m3 = 1 g/cm3 = 1 kg/liter = 62.428 lb/ft3 = 1.94 slugs/ft3

Specific heat of water at 14oC = 1.00002 calories/g·oC = 1 BTU/lb·oF = 4.1869 Joules/g·oC

Specific heat of ice ≈ 0.5 calories/g·oC

Specific heat of steam ≈ 0.48 calories/g·oC

Absolute viscosity of water at 20oC = 1.0019 centipoise (cp) = 0.0010019 Pascal-seconds (Pa·s)

Surface tension of water (in contact with air) at 18oC = 73.05 dynes/cm

pH of pure water at 25o C = 7.0 (pH scale = 0 to 14)

Properties of Dry Air at sea level

Density of dry air at 20oC and 760 torr = 1.204 mg/cm3 = 1.204 kg/m3 = 0.075 lb/ft3 = 0.00235slugs/ft3

Absolute viscosity of dry air at 20oC and 760 torr = 0.018 centipoise (cp) = 1.8 × 10−5 Pascal-seconds (Pa·s)

file conversion constants

19

Question 0

How to read actively:

• Avoid shallow annotation methods such as underlining and highlighting. Instead, express your owninterpretation of the text in a notebook or in the margins of the text. A suggestion is one sentence ofyour own thoughts per paragraph in the text. Expressing your own thoughts as you read is a far moreeffective way to digest the information than simply emphasizing portions of the text! If you do wish toemphasize some portion of the text that either makes perfect sense to you or causes confusion, writethat portion verbatim and include a page number reference in your notes so you may reference it duringclass.

• Identify as clearly as possible which concepts or points confuse you the most. This is the first andmost important step to overcoming confusion. The more specific you are, the better your instructor andclassmates will be able to help you overcome the confusion!

• If the text demonstrates a mathematical calculation, such as how to apply a new equation to solving aproblem, pick up your calculator and work through the example as you read! Applications of math arean ideal opportunity to actively read a technical book.

• Maintain a notebook where you express your understanding of general principles applicable to thesubject(s) you are studying, including mathematical formulae (a formula is really just a preciseexpression of a principle) with brief definitions of terms.

• Imagine trying to explain what you’ve just read to an intelligent child – someone with the capacity tounderstand but without the experience to immediately relate. This forces you to distill each concept toits essence. Your first attempt will rarely be right, but subsequent attempts will get better and better.Once you have an explanation that satisfies you, write it out using the fewest words possible.

Problem-solving tips:

• Always begin by identifying which general principles you’ve learned apply to the problem, then identifyhow the goal of the problem (i.e. what it is you’re asked to solve) and the “given” information fits withthose principles.

• Sketch a diagram to organize all “given” information and show where the answer will fit.

• Perform “thought experiments” to visualize the effects of different conditions.

• Work “backward” from a hypothetical solution to a new set of given conditions.

• Change the problem to make it simpler, and then solve the simplified problem (e.g. change quantitativeto qualitative, or visa-versa; substitute different numerical values to make them easier to work with;eliminate confusing details; add details to eliminate unknowns; consider limiting cases that are easierto grasp; put the problem into a more familiar context, or analogy).

• Specifically identify which portion(s) of the question you find most confusing and need help with. Themore specifically you are able to express your point(s) of confusion, the better.

Above all, cultivate persistence in your studies. Persistent effort is necessary for mastery of anythingnon-trivial. The keys to persistence are (1) having the desire to achieve that mastery, and (2) knowing thatchallenges are normal and not an indication of something gone wrong. A common error is to equate easywith effective: students often believe learning should be easy if everything is done right. The truth is thatmastery never comes easy, and that “easier” methods usually substitute memorization for understanding!

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20

Questions

Question 1

Read and outline the “Pressure” subsection of the “Fluid Mechanics” section of the “Physics” chapter inyour Lessons In Industrial Instrumentation textbook. Note the page numbers where important illustrations,photographs, equations, tables, and other relevant details are found. Prepare to thoughtfully discuss withyour instructor and classmates the concepts and examples explored in this reading.

file i03894

Question 2

Read and outline the “Pascal’s Principle and hydrostatic pressure” subsection of the “Fluid Mechanics”section of the “Physics” chapter in your Lessons In Industrial Instrumentation textbook. Note the pagenumbers where important illustrations, photographs, equations, tables, and other relevant details are found.Prepare to thoughtfully discuss with your instructor and classmates the concepts and examples explored inthis reading.

Suggestions for Socratic discussion

• Does Pascal’s Law apply only to liquids, or to gases as well?• Explain what is going on with the dimensional analysis example.

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21

Question 3

In this hydraulic system, a force of 25 pounds is applied to the small piston (area = 10 in2). How muchforce will be generated at the large piston (area = 40 in2)? Also, calculate the fluid’s pressure.

10 in2 40 in2

Fluid

25 lb Force = ???

5 inches

Finally, explain how Pascal’s Principle relates to this scenario.


• Identify which fundamental principles of science, technology, and/or math apply to each step of yoursolution to this problem. In other words, be prepared to explain the reason(s) “why” for every step ofyour solution, rather than merely describing those steps.

• Identify a practical application for a hydraulic system such as this.• Does the pressure/force/area equation hold true for all piston positions, or only with the pistons in

mid-stroke as shown in the illustration?• Does the pressure/force/area equation hold true for all fluids, or only for liquids and not gases?• This mechanism seems to multiply the applied force. How can it do so without violating the Law of

Energy Conservation (energy out cannot exceed energy in)?• Demonstrate how to estimate numerical answers for this problem without using a calculator.

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22

Question 4

A pressure calibration device called a deadweight tester generates very precise pressures by means ofcalibrated weights placed on top of a hydraulic piston:

weight

Primary piston

Secondary piston

oil

Gauge to becalibrated

Deadweight tester

The secondary piston is moved in and out by turning a handle on a threaded rod. Its sole purposeis to displace enough oil to force the primary piston to rise from its resting position, so that it is entirelysuspended by oil pressure. In that condition, the gauge will be subject to whatever pressure is proportionalto the weights placed on top of the primary piston, and the area of the primary piston.

What will happen to the gauge’s indication if the secondary piston is pushed in further? What willhappen to the gauge’s indication if the secondary piston is pulled out, but not so far that the primary pistoncomes down to its resting position? In other words, what effect does the secondary piston position have onpressure applied to the gauge?

weight

oil

weight

oil

Secondary pistonmoved out

Primary pistonmoves down

Secondary pistonmoved in

Primary pistonmoves up

In each condition, what happens to the gauge’s indication?Does the applied pressure increase, decrease, or stay the same?

??????


• Why are deadweight testers considered accurate standards for fluid pressure? What is it about theirdesign and operation that makes them so accurate? Conversely, what aspects of their constructionwould have to change in order to corrupt their inherent accuracy?

• If a technician changes the type of fluid used in a deadweight tester (for example, from one type of oilto another), will its accuracy change?

• Identify some potential problems one might encounter when using a deadweight tester. What things,specifically, do you see that could go wrong with this device?

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23

Question 5

Read and outline the “Manometers” subsection of the “Fluid Mechanics” section of the “Physics”chapter in your Lessons In Industrial Instrumentation textbook. Note the page numbers where importantillustrations, photographs, equations, tables, and other relevant details are found. Prepare to thoughtfullydiscuss with your instructor and classmates the concepts and examples explored in this reading.

file i03896

Question 6

Read and outline the “Systems of Pressure Measurement” subsection of the “Fluid Mechanics” section ofthe “Physics” chapter in your Lessons In Industrial Instrumentation textbook, particularly how to use “unityfractions” for cancellation of units, and how to manage conversions between units of pressure measurementthat do not share the same zero point. Then, use that same mathematical technique to convert between thefollowing units of pressure:

• 25 PSI = ??? kPa

• 40 ”W.C. = ??? PSI

• 5.60 bar (gauge) = ??? PSI

• 3 atm = ??? PSIA

• 1,200 ”Hg = ??? ”W.C.

• 12 feet W.C. = ??? PSI

• 4 PSI vacuum = ??? PSIA

• 110 kPa = ??? ”W.C.

• 982 mm Hg = ??? ”Hg

• 50 Pa = ??? PSI

• 21 atm = ??? ”Hg absolute

• 270 PSIG = ??? atm

There is a technique for converting between different units of measurement called “unity fractions”which is imperative for students of Instrumentation to master. A section entitled Unit Conversions andPhysical Constants in your Lessons In Industrial Instrumentation textbook describes and explains this “unityfractions” technique in detail.


• Demonstrate how to estimate numerical answers for these conversion problems without using acalculator.

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24

Question 7

Calculate the amount of force generated by this hydraulic ram for the given pressures, assuming a pistonrod length of 17 inches, a piston diameter of 5 inches, and a fluid temperature of 80 degrees Fahrenheit:

piston

rod

5"

Fluid pressure

(vented)

• P = 260 PSI F =

• P = 1100 PSI F =

• P = 461 kPa F =

• P = 399 ”W.C. F =

• P = 2.77 bar F =



• Why is it important that we know the top side of this cylinder is vented to atmosphere?• Do we need to know what type of fluid presses against the piston as we calculate its force? For example,

would it make a difference whether the fluid in this problem was assumed to be oil versus air?• How do you suppose the ram is constructed to minimize leakage of hydraulic fluid past the piston, and

also past the opening in the case where the rod projects through?• Demonstrate how to estimate numerical answers for this problem without using a calculator.

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Question 8

Electrically-powered air compressors are commonly used in many different industries for supplying clean,dry compressed air to machines, instrument systems, and pneumatic tools. A simple compressor systemconsists of a compressor which works much like a bicycle tire pump (drawing in air, then compressing itusing pistons), an electric motor to turn the compressor mechanism via a V-belt, a “receiver tank” to receivethe compressed air discharged by the compressor mechanism, and some miscellaneous components installedto control the pressure of the compressed air in the receiver tank and drain any condensed water vapor thatenters the receiver:

Compressor

MotorBelt

Receiver tank

PSV(lifts at 130 PSI)

S

Condensate drain valve

Electricalconduit To 480 VAC

power source

Electrical enclosure

PSL PSH

Electrical conduit

LSHElectrical conduit

Cable

Cable

Cable

"Boot"

PSLL

Buzzer

AlarmEnableDisable

RunStop On

Off

Electromechanical relay circuitry located inside the electrical enclosure decides when to turn thecompressor motor on and off based on the statuses of the high- and low-pressure control switches (PSH= high pressure switch ; PSL = low pressure switch).

Your task is two-fold. First, you must figure out how to wire a new low-low pressure alarm switch (PSLL,shown on the left-hand end of the receiver) so that an alarm buzzer will activate if ever the compressed airpressure falls too low. A newly-installed hand switch located on the front panel of the electrical enclosuremust be wired with this PSLL switch in such a way that the buzzer cannot energize if the hand switch is inthe “alarm disable” position. Second, you must figure out how to wire a new high-level switch (LSH, shownon the “boot” of the receiver tank) so that the condensate drain valve will energize automatically to openup and drain water out of the receiver boot when the level gets too high, and then automatically shut againwhen the water in the boot drops down to an acceptable level.

26

The following schematic diagram shows the basic motor control circuit for this air compressor, with thenew switches, buzzer, and drain valve shown unwired:

M1

M1 OL

motor

OL

To 3-phaseAC power

M1

H1 H2 H3 H4

F1 F2

F3A

B

C

D E

F G

120 VAC

PSLPSH

Compressor

X1 X2

(480 VAC)

L1

L2

L3

T1

T2

T3

H JK L

M N

Stop Run

LSH

Disable Enable

PSLL

80 PSI95 PSI

65 PSI

Buzzer

Condensatedrain valve

Complete this control circuit by sketching connecting wires between the new switches, buzzer, and drainvalve solenoid. Remember that the way all switches are drawn in schematic diagrams is in their “normal”states as defined by the manufacturer: the state of minimum stimulus (when the switch is un-actuated). Forpressure switches, this “normal” state occurs during a low pressure condition; for liquid level switches, this“normal” state occurs during a low-level (dry) condition. Note that each of the new process switches hasSPDT contacts, allowing you to wire each one as normally-open (NO) or as normally-closed (NC) as you seefit.

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Question 9

This Honeywell model UDC2500 controller needs to connect to a loop-powered pressure transmitter insuch a way that it displays the amount of pressure in the process vessel, and outputs a signal to the 120 VACalarm lamp if the process pressure becomes too great. Alarm relay #1 in the controller has been configuredfor a high-pressure trip point of 140 PSI:

250 Ω

L1

L2/N

Alarmrelay #1

Alarmrelay #2

Analog input #1

Analog input #2

Honeywell model UDC2500 controller

H L

Rosemount model 1151loop-powered pressure transmitter

3-valve isolationmanifold

Outputrelay #1

Isolationvalve

Processvessel

Alarm lamp(120 VAC)

250 Ω

Sketch all necessary connecting wires and tubes to make this a working system. Note: you will need toadd electrical power sources to the diagram! Also, identify the proper open/closed state for each valve inthe manifold.


• A problem-solving technique useful for making proper connections in pictorial circuit diagrams is tofirst identify the directions of all DC currents entering and exiting component terminals, as well as therespective voltage polarity marks (+,-) for those terminals, based on your knowledge of each componentacting either as an electrical source or an electrical load. Discuss and compare how these arrows andpolarity marks simplify the task of properly connecting wires between components.

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28

Question 10

Read selected portions of the National Transportation Safety Board’s Pipeline Accident Report, PipelineRupture and Subsequent Fire in Bellingham, Washington, June 10, 1999 (Document NTSB/PAR-02/02 ;PB2002-916502), and answer the following questions:

Page 6 of the report shows a graphical trend of pipeline pressure before, during, and after the rupture.How high did the pressure spike, in units of PSI? Do you suppose this was PSIG or PSIA? Convert thismeasurement into units of kilopascals (kPa) and into units of bar. Based on what you see on the trendgraph, was this pipeline carrying a gas or a liquid? How can you tell, from the shape of the trend alone?

Examine the photographs of the ruptured pipeline on page 41 of the report. Based on what you knowabout fluid pressure, determine where along the pipeline’s interior the force of the pressure was exerted.

Page 57 of the report discusses how the pipeline had been “hydrostatically tested” after its originalinstallation. This means it was pressure-tested with non-moving (static) water. Why was this detailimportant to the investigation?


• Is it possible to monitor over-pressure conditions in a pipeline anywhere along the pipe, or must we use amultitude of pressure sensors along the pipeline’s length to ensure we monitor pressure at all locations?

• How do you think an over-pressure condition in a pipeline may be prevented? What sort of devicesmight act as safety reliefs to ensure a pipeline does not become over-pressured?

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29

Question 11

Examine the overhead product pressure control loop (#33) in this distillation system (in the upper-rightcorner of the P&ID). Suppose PR-33 shows a pressure of 48.1 PSI, while PIC-33 shows a pressure of 50.0PSI (equal to setpoint):

C-5

RO

PG

PG

RO

PG

PG

M

PG

NC

NC

NC

NC

NC

C-5MAIN FRACTIONATION TOWER

PT

PIC

HP cooling waterDwg. 11324

Dwg. 11324

Cooling waterreturn

PY

FT

FT IAS

P

FC

LIC

LT

Overhead productDwg. 28542

Distillate productDwg. 28543

Bottoms productDwg. 28544

LG

LGLT

LSH

LSL

FT

LIC FIC

P

Sidedraw productDwg. 28545

NC

FT

FIC FY

FV

FT

FYFYLead/LagLead/Lag

AT

AIC

FY

Dwg. 10957

FT

P

IAS

IAS

AIC FY

Dwg. 10957Condensate return

FOUNDATION Fieldbus

FOUNDATION Fieldbus

FOUNDATION Fieldbus

IAS

P

FC

IAS

IAS

V-13

V-13OVERHEAD ACCUMULATOR

P-10 P-11

Dwg. 10957

Fractionator feed

Dwg. 27004from charge heater

E-5

E-6

E-7

E-8

E-9

FO

FC

FO

FC

FO

FO

PSL

PSL

SS

R

IAS

I

HC

RO

PG

PG

RO

PG

M

FO

PSL

PSL

SS

R

I

IAS

HC

PG

RO

PG

PGM

FO

PSL

PSL

SS

R

I

IAS

HC

RO

PG

PG


PG

PG

PG

PG

PG

PG

TT

TT

TT

TT

TT

TT

TIR

TIR

TIR

TIR

TIR

TIR

AITTT TIR

TTTIR

3131 30

3032

33

33

34

34 34

35

35 35

36

36

37

3738

39

40

40a 40b

40c

FFC

41

41

42

42

50 50

5151

5252

53 53

54 54

55 55

56 56

57

58

57

LAL

58

LAH

LLL = 3’-8"

NLL = 5’-4"

HLL = 7’-2"

33PR

33aPY

33b

106

107

60

61

62

63

64

65

59 59

108

PG

PG

109

110

111

112

113

114

115

116

117

118119

120

121

122

123 124

125

127

35

FV34

PV

FV31

FV41

FV37

Dwg. 62314

To LP flareFO

NC

33a

33bPV

3 to 9 PSI

9 to 15 PSI

PG130

PG131

PG132

PG133

PG134

PG135

PG136

PG137

PG138

PG139

P-12 P-13 P-14 P-15

P-15P-10 P-11 P-12 P-13 P-14MAIN OVERHEAD PRODUCT PUMP BACKUP OVERHEAD PRODUCT PUMPMAIN BOTTOMS PRODUCT PUMP BACKUP BOTTOMS PRODUCT PUMPMAIN CHARGE FEED PUMP BACKUP CHARGE FEED PUMP

E-5, E-6, E-7FEED HEAT RECOVERY EXCHANGERS

H

L

PSH

PAH

66

66

H

L

H

L

Note 1Note 1Note 1

NOTES:

1. Backup (steam-driven) pumps automatically started by 2oo2 triplogic, where both pressure switches must detect a low-pressurecondition in order to start the backup pump.

FOUNDATION Fieldbus

FOUNDATION FieldbusFOUNDATION Fieldbus

FOUNDATION Fieldbus

M

FT67

FOUNDATION Fieldbus

FIR

67

FT68 PT

68

68TT

FY

68

Modbus RS-485 FIQ

68

PT

TTFT69

69

69

FY

69

FIR

69

RTD

RTD

Note 2

2. Transit-time ultrasonic flowmeter with pressure and temperaturecompensation for measuring overhead gas flow to flare line.

Dia 10’-3" Height 93’DP 57 PSIG

Set @ 55 PSISet @ 55 PSI

Set @ 52 PSI Set @ 52 PSI

DT 650 oF top, 710 oF bottom

DP 81 PSIGDT 650 oF

E-9BOTTOMS REBOILER

E-8OVERHEAD PRODUCT CONDENSER

2100 GPM @ 460 PSID 1900 GPM @ 460 PSID 2880 GPM @ 70 PSID 2880 GPM @ 70 PSID 2350 GPM @ 55 PSID 2350 GPM @ 55 PSID80 MM BTU/hrShell 500 PSIG @ 650 oF

Tube 165 PSIG @ 400 oFTube 660 PSIG @ 730 oFShell 120 PSIG @ 650 oF

55 MM BTU/hr 70 MM BTU/hrShell 630 PSIG @ 800 oFTube 600 PSIG @ 880 oF

Set @410 PSI

Set @500 PSI

Set @100 PSI

Set @73 PSI

600 PSI steam

1000 PSI steam

PG140

PG141

LT

38a

38bLT38c

LY

38

Median

142 143 144

Radar

select

Magnetostrictive (float)

Identify which faults could account for the pressure indication discrepancy:

Fault Possible ImpossiblePR-33 calibration errorPT-33 calibration error

PIC-33 (input) calibration errorPY-33a calibration errorPY-33b calibration errorPV-33a calibration errorPV-33b calibration error

file i03514

30

Question 12

If force is exerted on the piston of this hydraulic cylinder, in what direction(s) will this force betransmitted to the cylinder walls? In other words, how does a fluid under pressure push against itssurrounding container?

Piston

Rod

Fluid

Force

Hydraulic cylinder

Steel cylinderwall

Steel cylinderwall

file i00142

Question 13

Suppose a small rubber ball is floating inside the fluid of a hydraulic cylinder as shown below. Whatwill happen to the ball when a pushing force is exerted on the cylinder’s rod? What will happen to the ballwhen a pulling force is exerted on the rod?

Rubber ball

file i00143

31

Question 14

A scuba diver’s air tank contains 2,000 PSI of air, as measured by a pressure gauge before descendinginto the water. The diver descends 50 feet into the water, where the surrounding water pressure caused bythe water’s weight (called hydrostatic pressure) is approximately 22 PSI. Assuming that the diver consumesan inconsequential amount of air from the tank during the 50 foot descent, express the air pressure insidethe tank in terms of absolute pressure, gauge pressure, and differential pressure (the differential pressurebetween the tank and the surrounding hydrostatic pressure of the water).

file i00145

Question 15

A surface-mounted water pump pulls water out of a well by creating a vacuum, though it might be moretechnically accurate to say that the pump works by reducing pressure in the inlet pipe to a level less thanatmospheric pressure, allowing atmospheric pressure to then push water from the well up the pump’s inletpipe:

Pump

Water

Atmosphericpressure

Based on this description of pump operation, what is the theoretical maximum height that any pumpcan lift water out of a well, assuming the well is located at sea level?

Water wells located at altitudes other than sea level will have different theoretical maximum liftingheights (i.e. the farthest distance a surface-mounted pump may suck water out of the well). Research theaverage barometric pressure in Denver, Colorado (the “mile-high” city) and determine how far up a surfacepump may draw water from a well in Denver.

Domestic water wells may be hundreds of feet deep. How can water be pumped out of wells this deep,given the height limitation of vacuum pumping?


• If the liquid in question was something other than water, would the maximum “lift” depth be different?Why or why not?

file i00147

32

Question 16

Water pressure available at a fire hydrant is 80 PSI. If a fire hose is connected to the hydrant and thehydrant valve opened, how high can the end of the hose be raised and still have water flow out the end?

80 PSI

How high???

Now, suppose that a spray nozzle attached to the end of the hose requires at least 30 PSI of pressureat the coupling in order to create a proper spray of water. How high can the hose be raised then, and stillhave enough water pressure at the nozzle to allow for the fighting of a fire?

80 PSI

How high???

required hereAt least 30 PSI


• How may firefighters ensure they are able to spray water high enough to put out tall building fires, ifthe hydrant pressure is insufficient?

33

file i00148

Question 17

Complete the following table of equivalent pressures:

PSIG PSIA inches Hg (G) inches W.C. (G)18

40033

60452

121

-5


file i02938

34

Question 18

A process called delayed coking is used in the oil refining industry to convert heavy oils and tars intohigher-valued products. A process vessel called a coke drum has a removable lid held down by a series ofbolts, and alternatively by a hydraulic ram. When it comes time to open up the coke drum, the hydraulicram is pressurized to maintain adequate force on the coke drum lid, the bolts are removed, and then theram’s fluid pressure is reduced until the lid springs open from the force of the gas pressure inside the cokedrum:

Top of coke drum

Lid

Ram

Hinge38o

Hydraulic hose

Coker deck

(contains 5 PSI gas)

Calculate the hydraulic pressure necessary to hold down the lid on the coke drum when the gas pressureinside the drum is 5 PSI and all hold-down bolts have been removed from the lid. Assume a lid diameter of30 inches, and a ram piston diameter of 4 inches. Hint: sketch a right triangle, representing forces as sidelengths on the triangle – the ram’s diagonal force will translate into both a horizontal force on the lid (whichyou may ignore) and a vertical force on the lid (which is what we’re interested in here).

P = PSIfile i04683

35

Question 19

How much pressure is being applied to this U-tube water manometer, in units of “inches of watercolumn” and “pounds per square inch”?

(vented)Appliedpressure

4.5"

4.5"

Water

Water levelat zero pressure

What would happen to the liquid levels if the water were replaced by an oil with a lesser density? Giventhe same applied pressure, would the distance between the two liquid columns be greater, less, or the sameas shown in the above illustration?

file i00161

36

Question 20

Determine what will happen at the following steps in the sequence (when prompted for a response):

Handpump

Pressurevessel

under test

Manometer

Vent

12

3

Vent

4HL

Instrument

• Step 1: Open valves 1 and 2

• Step 2: Close valves 3 and 4

• Step 3: Operate hand pump until manometer registers maximum pressure

• Step 4: (4 points) Quickly open and close valve 4 – does the manometer indication drop greatly,slightly, or not at all?

• Step 5: Close valve 2


• Step 7: Close valve 1


file i00463

37

Question 21

Skim the “Continuous Pressure Measurement” chapter in your Lessons In Industrial Instrumentationtextbook to identify several different mechanical technologies for measuring pressure, then briefly describethe operating principle of each one:

• Manometers (identify some of the different types!)

• Bellows

• Diaphragm

• Bourdon tube (identify some of the different types!)


• Discuss ideas for “skimming” a text to identify key points so you do not have to read the whole thing.• Explain why a raised well manometer is virtually blow-out proof.• Explain how each “differential” pressure sensing mechanism works.

file i03899

Question 22

Skim the “Continuous Pressure Measurement” chapter in your Lessons In Industrial Instrumentationtextbook to identify different electronic technologies for measuring pressure, then briefly describe theoperating principle of each one:

• Strain gauge (electronic sensing)

• Capacitance sensors (electronic sensing)

• Resonant sensors (electronic sensing)


• Discuss ideas for “skimming” a text to identify key points so you do not have to read the whole thing.• Explain how each “differential” pressure sensor works.

file i03902

Question 23

Read and outline the “DP Transmitter Construction and Behavior” subsection of the “DifferentialPressure Transmitters” section of the “Continuous Pressure Measurement” chapter in your Lessons InIndustrial Instrumentation textbook. Note the page numbers where important illustrations, photographs,equations, tables, and other relevant details are found. Prepare to thoughtfully discuss with your instructorand classmates the concepts and examples explored in this reading.

file i03900

Question 24

Read and outline the “DP Transmitter Applications” subsection of the “Differential PressureTransmitters” section of the “Continuous Pressure Measurement” chapter in your Lessons In IndustrialInstrumentation textbook. Note the page numbers where important illustrations, photographs, equations,tables, and other relevant details are found. Prepare to thoughtfully discuss with your instructor andclassmates the concepts and examples explored in this reading.

file i03901

38

Question 25

How much pressure, in inches of water column, is being applied to this inclined water manometerto create a total displacement of 14 inches along the length of the tubes, inclined at angles of 20o fromhorizontal? Assume the base of this manometer is located 24 inches above ground level.

14"

20o

Appliedpressure

(vented)

Next, convert this pressure into units of kPa.



• Does inclining a manometer make it more or less sensitive to applied pressure? Develop a “thoughtexperiment” where you could test a manometer to answer this question.

• Is it possible to make a well version of an inclined manometer so that we need only to read one liquidcolumn?

• What will happen to a manometer if it is exposed to a gas pressure greater than its measurement range?• Would a micromanometer be more or less sensitive to applied pressure than this inclined manometer?

file i00168

39

Question 26

Convert between the following units of pressure. Remember that any pressure unit not explicitly specifiedas either absolute (A) or differential (D) is to be considered gauge. Also, remember those units which alwaysrepresent absolute pressure, and have no need for a letter “A” suffix!


• 25 ”Hg vacuum = ??? PSIA

• 2,800 µ torr = ??? PaA

• -59 ”W.C. = ??? torr

• 4,630 PaA = ??? PSI

• 0.05 atm = ??? ”W.C.

• -3 kPa = ??? atm

• 10 feet W.C. vacuum = ??? ”HgA

• 300 cm Hg = ??? atm

• -2 mm W.C. = ??? bar (absolute)

• 4 atm = ??? ”W.C.A



• Which of these conversions require an additive or subtractive offset, and which of these may be performedusing multiplication and division alone?


file i00158

40

Question 27

Convert between the following units of pressure. Remember that any pressure unit not explicitly specifiedas either absolute (A) or differential (D) is to be considered gauge. Also, remember those units which alwaysrepresent absolute pressure, and have no need for a letter “A” suffix!

• 25 PSIA = ??? atm

• 340 ”W.C. = ??? PSIA

• 0.73 bar (gauge) = ??? ”Hg

• 5.5 atm = ??? torr

• 2,300 cm Hg = ??? ”W.C.A

• 500 m torr = ??? PSIA

• 91.2 cm W.C. = ??? kPa

• 110 kPa = ??? ”W.C.

• 620 mm HgA = ??? torr

• 77 Pa = ??? PSIA

• 1 atm = ??? ”W.C.A

• 270 PSIA = ??? atm



• Which of these conversions require an additive or subtractive offset, and which of these may be performedusing multiplication and division alone?


• Suppose a novice tries to convert 3.5 atmospheres into PSIG, and arrives at a result of 51.45 PSIG.Identify the mistake made here, and also the proper conversion to go from units of atmospheres to PSIG.

file i00157

41

Question 28

An operator reports a problem with the oily water filter instrumentation in this process: PDIR-136indicates a differential pressure of 1.8 PSID, while PG-417 reads 12.5 PSI and PG-421 reads 11.3 PSI. Yourfirst test is to check the indication of PIR-137, and you see that it reads 12.6 PSI:

P-407

SS lined

From unit 3oily water sewerDwg. 72113

oily water sewer

oily water sewerFrom unit 1

Dwg. 72111

From unit 2

Dwg. 72112

MW 30"

From 50#steam headerDwg. 13227

PG

PG

P-408

V-15

P

Slope

N2

LSH

LSL

LC

To incineratorDwg. 47221

PG PG

FO

M M

To oily watertreatmentDwg. 72000

S-401

PG

P-405

ST

ST

ST

ST ST

Steam trace forfreeze protection

2" thick

PG

LT LYWirelessHART

Radar

LIR H

V-15OILY WATER SUMP

MOC: Concrete w/ SS liningCap: 35,000 gal

133

133

133

132

PV132

FI416

415

417

418 419

420

134 134 134

421

P-405OILY WATER VENT EDUCTOR

85 CFM @ -2" H2O

P-407OILY WATER SUMP PUMP #1

200 GPM @ 40’ head 200 GPM @ 40’ head


S-401OILY WATER FILTER

Basket strainer with 100 mesh basketMOC: SS

MOC: SS

MOC: SS

134

LI

ST

Note 1

Notes:

1. Level controller alternates pumps ateach start-up. Turns both pumps onif high level persists longer than 1 minute

PT135

WirelessHART

PIR135

PY135

ST

Set @ +1" WC

PSV98

H

PDT136

136 136PDIRPDI

H

FI133

Note 2

2. Nitrogen gas purge for bubbler, suppliedfrom compressed nitrogen bottle.

DP 45 PSIG

PT137 WirelessHART

PIR H

137

PIC

WirelessHART136PDY

Capacity 450 GPM @ 1.5 PSID

HLL = 5’ 6"

LLL = 1’ 0"

Depth: 8 feet 11 inches

138LT

LI

138

PT139

PIR H

L139

WirelessHART

WirelessHART

WirelessHART

FIR

FIR

FIR

140

141

142

140FT

FT

FT

141

142

Identify the likelihood of each specified fault in this process. Consider each fault one at a time (i.e. nomultiple faults), determining whether or not each fault could independently account for all measurementsand symptoms in this process.

Fault Possible ImpossibleUpstream filter block valve partially shut

Downstream filter block valve partially shutPDT-136 calibration errorPT-137 calibration errorPG-417 calibration errorPG-421 calibration error

Filter drain valve to sump left open

Explain why the idea to check PIR-137 was a good first diagnostic test.



• Identify which port on each differential pressure indicator is the “high” and which is the “low”, explainingyour rationale.

• Identify a typographical error in this P&ID.

file i03511

42

Question 29

A large water filter occasionally plugs with debris, and operations wants to have a gauge indicationof this plugging. Since plugging of the filter will result in greater differential pressure drop across it forany given amount of water flow through it, measuring pressure drop with a differential pressure gauge willprovide a simple indication of filter plugging.

Draw the connecting tubes between the differential pressure gauge and the filter (the two “taps” shownon the pipes are ready to connect to instrument tubing) so that the gauge registers more pressure as thefilter becomes more plugged:

Water filter

Waterin

Waterout

H L

Tap

Tap

Differential pressuregauge

file i00215

43

Question 30

2.036 inches of mercury (”Hg) is an equivalent pressure to 27.68 inches of water (”W.C. or ”H2O). Thisfact allows us to create a “unity fraction” from these two quantities for use in converting pressure units frominches mercury to inches water or visa-versa. Two examples are shown here:

(

310 ”Hg

1

)(

27.68 ”W.C.

2.036 ”Hg

)

= 4215 ”W.C.

(

45 ”W.C.

1

)(

2.036 ”Hg

27.68 ”W.C.

)

= 3.31 ”Hg

But what if we are performing a unit conversion where the initial pressure is given in inches of mercuryor inches of water absolute? Can we properly make a unity fraction with the quantities 2.036 ”HgA and27.68 ”W.C.A as in the following examples?

(

310 ”HgA

1

)(

27.68 ”W.C.A

2.036 ”HgA

)

= 4215 ”W.C.A

(

45 ”W.C.A

1

)(

2.036 ”HgA

27.68 ”W.C.A

)

= 3.31 ”HgA

Explain why or why not.file i02942

Question 31

How much pressure, in inches of water column, is being applied to this inclined water manometer todisplace water 5 inches along the length of the tube, inclined at an angle of 30o from horizontal? Assume anegligible change in liquid level inside the “well” throughout the measurement range of the instrument:

water

Appliedpressure

(vented)

5"

30oWell

file i00167

44

Question 32

A simple way to make a micromanometer (an extremely sensitive manometer) is to connect two large-diameter vertical tubes by a small-diameter, transparent tube with an air bubble in it. The air bubblebecomes the marker for reading pressure along a scale:

bubbleair

Scale

A simple micromanometer

Water

If both of the large vertical tubes are 2.5 inches in diameter, and the transparent, horizontal tube is0.25 inches in diameter, how much differential pressure will be indicated by 1 inch of horizontal bubbledisplacement? Assume the use of water for the manometer liquid.

file i00169

45

Question 33

A manometer may be used to measure differential pressure across a restriction placed within a pipe.Pressure will be dropped as a result of flow through the pipe, making the manometer capable of (indirectly)measuring flow:

Flow

Higherpressure

Lowerpressure

Mercury manometer

Pipe Restriction

In the example shown above, the fluid moving through the pipe is air, and the manometer uses mercuryas the indicating liquid. If we try to measure the flow rate of a liquid such as water using the same technique,though, we will find that the manometer does not register quite the way we might expect:

Higherpressure

Lowerpressure

Mercury manometer

Pipe Restriction

Flow

That is to say, given the exact same amount of differential pressure generated by the restriction, themanometer will register differently than if it was measuring air pressure. Determine whether the manometerwill register falsely high or falsely low, and also why it will do so.

file i00796

46

Question 34

A very useful principle in physics is the Ideal Gas Law, so called because it relates pressure, volume,molecular quantity, and temperature of an ideal gas together in one neat mathematical expression:

PV = nRT

Where,P = Absolute pressure (atmospheres)V = Volume (liters)n = Gas quantity (moles)R = Universal gas constant (0.0821 L · atm / mol · K)T = Absolute temperature (K)

Apply this law to the scenario of a gas-filled cylinder and movable piston:

Gas Cylinder

Piston

In particular, sketch how the gas pressure inside the cylinder relates to changes in cylinder volumecaused by piston movement, assuming no change in gas temperature or leakage of gas molecules from thecylinder:

P

V

file i02923

47

Question 35

How much pressure, in units of “inches of water column,” is being applied to the right-hand tube of thisU-tube water manometer?

Appliedpressure

Water


= 20 "W.C.

Appliedpressure= ???

3.25"

3.25"

Also, convert this pressure into units of Pascals.file i00163

Question 36

How much pressure is being applied to this U-tube water manometer, in units of “inches of watercolumn” and “pounds per square inch”?

(vented)Appliedpressure

Water


1" diameter4" diameter

3"0.1875"

file i00162

48

Question 37

A steam eductor is a device used to create a vacuum, by passing steam through a “venturi” tube. In thisprocess, a steam eductor is used to apply a constant venting suction to an oily water sump (undergroundstorage vessel for collecting liquid):

P-407

SS lined

From unit 3oily water sewerDwg. 72113

oily water sewer

oily water sewerFrom unit 1

Dwg. 72111

From unit 2

Dwg. 72112

MW 30"

From 50#steam headerDwg. 13227

PG

PG

P-408

V-15

P

Slope

N2

LSH

LSL

LC

To incineratorDwg. 47221

PG PG

FO

M M

To oily watertreatmentDwg. 72000

S-401

PG

P-405

ST

ST

ST

ST ST

Steam trace forfreeze protection

2" thick

PG

LT LYWirelessHART

Radar

LIR H

V-15OILY WATER SUMP

MOC: Concrete w/ SS liningCap: 35,000 gal

133

133

133

132

PV132

FI416

415

417

418 419

420

134 134 134

421

P-405OILY WATER VENT EDUCTOR

85 CFM @ -2" H2O


200 GPM @ 40’ head 200 GPM @ 40’ head


S-401OILY WATER FILTER

Basket strainer with 100 mesh basketMOC: SS

MOC: SS

MOC: SS

134

LI

ST

Note 1

Notes:

1. Level controller alternates pumps ateach start-up. Turns both pumps onif high level persists longer than 1 minute

PT135

WirelessHART

PIR135

PY135

ST

Set @ +1" WC

PSV98

H

PDT136

136 136PDIRPDI

H

FI133

Note 2

2. Nitrogen gas purge for bubbler, suppliedfrom compressed nitrogen bottle.

DP 45 PSIG

PT137 WirelessHART

PIR H

137

PIC

WirelessHART136PDY

Capacity 450 GPM @ 1.5 PSID

HLL = 5’ 6"

LLL = 1’ 0"

Depth: 8 feet 11 inches

138LT

LI

138

PT139

PIR H

L139

WirelessHART

WirelessHART

WirelessHART

FIR

FIR

FIR

140

141

142

140FT

FT

FT

141

142

Calculate the amount of force applied to the “manway” cover on the sump when the educator is operatingat its rated capacity, and also the direction of this force.

Will the applied vacuum from the eductor help or hinder the two pumps’ ability to move liquid out ofthe sump and to water treatment? Will the effect be minimal or substantial?

file i03465

Question 38

Question 39

Question 40

Question 41

Read and outline the “Zero and Span Adjustments (Analog Instruments)” section of the “InstrumentCalibration” chapter in your Lessons In Industrial Instrumentation textbook. Note the page numbers whereimportant illustrations, photographs, equations, tables, and other relevant details are found. Prepare tothoughtfully discuss with your instructor and classmates the concepts and examples explored in this reading.

file i03903

49

Question 42

Read and outline the “Typical Calibration Errors” section of the “Instrument Calibration” chapter inyour Lessons In Industrial Instrumentation textbook. Note the page numbers where important illustrations,photographs, equations, tables, and other relevant details are found. Prepare to thoughtfully discuss withyour instructor and classmates the concepts and examples explored in this reading.

file i03908

Question 43

Read and outline the “Damping Adjustments” section of the “Instrument Calibration” chapter in yourLessons In Industrial Instrumentation textbook. Note the page numbers where important illustrations,photographs, equations, tables, and other relevant details are found. Prepare to thoughtfully discuss withyour instructor and classmates the concepts and examples explored in this reading.

file i03904

Question 44

Read and outline the “LRV and URV Settings, Digital Trim (Digital Transmitters)” section of the“Instrument Calibration” chapter in your Lessons In Industrial Instrumentation textbook. Note the pagenumbers where important illustrations, photographs, equations, tables, and other relevant details are found.Prepare to thoughtfully discuss with your instructor and classmates the concepts and examples explored inthis reading.

file i03905

Question 45

Read the “An Analogy for Calibration versus Ranging” section of the “Instrument Calibration”chapter in your Lessons In Industrial Instrumentation textbook. Note the page numbers where importantillustrations, photographs, equations, tables, and other relevant details are found. Prepare to thoughtfullydiscuss with your instructor and classmates the concepts and examples explored in this reading.

file i03907

Question 46

Read and outline the “Calibration Procedures” section of the “Instrument Calibration” chapter in yourLessons In Industrial Instrumentation textbook. Note the page numbers where important illustrations,photographs, equations, tables, and other relevant details are found. Prepare to thoughtfully discuss withyour instructor and classmates the concepts and examples explored in this reading.

file i03906

Question 47

Read and outline the “Instrument Turndown” section of the “Instrument Calibration” chapter in yourLessons In Industrial Instrumentation textbook. Note the page numbers where important illustrations,photographs, equations, tables, and other relevant details are found. Prepare to thoughtfully discuss withyour instructor and classmates the concepts and examples explored in this reading.

file i03909

Question 48

Read and outline the “NIST Traceability” section of the “Instrument Calibration” chapter in yourLessons In Industrial Instrumentation textbook. Note the page numbers where important illustrations,photographs, equations, tables, and other relevant details are found. Prepare to thoughtfully discuss withyour instructor and classmates the concepts and examples explored in this reading.

file i03910

50

Question 49

Shown here is a diagram of a standard pressure gauge, based on the pressure-sensing action of a hollow,C-shaped metal tube called a bourdon tube:

Appliedpressure

Pointer

Pressure gauge

Pinion gearSector gear

Link

Bourdontube

mechanism

(dots shownare pivot points)

Using arrows, trace the motions of all moving components in this mechanism as an increasing pressureis applied to the fitting at the bottom of the bourdon tube.

Also, describe how the measurement span of this pressure gauge could be changed. In other words,what would have to be moved, adjusted, or altered in this mechanism in order to change the proportionalityof applied pressure to pointer movement?


• Questions such as this tend to be challenging for people with limited experience working on mechanicaldevices. Identify some problem-solving strategies for a mechanically innocent student to apply toproblems such as this.

• What sort of device(s) would you suggest using to apply a precisely known pressure to a gauge forcalibration purposes?

• Suppose a pressure gauge is intended for service in a process measuring liquid pressure. Is it okay tocalibrate this gauge on a test bench using compressed air instead of the liquid it will be exposed to inthe field? Why or why not?

file i00173

51

Question 50

An operator claims pressure gauge PG-108 is defective and needs to be replaced. This pressure gaugeregisters 50 PSI, while pressure controller PIC-33 and pressure recorder PR-33 both register the pressureas being equal to setpoint: 43 PSI. Before replacing this pressure gauge, however, you decide to do somediagnostic thinking to see if there might be other causes for the abnormally high reading at PG-108. Thefirst thing you check is the position of control valve PV-33a, and you find its stem position to be at 35%open.

C-5

RO

PG

PG

RO

PG

PG

M

PG

NC

NC

NC

NC

NC

C-5MAIN FRACTIONATION TOWER

PT

PIC

HP cooling waterDwg. 11324

Dwg. 11324

Cooling waterreturn

PY

FT

FT IAS

P

FC

LIC

LT

Overhead productDwg. 28542

Distillate productDwg. 28543

Bottoms productDwg. 28544

LG

LGLT

LSH

LSL

FT

LIC FIC

P

Sidedraw productDwg. 28545

NC

FT

FIC FY

FV

FT

FYFYLead/LagLead/Lag

AT

AIC

FY

Dwg. 10957

FT

P

IAS

IAS

AIC FY


FOUNDATION Fieldbus

FOUNDATION Fieldbus

FOUNDATION Fieldbus

IAS

P

FC

IAS

IAS

V-13

V-13OVERHEAD ACCUMULATOR

P-10 P-11

Dwg. 10957

Fractionator feed

Dwg. 27004from charge heater

E-5

E-6

E-7

E-8

E-9

FO

FC

FO

FC

FO

FO

PSL

PSL

SS

R

IAS

I

HC

RO

PG

PG

RO

PG

M

FO

PSL

PSL

SS

R

I

IAS

HC

PG

RO

PG

PGM

FO

PSL

PSL

SS

R

I

IAS

HC

RO

PG

PG


PG

PG

PG

PG

PG

PG

TT

TT

TT

TT

TT

TT

TIR

TIR

TIR

TIR

TIR

TIR

AITTT TIR

TTTIR

3131 30

3032

33

33

34

34 34

35

35 35

36

36

37

3738

39

40

40a 40b

40c

FFC

41

41

42

42

50 50

5151

5252

53 53

54 54

55 55

56 56

57

58

57

LAL

58

LAH

LLL = 3’-8"

NLL = 5’-4"

HLL = 7’-2"

33PR

33aPY

33b

106

107

60

61

62

63

64

65

59 59

108

PG

PG

109

110

111

112

113

114

115

116

117

118119

120

121

122

123 124

125

127

35

FV34

PV

FV31

FV41

FV37

Dwg. 62314

To LP flareFO

NC

33a

33bPV

3 to 9 PSI

9 to 15 PSI

PG130

PG131

PG132

PG133

PG134

PG135

PG136

PG137

PG138

PG139

P-12 P-13 P-14 P-15

P-15P-10 P-11 P-12 P-13 P-14MAIN OVERHEAD PRODUCT PUMP BACKUP OVERHEAD PRODUCT PUMPMAIN BOTTOMS PRODUCT PUMP BACKUP BOTTOMS PRODUCT PUMPMAIN CHARGE FEED PUMP BACKUP CHARGE FEED PUMP

E-5, E-6, E-7FEED HEAT RECOVERY EXCHANGERS

H

L

PSH

PAH

66

66

H

L

H

L

Note 1Note 1Note 1

NOTES:

1. Backup (steam-driven) pumps automatically started by 2oo2 triplogic, where both pressure switches must detect a low-pressurecondition in order to start the backup pump.

FOUNDATION Fieldbus

FOUNDATION FieldbusFOUNDATION Fieldbus

FOUNDATION Fieldbus

M

FT67

FOUNDATION Fieldbus

FIR

67

FT68 PT

68

68TT

FY

68

Modbus RS-485 FIQ

68

PT

TTFT69

69

69

FY

69

FIR

69

RTD

RTD

Note 2

2. Transit-time ultrasonic flowmeter with pressure and temperaturecompensation for measuring overhead gas flow to flare line.

Dia 10’-3" Height 93’DP 57 PSIG

Set @ 55 PSISet @ 55 PSI

Set @ 52 PSI Set @ 52 PSI

DT 650 oF top, 710 oF bottom

DP 81 PSIGDT 650 oF

E-9BOTTOMS REBOILER

E-8OVERHEAD PRODUCT CONDENSER

2100 GPM @ 460 PSID 1900 GPM @ 460 PSID 2880 GPM @ 70 PSID 2880 GPM @ 70 PSID 2350 GPM @ 55 PSID 2350 GPM @ 55 PSID80 MM BTU/hrShell 500 PSIG @ 650 oF

Tube 165 PSIG @ 400 oFTube 660 PSIG @ 730 oFShell 120 PSIG @ 650 oF

55 MM BTU/hr 70 MM BTU/hrShell 630 PSIG @ 800 oFTube 600 PSIG @ 880 oF

Set @410 PSI

Set @500 PSI

Set @100 PSI

Set @73 PSI

600 PSI steam

1000 PSI steam

PG140

PG141

LT

38a

38bLT38c

LY

38

Median

142 143 144

Radar

select

Magnetostrictive (float)

Identify the likelihood of each specified fault in this process. Consider each fault one at a time (i.e. nomultiple faults), determining whether or not each fault could independently account for all measurementsand symptoms in this process.

Fault Possible ImpossiblePG-108 calibration errorPT-33 calibration error

PIC-33 left in manual modePY-33a calibration errorPY-33b calibration error

Finally, identify the next diagnostic test or measurement you would make on this system. Explain howthe result(s) of this next test or measurement help further identify the location and/or nature of the fault.

52


• Based on the information you have at this point, can you tell whether any suspected calibration erroris due to a mis-adjustment of zero or of span? Explain why or why not.

• Is controller PIC-33 direct-acting or reverse-acting? How can you tell?• Does control valve PV-33a throttle gas or liquid? How can you tell?• Identify a typographical error in this P&ID.

file i03512

Question 51

Answer the following four questions about deadweight testers:

(1) What is it about the nature of a deadweight tester that makes it so accurate and repeatable?To phrase this question in the negative, what would have to change in order to affect the accuracyof a deadweight tester’s output pressure?

(2) Why is it important for a deadweight tester to be level while it is being used to calibrate apressure instrument?

(3) What effect will trapped air have inside a deadweight tester?

(4) Why is it advisable to gently spin the primary piston and weights while the piston is suspendedby oil pressure?

file i00154

53

Question 52

A device called a manometer is a very simple and yet very precise pressure measuring instrument. Itworks on the principle of a differential pressure displacing a vertical liquid column. The distance betweenthe tops of the two liquid columns is proportional to the difference in pressure applied to tops of thetwo vertical tubes. This is where we get pressure units of “inches/centimeters of water column” and“inches/centimeters/millimeters of mercury” – from the operation of a manometer:

Appliedpressure(greater)

Appliedpressure(lesser)

HeadTransparenttube allows

liquid columnsto be seen

Manometer

Explain how this instrument may serve as a standard for pressure measurement, just as a deadweighttester may serve as a standard for pressure generation. To phrase this question in the negative, what wouldhave to change in order to affect the pressure measurement accuracy of a manometer?

file i00160

54

Question 53

A free-floating piston inside a hydraulic cylinder has a 1000 PSI of fluid pressure applied to one side ofthe piston, and 850 PSI of pressure applied to the other side of the piston. The piston itself is 2.75 inches indiameter. How much force will act on the piston, with these pressures applied to it?

850 PSI

1000 PSI

2.75"

piston

Force on piston ???

tubing

tubing

file i00155

55

Question 54

A double-acting hydraulic cylinder has 500 PSI of pressure applied to the side without the rod and 750PSI of pressure applied to the rod-side. Calculate the resultant force generated at the piston and transmittedthrough to the rod, and also determine this force’s direction. The piston is 5 inches in diameter, and therod is 1 inch in diameter.

piston

rod

5"

1"

750 PSI

500 PSI

Force ???



• Would the piston experience a resultant force if both ports were connected together with a length oftubing (made “common” to each other) and then pressurized with the exact same amount of fluidpressure? Why or why not?

file i00156

56

Question 55

A very useful principle in physics is the Ideal Gas Law, so called because it relates pressure, volume,molecular quantity, and temperature of an ideal gas together in one neat mathematical expression:

PV = nRT

Where,P = Absolute pressure (atmospheres)V = Volume (liters)n = Gas quantity (moles)R = Universal gas constant (0.0821 L · atm / mol · K)T = Absolute temperature (K)

Although this “law” is not perfectly accurate for real gases, especially at high pressures and/or near thepoint of liquefaction, it is quite accurate for air near ambient temperature and pressure.

One very practical application of this law is found in a method for generating low air pressures suchas those easily measured by water- or oil-based manometers. Most mechanical air compressors generatepressures far exceeding the range of all but the largest manometers. Though it is possible to purchaseprecision pressure regulators for reducing such large pressures down to a level measurable by a manometer,these devices are expensive. An alternative is to generate the air pressure with a hand pump (such as abicycle tire pump) connected to a relatively large pressure vessel:

Handpump

Pressurevessel

To instrumentunder test

Manometer

Vent

12

3

Without the volume of the pressure vessel connected to the tubing system, the air pressure wouldincrease dramatically for each stroke of the air pump. With the pressure vessel connected, each pump strokecontributes a much smaller amount of additional pressure to the system. Use the Ideal Gas Law equationto explain why this is.

file i00286

57

Question 56

One challenge technicians face when calibrating low-pressure instruments is how to generate very lowair pressures to simulate different low-pressure conditions for the pressure instrument under test. Measuringlow pressures is no problem at all: very simple manometers will do the job quite nicely. Most mechanical aircompressors, however, generate pressures far exceeding the range of most manometers. Though it is possibleto purchase precision pressure regulators for reducing such large pressures down to a level measurable by amanometer, these devices are expensive.

A simple way to “divide” the pressure output of a standard pressure regulator from a few PSI to a fewinches of water is to use a pair of small valves (preferably needle valves allowing for precise adjustment) tothrottle the flow of compressed air and vent the regulator’s output to atmosphere, then tap between thosevalves to obtain a reduced pressure:

Air compressor

Manometer

Receiver

Vent


Pressureregulator

Complete the following schematic diagram showing an electrical model for this pneumatic system, andthen explain how it works:


Low-rangevoltmeter+

−High voltage

source

3-terminalIC regulator

file i00287

58

Question 57

Suppose a pressure gauge uses a diaphragm as its pressure-sensing element, like this:

fulcrum

pivots

Scale

Pressure to bemeasured

pointer

spring

This mechanism will work, but what if we desired to make it more sensitive? That is, we wished todecrease its measurement span so that less pressure would drive the pointer to full-scale. What could wealter in this mechanism to decrease the measurement span?

file i00172

59

Question 58

Some bourdon tube gauges are equipped with a very small spiral spring attached to the pointer shaft:

Pointer

Link

spring

anchorpoint

Now, this spring is much too weak to have any detectable effect on the span of the gauge. In otherwords, it does not measurably resist the bending action of the bourdon tube, as a “range spring” would inanother design of instrument.

Given its weakness, what possible purpose does this spring serve in the gauge mechanism?

file i00175

60

Question 59

An important part of performing instrument calibration is determining the extent of an instrument’serror. Error is usually measured in percent of span. Calculate the percent of span error for each of thefollowing examples, and be sure to note the sign of the error (positive or negative):

• Pressure gauge• LRV = 0 PSI• URV = 100 PSI• Test pressure = 65 PSI• Instrument indication = 67 PSI• Error = % of span

• Weigh scale• LRV = 0 pounds• URV = 40,000 pounds• Test weight = 10,000 pounds• Instrument indication = 9,995 pounds• Error = % of span

• Thermometer• LRV = -40oF• URV = 250oF• Test temperature = 70oF• Instrument indication = 68oF• Error = % of span

• pH analyzer• LRV = 4 pH• URV = 10 pH• Test buffer solution = 7.04 pH• Instrument indication = 7.13 pH• Error = % of span

Also, show the math you used to calculate each of the error percentages.

Challenge: build a computer spreadsheet that calculates error in percent of span, given the LRV, URV,test value, and actual indicated value for each instrument.

file i00089

61

Question 60

A pressure gauge is supposed to accurately indicate applied pressure over its full calibrated range. Inthis example, a gauge with a range of 0 to 500 PSI is subjected to five different pressures along that range,and its response is accurate at all those points:

0 500

250

125 375

0 500

250

125 375

0 500

250

125 375

0 PSI applied 125 PSI applied 250 PSI applied

0 500

250

125 375

0 500

250

125 375

375 PSI applied 500 PSI applied

Describe, by drawing a set of five meter readings such as the set shown above, how a pressure gaugeaccurate at 0% and 100% of applied pressure – but with a nonlinearity problem between the LRV and URVpoints – might respond to the same five applied pressures.

Furthermore, describe how a bourdon tube pressure gauge instrument might be adjusted for linearity.In other words, how may a nonlinear pressure gauge be calibrated to become more linear?


• Explain how keeping both “As-Found” and “As-Left” calibration records on instruments such as thispressure gauge make it possible to track long-term calibration drift.

• Can a non-linearity error be corrected by adjusting the zero and/or span screws on an instrument? Whyor why not?

file i00174

62

Question 61

Pressure transmitter PT-89 on this natural gas separator vessel presently has a calibrated range of 0 to400 PSIG. Operations personnel would like you to re-range this transmitter for 300 to 375 PSIG instead:

V-65

M

To gas coolingDwg. 10921

From natural gas

Dwg. 38422

From natural gas

Dwg. 38422

From natural gas

Dwg. 38422

P-8

FT

TERTD

PDT

LSHH LGLT

LIC

FC

H

L

Vent stacks 20’ above grade

PT

TERTD

1:1

I/P

P

Anti-surge

VXE VYEVXE VYE

VZE

VXE VYE

Vibration monitor

TIR PIR

Rod out

IAS

I

To motor controlsDwg. 52331

Bently-Nevada 3300 series

(See dwg. 58209 for wiring details)

V-65COMPRESSOR INLET SEPARATOR

DP 450 PSIGDT 100 deg F

Size 3’ 5" ID x 12’ 0" length

PSV PSV PSV

Set @405 PSIG 410 PSIG408 PSIG

Set @ Set @

P-8COMPRESSOR

50 MSCFH @ 315 deg F dischand 175 PSID boost pressure

OWS

TERTD

TSH

TT

Set @325 deg F

TT

ETET

vent

NDE

DE

ESD

HS

LPDT

ETET

Slope

Slope

PDIR H

FIR

FY

PT

FSL

I

PDSH

HS

AND

RTD

TE

RTD

TE

M

JT

JIRJAHH

H

L

IAS

IAS

M

Set @

Set @30 MSCFH

12"x6"

12"x6"

12"x6"

12" 12"4" 4" 4" 1"

1" 1"

2"

2"

2"

2"

2"

2"

2"

2"12" 8"

12"x8"

12"x8"

220

220220

221

222 223224

225 226 227 228

229

230

75

75

75

75

93

93

93

91

88

88

88 89

89

92

LV

92

92

93231

232 232

232

11 12 13

SV92

XAXC

XY

XY

74

73

76 76

76a

76b

77

0.9 PSID

1"x1/2" 1"x1/2"

NLL = 1’ 4"

LLL = 0’ 7"

HLL = 1’ 11"

HHLL = 2’ 6"(ESD)

LIR92

H

L

PG131

PG

1/2"

132

PG133

PG134

PG135

source A-3

source A-2

source A-1

72TG

Answer the following questions about the task of re-ranging, explaining each of your answers:

• Does the new, requested range constitute a zero shift, a span shift, or both?

• If this is a “smart” (digital) transmitter, does it need to be re-trimmed as well as re-ranged?

• Will the control room indicator PIR-89 need to be re-calibrated, re-ranged, or both?

• Will the local pressure gauge PG-131 need to be re-calibrated as well?

• Will the pressure safety valves PSV-11, PSV-12, and/or PSV-13 need to be set for lower “lift” pressures?

• If the maximum (factory) range of this pressure transmitter is 0 to 750 PSI and the maximum turndownratio for the required accuracy is 20:1, will it be able to meet the new range? If not, what might youhave to do in order to fulfill operations’ request?

63

• Why do you suppose operations would like you to re-range this transmitter? In other words, whatoperational advantage(s) might be gained from doing so? Are there any potential disadvantages ofhaving the new range versus the old?

file i03524

Question 62

Read the product manual for the WIKA (brand) “DELTA-trans” (model 891-34-2189) differentialpressure transmitter, which uses a Hall Effect sensor to generate an electronic output signal from a senseddifferential pressure. Then, answer the following questions:

Explain how an applied pressure is sensed by this DP transmitter, and how the mechanical motion isconverted into an electronic signal. You may need to do some research on “Hall Effect” sensors in order tofully answer this question.

Identify how the zero and span adjustments are implemented – are they mechanical, or electrical?

Identify how the “high” and “low” ports of this DP instrument are labeled. Which way does the sensingelement move when a fluid pressure is applied to the “low” port?

How is this electronic device powered? Is there a battery that needs to be replaced periodically?


• Cut-away diagrams such as the one shown in the manual for this Wika pressure gauge/transmitter canbe confusing for those unaccustomed to interpreting mechanical drawings. To try explain what thedifferent shadings and “hatchings” in this diagram represent, and also how to visualize the mechanismin motion from applied pressure.

file i03911

Question 63

Read and outline the “Piezoresistive (Strain Gauge) Sensors” subsection of the “Electrical PressureElements” section of the “Continuous Pressure Measurement” chapter in your Lessons In IndustrialInstrumentation textbook. Note the page numbers where important illustrations, photographs, equations,tables, and other relevant details are found. Prepare to thoughtfully discuss with your instructor andclassmates the concepts and examples explored in this reading.

file i03912

Question 64

Read and outline the “Differential Capacitance Sensors” subsection of the “Electrical Pressure Elements”section of the “Continuous Pressure Measurement” chapter in your Lessons In Industrial Instrumentationtextbook. Note the page numbers where important illustrations, photographs, equations, tables, and otherrelevant details are found. Prepare to thoughtfully discuss with your instructor and classmates the conceptsand examples explored in this reading.

file i03913

64

Question 65

Read and outline the “Resonant Element Sensors” subsection of the “Electrical Pressure Elements”section of the “Continuous Pressure Measurement” chapter in your Lessons In Industrial Instrumentationtextbook. Note the page numbers where important illustrations, photographs, equations, tables, and otherrelevant details are found. Prepare to thoughtfully discuss with your instructor and classmates the conceptsand examples explored in this reading.

file i03914

Question 66

Research specifications for the Rosemount model 3051S Series “coplanar” differential pressuretransmitter (model 3051S C), located in the Product Data Sheet document (00813-0100-4801 Revision GA,April 2006). Then, answer the following questions:

Identify the different “performance classes” for this instrument model. Specifically, identify thepercentage accuracy and the rangedown limits for each.

Identify some of the different codes for pressure measurement ranges. What is the lowest pressuremeasurement range you can order this instrument in? What is the highest pressure measurement range?

Identify some of the maximum working pressures (“overpressure limits”) for different range codes. Whatconsequence(s) might follow exceeding these limits, according to the manual?

Explain why the higher gage pressure ranges are asymmetrical (i.e. why their negative pressure limitsare so much less than their positive pressure limits). All the differential models have symmetrical ranges, sowhy don’t the gage models?

Identify some of the different isolating diaphragm materials available for this instrument. Explain whythe sensing diaphragms don’t come in different material types as well.

Identify the sensor fill fluid options available for this “coplanar” model. Note: this is the fill fluid usedto fill the transmitter’s internal sensor, not to fill remote-seal capillary tubes and diaphragms (that would bethe model 3051S L). Explain why the coplanar models do not come with food-grade fill fluid as an option.


• Suppose you had a model 3051S CD transmitter with range code 1. Determine the lower range limit(LRL), upper range limit (URL), overpressure limit, static pressure limit, and burst pressure limit forthis particular transmitter, explaining how each of these parameters differ from the others in meaning.

file i03915

65

Question 67

A strain gauge is a device used to measure the strain (compression or expansion) of a solid object byproducing a resistance change proportional to the amount of strain. As the gauge is strained, its electricalresistance alters slightly:

Straingauge

(glued to specimen)

Metal specimenApplied force Applied force

Change in R

Explain why the electrical resistance of a strain gauge changes as it stretches and shrinks, and alsocorrelate the direction of resistance change (more or less) with the direction of applied force.

The following strain gauge is shown connected in a “quarter-bridge” circuit (meaning only one-quarterof the bridge actively senses strain, while the other three-quarters of the bridge are fixed in resistance):

Metalspecimen

Straingauge

(glued to specimen)

VA B

Explain what would happen to the voltage measured across this bridge circuit (VAB) if the strain gaugewere to be compressed, assuming that the bridge begins in a balanced condition with no strain on the gauge.


• A good problem-solving technique to apply when analyzing directions of change in a Wheatstone bridgecircuit is to consider limiting cases. Instead of asking ourselves what would happen in the circuit if thestrain gauge resistance changed slightly, we ask ourselves what would happen if the resistance changeddramatically (i.e. full open or full short). Explain how we could apply this problem-solving techniqueto this circuit.

• Strain gauges are widely used in the automotive and aerospace industries to study the strain ofmechanical assemblies. Explain how a strain gauge might be used to measure the strain of somethinglike a truck axle.

file i00181

66

Question 68

The following bridge circuit uses two strain gauges (one to measure strain, the other to compensatefor temperature changes), the amount of strain indicated by the voltmeter in the center of the bridge.Unfortunately, though, it has a problem. Instead of registering a very small voltage as it normally does, thevoltmeter is “pegged” (driven beyond its normal full-range measurement) by a large voltage difference, withpoint B positive and point A negative as shown here:

Straingauge

VA B

"Dummy"gauge

R1 R2

Abnormally large voltage

Something is wrong in the bridge circuit, because this voltage is present even when there is no physicalstress on the specimen. Identify which of the following faults could cause the excessive voltage to appearacross the voltmeter, and which could not. Consider only one of these faults at a time (no multiple,simultaneous faults):

Fault Possible ImpossibleR1 failed openR2 failed open

Strain gauge failed openDummy gauge failed open

R1 failed shortedR2 failed shorted

Strain gauge failed shortedDummy gauge failed shorted

Voltage source dead


• Identify which fundamental principles of electric circuits apply to each step of your analysis of thiscircuit. In other words, be prepared to explain the reason(s) “why” for every step of your analysis,rather than merely describing those steps.

file i00188

67

Question 69

Convert between the following units of pressure:

• 22 PSI = ??? PSIA

• 13 kPa = ??? ”W.C.

• 81 kPa = ??? PSI

• 5 atm = ??? PSIA

• 200 ”Hg = ??? ”W.C.

• 17 feet W.C. = ??? ”Hg


• 900 Torr = ??? ”W.C.A

• 300 mm Hg = ??? PSI

• 250 ”W.C. = ??? bar (gauge)

• 70 ”W.C. = ??? ”Hg

• 300 PSIG = ??? atm




file i00226

Question 70

Complete the following table of equivalent pressures:

Atm PSIG inches W.C. (G) PSIA3.5

818834

07.12

3682

100

file i02939

68

Question 71

The following differential pressure sensor uses a matched pair of strain gauges. As the differentialpressure increases, one strain gauge becomes compressed while the other becomes stretched. A voltmeterregisters the bridge circuit’s imbalance and displays it as a pressure measurement:

Diaphragm

Straingauge

Straingauge

#1

#2

Port "A"

Port "B"

Straingauge#1

Straingauge#2

R1 R2

+− V

Voltmeter

Vsource

Pressure sensor illustration Schematic diagram

Determine the following:

• Identify which port is the “high” pressure port• Identify what the voltmeter will register if fixed resistor R1 fails open• Identify a component fault that would drive the voltmeter full upscale (“peg” positive)• Identify another component fault that would drive the voltmeter full upscale (“peg” positive)

file i02944

69

Question 72

A simple form of electronic pressure transmitter could be made with a bourdon tube and a LinearVariable Differential Transformer, or LVDT:

Appliedpressure

Bourdontube

Outputterminals

Movablecore

Explain how this instrument works, what type of electrical output signal it generates (e.g. current,voltage, resistance, etc.), and what polarity (if any) that output signal has.

file i00183

70

Question 73

A simple form of electronic pressure transmitter could be made with a bourdon tube and a LinearVariable Differential Transformer, or LVDT:

Appliedpressure

Bourdontube

Outputterminals

Movablecore


file i00183

71

Question 74

A simple form of electronic pressure transmitter could be made with a bourdon tube and a differentialcapacitor:

Appliedpressure

Bourdontube

Movabledielectric Output

terminals


file i00184

Question 75

An ingenious circuit used to convert the output of a differential capacitance sensor into a DC voltagesignal is the diode twin-t circuit shown here:

C C’

Vout

R

R

Rload

D

D

The AC “excitation” voltage source is typically of high frequency, at least 1 MHz. The diodes arefast-switching units, ideally Schottky diodes. Resistors R must be equal in value, but Rload is usually muchgreater than R. Together, the two matched resistors (R) form an averaging network for the two capacitancesC and C ′ as they alternately discharge through Rload.

Identify which capacitance (C or C ′) must increase in value to generate a positive DC output voltage,and why this is so.

file i00186

72

Question 76

As any musician who plays a stringed instrument knows, the resonant frequency of a string changeswith the amount of tension applied to that string. A tensed string is nothing more than a spring, and allsprings have a natural frequency related to their spring constant (k) and mass (m):

f =1

2π

√

k

m

Explain how the formula for the resonant frequency of a spring/mass system (shown above) is verysimilar to the resonant frequency of an LC electrical circuit, and use the spring/mass formula to explain whya stringed instrument changes pitch when string tension changes.

This principle of mechanical resonance may be applied to the measurement of tension, which in turnmay be applied to the measurement of fluid pressure. Some years ago, the Foxboro corporation introduceda pressure transmitter using a “resonant wire” as the sensing element, and more recently the Yokogawacorporation introduced its “DPharp” series of pressure transmitters using micro-miniature silicon resonatorsto sense pressure. Research either one or both of these pressure transmitter technologies and explain howthe principle works.

file i00187

Question 77

The Hall Effect describes the voltage generated across the width of a conductive strip (VHall) with acertain thickness (x), given a perpendicular magnetic field (B) and electric current (I):

VHall = KIB

x

I

B

B

I

x

VHall

Manipulate the Hall Effect equation to solve for magnetic flux density B in terms of the other variables.Be sure to show all your work!

B =file i03295

73

Question 78

A Pirani gauge is a special pressure instrument designed to measure very low pressures (i.e. hardvacuums). It uses two electrically heated filaments, one of which is dealed in a vacuum “reference” chamber,while the other is exposed to the process gas pressure under test. Gas molecules contacting the measurementfilament causes it to cool and decrease resistance:

Referencefilament

Measurementfilament

R1

R2 R3Voltmeter

(vacuum)

Low pressureunder test

+−

Voltagesource

A

B

C D

Measurement filament cools and decreases resistance whenit contacts air molecules (i.e. when test pressure increases)

This Pirani gauge, however, has a problem. It registers a high pressure all the time, regardless of thestrength of the vacuum connected to the measurement cell. A digital multimeter connected between testpoints D and ground registers 0 volts.

Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. nomultiple faults), determining whether or not each fault could independently account for all measurementsand symptoms in this circuit.

Fault Possible ImpossibleR1 failed open

R1 failed shortedR2 failed open

R2 failed shortedR3 failed open

R3 failed shortedReference filament burned out

Measurement filament burned out

file i00300

74

Question 79

Shown here is a very simple pressure transmitter, a device that measures a fluid pressure and convertsthat measurement into an electrical signal:

Appliedpressure

Box

Thin, flexiblemetal diaphragm

+−10 V

Vout

Pressure transmitter

Powerterminals

Outputterminals

5 kΩPotentiometer

Suppose the potentiometer wiper will be at its full-down position with no pressure applied to thediaphragm, and will be at its full-up position with 15 PSI (15 pounds per square inch) of pressure applied tothe diaphragm. Based on this information, and what you see in the schematic diagram, answer the followingquestions:

• Lower Range Value (LRV) of input, in units of PSI:

• Upper Range Value (URV) of input, in units of PSI:

• Input span, in units of PSI:

• Lower Range Value (LRV) of output, in units of volts:

• Upper Range Value (URV) of output, in units of volts:

• Output span, in units of volts:

Now, suppose we make a modification to the electrical circuit portion of the pressure transmitter.Assume the diaphragm still responds to pressure and moves the potentiometer wiper the same way it didbefore. Answer the same questions again:

75

Appliedpressure

Box

Thin, flexiblemetal diaphragm

+−10 V

Vout

Pressure transmitter

Powerterminals

Outputterminals

5 kΩPotentiometer

1.25 kΩ

6.25 kΩ

• Lower Range Value (LRV) of input, in units of PSI:• Upper Range Value (URV) of input, in units of PSI:• Input span, in units of PSI:

• Lower Range Value (LRV) of output, in units of volts:• Upper Range Value (URV) of output, in units of volts:• Output span, in units of volts:

The latter design outputs what is commonly called a live-zero signal, whereas the first transmitteroutputs a dead-zero signal. Live-zero signals are much preferred in industrial instrumentation, because theymore readily betray wiring failures than dead-zero signals.

Explain how you answered all the questions, and also show currents and voltage drops in both circuits(complete with arrows showing directions of current). Then, elaborate on why you think live-zero signalsare preferable to dead-zero signals.

file i00083

Question 80

76

Question 81

Complete the following table of equivalent pressures. Show enough of your work that it is clear how youperformed each type of conversion (e.g. from PSIG to PSIA, from Torr to PSIA, etc.):

PSIG PSIA Torr inches W.C. (G)15

2.1900

1005

-3010

85

file i00020

77

Question 82

Suppose a differential pressure transmitter is used to measure the pressure dropped across a baghouse,an assembly using multiple fabric “socks” to filter particulate material from a gas stream, like a large-scalevacuum cleaner. Gas passes through the socks, filtering out the particulate matter. The DP transmitter’spressure measurement serves to indicate how clogged the socks are:

Dirty gasinlet

Clean gasoutlet

Fabric "socks"

Dust falls downRotary feeder

Dust extraction

H L

Fan

DP transmitter

(from process)

When the transmitter signal reaches a certain value (indicating clogged filter socks), a control systemtriggers either a mechanical shaker or a blast of gas from jets located near each sock shakes the dust fromthe outside area of each sock, the dust falling down into the narrow area below where it is extracted overtime from the baghouse.

Suppose an instrument technician leaves the three valves in the positions shown (hollow = open ; solid= closed). What effect will this have on the socks over time as they perform their filtering job, assuming thecontrol system continues to operate as designed?

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78

Question 83

Determine what pressure conditions must be met at each of the four pressure switches in order for thelamp to energize:

PS1 PS2 PS3

L1 L2120 VAC power source

PS4

Lamp

Trip settings for each pressure switch:

• PS1 = 50 PSI• PS2 = 31 PSI• PS3 = 77 PSI• PS4 = 8 PSI

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79

Question 84

Sketch the necessary connecting tubes and wires to calibrate a DP transmitter to a low pressure range(somewhere in the range of a few inches of water), using a hand (bicycle-style) air pump as the pressuresource and a U-tube manometer as a pressure standard. As pressure increases, the transmitter’s outputsignal should increase as well:

Handpump

Manometer

H L

+−

24 VDC

COMA

V

V A

AOFFTank

Transmitter under test

source

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80

Question 85

An ingenious circuit used to generate an electrical voltage signal from a differential capacitance sensoris the Twin-T diode circuit, shown here connected to a Rosemount-style differential capacitance pressuresensor:

Vout

R

R

Rload

D

D

Sensingdiaphragm

Isolatingdiaphragmdiaphragm

Isolating

Siliconefill fluid

Pressure Pressure

Solid metal

One capacitor is charged positive with respect to ground, while the other is charged negative withrespect to ground, as the AC voltage source alternates positive and negative. While one capacitor of thepressure sensor is charging, the other is discharging through Rload, producing an output voltage (Vout).

If both capacitances are equal, the output voltage will alternate equally between positive and negativevalues, having a DC average value of zero. If one capacitance is larger than the other, it will store additionalcharge on its plates, causing it to sway the output voltage of the Twin-T circuit in the direction of itspolarity. Thus, Vout becomes more positive as pressure increases on one side of the sensor, and morenegative as pressure increases on the other side of the sensor.

Based on this explanation of the Twin-T circuit’s operation, determine which side of the pictureddifferential capacitance sensor is the “High” pressure side, and which is the “Low” pressure side. Be sure toexplain your reasoning!

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81

Question 86

Small relays often come packaged in clear, rectangular, plastic cases. These so-called “ice cube” relayshave either eight or eleven pins protruding from the bottom, allowing them to be plugged into a specialsocket for connection with wires in a circuit. Note the labels near terminals on the relay socket, showing thelocations of the coil terminals and contact terminals:

Relay

(top views)

socketRelay

coil

coil

Com

#1

Com

#2

N.O

. #1

N.C

. #1

N.C

. #2

N.O

. #2

Draw the necessary connecting wires between terminals in this circuit, so that actuating the normally-open pushbutton switch sends power from the battery to the coil to energize the relay:

Relay(plugged into socket)

+-

Battery

N.O.switch

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82

Question 87

Solve for values of x and y that will satisfy both of the following equations at the same time:

3x − y = 17

x + 2y = 1

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83

Question 88

Complete the table of values for this circuit. Be sure to show all your work!

V

I

R

P

R2

R3

R1 R2 R3 Total

12 volts

R1

220 Ω

130 Ω

470 Ω

220 Ω 130 Ω 470 Ω

As you solve this problem, be sure to store all intermediate calculations (i.e. answers given to you byyour calculator which you will use later in the problem) in your calculator’s memory locations, so as to avoidre-entering those values by hand. Re-entering calculated values unnecessarily introduces rounding errorsinto your work, as well as invites keystroke errors. Avoiding the unnecessary introduction of error is a veryimportant concept in Instrumentation!

If your final answers are rounded as a result of not doing this, you will only receive half-credit for yourwork. This is a general policy for all your mathematical work in this program, not just this particularproblem!

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84

Question 89

Suppose you are going to install a Rosemount model 1151 “Alphaline” (analog) differential pressuretransmitter in a process, calibrated to a range of 0 to 100 inches W.C. The transmitter’s model numbershows the following specifications:

• Model = 1151DP• Pressure range code = 4• Output code = E• Material code = 22

Answer the following questions regarding this transmitter as it applies to the application you intend toinstall it in:

• Does this transmitter have sufficient turndown (“rangeability”) for the application? Show yourcalculation to prove whether it does or not.

• Calculate the expected accuracy for this transmitter once installed, expressed in ± inches of watercolumn.

• Calculate the six-month calibration stability of this transmitter after installation, expressed in ± inchesof water column.

• Calculate the amount of total measurement error this transmitter may exhibit given an ambienttemperature shift of 65 degrees Fahrenheit, expressed in ± inches of water column.

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85

Question 90

Suppose a voltmeter registers 0 volts between test points F and E in this series-parallel circuit:

+ −

R1

R2

R3

12 volts

1 kΩ

1 kΩ

A

B

C

D

E

F

(0.25 ampscurrent-limited)

1 kΩ

Identify the likelihood of each specified fault for this circuit. Consider each fault one at a time (i.e. nomultiple faults), determining whether or not each fault could independently account for all measurementsand symptoms in this circuit.

Fault Possible ImpossibleR1 failed openR2 failed openR3 failed open

R1 failed shortedR2 failed shortedR3 failed shorted

Voltage source dead

Finally, identify the next diagnostic test or measurement you would make on this system. Explain howthe result(s) of this next test or measurement help further identify the location and/or nature of the fault.

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86

Question 91

Lab Exercise – introduction

Your task is to build, document, and troubleshoot a pressure measurement system consisting of anelectronic ∆P or gauge pressure transmitter connected to an electronic indicator, recorder, or indicatingcontroller. Instrument air pressure, either regulated or unregulated, is the suggested process variable tomeasure. Other process variables are open for consideration, though. Alternatives to the standard pressure-measurement lab are authorized by instructor permission only.

The following table of objectives show what you and your team must complete within the scheduledtime for this lab exercise. Note how some of these objectives are individual, while others are for the team asa whole:

Objective completion table:

Performance objective Grading 1 2 3 4 TeamPrototype sketch (before building the system!) mastery – – – –

Final loop diagram and system inspection mastery – – – –Digital trim (sensor and output) mastery – – – –

Loop ranging (± 1% of span accuracy) mastery – – – –Deadweight tester usage mastery – – – –

Transmitter valve manifold usage mastery – – – –Troubleshooting (5 minute limit) mastery – – – –Lab question: Selection/testing proportional – – – –Lab question: Commissioning proportional – – – –Lab question: Mental math proportional – – – –Lab question: Diagnostics proportional – – – –

Decommission and lab clean-up mastery – – – –

The only “proportional” scoring in this activity are the lab questions, which are answered by eachstudent individually in a private session between the instructor and the team. A listing of potential labquestions are shown at the end of this worksheet question. The lab questions are intended to guide yourlabwork as much as they are intended to measure your comprehension, and as such the instructor may askthese questions of your team day by day, rather than all at once (on a single day).

It is essential that your team plans ahead what to accomplish each day. A short (10minute) team meeting at the beginning of each lab session is a good way to do this, reviewingwhat’s already been done, what’s left to do, and what assessments you should be ready for.There is a lot of work involved with building, documenting, and troubleshooting these workinginstrument systems!

As you and your team work on this system, you will invariably encounter problems. You should alwaysattempt to solve these problems as a team before requesting instructor assistance. If you still requireinstructor assistance, write your team’s color on the lab whiteboard with a brief description of what youneed help on. The instructor will meet with each team in order they appear on the whiteboard to addressthese problems.

CALIBRATED

By: Date:

Range:

CALIBRATED

By: Date:

Range:

CALIBRATED

By: Date:

Range:

CALIBRATED

By: Date:

Range:

Cut out tag(s) with scissors, then affix to instrument(s) using transparent tape to show calibration:

87

Lab Exercise – selecting components and planning the system

One of the most common problems students encounter when building any working system, whether it bea circuit on a solderless breadboard or an instrument loop spanning an entire room, is properly connecting andconfiguring all components. An unfortunate tendency among most students is to simply start connectingparts together, essentially designing the system as they go. This usually leads to improperly-connectedcomponents and non-functioning systems, sometimes with the result of destroying components due to thoseimproper connections!

An alternative approach is to plan ahead by designing the system before constructing it. This is easilydone by sketching a diagram showing how all the components should interconnect, then analyzing thatdiagram and making changes before connecting anything together. When done as a team, this step ensureseveryone is aware of how the system should work, and how it should go together. The resulting “prototype”diagram need not be complex in detail, but it should be detailed enough for anyone to see which componentterminals (and ports) connect to terminals and ports of other devices in the system. For example, yourteam’s prototype sketch should be clear enough to determine all DC electrical components will have thecorrect polarities. If your proposed system contains a significant amount of plumbing (pipes and tubes),your prototype sketch should show all those connections as well.

Your first step should be selecting proper field instruments from the instrument storage area to use inbuilding your system. In this particular lab, you are looking for a pressure transmitter with electronic (4-20mA) signal output, and a valve “manifold” to isolate that transmitter from the process pressure. Refer tothe “Valve manifolds” subsection of Lessons In Industrial Instrumentation for more detail on what thesemanifolds look like and how they are used. You should choose a transmitter with a pressure range somewherebetween 10 PSI and 200 PSI. Avoid low-range (“draft”) transmitters with ranges of just a few inches of watercolumn, and also high-pressure transmitters ranged for hundreds or thousands of PSI.

The next step should be finding appropriate documentation for your pressure transmitter. Nearly everyinstrument in the lab is documented electronically at the manufacturer’s website, so your best resource isthe Internet (and/or your Instrumentation Reference where a variety of instrument manuals have beendownloaded for you). Use this documentation to identify how to properly wire, power, and calibratethe transmitter. Your instructor will check to see you have located and are familiar with the equipmentmanual(s).

After locating a suitable instrument and its associated documentation, you should qualitatively test itprior to installing it in your system. For a pressure transmitter, this entails applying an air pressure to the“high” pressure port and measuring the transmitter’s milliamp output signal to see if it responds to theapplication of pressure. If the transmitter fails to respond properly, tag it with a label explaining what itdoes (or what it fails to do).

Your team’s prototype sketch is so important that the instructor will demand you provide this planbefore any construction on your team’s working system begins. Any team found constructing their systemwithout a verified plan will be ordered to cease construction and not resume until a prototype plan has beendrafted and approved! Each member on the team should have ready access to this plan (ideally possessingtheir own copy of the plan) throughout the construction process. Prototype design sketching is a skill anda habit you should cultivate in school and take with you in your new career.

Planning a functioning system should take no more than an hour if the team is workingefficiently, and will save you hours of frustration (and possible component destruction!).

88

Lab Exercise – building the system

The Instrumentation lab is set up to facilitate the construction of working instrument “loops,” with overa dozen junction boxes, pre-pulled signal cables, and “racks” set up with 2-inch vertical pipes for mountinginstruments. The only wires you should need to install to build a working system are those connecting thefield instrument to the nearest junction box, and then small “jumper” cables connecting different pre-installedcables together within intermediate junction boxes.

After getting your prototype sketch approved by the instructor, you are cleared to begin building yoursystem. Transmitters attach to 2-inch pipes using special brackets and U-bolts. These brackets and U-boltsare located along with the transmitters in the instrument storage area. You will also need to install liquid-tight flexible conduit between the transmitter and the nearest junction box to route signal wires through.Conduit and fittings are located in a drawer in the back of the lab near the instrument storage area. Thisensures your installation will have a professional appearance with no exposed signal wiring.

Select a specific controller to act as a display indicator for the measured pressure. Your instructor maychoose the controller for your team, to ensure you learn more than one type of controller during the courseof a quarter.

Finally, your pressure-measurement system needs to have a loop number, so all instruments may beproperly labeled. This loop number needs to be unique, so that another team does not label their instrumentsand cables the same as yours. One way to make your loop number unique is to use the equivalent resistorcolor-code value for your team’s color in the loop number. For example, if you are the “Red” team, yourloop number could be “2”.

Common mistakes:

• Neglecting to consult the manufacturer’s documentation for field instruments (e.g. how to wire them,how to calibrate them).

• Mounting the field instrument(s) in awkward positions, making it difficult to reach connection terminalsor to remove covers when installed.

• Improper pipe/tube fitting installation (e.g. trying to thread tube fittings into pipe fittings and visa-versa).

• Failing to tug on each and every wire where it terminates to ensure a mechanically sound connection.• Students working on portions of the system in isolation, not sharing with their teammates what they

did and how. It is important that the whole team learns all aspects of their system!

Building a functioning system should take no more than one full lab session (3 hours) ifall components are readily available and the team is working efficiently!

89

Lab Exercise – documenting the system

Each student must sketch their own loop diagram for their team’s system, following proper ISAconventions. Sample loop diagrams are shown in the next question in this worksheet. These loop diagramsmust be comprehensive and detailed, showing every wire connection, every cable, every terminal block, rangepoints, etc. The principle to keep in mind here is to make the loop diagram so complete and unambiguous thatanyone can follow it to see what connects to what, even someone unfamiliar with industrial instrumentation.In industry, loops are often constructed by contract personnel with limited understanding of how the systemis supposed to function. The loop diagrams they follow must be so complete that they will be able to connecteverything properly without necessarily understanding how it is supposed to work.

Every instrument and every signal cable in your loop needs to be properly labeled with an ISA-standardtag number. An easy way to do this is to wrap a short piece of masking tape around each cable (and placedon each instrument) then writing on that masking tape with a permanent marker. Although no industrystandard exists for labeling signal cables, a good recommendation is to label each two-wire cable with thetag number of the field instrument it goes to. Thus, every length of two-wire cable in a pressure transmittercircuit should be labeled “PT-x” (where “x” is the loop number), every flow control valve should be labeled“FV-x”, etc. Remember that the entire loop is defined by the process variable it measures: if the PV istemperature then the transmitter with be a TT, the control valve will be a TV, the controller with be a TC,etc.

When your entire team is finished drafting your individual loop diagrams, call the instructor to do aninspection of the loop. Here, the instructor will have students take turns going through the entire loop,with the other students checking their diagrams for errors and omissions along the way. During this timethe instructor will also inspect the quality of the installation, identifying problems such as frayed wires,improperly crimped terminals, poor cable routing, missing labels, lack of wire duct covers, etc. The teammust correct all identified errors in order to receive credit for their system.

After successfully passing the inspection, each team member needs to place their loop diagram in thediagram holder located in the middle of the lab behind the main control panel. When it comes time totroubleshoot another team’s system, this is where you will go to find a loop diagram for that system!

Common mistakes:

• Forgetting to label all signal wires (see example loop diagrams).• Forgetting to label all field instruments with their own tag names (e.g. PT-83).• Forgetting to note all wire colors.• Forgetting to put your name on the loop diagram!• Basing your diagram off of a team-mate’s diagram, rather than closely inspecting the system for yourself.• Not placing loop sheet instruments in the correct orientation (field instruments on the left, control room

instruments on the right).

Creating and inspecting accurate loop diagrams should take no more than one full labsession (3 hours) if the team is working efficiently!

90

Lab Exercise – instrument calibration

Each team must calibrate the transmitter (“trim” both the sensor and the output) to ensure itinterprets pressure accurately and outputs an accurate current. Then, each team member must configurethe transmitter for a unique range (set the LRV and URV parameters) and scale the indicator (or indicatingcontroller) to register in the proper engineering units (e.g. a pressure transmitter ranged for 30 to 70 PSIshould actually register 30 to 70 PSI back at the control room display). The accuracy of this ranging willbe checked by the instructor by applying random air pressures to the transmitter while each student verifiesthe indicator display.

As in all cases where an instrument must be calibrated, you will need to check the instrument’s responseagainst one or more standards. In this case, the ideal standard to use for setting the input pressure to thetransmitter is a precision test gauge (either mechanical or electronic), and the ideal standard to use formeasuring the transmitter’s electronic output signal is a multimeter configured to measure DC milliamps:

Compressedair supply

Pressure regulator

In Out

Precision

(Alternative: use a hand air pump

to generate low pressures rather

than a precision regulator)

(Input standard)

(Output standard)

H L

COMA

V

V A

AOFF

Multimeter

+−

DC powersupply

Loop resistance(necessary for HART communications)

test gauge

Typical calibration setup for an electronic pressure transmitter

The difference between “calibrating” a transmitter and “ranging” a transmitter is confusing to manystudents. With legacy-style analog transmitters, calibrating and ranging are one and the same. With moderndigital instruments, calibration and ranging are separate tasks. To calibrate a digital instrument meansto subject it to a known (standard) stimulus and adjust the “trim” settings to ensure the instrument’smicroprocessor accurately recognizes that stimulus condition. To “range” a digital instrument means todefine the values of measurement for its 0% and 100% scale points. For more information on this distinction,refer to the “Instrument Calibration” chapter of Lessons In Industrial Instrumentation.

91

Document the accuracy of your transmitter’s sensor trim before and after adjustment in this table, atfive different points throughout its sensing range. The “Applied” pressure is the amount of air pressure youapply to the transmitter’s pressure port using an air pressure regulator (as sensed by a calibration-qualitygauge), and the “Indicated” pressure is what the HART communicator registers for the process variable:

Applied pressure Indicated pressure (As-Found) Indicated pressure (As-left)

When finished calibrating your team’s transmitter, be sure to place a calibration tag on it showing therange and the date it was calibrated. The first page of this lab exercise has cut-out calibration tags you maytape to the transmitter for this purpose.

Each student, however, must individually re-range the transmitter and the receiving instrument(indicator, controller, and/or recorder). Re-ranging a digital instrument is a brief procedure using either aHART communicator or a computer-based tool such as Emerson AMS (if the instrument is connected to ahost system with that software). Each student’s ranging is confirmed by the instructor by applying randompressures to the transmitter and verifying that the indicating controller reads the same (to within ± 1%of span). This is also a good opportunity for students to demonstrate the use of the transmitter’s valvemanifold, showing how to “block in” the transmitter so it does not “see” process pressure.

Common mistakes:

• Failing to closely inspect pressure regulators before connecting them to an air source (e.g. connectingthe air supply to the “out” port)

• Improper pipe/tube fitting installation (e.g. trying to thread tube fittings into pipe fittings and visa-versa).

• Choosing a calibration (“trim”) range that is substantially less than the final range of measurementwhen installed. As a general rule, you should trim the sensor of the transmitter to cover the broadestrange of measurement possible with your calibration equipment.

• Choosing a poor-accuracy calibration standard (e.g. trying to calibrate your $1500 precision Rosemountpressure transmitter to ± 0.1 PSI using a $30 pressure gauge that only reads to the nearest 5 PSI!).

• Neglecting to place a calibration tag on the transmitter after “trimming” it.

Trimming and individually ranging your transmitter should take no more than one full labsession (3 hours) if the team is working efficiently!

92

Lab Exercise – deadweight tester usage

Deadweight testers are used to generate known amounts of fluid pressure, to be used as standardsfor calibrating pressure-measuring instruments. Part of this lab exercise is for each student to properlydemonstrate the use of a deadweight tester to check the calibration of a pressure gauge. Several deadweighttesters are located in the lab, using oil as the working fluid.

Information on how to use a deadweight tester may be found in the Lessons In Industrial Instrumentationtextbook, as well as in manufacturer’s literature for the deadweight testers themselves. You are expected toread this documentation before using a deadweight tester.

When you are ready to demonstrate, the instructor will observe you safely applying pressure to thegauge under test, showing and explaining how the deadweight tester functions. You will be expected toanswer some basic questions about how and why the deadweight tester works.

Common mistakes:

• Not understanding the operation of the device prior to trying to demonstrate it!• Failing to bleed air out of the lines when setting up the tester.• Not recognizing when the piston is “bottomed” or “topped” out.• Not spinning the weights (gently!) to eliminate static friction on the piston.• Removing weights from the piston while pressure still remains in the system.

93

Lab Exercise – troubleshooting

The most challenging aspect of this lab exercise is troubleshooting, where you demonstrate your abilityto logically isolate a problem in the system. All troubleshooting is done on an individual basis (no teamcredit!), and must be done on a system you did not help build, so that you must rely on loop diagrams tofind your way around the system instead of from your own memory of building it.

Each student is given 5 minutes to identify both the general location and nature of the fault, logicallyjustifying all diagnostic steps taken. All troubleshooting activities will take place under direct instructorsupervision to ensure students are working independently and efficiently.

Failure to correctly identify both the general location and nature of the fault within the allotted time,and/or failing to demonstrate rational diagnostic procedure to the supervising instructor will disqualify theeffort, in which case the student must re-try with a different fault. Multiple re-tries are permitted with noreduction in grade.

A standard multimeter is the only test equipment allowed during the time limit. No diagnostic circuitbreaks are allowed except by instructor permission, and then only after correctly explaining what troublethis could cause in a real system.

The instructor will review each troubleshooting effort after completion, highlighting good and bad pointsfor the purpose of learning. Troubleshooting is a skill born of practice and failure, so do not be disappointedin yourself if you must make multiple attempts to pass! One of the important life-lessons embedded in thisactivity is how to deal with failure, because it will eventually happen to you on the job! There is no dishonorin failing to properly diagnose a fault after doing your level best. The only dishonor is in taking shortcutsor in giving up.

Common mistakes:

• Neglecting to take measurements with your multimeter.• Neglecting to check other measurements in the system (e.g. pressure gauge readings).• Incorrectly interpreting the loop diagram (e.g. thinking you’re at the wrong place in the system when

taking measurements).• Incorrect multimeter usage (e.g. AC rather than DC, wrong range, wrong test lead placement). This is

especially true when a student comes to lab unprepared and must borrow someone else’s meter that isdifferent from theirs!

Remember that the purpose of the troubleshooting exercise is to foster and assess yourability to intelligently diagnose a complex system. Finding the fault by luck, or by trial-and-error inspection, is not a successful demonstration of skill. The only thing that counts ascompetence is your demonstrated ability to logically analyze and isolate the problem, correctlyexplaining all your steps!

Troubleshooting takes a lot of lab time, usually at least two 3-hour lab sessions for everyonein a full class to successfully pass. Be sure your team budgets for this amount of time as youplan your work, and also be sure to take advantage of your freedom to observe others as theytroubleshoot, to better learn this art.

94

Lab questions – (reviewed between instructor and student team in a private session)

• Selection and Initial Testing• Explain how a tube fitting seals against fluid leaks, especially how this differs from pipe fittings• Explain how a tapered-thread pipe fitting seals against fluid leaks, especially how this differs from tube

fittings• Identify the “high” and “low” pressure ports on your pressure transmitter, and explain their significance• Explain how to use a ∆P gauge or transmitter to measure positive pressure versus measuring a vacuum• Identify and explain maximum working pressure (MWP, also known as “maximum static pressure”) of

your pressure transmitter, especially how it differs from the maximum calibrated range (LSL and USL)of the transmitter

• Commissioning and Documentation• Demonstrate how to isolate potentially hazardous energy in your system (lock-out, tag-out) and also

how to safely verify the energy has been isolated prior to commencing work on the system• Identify and explain range turndown on your transmitter (also called rangedown)• Identify and explain the purpose of damping on your transmitter• Explain the operating principle of the pressure transmitter (as detailed as possible)• Identify and explain zero and span adjustments on your transmitter• Identify the purpose of having a fill fluid inside the pressure transmitter’s sensor• Explain the applicability of different remote-seal fill fluids to particular process types (pure oxygen,

food, pharmaceutical, etc.). In other words, identify the properties of certain fill fluids necessary forcompatibility with pure oxygen service, or with food-processing service.

• Mental math (no calculator allowed!)• Calculate the correct loop current value (mA) given a pressure transmitter calibration range and an

applied pressure• Calculate the pressure applied to a transmitter given a calibration range and the measured loop current

value• Calculate the percentage of span error for a transmitter given a calibration range and an As-Found

calibration table• Calculate the allowable pressure error for a transmitter given an allowable percentage of span error and

a calibration range• Convert between different pressure units, without relying on the use of a reference for conversion factors

(i.e. you must commit the major conversion factors to memory)

• Diagnostics• “Virtual Troubleshooting” – referencing their system’s diagram(s), students propose diagnostic tests

(e.g. ask the instructor what a meter would measure when connected between specified points; ask theinstructor how the system responds if test points are jumpered) while the instructor replies accordingto how the system would behave if it were faulted. Students try to determine the nature and locationof the fault based on the results of their own diagnostic tests.

• Explain what will happen (and why) if the 250 ohm resistor fails open in the transmitter circuit• Explain what will happen (and why) if the 250 ohm resistor fails shorted in the transmitter circuit• Explain what will happen (and why) if the transmitter cable fails open• Explain what will happen (and why) if the transmitter cable fails shorted• Explain what will happen (and why) if loop power supply voltage is too low• Explain proper three-valve manifold operating procedures (for both placing in and taking out of service)• Explain how to distinguish an “open” cable fault from a “shorted” cable fault using only a voltmeter

(no current or resistance measurement, but assuming you are able to break the circuit to perform thetest)

95

Lab Exercise – decommissioning and clean-up

The final step of this lab exercise is to decommission your team’s entire system and re-stock certaincomponents back to their proper storage locations, the purpose of which being to prepare the lab for thenext lab exercise. Remove your system documentation (e.g. loop diagram) from the common holding area,either discarding it or keeping it for your own records. Also, remove instrument tag labels (e.g. FT-101)from instruments and from cables. Perform general clean-up of your lab space, disposing of all trash, placingall tools back in their proper storage locations, sweeping up bits of wire off the floor and out of junctionboxes, etc.

Leave the following components in place, mounted on the racks:

• Large control valves and positioners• I/P transducers• Large electric motors• Large variable-frequency drive (VFD) units• Cables inside conduit interconnecting junction boxes together• Pipe and tube fittings (do not unscrew pipe threads)• Supply air pressure regulators

Return the following components to their proper storage locations:

• Sensing elements (e.g. thermocouples, pH probes, etc.)• Process transmitters• “Jumper” cables used to connect terminal blocks within a single junction box• Plastic tubing and tube fittings (disconnect compression-style tube fittings)• Power cables and extension cords• Adjustment (loading station) air pressure regulators

Finally, you shall return any control system components to their original (factory default) configurations.This includes controller PID settings, function block programs, input signal ranges, etc.

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Question 92

The Rules of Fault Club

(1) Don’t try to find the fault by looking for it – perform diagnostic tests instead

(1) Don’t try to find the fault by looking for it – perform diagnostic tests instead!

(3) The troubleshooting is over when you have correctly identified the nature and location of the fault

(4) It’s just you and the fault – don’t ask for help until you have exhausted your resources

(5) Assume one fault at a time, unless the data proves otherwise

(6) No new components allowed – replacing suspected bad components with new is a waste of time andmoney

(7) We will practice as many times as we have to until you master this

(8) Troubleshooting is not a spectator sport: you have to troubleshoot!

These rules are guaranteed to help you become a better troubleshooter, and will be consistentlyemphasized by your instructor.

96

Loop

dia

gra

mte

mpla

te

Description Manufacturer Model Notes

Loop Diagram: Revised by: Date:

Tag # Input range Output range

97

Loop diagram requirementsPerhaps the most important rule to follow when drafting a loop diagram is your diagram should be

complete and detailed enough that even someone who is not an instrument technician could understandwhere every wire and tube should connect in the system!

• Instrument “bubbles”• Proper symbols and designations used for all instruments.• All instrument “bubbles” properly labeled (letter codes and loop numbers).• All instrument “bubbles” marked with the proper lines (solid line, dashed line, single line, double lines,

no lines).• Optional: Calibration ranges and action arrows written next to each bubble.

• Text descriptions• Each instrument documented below (tag number, description, etc.).• Calibration (input and output ranges) given for each instrument, as applicable.

• Connection points• All terminals and tube junctions properly labeled.• All terminal blocks properly labeled.• All junction (“field”) boxes shown as distinct sections of the loop diagram, and properly labeled.• All control panels shown as distinct sections of the loop diagram, and properly labeled.• All wire colors shown next to each terminal.• All terminals on instruments labeled as they appear on the instrument (so that anyone reading the

diagram will know which instrument terminal each wire goes to).

• Cables and tubes• Single-pair cables or pneumatic tubes going to individual instruments should be labeled with the field

instrument tag number (e.g. “TT-8” or “TY-12”)• Multi-pair cables or pneumatic tube bundles going between junction boxes and/or panels need to have

unique numbers (e.g. “Cable 10”) as well as numbers for each pair (e.g. “Pair 1,” “Pair 2,” etc.).

• Energy sources• All power source intensities labeled (e.g. “24 VDC,” “120 VAC,” “20 PSI”)• All shutoff points labeled (e.g. “Breaker #5,” “Valve #7”)

98

Sam

ple

Loop

Dia

gra

m(u

sing

asin

gle

-loop

contro

ller)

Process areaField panel Control room panel

Controller

Resistor

I/P transducer

Control valve

I/P

ES 120 VAC

AS 20 PSI

Loop Diagram: Furnace temperature control

TT205

JB-12

TB-15

TB-15

3

4

1

2

Temperature transmitterTT-205 Rosemount 444

TE205

CP-1

TB-11

TB-11

1

2

7

Vishay 250 ΩTY-205a

TIC-205 Siemens PAC 353

TY-205b

TV-205 Fisher Easy-E 3-15 PSI

Fisher

H

N

3

4

22

21

19

18

TY205b

TY

205a

Breaker #4Panel L2

5

6Cable TY-205b

Cable TT-205 Cable TT-205

Cable TY-205b

TIC205

Revised by: Mason Neilan

TV205

Tube TV-205

Column #8Valve #15

546

0-1500oF 0-1500oF

Fail-closed

Reverse-acting control

TE-205 Thermocouple Omega Type K Ungrounded tip

Red

BlkRed

Yel Red

Blk

Red

Blk

Red

Blk

Wht/Blu

Blu Blu

Wht/Blu

Cable 3, Pr 1

Cable 3, Pr 2

Wht/Org

Org Org

Wht/Org

Blk

Red

Blk

Red

Blk

Wht

Red

Blk

Red

Blk

Upscale burnout


Date:


0-1500o F 4-20 mA

4-20 mA 3-15 PSI

0-100%

1-5 V 0-1500o F

April 1, 2007

99

Sam

ple

Loop

Dia

gra

m(u

sing

DC

Scontro

ller)

Field process area



DCS cabinet

Red

Blk

Red

Blk

Red

Blk

Fisher

Fisher


Blue team pressure loop April 1, 2009

Card 4

Card 6Channel 6

Channel 611

12

29

30

Red

Blk

TB-80

TB-80

Field panel JB-25

TB-52

TB-52

PT-6 Pressure transmitter Rosemount 3051CD 0-50 PSI 4-20 mA

PIC6

PT6

Cable 4, Pr 1

Cable 4, Pr 8

1

2

15

16

Cable PT-6

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Red

Blk

Cable PV-6

11

12

11

12PY6

AS 20 PSI

PV6

0-50 PSI

I/P

0-50 PSI

846

Emerson DeltaV 4-20 mA 4-20 mA HART-enabled inputPIC-6

PY-6

PV-6

I/P transducer

Controller

Control valve Vee-ball

4-20 mA 3-15 PSI

3-15 PSI 0-100% Fail-open

Duncan D.V.

Tube PV-6

Cable PT-6

Cable PV-6

Analog input

Analogoutput

Direct-acting control

H

L

73

73

73 Cable PT-73 Cable PT-73

Cable PV-73Cable PV-73

PT-73

PIC-73

PY-73

PV-73

73

PIC

100

Sam

ple

Loop

Dia

gra

m(u

sing

pneum

atic

contro

ller)




LT24

In

H

LOut

C

D

A.S. 21 PSI

Tube LT-24a Tube LT-24b

A.S. 21 PSI

Process areaBulkhead panel

14

B-104Control panel CP-11

Tube LV-24

LV24

Tube LV-24

Supply

LIC

24

Tube LV-24

(vent)

Sludge tank level control I. Leaky April 1, 2008

LT-24 Level transmitter Foxboro 13A 25-150 "H2O 3-15 PSI

3-15 PSI 3-15 PSIFoxboroLIC-24 130

LV-24 Fisher Easy-E / 667 3-15 PSI 0-100% Fail closedControl valve

Controller

file

i00654

101

Question 93

Connect an “ice-cube” relay to a DC voltage source and a switch such that the relay will energize whenthe switch is closed. All electrical connections must be made using a terminal strip (no twisted wires, crimpsplices, wire nuts, spring clips, or “alligator” clips permitted).

This exercise tests your ability to properly interpret the “pinout” of an electromechanical relay, properlywire a switch to control a relay’s coil, and use a terminal strip to organize all electrical connections.

Terminal strip SwitchRelayRelay socket

The following components and materials will be available to you during the exam: assorted “ice cube”relays with DC-rated coils and matching sockets ; assorted switches ; terminal strips ; lengths ofhook-up wire ; battery clips (holders).

You will be expected to supply your own screwdrivers and multimeter for assembling and testing thecircuit at your desk. The instructor will supply the battery(ies) to power your circuit when you are readyto see if it works. Until that time, your circuit will remain unpowered.

Study reference: the “Control Relays” section of Lessons In Industrial Instrumentation.file i03772

102

Answers

Answer 1

Answer 2

Answer 3

Force at large piston = 100 pounds. I’ll let you calculate the fluid pressure on your own, as well asexplain the relationship of Pascal’s Principle to this system.

Answer 4

Ideally, the secondary piston’s position will have no effect on the oil pressure sent to the gauge.Consequently, the gauge indication should not change.

Answer 5

103

Answer 6

• 25 PSI = 172.37 kPa

• 40 ”W.C. = 1.4451 PSI

• 5.60 bar (gauge) = 81.221 PSI

• 3 atm = 44.088 PSIA

• 1,200 ”Hg = 16,314.51 ”W.C.

• 12 feet W.C. = 5.2022 PSI

• 4 PSI vacuum = 10.7 PSIA

• 110 kPa = 441.622 ”W.C.

• 982 mm Hg = 38.661 ”Hg

• 50 Pa = 0.007252 PSI

• 21 atm = 628.522 ”Hg absolute

• 270 PSIG = 19.367 atm

Complete work to obtain answers:

1 pound per square inch (PSI) = 2.03603 inches of mercury (in. Hg) = 27.6807 inches of water (in.W.C.) = 6894.757 Pascals (Pa) = 6.894757 kilopascals (kPa) = 0.0680460 atmospheres (Atm) = 0.0689476bar (bar)

Approximate answers may be obtained by rounding the above factors to four significant figures:

1 pound per square inch (PSI) = 2.036 inches of mercury (in. Hg) = 27.68 inches of water (in. W.C.)= 6895 Pascals (Pa) = 6.895 kilopascals (kPa) = 0.068 atmospheres (Atm) = 0.069 bar (bar)

A few other conversion constants are used here, but not listed officially with the others because theyshould be well known to you by now. They are:

• 12 inches = 1 foot• 2.54 cm = 1 inch• 25.4 mm = 1 inch• 1 atm = 14.7 PSIA

Since all of the pressure figure shown above are equal to each other, they may be arranged at will toform unity fractions. For example, to form a unity fraction for converting inches of water into inches ofmercury, simply write: (2.03603 ”Hg / 27.6807 ” W.C.). Just remember, place the unit you wish to convertto in the numerator of the unity fraction, and the unit you wish to cancel out in the denominator of thefraction. And now, the conversions:

(25 PSI)(6.894757 kPa / 1 PSI) = 172.37 kPa

(40 ”W.C.)(1 PSI / 27.6807 ”W.C.) = 1.4451 PSI

(5.60 bar)(100 kPa / 1 bar)(1 PSI / 6.894757 kPa) = 81.221 PSI

(3 atm)(1 PSIA / 0.0680460 atm) = 44.088 PSIA

Of course, we can convert from atmospheres into PSIA more simply if we know that there are 14.7 PSIAin 1 atmosphere. (3 atm)(14.7 PSIA / 1 atm) = 44.1 PSIA

104

(1,200 ”Hg)(27.6807 ”W.C. / 2.03603 ”Hg) = 16,314.51 ”W.C.

(12 feet W.C.)(12 inches / 1 foot)(1 PSI / 27.6807 ”W.C.) = 5.2022 PSI

In the problem with 4 PSI of vacuum, there is no direct unity fraction conversion into PSIA. Rather,the vacuum must be represented as a negative pressure. In other words, 4 PSI (vacuum) is the same as -4PSIG, or 4 PSI below the standard 14.7 PSI of atmospheric pressure. This is, of course, equal to 10.7 PSIA,since 0 PSIG is 14.7 PSIA.

(110 kPa)(27.6807 ”W.C. / 6.894757 kPa) = 441.622 ”W.C.

(982 mm Hg)(1 inch / 25.4 mm) = 38.661 ”Hg

(50 Pa)(1 PSI / 6894.757 Pa) = 0.007252 PSI

(21 atm)(14.7 PSIA / 1 atm)(2.03603 ”Hg / 1 PSI) = 628.522 ”HgA

Note in this problem how the “Absolute” unit suffix nicely transfers to the answer after all thecancellations:

21 atm

1

14.7 PSIA

1 atm

2.03603 "Hg

1 PSI= 628.522 "HgA

This is just another example of why it is helpful to include all the units while working with physics-relatedequations.

To convert PSIG into atmospheres, we must first convert PSIG into PSIA. Then, since we know thereare 14.7 PSIA in every atmosphere, we can convert using a unity fraction:

270 PSIG + 14.7 PSI = 284.7 PSIA

(284.7 PSIA)(1 atm / 14.7 PSIA) = 19.367 atm

Answer 7

Partial answer:

• P = 1100 PSI F = 21,598.4 lbs

• P = 461 kPa F = 1312.8 lbs

• P = 2.77 bar (gauge) F = 788.8 lbs

105

Answer 8

Partial answer (this is just one possible solution to the wiring of the pressure switch):

M1

M1 OL

motor

OL

To 3-phaseAC power

M1

H1 H2 H3 H4

F1 F2

F3A

B

C

D E

F G

120 VAC

PSLPSH

Compressor

X1 X2

(480 VAC)

L1

L2

L3

T1

T2

T3

H JK L

Stop Run

LSH

Disable Enable

PSLL

80 PSI95 PSI

65 PSI

Buzzer

Condensatedrain valve

106

Answer 9

Partial answer:

250 Ω

L1

L2/N

Alarmrelay #1

Alarmrelay #2

Analog input #1

Analog input #2

Honeywell model UDC2500 controller

H L

Rosemount model 1151loop-powered pressure transmitter

3-valve isolationmanifold

Outputrelay #1

Isolationvalve

Processvessel

Alarm lamp(120 VAC)

+−24 VDC

Load

Load

Source

(vent)

Open

Closed

Open

250 Ω

Answer 10

Answer 11

Fault Possible ImpossiblePR-33 calibration error

√

PT-33 calibration error√

PIC-33 (input) calibration error√

PY-33a calibration error√

PY-33b calibration error√

PV-33a calibration error√

PV-33b calibration error√

107

Answer 12

The fluid pressure will exert an outward force on the cylinder walls, like this:

Force

pres

sure

Answer 13

A pushing force on the rod will compress the rubber ball to a smaller diameter. A pulling force willexpand it to a larger diameter.

Rubber ball Rubber ballcompresses expands

108

Answer 14

Absolute pressure = 2,014.7 PSIA. Gauge pressure = 2,000 PSIG. Differential pressure (between tankand water) = 1,978 PSID.

Gauge pressure is simple: it is the figure initially measured by the pressure gauge (2,000 PSIG). Again,we are assuming that the diver has not significantly decreased the tank’s air pressure by consuming air fromit as he or she descended to the specified depth. In reality, the pressure in the tank would have decreased abit in supplying the diver with air to breathe during the descent time.

Absolute pressure is simply gauge pressure added to the pressure of Earth’s atmosphere. Since thegauge pressure measured at the water’s surface was (obviously) at sea level, and atmospheric pressure at sealevel is approximately 14.7 PSIG, absolute air pressure inside the tank is 2,000 PSI + 14.7 PSI = 2,014.7PSIG.

Differential pressure is simply the difference (subtraction) between the tank’s gauge pressure of 2,000PSI and the water’s hydrostatic pressure (gauge) of 22 PSI. This is equal to 1,978 PSID. The same differentialfigure will be found even if atmospheric pressure is taken into consideration: the tank’s absolute air pressure is2,014.7 PSIA and the water’s hydrostatic pressure is 36.7 PSIA (22 PSI + 14.7 PSI), resulting in a differencethat is still 1,978 PSID. The key here in figuring differential pressure is to always keep pressure units thesame: don’t mix gauge and absolute pressures!

Answer 15

406.91 inches, which is a little bit less than 34 feet.

Deeper wells may be tapped by using submersible pumps (pumps located inside the well, near thebottom):

Pump

109

Answer 16

With no nozzle on the end of the hose, the end may be raised a maximum of 184.54 feet. With a nozzlein place, the hose end may be raised only 115.34 feet.

Essentially, this is just another pressure unit conversion problem: in this case, PSI-to-feet of watercolumn. 80 PSI is equivalent to 184.54 feet, so that is how high 80 PSI can force a column of water.

With a nozzle attached to the end of the hose, though, we are only allowed to “drop” 50 feet ofhydrostatic pressure, in order to leave 30 PSI remaining at the nozzle coupling for proper operation. 50 PSIis equivalent to 115.34 feet, so this is how high we may raise the hose end with a nozzle on it.

It must be understood that the first calculation is not a very practical one. 80 PSI of pressure at thehydrant will just push water 184.54 feet high. If the hose were 190 feet and poised vertically, there wouldbe a column of water inside 184.54 feet tall, with no water at all coming out the end. If the hose end werebrought exactly to a height of 184.54 feet, water would be right at the lip of the hose, not even trickling out.Obviously, some pressure is needed at the hose end in order to push water out onto a fire, so the practical,no-hose height for 80 PSI will be somewhat lower than 184.54 feet.

The hose-with-nozzle scenario is more realistic, because an actual figure for minimum hose-end pressureis given for us to incorporate into our calculations.

Answer 17

PSIG PSIA inches Hg (G) inches W.C. (G)18 32.7 36.65 498.25

385.3 400 784.5 1066516.21 30.91 33 448.62.168 16.87 4.413 60222.0 236.7 452 6145.10.4335 15.13 0.8826 12-13.7 1 -27.89 -379.2-5 9.7 -10.18 -138.4

Answer 18

The force on the lid from the coke drum’s internal pressure of 5 PSI will be 3534.3 pounds, which is howgreat the ram’s vertical force component must be to successfully hold down the lid when all the bolts havebeen removed. The ram’s angle of 38 degrees from horizontal means the vertical force component will onlybe 0.6157 of its diagonal force (sine of 38o = 0.6157). This necessitates a direct ram force of 5740.6 pounds.

With a piston diameter of 4 inches, a hydraulic pressure of 456.83 PSI is necessary to generate 5740.6pounds. This is a minimum pressure, for safety reasons. More than 456.83 PSI won’t do any harm, but lessthan this amount will fail to hold down the lid!

110

Answer 19

Applied pressure = 9 ”W.C., which is equal to 0.32514 PSI.

For the same applied pressure, the distance between the two liquid columns will be greater than withwater. In other words, for a pressure of 9” W.C., there will be more than 9 inches of vertical distanceseparating the two liquid columns.

Essentially, manometers work on the principle of balanced pressures: the applied gas pressure forcesthe liquid columns to shift height. When they do so, they generate a hydrostatic pressure proportional totheir differential height. When this hydrostatic pressure equals the applied pressure, the liquid columns stopmoving and a condition of equilibrium is reached.

If a lighter fluid such as oil is used instead of water, a greater height will have to be developed togenerate the same amount of hydrostatic pressure to oppose the applied gas pressure and reach equilibrium.Conversely, if a heavier (denser) liquid such as mercury were to be used, a much smaller vertical height woulddevelop between the two columns for the same pressure.

Answer 20

• Step 4: Quickly open and close valve 4 – manometer indication drops slightly• Step 6: Quickly open and close valve 4 – manometer indication does not drop at all• Step 8: Quickly open and close valve 3 – manometer indication drops greatly

Answer 21

Answer 22

Answer 23

Answer 24

Answer 25

Applied pressure = 1.193 kPa

Answer 26


• 25 ”Hg vacuum = 2.421 PSIA

• 2,800 µ torr = 0.3733 PaA

• -59 ”W.C. = 649.98 torr

• 4,630 PaA = -14.028 PSI

• 0.05 atm = -386.56 ”W.C.

• -3 kPa = 0.9704 atm

• 10 feet W.C. vacuum = 21.103 ”HgA

• 300 cm Hg = 4.946 atm

• -2 mm W.C. = 1.0133 bar (absolute)

• 4 atm = 1,627.63 ”W.C.A

111

Answer 27

• 25 PSIA = 1.701 atm

• 340 ”W.C. = 26.983 PSIA

• 0.73 bar (gauge) = 21.557 ”Hg

• 5.5 atm = 4,180 torr

• 2,300 cm Hg = 12,717.72 ”W.C.A

• 500 m torr = 0.0096683 PSIA

• 91.2 cm W.C. = 8.9434 kPa

• 110 kPa = 441.62 ”W.C.

• 620 mm HgA = 620 torr (A “trick” question . . .)

• 77 Pa = 14.711168 PSIA

• 1 atm = 406.91 ”W.C.A

• 270 PSIA = 18.367 atm

Answer 28

Fault Possible ImpossibleUpstream filter block valve partially shut

√

Downstream filter block valve partially shut√

PDT-136 calibration error√


PG-417 calibration error√

PG-421 calibration error√

Filter drain valve to sump left open√

Answer 29

112

Answer 30

This is perfectly legitimate, because in either case all the pressure units involved in each conversion areof the same type: either all gauge or all absolute. Where we encounter difficulties is if we try to mix differentunits in the same “unity fraction” conversion that do not share a common zero point.

A classic example of this mistake is trying to do a temperature conversion from degrees F to degrees Cusing unity fractions (e.g. 100o C = 212o F):

(

60o F

1

) (

100o C

212o F

)

6= 28.3o C

This cannot work because the technique of unity fractions is based on proportion, and there is no simpleproportional relationship between degrees F and degrees C; rather, there is an offset of 32 degrees betweenthe two temperature scales. The only way to properly manage this offset in the calculation is to include anappropriate addition or subtraction (as needed).

However, if there is no offset between the units involved in a conversion problem, there is no need toadd or subtract anything, and we may perform the entire conversion using nothing but multiplication anddivision (unity fractions). Such is the case if we convert pressure units that are all gauge, or if we convertpressure units that are all absolute.

To summarize, it is perfectly acceptable to construct a unity fraction of 27.68 ”W.C.2.036 ”Hg

because 0 ”W.C.

is the same as 0 ”Hg (i.e. they share the same zero point; there is no offset between units ”W.C. and ”Hg).

Likewise, it is perfectly acceptable to construct a unity fraction of 27.68 ”W.C.A2.036 ”HgA

because 0 ”W.C.A is the

same as 0 ”HgA (i.e. they share the same zero point; there is no offset between units ”W.C.A and ”HgA).

Answer 31

Applied pressure = 2.5 ”W.C.

What matters in manometer calculations is the vertical height difference between the two liquid columns.Inclining one or more of the tubes only causes the liquid to displace further along the tube(s); it does notchange the vertical height necessary to balance the applied pressure.

Thus, with a 30o inclined tube, a liquid displacement of 5 inches along the length of the tube equatesto one-half that (sin 30o = 0.5). Therefore, the applied pressure is 2.5 inches of water column.

Note that the inclined manometer makes very sensitive pressure measurements possible using standard-density liquids such as water! Great care, though, must be taken in ensuring the instrument is level (thatthe inclined tube is at precisely the angle it should be).

113

Answer 32

1 inch of bubble motion represents 0.02 inches of water column pressure (differential), or 2/100 ”W.C.,applied across this micromanometer.

To solve for this pressure, first determine the amount of liquid volume that would have to be displacedto move the bubble 1 inch. Since the bubble resides in a tube 0.25 inches in diameter, the volume for 1 inchof bubble motion is:

(1 inch)[π(0.25 inch / 2)2] = 0.04909 in3

This is a very small amount of liquid volume! The water levels in the larger (2.5 inch diameter) tubeswill not have to change much to accommodate this tiny amount of displacement. Dividing the displacedfluid volume by the area of the vertical tubes will tell us how far the water levels must change in each of thevertical tubes:

(0.04909 in3) / [π(2.5 inch / 2)2] = 0.01 inch

So, a vertical liquid column height change of only 0.01 inch will cause a horizontal bubble displacementof 1 inch. Since there will be 0.01 inch of movement in each vertical tube, the combined total verticaldisplacement is twice this figure, or 0.02 inches of water column.

A much simpler way to solve this problem is to recognize that the vertical tube areas are 100 timesas great as the horizontal tube (2.5 inches is ten times as large as 0.25 inches, and area is proportional todiameter squared), so 1 inch of horizontal fluid displacement is proportional to 1/100 inch of vertical fluiddisplacement. Once again, since each vertical tube experiences 0.01 inch of vertical water level displacement,the total water column shift is 0.02 inches.

Answer 33

The manometer will register falsely high, showing greater differential pressure than what is actuallythere. If you are having difficulty figuring this out, imagine if the liquid moving through the pipe was justas dense as the mercury within the manometer: what would that do to the mercury in the manometer givenany applied ∆P? In other words, set up a thought experiment with absurdly (simple) conditions and thenlook for patterns or trends which you may generalize for any condition.

Challenge question: derive a mathematical correction factor for interpreting the manometer’s indicationto yield true inches of mercury ∆P.

114

Answer 34

P

V

Note that the function is a curve and not a straight line! In essence, the function plotted is this:

P =k

V

Where k is a constant equal to nRT .

Answer 35

Pressure applied to right-hand tube = 26.5 ”W.C = 6600.8 Pa.

Follow-up question: demonstrate how we could have arrived at an approximate answer by using roundedfigures for our unit-conversion constants, and “mental math” instead of a calculator.

Answer 36

Applied pressure = 3.1875 ”W.C., which is equal to 0.1152 PSI.

Follow-up question: demonstrate how we could have arrived at an approximate answer by using roundedfigures for our unit-conversion constants, and “mental math” instead of a calculator.

Answer 37

F = 51.07 pounds of force, downward (holding the cover onto the flange).

Although the eductor’s suction will in fact hinder the pumps’ ability to move liquid out of the sump totreatment, the effect will be minimal since 2 inches WC is tiny compared to the rated head (pressure) of thepumps at 40 feet WC.

Answer 38

Answer 39

Answer 40

Answer 41

Answer 42

Answer 43

115

Answer 44

Answer 45

Answer 46

Answer 47

Answer 48

Answer 49

The parts in this gauge mechanism would move as such:

Appliedpressure

Pointer

Pressure gauge

Bourdontube

mechanism

Possible things to change to make this pressure-measuring mechanism more sensitive:

• Decrease the spring rate (“stiffness”) of the bourdon tube• Shorted the arm of the sector gear (the portion to the right of the pivot, joining with the link)• Increase the sector gear radius• Decrease the pinion gear radius

Answer 50

Fault Possible ImpossiblePG-108 calibration error

√


PIC-33 left in manual mode√

PY-33a calibration error√

PY-33b calibration error√

116

Answer 51

(1) The accuracy of a deadweight tester is fixed by three fundamental variables, all of which arequite constant, two of which can be manufactured to highly accurate specifications, and the thirdbeing a constant of nature:

• The mass of the calibration weights• The area of the primary piston• The gravity of the Earth

(2) If a deadweight is not level, the force generated by the precision weights will not be parallel tothe primary piston’s axis of travel, meaning that the piston will not support their full weight.

(3) Entrapped air will make the piston’s motion “springy” rather than solid and secure.

(4) Spinning the primary piston eliminates static friction, leaving only dynamic friction (which ismuch less) to interfere with gravity’s force on the primary piston.

Answer 52

The accuracy of a manometer is fixed by two fundamental variables, both of which are quite constant:

• The density (mass per unit volume) of the manometer liquid• The gravity of Earth

So long as these two variables do not change, neither will the accuracy of the manometer.

Answer 53

Net piston force = 890.936 pounds.

In this scenario, there are two pressures fighting against each other: the 850 PSI pressure is pressingdownward on the piston while the 1000 PSI pressure is pressing upward. The resultant (differential) pressureis 150 PSI (1000 PSI - 850 PSI). This is the pressure figure to be used in the final force calculation.

Answer 54

Net force = 4,319.69 pounds, in the downward direction.

Answer 55

Actuating the hand pump introduces more air molecules to the system (n). Assuming temperature (T )remains constant, the air pressure (P ) will increase in inverse proportion to the volume (V ) of the pressurevessel for each additional stroke of the pump.

Follow-up question: If we wished the pressure to increase less for every stroke of the pump, would wewant a smaller pressure vessel or a larger pressure vessel? Explain your answer.

Challenge question: suppose a technician follows these steps in using this system.

• Close valve 2, open valves 1 and 3• Pump several strokes’ worth of air into the pressure vessel• Close valves 1 and 3• Slowly open valve 2 until manometer registers desired pressure, then close

Is the air pressure going to the instrument under test greater than, less than, or equal to the air pressurein the vessel?

117

Answer 56


Low-rangevoltmeter+

−High voltage

source

3-terminalIC regulator

I’ll leave the explanation to you!

Follow-up question #1: explain what you could do with one or both of the two needle valves to increasethe amount of pressure sent to the instrument under test.

Follow-up question #2: explain why placing a valve in “series” with the regulator’s output will notadjust pressure to the instrument under test or the manometer.

Air compressor

Manometer

Receiver


Pressureregulator

This valve will notadjust pressure!

Answer 57

Possible things to change to make this pressure-measuring mechanism more sensitive:

• Increase the area of the diaphragm• Decrease the spring rate of the diaphragm• Move the fulcrum towards the linkage, to the left, away from the scale

118

Answer 58

It is an “anti-backlash” spring, supplying enough torque to rid the sector/pinion gear set of any “slack”or “play,” so that the pointer always responds to the slightest change in bourdon tube position.

Answer 59

• Pressure gauge• LRV = 0 PSI• URV = 100 PSI• Test pressure = 65 PSI• Instrument indication = 67 PSI• Error = +2 % of span

• Weigh scale• LRV = 0 pounds• URV = 40,000 pounds• Test weight = 10,000 pounds• Instrument indication = 9,995 pounds• Error = -0.0125 % of span

• Thermometer• LRV = -40oF• URV = 250oF• Test temperature = 70oF• Instrument indication = 68oF• Error = -0.69 % of span

• pH analyzer• LRV = 4 pH• URV = 10 pH• Test buffer solution = 7.04 pH• Instrument indication = 7.13 pH• Error = +1.5 % of span

119

Answer 60

Here is one example of how a pressure gauge might respond in a non-linear fashion to the same fiveapplied pressures, while still being accurate at the LRV and URV points:

0 500

250

125 375

0 500

250

125 375

0 500

250

125 375

0 PSI applied 125 PSI applied 250 PSI applied

0 500

250

125 375

0 500

250

125 375

375 PSI applied 500 PSI applied

actual

(desired)

actual (desired)

actual

(desired)

Here, the gauge reads high at the 25% point (125 PSI), slightly low at the 50% point (250 PSI), andlow at the 75% point (375 PSI), while still accurate at 0% (0 PSI) and 100% (500 PSI).

Any adjustment that affects the traveling angle of the mechanism will have an effect on linearity. Some(high-quality) pressure gauge mechanisms are equipped with an adjustable-length link to facilitate changesto this angle:

Appliedpressure

Pointer

Link

Bourdontube

(adjustable length)

Travelingangle

It is sage advice to leave all angle adjustment(s) untouched until all possible zero and span adjustmentshave been made to the instrument. Usually, it is possible to get a nonlinear instrument to read withinspecified tolerance in a 5-point calibration just by adjusting the zero and span adjustments.

120

In many mechanical instruments, a simple linearity alignment is to apply a 50% input signal and checkfor link/lever perpendicularity (that all links and levers intersect at 90o angles to each other).

Answer 61

Answer 62

Answer 63

Answer 64

Answer 65

Answer 66

Answer 67

Answer 68

Partial answer:


√

R2 failed openStrain gauge failed open

√

Dummy gauge failed openR1 failed shortedR2 failed shorted

Strain gauge failed shortedDummy gauge failed shorted

Voltage source dead√

Answer 69

• 22 PSIG = 36.7 PSIA

• 13 kPa = 52.19 ”W.C.

• 81 kPa = 11.75 PSI

• 5 atm = 73.5 PSIA

• 200 ”Hg = 2719 ”W.C.

• 17 feet W.C. = 15.01 ”Hg


• 900 Torr = 481.9 ”W.C.A

• 300 mm Hg = 5.801 PSI

• 250 ”W.C. = 0.6227 bar (gauge)

• 70 ”W.C. = 5.149 ”Hg

• 300 PSIG = 21.41 atm

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Answer 70

Atm PSIG inches W.C. (G) PSIA3.5 36.75 1017.3 51.456.51 81 2242 95.722.71 319.1 8834 333.8

0 -14.7 -406.9 01.017 0.2572 7.12 14.9625.03 353.3 9779.6 3681.136 2 55.36 16.7100 1455.3 40284 1470

Answer 71

• Which port is the “high” pressure port: Port “B”• What will happen if fixed resistor R1 fails open: Voltmeter will drive fully upscale (“peg”

positive)• Identify a component fault that would drive the voltmeter full upscale (“peg” positive):

• Strain gauge #1 fails shorted• Strain gauge #2 fails open• R1 fails open• R2 fails shorted

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Answer 72

Note very carefully how the two secondary coils are connected in series-opposing (as denoted by thephase dots)! This detail is essential in figuring out how the LVDT works.

The output is an AC voltage, the magnitude of which is proportional to core position, which in turn isproportional to applied pressure. For what it’s worth, the phase of the output voltage will be inverted withrespect to the excitation voltage as the bourdon tube draws the core up:

Appliedpressure

Bourdontube

Movablecore

LVDTs have several advantages over potentiometers:

• No friction• No wear• No potential to generate a spark in normal operating conditions

Their major disadvantage is requiring an AC excitation voltage. The frequency of this excitation voltageis important as well: it must be much larger than the highest frequency of pressure changes you wish tomeasure (as per the Nyquist sampling theorem).

123

Answer 73

Note very carefully how the two secondary coils are connected in series-opposing (as denoted by thephase dots)! This detail is essential in figuring out how the LVDT works.

The output is an AC voltage, the magnitude of which is proportional to core position, which in turn isproportional to applied pressure. For what it’s worth, the phase of the output voltage will be inverted withrespect to the excitation voltage as the bourdon tube draws the core up:

Appliedpressure

Bourdontube

Movablecore

LVDTs have several advantages over potentiometers:

• No friction• No wear• No potential to generate a spark in normal operating conditions

Their major disadvantage is requiring an AC excitation voltage. The frequency of this excitation voltageis important as well: it must be much larger than the highest frequency of pressure changes you wish tomeasure (as per the Nyquist sampling theorem).

Answer 74

Hint: although it may not look like it at first, the two resistors form a bridge circuit with the differentialcapacitor.

Answer 75

The output voltage will be positive with respect to ground if C > C ′ and negative if C ′ > C.

Answer 76

Hint: you may find that Yokogawa’s DPharp product is easier to obtain information on, being a morerecent product.

Answer 77

B =xVHall

KI

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Answer 78


√

R1 failed shorted√

R2 failed open√


R3 failed open√


Reference filament burned out√

Measurement filament burned out√

Answer 79

First transmitter design:Input range: 0 to 15 PSIOutput range: 0 to 10 volts DC

Last transmitter design:Input range: 0 to 15 PSIOutput range: 1 to 5 volts DC

Follow-up question: show the current in both circuits using both conventional flow notation and electronflow notation.

Answer 80

Answer 81

This is a graded question – no answers or hints given!

Answer 82


Answer 83


Answer 84


Answer 85


Answer 86


Answer 87


Answer 88


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Answer 89


Answer 90


Answer 91

Answer 92

Your loop diagram will be validated when the instructor inspects the loop with you and the rest of yourteam.

Answer 93

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