Relation between flow and differential pressure.

Answer# 1

Flow is a continuous process of flowing of any liquid. Differential pressure is the pressure difference between Suction pressure and Discharge pressure.

# 2 If we are using "restricted type flow measurement principle such as Orifice, venture, V-Cone flow meters, anu-bar etc. then the Pressure drop across the element i.e. let P, then Flow is proportional to the square root of differential pressure.

# 3 flow is directly proportional to the square root of differential pressure(f=k*sqrt(p1-p2))

#4 If pressure difference is high definitely the flow will high and if DP(differential press.) became low or zero, means line is partially/ fully chocked. and as we know Flow = square root(DP.

Why three wires are using with a RTD?

Answer

# 1

Resistance Temperature Detector(RTD)incorporates two basic concepts1) Variation of temperature varies the resistance of Pt wire.2) Variation in resistance affects the balancing of DC Bridge circuit.For measurement purposes lead wires are brought out to make external connections. These lead wires have some resistances which affect the bridge balancing. Since we cannot reduces the resistances of lead wire to zero. So, either 3 wires or 4 wire connection is employed to ELIMINATES THE IMBALANCING TO THE BRIDGE CIRCUIT caused by resistances of lead wires so that an accurate measurement can be made. These wires (3 or 4) are called compensating leads.

# 2 You are right, and the temperature indication does not increase so significantly that it is worth the effort to use a 3 or 4 wire RTD. It might increase with something like 0,001Deg C so that is so small you might as well say there is no difference in the accuracy of a 2,3 and 4 wire RTD, using a local or smart transmitter.In the old days we use to use a 2 wire RTD in the field and then run a cable say 200m to the temperature indicator. By the time it gets to the indicator the temperature is completely different from what it was in the field due tothe cable resistance that add itself the RTD resistance.We compensated for that by installing a 3de wire for the sole propose to measure the resistance of the cable itself and deduct that from the total resistance measured at the temperature indicator. So the actual resistance of the RTD as measured at the temperature indicator is RTD - RLine1.(or (Rline1/2)x2]if you want)With the 4 wire it makes it more accurate in that you can now measure line one and line 2. The theory is that the one line might have a small difference compare to the other line. So the actual RTD resistance at the temperature indicator is measured RTD - [(RLine1/2)+(RLine2/2)]But since we all use the small compact local and smart temperature transmitters these days, 3 and 4 wires are no longer needed since the distance from the RTD to thetransmitter is only from about 50 to 500mm and but it seems it have stayed due to some design engineer always saying, why buy a 2 wire if you can get the 3 and 4 wire for just about the same price. It will make the indication just more accurate, but they never say by how much (0,001Deg C).

how to calibrate a new i/p converter

Answer# 1

Connect the input air supply of around 5 to 7 Bar Feed 4 mA through the calibrator; the output air pressure gauge shall indicate 3 psi. Feed 20mA through the calibrator, the output air pressure gauge shall indicate 15 psi.

# 2

I follow your above procedure I use 0-30 psi pressure gaugeWhen I feed 4 mA gauge show 3 psi, gradually I increase mA simultaneously pressure increase. At 10 mA gauge shows max 20 psi. I little adjust the range screw but no change on gauge. now what will I do.

3 Hope you are adjusting 4mA with "Zero" screw and 20mA with "Span/range" screw. I feel that you might have adjusted the 3 psi with range screw.

# 4 FIRST SEE ITS PRESSURE RANGE APPLY INPUT PRESSUR 5PSI MORE THEN MAXIMUM RANGE OF OUTPUT PRESSURE AND SEE ITS OUT PUT THEN APPLY 4MA AND SEE OUTPUT SIGNAL 3 PSI NOW ADJUST 3 PSI FROM ZERO ADJUSTMENT SCREW NOW 8 12 16 & 20MAAPLY AND CHECK MAX PRESSURE RANGE NOW ADJUST FROM SPAN SCREW ( RANGE CAN BE DIFFERENT FROM 3 TO 15 PSI )

# 5 1. AIR SUPPLY I/P input - 1.4kg/cm2 Output - 0.2 to 1kg/cm2 ok

2.input signal= 4-20 mA

i.connect the air supply to input with the hepl of REGULATOR i.e 1.4kg/cm2 ii.connect the MASTER GAUGE to OUT PUT ok Apply the signal

i. 4mA- 0 kg/cm2 (if not Zero/0.2kg/cm2 Adjust Zero adjustment Screw) ii. 20mA-1 kg/Cm2 (if not 1kg/cm2 Adjust Span adjustment Screw) ok.

then 8, 12, 16mA. min. and max. is ok the remaining will perfect automatically i.e 8,12,16mA.

and MAIN IMP POINT is ON the I/P's Ckt board Side 4 adjust ment buttons is there and adjust that buttons Direct and Revese Actions ok

# 7 Friends, plz understand the question first. The interviewer has mentioned "how to calibrate a NEW i/p Converter?" "Sir, the new i/p would be factory calibrated with high accuracy master instruments, so before we commission it in the plant we have can check its output by applying proper signal, unless we have good accuracy masters we no need to disturb the calibration. If yes, we can do the calibration using the 30psi regulated supply, 4-20 mA source, and receiver gauge."

What is the difference between sensor and transducers?

Answer# 1

Sensor is a receiving a signal. Transducers is a transmitting a data a data one device to another device.

# 2 Sensor is an element which Receives a signal that is to be measured. Where as a transducer is a device or a sensor which converts a physical data to an electrical data.

# 3 a sensor is one which measures a physical variable. a transducer is one which transforms the physical variable into some other form which can be easily processed by the remaining measurement system. if it is converting the signal Into electrical form it is called electrical transducers.

# 4 Sensor can only sense the element but transducer can convert physical energy to another form. So sensor is not transducer but transducer is sensor.

# 5 Sensor is a device which converts any physical quantity into electrical quantity. But the transducer converts one form of energy into another form of energy; it may either electrical or any other physical quantity.

# 6 Sensor can only sense the physical quantity and convert into electric signal (24v). But transducer senses the physical quantity then converts it into other form of energy as type of transducer.

# 7 Sensor is a device which can only sense the physical Quantity like temperature, pressure etc. FOR PRESSURE BELLOWS IS A SENSORTransducer is a device which senses the physical quantity and converts that physical quantity into electrical quantity eg. THERMOCOUPLE

# 8 sensor is only used to measure the physical quantity such as (temp, flow, level, pressure) but transducer is a device used to measure the physical quantity and convert the electrical energy.

Can anybody will tell me about PID controller.

Answer# 1

PID CONTROLLER is a proportional integral differential controller that may b used at any electrical control application as the response of any system is resulting from the multiplication of any gain "prop" , differentiate it "diff" and then integrate it.PSS is the most device at which we design it by PID either with FLC or using POLE Placement can make a small pid using OPERATIONAL AMPLIFIER OR SIMPLE RLC CIRCUIT.

# 2 For PID controller the actuating signal consists of proportional error signal added with derivative and integral of the error signal. Therefore the actuating signal for PID control is ea (t)=e(t)+Td de(t)/dt + Kt}e(t)dt

# 3 Its a one type of feedback system. PID controller try to correct the error between a measured process variable and desired set point by calculating and then it generates the corrective action accordingly

# 4 Actually we can make it simple:# P:Its controller gains which modify the controller o/p proportional to the error.

# I:It’s a controller gain which modifies the controller o/p proportional to

the integral of the error.# D:It’s a controller gain which modify the controller o/p Proportional to error rate of change.We have 4 parameters in our control loop to focus on: 1 - the rise time: the period of time during which the pv get 90% of the desired sp value2 - max overshoot3 - Settling time: the period of time during which the pv gets the desired sp value and saturate.4 - error/offsetwe can get it clear from this pic:Now we will take a look about the effect of each controller gain on these parameters:# P gain:Decrease rise time increase max. over shoot increase settling time decrease error (but not eliminate)# I gain:Decrease rise time increase max over shoot increase settling time eliminates error.# D gain:no effect on rise timedecrease max over shootdecrease settling timeDecrease error.

How u measure flow? Orifice measurement? Why all ft in square root?

Answer# 1

There are several ways to measure the flow of fluid & gas like magnetic flow meter, mass flow meter, based on measurement of differential pressure like venture, orifice etc, turbine flow meter, positive displacement flow meter, vortex flow meter.Measurement of flow with the help of orifice is based on the measurement of differential pressure across the orifice plate. Tapings are either on the supporting flange or at D & D/2 m away for upstream and downstream of the orifice respectively where D id Pipe diameter in which plate is installed.Not all the transmitters are square root. Those transmitters which are based on differential pressure are square root. We can use square root at the transmitter itself or we can make the calculation in the DCS/PLC program. Since Q(flow) is directly proportional to square root of the differential pressure we do the square root extraction to measure the flow.

what should be the distance of vibration sensor & to the point where vibration to be measured Ex turbine axial displacement

Answer# 1

The distance of vibration sensor and the point where the vibration is to be measured is should be 1.5 mm.

# 2 The philosophy is different for Axial and Radial measurement. For radial measurement the AC component voltage is directly proportional to the magnitude of vibration so the gap is fixed based on the probe linearity (usually 10vdc for Bentley Nevada probes).For axial measurement the AC component voltage is not important and only the DC component is considered which varies proportional to the distance between the probe and the shaft. Conversely, the shaft is centered and the probe voltage is adjusted to 10Vdc and the same voltage is also referenced in the system for shaft zero position. While the unit/turbine is running the position of the shaft is proportional to the dc component measured.

What is DCS architecture? Can u give example?

Answer# 1

DCS ARCH:- it means total dcs system , it includes engineering station , operating station , dcs panel like analog panel(AO&AI) , digital panel (DO & DI), system cabinet , pdb cabinet , and all DI, DO, AI , AO from Field terminals , also from mcc , from drive panel . this iswhole dcs arch.

# 2 DCS ARCHITECHTURE IS RELATED WITH "FIELD CONTROL STATION" (FCS) AND HUMAN INTERFACE SYSTEM (HIS).

FIELD SIGNAL FOR EG.(DI,DO,AI,AO) IS CONNECTED WITH FCS PANEL AND IN FCS USED NEST,VLNET,VNET, DEPEND UPON TYPES ON DCS.

Why OPC server is used in DCS?

Answer# 1

OPC server is used to hook up or share the information across third Party DCS into the EXISTING DCS.For Eg. I want to have CS3000 (Yokogawa) sharing some information exchange on EXPERION PKS (Honeywell) System, I will Need OPC integrator for the same.

# 2 OPC stands for “OLE for Process control”, again OLE stands for “Object Linking and Embedding”, to link the different objects from different user and make it used or available in DCS for process a task, OPC server is used.

what is the reason for flow fluctuations happen on differential flow transmitter during in service

Answer# 1

Change in process pressure, restriction in one of the sensing lines, rapid change in temperature, and noise in the signal being returned to the source of indication. (Check for noise in the shielding-blow down sensing lines-check if the process media is at the correct operating temp.-make sure the equalizer valve is closed and the sensing (hi and lo) lines are open.

We have ZR22G-100-S-A-E-T-T--E-A/CV/F1 Model Zirconia Oxygen analyzer which is Yokogawa make. I kept the analyzer in Flue gas path at Air pre heater area. My plant is 7.5MW Biomass power plant. For a particular fuel, Coconut Husk which contains Sodium and Potassium chlorides iam not getting proper reading, Analyzer output always Zero. I calibrated the analyzer and it is OK. For Other fuels like Wood chips, Cholam waste, DOB, Ground nutshells, Ply wood waste and all iam getting actual percentage of Oxygen. What is the main reason behind this draw back?

Answer# 1

please check your heater which is used in zirconia change your load air percentage in firing and observe changing or not if changing means actual is zero

# 2 Pls. set your fuel temperature bcs. Normally zirconia o2 analyzer work on 800-900 deg. centigrade temperature.

So set the temp. Still you not get result then pls regulate your flow and also with your process gas you have to provide atmospheric air with set pressure (>=1kg/cm2).

How u measure rooms temp? Is it possible 2 measure room temp by RTD or thermocouple? Between RTD n thermocouple which is more regard?3 measure diff. between RTD n thermocouple?

Answer# 1

RTD is low range temp. Sensor (0-300) but thermocouple is for high range temp. (0-1400)RTD measures temp. With change in resistance, thermocouple measures temp. With reference of

cold junction, its output in mV.

Functions of electro pneumatic valve positioner?

Answer# 1

To reduce and to control the flow of the service which is passing through

# 2 All valve cannot be actuate directly using I to P converter. Using electro pneumatic valve positioner we can boost the air signal to the required level to actuate valve and position it such that the flow of material passing through line is maintain.

What is difference between two wire &three wire pt 100?

Answer# 1

two wire RTD use for short distance, three wire RTD use for long distance because of resistance compensation.

What is DCS and PLC scanning time?

Answer# 1

Scan time is time required for checking i/p, to executiveProgram and give output. generally 5msecfor plc

# 2 SCANNING TIME OF PLC DEPENDS ON THE NUMBER OF RUNGS, JUMP COMMANDS, SUB ROUTINES, AND INTERFACING DRIVER CONFIGURATION. THERE IS NO FIXED SCAN TIME FOR PLC.

WHAT IS CV OF CONTROL VAVLE

Answer# 1

The Cv is actually the Flow Coefficient of control valves. It actually measures the friction experienced by a fluid as it moves through some pipe / valve. The standard definition of Cv is:"the flow of water through a valve at 60 oF in US Gallon/minute at a pressure drop of 1 lb/in2."

# 2 Coefficient valve one cv equal the flow of one u.s galleon (3.8 litter)per minutes of water at 60 F under a pressure drop of value of 1psi.

# 3 flow coefficient of control valve.its calculated by the given below formula: CV = Q/(P/SG)^1/2 where: CV -flow coefficient Q -flow of liquid P-pressure drop across the flow SG-specific gravity of the liquid

CV=1.17KV => KV=.86CV

KV is metric unit of CV

The flow of water through a valve at 60 oF in US gallon/minute at a pressure drop of 1 lb/in2.

what is full form of SMART

Answer# 1

Self-Monitoring, Analysis, and Reporting Technology