sis “final element” diagnostics including the sov, using a digital valve controller

SIS “Final Element” Diagnostics Including The SOV, Using A Digital Valve

Controller

SIS “Final Element” Diagnostics Including The SOV, Using A Digital Valve

ControllerC B Chakradhaar– Instrument & Control Specialist

Riyaz Ali – Director Instruments

PresentersPresenters

C B Chakradhaar - I & C Specialist

Riyaz Ali – CFSP

IntroductionIntroduction

SIS “Final Control Element” Diagnostics by Digital Valve Controller

Basic Concepts and Need Traditional Test Methods Present Field Issues & Pains Digital Valve Controller to the Rescue SOV Health Monitoring Critical Evaluation of Solution Ras Gas (End User) Field Experience Evaluation of Solution Lesson Learned

Dike Passive protection layer

Emergency response layerPlant and

Emergency

Response

Process

Value Normal behaviour

Basic

Process

Control

System

Process control layer

Basic Concepts and Need Basic Concepts and Need

Operator

Intervention

Process control layer

Process alarm

Process

Shutdown

Trip level alarm

Safety

Instrumented

System

Safety layerEmergency

Shut Down

Prevent

Mitigate

x x

Relief valve,

Rupture diskActive protection layer

Safety Through Layers of Protection


50% failures are in Final

Control Element

Safety Instrumented SystemSafety Instrumented System

Basic Process Control SystemBasic Process Control System

Why Focus on the Final Element ?

Typically operate in one position - only move upon an emergency

Without mechanical movement, unreliability inherently increases

Frequent testing ensures valve availability upon Demand

Historically, inexpensive mechanical jammer or expensive labor intensive pneumatic testing methods are used


Why does the SIS Final Element account for 50% of failures?

Traditional Test MethodsTraditional Test Methods

Objective:

Reduce the Probability of Failure on Demand (PFD)

OFF LINE

Total Stroke

Process Down

ON LINE

Total StrokeBy-Pass In Service

Component Test

Partial Stroke

Solenoid (SOV)

Traditional test methods (pneumatic local panels, pin retainers, by-passing, etc.) are difficult

to operate and maintain with risks and high operational costs

Test Methodology

Present Field Issues & PainsPresent Field Issues & Pains

By-pass Valve

Pneumatic panels Mechanical retainers

Existing Test Methods Have High Costs

Logic Solver with Limit Switch

Digital Valve Controller to the RescueDigital Valve Controller to the Rescue

Simple Operation

Safety Audit

Ensures Valve Returns to Normal Position

Stroke Test Speed

Final Element Variation

Avoiding Accidental Closure Testing

Maintaining the Process

The Test objectives


Simple Operation

Safety Audit


Stroke Test Speed




The Test objectives

IMPROVE PFD

Reduce labor costs

Improve flexibility

Valve exercised to an

extent


Simple Operation

Safety Audit


Stroke Test Speed




The Test objectives

FIELDVUE Partial Stroke

is done on-line.


capable of being trimmed

to suit the process.


Simple Operation

Safety Audit


Stroke Test Speed




The Test objectives


Test avoid to casually

close the valve


Simple Operation

Safety Audit


Stroke Test Speed




The Test objectives


Test checks valve

movement and collects

travel and pressure data.


Simple Operation

Safety Audit


Stroke Test Speed




The Test objectives


could be start using a

simple push button


Simple Operation

Safety Audit


Stroke Test Speed




The Test objectives


test Speed can be varied

to Suit Process.


Simple Operation

Safety Audit


Stroke Test Speed




The Test objectives


Test takes valve to its

original position. If stuck,

will provide an alert.

Travel, pressure and

device condtion

monitored regularly.


Simple Operation

Safety Audit


Stroke Test Speed




The Test objectives


Test result stored in the

instrument.

ValveLink Audit Trail &

Documentation


Increase SIL Level

–Implementation of Partial Stroking on Final Control Element improves PFD to

achieve better SIL level

Validation of SIS

–Partial Stroking Validates the proper operation of the FCE

–Final Control Elements are commonly untested and are inherently unreliable

Maintains SIL Level

–Safely extend turnaround times

1/PFD(t)

Time

Test Interval

Without testing the PFD increases

PFDavg

The Influence of Partial Stroke testing


Partial Stroke “Valve Stuck” ALERT– If the valve does not move or sticks the Digital

Valve Controller STOPS the test– Valve returns to normal operation position and

alert is generated– The valve will not slam shut, causing a plant

“Spurious Trip” Trigger ALERT

– Captures valve movement or pressure changes– Automatically stores travel, pressure and

deviation data in the digital valve controller Supply Pressure ALERT

– Low supply pressure causes an alert

Unique Alert Features

http://www.riverrockchurch.com/images/stop.gif

Digital Valve Controller to the Rescue Digital Valve Controller to the Rescue

Any safety DEMAND overrides Partial Stroke Test Mode

Remote push button test returns to normal operation if:– partial stroke fails– push button is held outside 3-5 seconds

timeframe– Safety DEMAND occurs

Write Protection or ‘tamper-proof’ lock– Deters local unauthorized access to

calibration or configuration parameters

Specific Safeguards

http://www.riverrockchurch.com/images/stop.gif


Diagnose VALVE failures before they happen– Moves the SIS valve into

predictive maintenance regimes

– Additional diagnostics• Friction buildup• Valve shaft shear• Air supply pressure

deviations– Option to collect data during

a demand

Diagnostics


Diagnostics Enhancements


Companion Software Alert Log

Companion Software Audit Log

Companion Software Test DataBase

Intrument Alert Log

Last Partial Stroke Test Stored in the Intrument

Audit Documentation

Port B

Port A

Supply Pressure

0-20 mA Point To Point

Or 0-24 Volts Multidrop

From Logic Solver

0 mA or 0 Volt ESDV Closed

20 mA or 24 Volts ESDV Open

24 Volts DC From Logic Solver

Solenoid Valve Health MonitoringSolenoid Valve Health Monitoring

Port B

Port A

Supply Pressure



From Logic Solver



24 Volts DC from Logic Solver

Pressure Measurement Downstream SOV


Port B

Port A

Supply Pressure



From Logic Solver



24 Volts DC From Logic Solver

PULSE


Solenoid Valve Health MonitoringSolenoid Valve Health Monitoring The solenoid valve can be pulsed for a split second

– Long enough so that the solenoid vents (verification that the solenoid valve is functional)

– Short enough so that the actuator doesn’t bleed enough pressure to make the SIS valve move.

Critical Evaluation for Solution Critical Evaluation for Solution

PST Scripted avoiding Human Error Chances of Spurious Trip Reduced during PST Demand Overrides PST “Valve Stuck” Conditions Alerted Health Detection of “Final Element” SOV Health Monitoring Trigger Capability to Capture Safety Demand

Event Compare and Overlay Previous Results to Predict

Valve state Audit Documentation by Date and Time Stamp

Real Life Examples from Ras Gas - QatarReal Life Examples from Ras Gas - Qatar


IAMS Hardware Architecture in each SIH

IAMS W/S

Field Devices

Hart Mux

Field Devices

I/A DCS


AMS Valve Link Suite opened Via Pactware

Real Life Examples from Ras Gas - QatarReal Life Examples from Ras Gas - Qatar Digital Valve Controller access via AMS ValveLinkTM

Software


Full Stroke Test Initiated


FST signature taken and saved


Initiating a PST


PST signature taken and saved


SOV test setup


SOV test initiated from DCS


Response graph taken and saved


Valve Step Response Test


Benefits realized

FST and PST signatures taken during loop check FST signature compared with Factory signature

to study valve wear and tear PST performed with 10% valve movement PST – SOV test signature saved Diagnostic errors assist in identifying issues and

enable taking necessary corrective actions

Lesson LearnedLesson Learned

PST Recommendations / Learning– Use the valve signature to refine the partial stroke test

parameters, such as minimum pressure and upper operating pressure.

– When a valve fails to move, adjust the speed, minimum pressure or pause time.

– Map the HART bit of FIELDVUE Instruments to HOST for getting SOV Health

– Check travel deviation or pressure deviation alert point to ensure correct configuration, this can be the cause of failure.

– Enable pressure mode to reduce stroke time of valve.– Test more often than required to exercise valves if necessary.– Baseline data from initial valve signature is PRICELESS!!!

Business Results AchievedBusiness Results Achieved

Testing valve On Line Improves Reliability and Plant Availability

Trigger Data Available in case of “Safety Demand”

Continuous Health Monitoring of Final Element SOV Integrity Check Predictive Maintenance Improved PST Flexibility Reduced Labor Cost Compliance to Regulatory Requirements Integration to Logic Solver Possible

SummarySummary

Possible Issues on Final Element Testing Customer Needs and Requirements Field Issue and Concerns Possible Remedy – Digital solution Critical Evaluation of Solution Field Experience from Ras Gas

Where To Get More InformationWhere To Get More Information

IEC61508 – Functional Safety of Electrical / Electronic / Programmable Electronic Safety Related Systems

IEC61511 – Functional Safety – Safety Instrumented Systems for Process Industry Sector

ISA-TR84.00.02-2002 – Part 1 to 5 Control System Safety Evaluation & Reliability – W M Goble Safety Integrity Level Selection – Ed Marszal and Eric

Scharpf

sis “final element” diagnostics including the sov, using a digital valve controller

Education