This document discusses using a digital valve controller to improve diagnostics and testing of safety instrumented system (SIS) final control elements. Traditional testing methods are difficult and costly. A digital valve controller allows for partial stroke testing online which improves reliability while reducing costs. It also enables solenoid valve health monitoring and diagnostic capabilities. Field experience from Ras Gas in Qatar demonstrated benefits like reduced labor and improved predictive maintenance through signature-based testing and continuous monitoring.

1. SIS “Final Element” Diagnostics
Including The SOV, Using A
Digital Valve Controller
C B Chakradhaar– Instrument & Control Specialist
Riyaz Ali – Director Instruments

2. Presenters
 C B Chakradhaar - I & C Specialist
 Riyaz Ali – CFSP

3. Introduction
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

4. Dike Passive protection layer
Emergency response layer
Plant and
Emergency
Response
Process
Value
Normal behaviour
Basic
Process
Control
System
Process control layer
Basic Concepts and Need
Operator
Intervention
Process control layer
Process alarm
Process
Shutdown
Trip level alarm
Safety
Instrumented
System
Safety layer
Emergency
Shut Down
Prevent
Mitigate
x x
Relief valve,
Rupture disk Active protection layer
Safety Through Layers of Protection

5. Basic Concepts and Need
50% failures are in
Final Control Element
Safety Instrumented System
Basic Process Control
System
Why Focus on the Final Element ?

6.  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
Basic Concepts and Need
Why does the SIS Final Element account for 50% of failures?

7. Traditional Test Methods
 Objective:
Reduce the Probability of Failure on Demand (PFD)
OFF LINE
Total Stroke
Process Down
ON LINE
Total Stroke
By-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

8. Present Field Issues & Pains
By-pass Valve
Pneumatic panels Mechanical retainers
Existing Test Methods Have High Costs
Logic Solver with Limit Switch

9. Digital 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

10. Digital 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
IMPROVE PFD
Reduce labor costs
Improve flexibility
Valve exercised to an
extent

11. Digital 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
FIELDVUE Partial
Stroke is done on-line.
FIELDVUE Partial
Stroke capable of
being trimmed to suit
the process.

12. Digital 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
FIELDVUE Partial
Stroke Test avoid to
casually close the
valve

13. Digital 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
FIELDVUE Partial
Stroke Test checks
valve movement and
collects travel and
pressure data.

14. Digital 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
FIELDVUE Partial
Stroke could be start
using a simple push
button

15. Digital 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
FIELDVUE Partial
Stroke test Speed can
be varied to Suit
Process.

16. Digital 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
FIELDVUE Partial
Stroke Test takes
valve to its original
position. If stuck, will
provide an alert.
Travel, pressure and
device condtion
monitored regularly.

17. Digital 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
FIELDVUE Partial
Stroke Test result
stored in the
instrument.
ValveLink Audit Trail &
Documentation

18. Digital Valve Controller to the
Rescue
 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

19. Digital Valve Controller to the Rescue
 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

20. 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

21. Digital Valve Controller to the Rescue
 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

22. Digital Valve Controller to the
Rescue
Diagnostics Enhancements

23. Digital Valve Controller to the Rescue
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

24. 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 Monitoring

25. 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
Pressure Measurement Downstream
SOV
Solenoid Valve Health Monitoring

26. 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
PULSE
Solenoid Valve Health Monitoring

27. Solenoid 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.

28. 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

29. Real Life Examples from Ras Gas - Qatar

30. Real Life Examples from Ras Gas - Qatar
IAMS Hardware Architecture in each SIH
IAMS W/S
Field Devices
Hart Mux
Field Devices
I/A DCS

31. Real Life Examples from Ras Gas - Qatar
AMS Valve Link Suite opened Via Pactware

32. Real Life Examples from Ras Gas - Qatar
Digital Valve Controller access via AMS
ValveLinkTM Software

33. Real Life Examples from Ras Gas - Qatar
Full Stroke Test Initiated

34. Real Life Examples from Ras Gas - Qatar
FST signature taken and saved

35. Real Life Examples from Ras Gas - Qatar
Initiating a PST

36. Real Life Examples from Ras Gas - Qatar
PST signature taken and saved

37. Real Life Examples from Ras Gas - Qatar
SOV test setup

38. Real Life Examples from Ras Gas - Qatar
SOV test initiated from DCS

39. Real Life Examples from Ras Gas - Qatar
Response graph taken and saved

40. Real Life Examples from Ras Gas - Qatar
Valve Step Response Test

41. Real Life Examples from Ras Gas - Qatar
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

42. Lesson 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!!!

43. Business 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

44. Summary
 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

45. Where 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