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