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Subramanian Ramanathan

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Subramanian Ramanathan

Subramanian Ramanathan

Senior Process Automation Engineer, Technology Improvement Department, EQUATE Petrochemical Company

Working as Senior Process Automation Engineer with M/s EQUATE Petrochemical Company, Kuwait. Have about 24+ years of experience in the field of Industrial Control Systems in Refinery / Petrochemicals. Certified Functional Safety Engineer by TUV Rheinland. Certified Lean Six Sigma Green Belt Project Leader. Certified Mentor (Level-5)by ILM, UK

Process Safety: Challenges in SIS instruments in an operating plant

Process Safety

Abstract: Safety Instrumented Functions (SIF) is one of the independent protection layers in LOPA. Some of the key attributes of SIF are Independence, Integrity, Reliability, Auditability, Change management etc. It is very critical to ensure the integrity level of SIF so that it always performs the required function on demand.

Proof testing serves as the primary purpose in the safety lifecycle to detect hidden dangerous (dangerous undetected) failures that can adversely affect the SIF performance and increase the probability of failure on demand (PFD).

Proof testing of SIS Instruments and valves pose challenges technically and administratively, especially with plants having longer turnaround intervals.

We will discuss some of the challenges we faced in EQUATE and how did we resolve them.

Advent of Smart instrumentation and digitization has paved the way to extend the proof test intervals. Some of these techniques include –

(a) Challenge: Proof testing of inline meters.
Difficult to get outage for dropping inline meter for proof testing. Local flow labs are not available and becomes costlier and risky affair to send out for calibration.
- Diagnosis with Visual inspection and Electronics check
- Advanced Diagnostics with Smart meter verification
Allows to extend the period for dropping of inline meter for proof testing

Discussion: User experience in maintaining inline instruments in SIS applications.

(b) Challenge: Proof testing of SIS valves – Partial Stroking.

For plants with longer run length it becomes difficult to release some of the SIS valves online for proof testing. Partial Stroking is one of the method to extend the proof test intervals for these valves.

Discussion: What is our experience with partial stroking? Is partial stroking always effective? Did we have any spurious trip during partial stroking ?

(c) Challenge: Proof testing of SIS valves – Higher MTBF valves.

Similar to partial stroking installing higher MTBF valves is becoming another solution to meet the required PFD.

Discussion: Can High MTBF valves installed for all applications (ex. Steam)? Are they really high MTBF valves? User experience with such valves

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