Safety Integrity Level (SIL) Case Study for IOCL-Gujarat Refinery

Gujarat Refinery is the Mother Industry of Vadodara, catering to the increasing energy demand due to fast-paced development and economic prosperity of the vibrant state of Gujarat. Safety Integrity Level (SIL) study has been carried out by iFluids Engineering for 18 Operating Units which includes Atmospheric Distillation Unit-1, Au-I -Atmospheric Distillation Unit-2, Atmospheric Distillation Unit-3, Atmospheric Distillation Unit-4, Bitumen Blowing Unit, Catalytic Reforming Unit, Delayed Coker Unit, Fluidised Catalytic Cracking Unit, Food Grade Hexane, Feed Preparation Unit, Feed Preparation Unit -2, Hydrogen Generation Unit, Methyl Tertiary Butyl Ether, Sulphur Recovery Unit-3, Sour Water Stripper 1, Sour Water Stripper 2, Vis –Breaker Unit, Vacuum Distillation Unit.

Layer of Protection Analysis (LOPA) method is used for the risk assessment that determines the SIL value associated with the protective instruments, that mitigates the same risks for which the instrumented function exists. 

Safety Integrity Level, usually referred to as “SIL” or “SIL level”, is a unit of measurement for quantifying risk reduction. Layers of Protection Analysis (LOPA) is a powerful analytical tool for assessing the adequacy of protection layers used to mitigate process risk. LOPA builds upon well-known process hazard analysis techniques, applying semi-quantitative measures to the evaluation of frequency of potential incidents and the probability of failure of the protection layers. It is a simple tool and identifies the Independent Layer of Protection to be considered for risk Classification and risk reduction.

SIL identifies all the hazards of a process and estimates the risks inherently involved and determines if that risk is tolerable/acceptable. All instruments/devices in a SIF loop must work together to meet the SIL requirement. A SIL Assessment or SIL Study is a formal documented method that enables a team of suitably qualified and experienced engineers to determine a SIL level, based on relevant criteria and analyses for any particular control or safety loop.

As per the scope of this SIL Classification study, safety instrumented functions (SIFs) were identified in the P&IDs and the C&E matrices relevant to the project, having the main objective to:

  • Identify potential risks to the people, environment and assets due to failure of Safety Related Systems and associated facilities in the plant to operate on demand.
  • Define the basic performance requirements of all Safety Related Instrumented systems to reduce the above risks to “As Low as Reasonably Practicable”.