Method Process Safety

SIL Determination

In the Functional Safety Lifecycle, the next step after hazard and risk assessment is “allocation of safety functions to protection layers”. This is a process whereby suitable control measures are specified for each of the potential hazardous events found during the H&RA. This includes mechanical safeguards such as pressure relief valves, and also Safety Instrumented Systems (SIS).

The process of “allocation” is deciding which protective measures will be put in place, and how reliable they need to be. If a safety instrumented function (SIF) is to be used, the reliability required from it will be expressed as a safety integrity level, or SIL. There are four SILs – 1, 2, 3 and 4, which give increasing levels of reliability. The next task during “allocation” is to carry out “SIL determination”; in other words to decide what SIL is required from each SIF.

The most common technique used for SIL determination is layer of protection analysis (LOPA).  See “what is a LOPA?” for more information.

What =Method can do for you

  • Provide experienced LOPA study facilitators
  • Train and give mentoring support to aspiring LOPA study leaders

Process Safety Lifecycle

SIL Determination

Most recent projects for SIL Determination

LOPA of oil storage site (based on typicals approach)

Industry: Water + Waste
Topic: Layer of Protection Analysis (LOPA)

LOPA of continuous annealing process in steel industry

Industry: Mining / Metal / Cement
Topic: Layer of Protection Analysis (LOPA)

Review of earlier LOPA and PHR studies

Industry: Mining / Metal / Cement
Topic: Layer of Protection Analysis (LOPA)

Review of earlier LOPA in preparation for HSE intervention visit

Industry: Oil and Gas Onshore
Topic: Layer of Protection Analysis (LOPA)

HazOp of foam manufacturing process

Industry: Chemical
Topic: Layer of Protection Analysis (LOPA)

View all of our recent projects here

Initial Conceptual Design & Feasability Study

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