Project Flow - C. HAZOP/SIF Review – SIL Assignment

IEC 61511 and ANSI/ISA S84.01-2003, as well as Regulatory Agencies, require that a process hazard analysis (PHA) be performed to identify potential hazards in the operation of a process unit.

The PHA is a methodical examination of the process design that involves the participation of a multidisciplinary team to identify potential hazards and operability problems that could result in undesired consequences with adverse impact on personnel, equipment or the environment. The initial "process" PHA is normally performed by the plant operator in conjunction with the process licensor or basic design team.

The process design drawings and narratives together with the P&ID’s and the PHA documents, form the basis for the identification of the safety instrumented functions (SIF) required to mitigate the potential hazards.

Premier Safety Consulting (PSC) provides industry experts in the review process of the PHA results and allocation of Safety Instrumented Functions (SIF), leading to the assignment of a target Safety Integrity Level (SIL) for each SIF.

Safety integrity is a measure of the likelihood that the SIF will achieve the specified safety function.

A PSC senior consultant performs the role of facilitator and provides guidance to a multidisciplinary team consisting of plant experts in the areas of process, operations, safety, maintenance, instrumentation and electrical.

The standards do not mandate any specific method for assigning the target SIL rating, but do provide examples of industry-recognized techniques. The PSC facilitator reviews the different methodologies (Risk Matrix, Risk Graph, LOPA, Semi-quantitative, etc) and applicability to each situation, leading to a consensus on the techniques to be utilized.

PSC provides further guidance in the approach to aligning the SIL assignment method selected with the corporate risk tolerance criteria. Where necessary, the ALARP risk tolerance principle is discussed and taken in to account.

The multidisciplinary team reviews every SIF, and with PSC guidance, a SIL rating is assigned to each safety instrumented function.

SILassign™ software tool-set is made available for the target SIL determination process. The final report reflects the assumptions made with regards to potential hazards likelihood, consequence and risk tolerance criteria in conjunction with the target SIL assigned to each independent SIF.

Premier Safety Consulting reports are recognized world wide for their integrity and professionalism by plant operators, regulators and risk insurers.

HAZOP/SIF Review – SIL Assignment