SIL Assessment using LOPA

SIL Assessment

PetroRisk will facilitate the SIL Assessment process, by providing an experienced SIL Chairman and Scribe.  There are two steps in this process:

  • Identifying the events which may require a SIS
  • Assigning the SIL based upon the SIL Assessment Methodology LOPA (Layers of Protection Analysis)

Identifying the events which may require a SIS

A HAZOP must have been conducted before this assessment.  The documentation from the HAZOP analysis, the process P&IDs and the Cause and Effects Diagrams will serve as the basis for the identification of the Safety Instrumented Functions (SIF) associated with the process. PetroRisk will develop the list of SIFs with the client, to be studied in the SIL Assignment workshop.

SIL Assessment

Once the SIS functions have been identified, the SIL for each can be assigned.  A small team up to 8 people (maximum) will meet to consider the risk associated with each event.  This team will comprise COMPANY and other specialists. Through the application of the SIL Assessment method chosen (LOPA), the SIL level will be assigned in line with the guidelines of IEC-61508 & IEC-61511 Part 3, Annex F.

PetroRisk will facilitate this meeting and generate a report that thoroughly documents the basis for each SIL Assessment.

Prior to the SIL Workshop, COMPANY will provide PetroRisk the set of documents to be reviewed and referred to during the sessions which shall consist of, but not be limited to:

  • Design Basis Memorandum
  • Process and Instrumentation Diagrams (P&IDs)
  • Process Flow Diagram (PFDs)
  • HAZOP worksheets
  • Cause and Effects Charts
  • List of SIFs to be studied
  • Any other Logic Diagram or IPF details

COMPANY will provide all required facilities for the SIL workshop, including a projector for displaying the worksheets as they are populated.  COMPANY is to ensure the SIL package containing all necessary drawings and marker pens are distributed to participants in the session.

The SIL assessment by LOPA will be undertaken using Exida’s ExSILentia software.

Output: SIL Assessment report