ISA TR84.00.02

ISA-TR84.00.02-2015 is informative and does not contain anymandatory clauses. ISA-TR84.00.02 is intended for use by those witha thorough understanding of ISA-84.00.01-2004 Part 1. This documentassumes that a SIS is required. It does not provide guidance on thehazard and risk assessment used to identify the need for a SIS. Theuser is referred to ISA-84.00.01-2004 Part 3, and CCPS’s HazardEvaluation Procedures and Layers of ProtectionAnalysis:Simplified Risk Assessment for guidance onassigning the SIL.

Prior to proceeding with use of ISA-TR84.00.02-2015, the hazardsand risk assessment and the allocation of safety functions toprotection layers should be completed and the following informationprovided:

At least one SIF is required

The functional requirements of the SIF

The integrity requirements of the SIF

ISA-TR84.00.02-2015 provides guidance on different issues thatimpact SIL verification:

Assessing random and systematic failures, classifying failuremodes, and estimating the failure rates for individual devices ofan SIF;

Assessing the impact of diagnostic and mechanical integritychoices on the performance of the SIF and its devices;

Assessing and estimating the potential for common cause andcommon mode failures; and Verifying that the SIF achieves aspecified SIL and spurious trip rate.

ISA-TR84.00.02 provides guidance on techniques for evaluatingthe following:

Average probability of failure on demand for low demand modeSpurious trip rate

There are four topics that are being held until the nextrevision of ISA-TR84.00.02. Until then, the reader should refer toISO 12489 for appropriate methodologies.

• Modeling of continuous and high demand mode systems

• Understanding proof test effectiveness and how this is addressedby design and mechanical integrity practices

• Understanding how to model common cause and systematiccontribution to the failure of subsystems and systems and to theoccurrence of the hazardous event

• Expanding the discussion of common cause and systematic error toaddress these issues across the entire lifecycle

Edition:

15

Published:

09/08/2015

Number of Pages:

138

File Size:

1 file , 2.9 MB