ISA-TR84.00.02-2002 - Part 4 is informative and does not contain any mandatory requirements. ISA-TR84.00.02-2002 - Part 4 is intended to be used only after a thorough understanding of ISA-TR84.00.02-2002 - Part 1. This technical report is intended to provide

a) technical guidance in Safety Integrity Level (SIL) Analysis;

b) ways to implement Safety Instrumented Functions (SIF) to achieve a specified SIL;

c) failure rates and failure modes of SIF components;

d) diagnostics, diagnostic coverage, covert faults, test intervals, redundancy of SIF components; and

e) tool(s) for SIL verification of SIF.

ISA-TR84.00.02-2002 - Part 4 provides one possible technique for calculating PFDavg values for Safety Instrumented Systems (SIS) installed in accordance with ANSI/ISA-84.01-1996, "Application of Safety Instrumented Systems for the Process Industries."

Persons using ISA-TR84.00.02-2002 - Part 4 require knowledge of the Markov modeling technique. The reader who is interested in learning more about Markov modeling is referred to:

• Evaluating Control Systems Reliability, Chapter 5;

• Reliability Evaluation of Engineering Systems, Chapter 8 and 9;

• Introduction to Reliability Engineering, Chapter 9;

• ISA-TR84.00.02-2002 - Part 5.

ISA-TR84.00.02-2002 - Part 4 introduces the reader to three examples, which explain the Markov theory and capabilities. These three examples make it possible to better understand the Base Example, which is also presented in ISA-TR84.00.02-2002 - Part 2 and ISA-TR84.00.02-2002 - Part 3.