ISA TR84.00.02-Part 2-2002

1.1 ISA-TR84.00.02-2002 – Part 2 is informative and does not contain any mandatory
requirements. This part of the technical report is intended to be used only after a thorough
understanding of ISA-TR84.00.02-2002 ? Part 1, which defines the overall scope. ISATR84.00.02-
2002 – Part 2 provides:

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

1.2 ISA-TR84.00.02-2002 – Part 2 provides one possible technique for calculating PFDavg
values for Safety Instrumented Functions (SIF) installed in accordance with ANSI/ISA-84.01-
1996, ?Application of Safety Instrumented Systems for the Process Industries?.

1.3 ISA-TR84.00.02-2002 – Part 2 provides the engineer(s) performing design for a SIF with a
relatively simple technique generally following the simplified equation approach for assessing the
capability of the designed SIF.

1.4 The procedures outlined in ISA-TR84.00.02-2002 – Part 2 provide the engineer with steps
to follow in estimating a mathematical value for PFDavg for typical configurations of SIF designed
according to ANSI/ISA-84.01-1996. This procedure is appropriate for SIL 1 and SIL 2 SIFs. This
procedure should not be used for SIL 3 SIFs unless the User has a thorough understanding of the
SIL Verification mathematics and fully understands the limitations of the simplified equations.

1.5 ISA-TR84.00.02-2002 – Part 2 does not cover modeling of external communications or
operator interfaces. The SIL analysis includes the SIF envelope as defined by ANSI/ISA-84.01-
1996 (see Figure I.2).