Table 4.25 Minimal Cutset Documentation

DOE-HDBK-1100-2004

Table 4.25 Minimal Cutset Documentation

TOP EVENT:

Date:

Page:

CUTSET

CONSEQUENCE

SCENARIO #

COMMENTS

Time and cost requirements for a FTA depend on the complexity of the process being analyzed

and the level of resolution. With an experienced team, modelling a single top event involving a

simple process could require one day or less. Complex processes or large systems with many

potential accident events could require many weeks or months, even with an experienced

analysis team. Table 4.26 presents estimates of the time needed to perform a PrHA using the

FTA method.

Table 4.26 Time Estimates for Using the Fault Tree Analysis Method

MODEL

QUALITATIVE

SCOPE

PREPARATION

DOCUMENTATION

CONSTRUCTION

EVALUATION

Simple/Small

1 to 3 days

3 to 6 days

2 to 4 days

3 to 5 days

System

4 to 6 days

2 to 3 weeks

1 to 4 weeks

3 to 5 weeks

Complex/Large

Process

Source: CCPS, 1992.

4.6.4 Limitations of Fault Tree Analyses

FTA is designed to develop the logical combinations of failures required to cause a given event

to occur. It is not an efficient, straightforward, practical method for identifying the hazards

present in most systems or processes, nor does it necessarily promote a more practical

understanding of the hazards, which is the intent of the PSM Rule.

4.6.5 Example Fault Tree Analyses

Partial FTAs for the example processes described in Section 4.0 are shown in Figures 4.3

and 4.4.