Staffing Needs and Time

DOE-HDBK-1100-2004

example, a traditional checklist is, by definition, based on the process experience the

author accumulates from various sources. The checklist is likely to provide incomplete

insights into the design, procedural, and operating features necessary for a safe process.

The what-if part of the analysis uses a team's creativity and experience to brainstorm

potential accident scenarios. However, because the what-if analysis method is usually

not as detailed, systematic, or thorough as some of the more regimented approaches (e.g.,

HAZOP study, FMEA), use of a checklist permits the PrHA team to fill in any gaps in

their thought process.

4.3.4 Staffing Needs and Time

The number of individuals needed depends upon the complexity of the process and, to

some extent, the stage at which the process is being evaluated. Normally, a PrHA using

this method requires fewer people and shorter meetings than does a more structured

method such as a HAZOP study. Estimates of the time needed to perform a PrHA using

the what-if/checklist analysis method are shown in Table 4.11.

Table 4.11 Approximate What-If/Checklist Analysis Time Requirements

PREPARATION(a)

DOCUMENTATION(a)

SCOPE

EVALUATION

Simple/Small

System

6 to 12 hours

4 to 8 hours

Complex/Large

Process

1 to 3 days

4 to 7 days

1 to 3 weeks

(a) Primarily, team leader and scribe.

Source: CCPS, 1992.

4.3.5 Example What-If/Checklist Analyses

To fill in the gaps in the standard what-if analyses given as examples in Section 4.2, the

checklists used for the examples in Section 4.1 were used here. The resulting what-

if/checklist analyses for the two example processes are shown in Tables 4.12 and 4.13.

The tables show only additional scenarios identified by applying the checklist.

4.4

Hazard and Operability Study

The HAZOP study was developed to identify hazards in process plants and to identify

operability problems that, although not hazardous, could compromise a plant's

productivity. The basic concept behind HAZOP studies is that processes work well when

operating under design conditions. When deviations from the process design conditions

occur, operability problems and accidents can occur. The HAZOP study method uses

guide words to assist the analysis team in considering the causes and consequences of