Consider Facility Siting

DOE-HDBK-1100-2004

explosions or toxic releases, but does not study the severity of the top event's consequences. To

fully comply with the PSM Rule, it may be necessary to include in the PrHA report an analysis

of mitigation systems that are in place to reduce the severity of consequences of accidents.

3.2.5 Consider Facility Siting

The PSM Rule requires facility siting to be addressed in all PrHAs. For a new facility, fulfilling

this requirement can involve an analysis of plant layout and spacing between process units.

However, most PrHAs are performed on existing facilities. For existing facilities, PrHAs should

include the severity of consequences of potential accidents involving co-located workers and

adjacent facilities. Shielding, barricades, escape routes, control room location, and control room

design for employees involved in the operation of the process should also be discussed. In

addition, the impacts of vehicular traffic and of adjacent operations should be considered.

It may be desirable to discuss facility siting issues at the beginning of the PrHA sessions. As a

minimum, comments and assumptions about siting and plant layout can be included in the PrHA

analysis documentation, such as on HAZOP study worksheets. Table 3.2 provides a sample

checklist for worker/co-located worker exposures. A sample checklist for facility siting issues is

presented in Table 3.3.

3.2.6 Address Human Factors

When operator error/response is involved in an initiating event or when operator action

influences the level of protection, the PrHA team should discuss the circumstances under which

failures might occur. For example, for a cylinder hook-up operation, an operator might connect

the wrong cylinders. Uncovering the underlying causes of the error may lead to discussions of

cylinder labeling, physical layout of the cylinder bay, or interchangeable threaded connections.

These discussions should identify situations likely to lead to errors and the corrective actions

that can be taken.

Table 3.4 presents a list of human factors that may positively or negatively influence the

likelihood of operator error. This list may be used prior to, and/or during the analysis. In

addition, the PrHA team may determine that human factors problems are of sufficient

importance or complexity to require the assistance of a human factors specialist.

3.2.7 Evaluate Incident Effects

Quantitative evaluation of the severity of accident consequences is not required. However, the

PrHA team must qualitatively evaluate the range of the possible employee safety and health

effects. Such evaluation is generally made by discussing the severity of consequences of each

scenario (see Section 4).