ABSTRACT
The material in this chapter should help a design team perform a preliminary hazard analysis (PHA). PHA is a design tool that helps engineers identify and deal with hazards in the initial stages of design. Performing a PHA allows engineers and management to better recognize and correct the hazards associated with designs for plants, units, and/ or equipment. For an overview of a PHA, see Figure 4.1. Specifically, a PHA is a qualitative analysis performed in the earliest stages of design primarily to:
1. Identify all potential hazards and accidental events that may lead to an accident
2. Rank the identified accidental events according to their severity 3. Identify required hazard controls and follow-up actions 4. Formulate appropriate measures to deal with hazards
These four expectations may be also identified and rearranged in an order of mitigation goals:
1. Eliminate hazard 2. Control hazard with design methods 3. Incorporate safety devices to control hazard 4. Provide warning devices if hazard materializes 5. Provide procedures and training for operators
Other approaches may also be used to evaluate hazards. The most common ones are (1) rapid risk ranking and (2) hazard identification (HAZID). Although a PHA is conducted very early in the design, the subsequent benefits warrant the effort. The three major benefits are:
1. Product safety is ensured. 2. Modifications are less expensive and easier to implement in early
design stages. 3. Design time is decreased because “surprises” are minimized.
