The what-if analysis encourages a PrHA team to think of questions that begin with
"What-if." Through this questioning process, an experienced group of individuals
identify possible accident events, their consequences, and existing safety levels, then
suggest alternatives for risk reduction. The potential accidents identified are neither
ranked nor given quantitative implications.
The what-if analysis method may simply generate a list of questions and answers about
the process. However, it usually results in a tabular listing of hazardous situations, their
consequences, safety levels, and possible options for risk reduction.
4.2.2 Analysis Procedure
PREPARING FOR THE ANALYSIS.
The information needed for a what-if analysis includes
process descriptions, operating parameters, drawings, and operating procedures. All
information must be available to the PrHA team, if possible, in advance of the team
For analysis of an existing plant, the PrHA team may want to interview personnel
responsible for operations, maintenance, utilities, or other services, if they are not on the
PrHA team. In addition, if the analysis is performed offsite, the PrHA team should walk
through the facility to better understand its layout, construction, and operation. Thus,
visits and interviews should be scheduled before the analysis begins. Finally, some
preliminary what-if questions should be prepared to "seed" the team meetings. If the
analysis is an update of a previous PrHA, then questions listed in previous reports can be
used. For a new process or a first-time application, preliminary questions should be
developed by team members before the meetings, although additional questions
formulated during the meetings are essential. The cause-and-effect thought process used
in other types of analyses described in this section, such as HAZOP studies and FMEAs,
can help formulate questions.
PERFORMING THE ANALYSIS.
The scope of the study should be agreed upon by the team
members. The analysis meetings should begin with a basic explanation of the process by
operations staff who have overall facility and process knowledge, plus expertise relevant
to the team's area of investigation. The presentation should also describe the facility's
safety precautions, safety equipment, and health control procedures.
The meetings then revolve around potential safety issues identified by the analysts. The
analysts are encouraged to voice any potential safety concern in terms of questions that
begin with "what-if." However, any process safety concern can be voiced, even if it is
not phrased as a question. For example:
"I wonder what would happen if the wrong material was delivered."
"What if Pump Y seals begin to leak?"
"What if valve X fails open?"
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