Staffing Needs and Time - DOE-HDBK-1100-20040059

DOE-HDBK-1100-2004

In the first example, the guide word "No" combined with the process parameter "Flow" results

in the deviation "No flow." Considering this deviation, the study team agrees on its possible

causes (e.g., operator error causes block in pump), the consequences of the deviation (e.g., line

rupture due to high pressure), and the safety levels which prevent the cause from leading to the

consequence (e.g., pressure relief valve on pump discharge line). The consequence specified

presupposes the failure of active protection systems (e.g., relief valves, process trip signals). If

the causes and consequences are significant, and the safety levels are inadequate, the team may

recommend a follow-up action. In some cases, the team may identify a deviation with a realistic

cause but unknown consequences (e.g., an unknown reaction product) and recommend follow-

up studies to determine the potential consequences.

The HAZOP study should be performed in a deliberate, systematic manner to reduce the

possibility of omissions. Within a study node, all deviations associated with a given process

parameter should be analyzed before the next process parameter is considered. All of the

deviations for a given study node should be analyzed before the team proceeds to the next node.

DOCUMENTING THE RESULTS.

The documentation of a HAZOP study is a systematic and

consistent tabulation of the effects of process deviations. The study generates narratives about

the normal operating conditions and analysis boundary conditions for each equipment item. In

addition, it provides a list of potential actions that should be evaluated. Table 4.16 is an

example of a HAZOP study worksheet. A typical HAZOP study report should include a brief

system description, a list of drawings or equipment analyzed, the design intents, the HAZOP

study tables, and a list of actions items.

4.4.3 Staffing Needs and Time

Staff requirements for HAZOP studies vary with the size and complexity of the process. Time

and cost are proportional to the size of the process being analyzed and the experience of the

study leader and team members. Table 4.17 presents estimates of the time needed to perform a

PrHA using the HAZOP study method (CCPS, 1992). Study sessions should be limited to 3

consecutive days.

4.4.4 Limitations of the Hazard and Operability Study

The primary limitation of a HAZOP study is the length of time required to perform it. Because

the study is designed to provide a complete analysis, study sessions can be intensive and tiring.

HAZOP studies typically do not look at occupational hazards (e.g., electrical equipment,

rotating equipment, hot surfaces) or chronic hazards (e.g., chronic chemical exposure, noise,

heat stress).