The hazards you need know: Process Hazard Analysis (PHA)
Process Hazard Analysis (PHA) is a method to evaluate and identify
credible hazardous scenarios. PHA is a
The process hazard analysis methodology selected must be appropriate to the complexity of the process and must identify, evaluate, and control the hazards involved in the process. One or more of the following methods is used, as appropriate, to determine and evaluate the hazards of the process being analyzed:
The PHA must address the following:
The PHA is performed by a team with expertise in engineering and process operations. The PHA team should include at least one employee who has experience with and knowledge of the process being evaluated. One member of the team must be knowledgeable in the specific analysis methods being used.
In performing a PHA, the first step is to define the purpose, scope and objectives of the study. The purpose defines why the PHA is being performed, e.g. to identify hazardous scenarios, to meet a regulatory requirement, etc. The scope defines the boundaries of the process being studied. The objectives define the expectations of the PHA results.
Next step is amass all the pertinent Process Safety Information (PSI) [see The more you know: Process Safety Information (PSI)] and appropriate Standard Operating Procedures. To plan the PHA, the process is divided into smaller manageable sections.
The PHA is conducted by identifying deviations from the design intent. The design intent includes values for operating conditions (e.g. temperature, pressure, flow, etc.), equipment (e.g. materials of construction, etc.) or external events (e.g. general loss of electrical power, etc.). There may be one or several causes of deviations. Causes are categorized as: 1.) Human Error, 2.) Equipment Failure or 3.) External Events. The team brainstorms and decides the credible causes of these deviations. If one of these deviations may occur, there are consequences that may result. The consequences may impact operability, quality or may be hazardous. Each scenario (deviation/cause consequence combination) is evaluated further, particularly the hazardous scenarios. In evaluating these scenarios, existing safeguards are documented that prevent, detect or mitigate the scenarios. The team then determines if a recommendation is appropriate to prevent, detect or mitigate the scenarios.
By: Mike McCue, Process Safety Columnist for Cheresources.com
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