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PHA Methodologies – When To Use Each

July 3rd, 2023 by Taylor Jones

According to the Occupational Safety and Health Administration (OSHA), a Process Hazard Analysis (PHA) is defined as “A systematic effort designed to identify and analyze hazards associated with the processing or handling of highly hazardous materials; and a method to provide information which will help workers and employers in making decisions that will improve safety.”

A PHA analyzes the potential causes and consequences of fires, explosions, and releases of toxic chemicals the equipment, instrumentation, human actions, and other factors which might affect the process. There are several common methodologies used to complete PHAs:

• Hazard and Operability (HAZOP) Study: One of them most common, a HAZOP the systematic assessment tool used to evaluate an industrial process for potential deviations by breaking it in small, manageable steps. A HAZOP may be best for more experienced groups. HAZOPs conduct a PHA by looking at guide words and parameters of the process including High/Low Flow, High/Low Pressure, High/Low Temperature, and other process parameters. From here, consequences of exceeding parameters are determined and the likelihood and severity of the consequences are found, creating risk scores. Finally, the team identifies the safeguards in place to prevent the consequences and recommendations are created to reduce the risk scores.
• What If Checklist: A What-If Checklist may be best for groups that have never completed a PHA or want to start simply. What-If is a structured brainstorming session about what could go wrong within an operational process from human error to equipment failures. The goal is to identify hazard scenarios and ensure safeguards are in place to prevent these scenarios from occurring. During the what if checklist questions are asked to determine what issues could happen during the life of the process, the team determines what consequences could occur because of those issues, safeguards to protect against the issues are identified, the team discusses the likelihood and severity of the consequences, and recommendations on how to reduce the likelihood of the issues.
• Failure Mode Effects Analysis (FMEA): An FMEA is a commonly used method in Quality departments that is very similar to a HAZOP. FMEA helps evaluate design failures by first identifying “failure modes” or how an operation would play out given potential failures. Then an effects analysis is conducted to outline outcomes for each failure mode.
• Layer of Protection Analysis (LOPA): defined by the Center for Chemical Process Safety as a method that analyzes independent incident scenarios to compare a scenario risk estimate to its risk criteria. A LOPA may be necessary if there are multiple catastrophic consequences of the process so the company can identify further safeguards to their process. LOPA helps companies determine how many independent protection layers are needed, as well as how much risk reduction each layer needs to provide, for the scenario to fall within the company’s tolerance for risk.

Taylor Jones, EIT, Project Consultant at HRP Associates, Inc.