The Definition of Process Hazard Analysis (PHA)

Definition of Process Hazard Analysis (PHA)

A process hazard analysis (PHA) is a structured, team-based review of a process that handles hazardous chemicals. It identifies potential deviations and failures, such as loss of cooling, overpressure or a leak, evaluates their causes and consequences and judges whether existing safeguards are adequate. The output is a set of recommendations to reduce risk.

Under OSHA's Process Safety Management standard, 29 CFR 1910.119(e), a PHA is required for covered processes, must be performed by a team that includes engineering and operating expertise and at least one person who knows the PHA method being used, and must be updated and revalidated at least every five years.

Key Facts About Process Hazard Analysis

• Accepted methods include HAZOP, what-if, checklist, what-if/checklist, FMEA and fault tree analysis.
• HAZOP is the most common method for complex processes and uses guidewords such as "more," "less" and "no" to find deviations.
• A PHA must address previous incidents with catastrophic potential, engineering and administrative controls, facility siting and human factors.
• Employers must resolve recommendations promptly and document the actions taken.
• PHAs are often paired with layer of protection analysis (LOPA) to assess safeguards.

Example of a Process Hazard Analysis

During a HAZOP of an ammonia refrigeration system, the team considers "more pressure" in a receiver. They find that a single relief valve vents to a location near an occupied building, so they recommend rerouting the discharge and adding a high-pressure alarm.

How to Conduct a PHA

1. Gather up-to-date process safety information, such as P&IDs and chemical data.
2. Assemble a multidisciplinary team with a trained facilitator.
3. Choose a method suited to the process complexity.
4. Work through each node or step, recording causes, consequences, safeguards and recommendations.
5. Track recommendations to closure and revalidate the PHA at least every five years or after major changes.

Related Terms

• Process Safety Management (PSM)
• Pre-Startup Safety Review (PSSR)
• Management of Change (MOC)
• Quantitative Risk Assessment
• Hazard Identification

Frequently Asked Questions: Process Hazard Analysis

Is a HAZOP the same as a PHA?

A HAZOP is one method of performing a PHA. PHA is the broader requirement, and teams can choose HAZOP, what-if, checklist or other recognized methods.

How often must a PHA be revalidated?

At least every five years under OSHA PSM, and sooner if significant changes or incidents warrant it.

Who should be on a PHA team?

Engineers, experienced operators, maintenance staff and a facilitator skilled in the method. Including operators is essential because they know how the process really runs.