What is a Process Hazard Analysis (PHA), and when should we do one?

In IEC 61511’s safety lifecycle, risk assessment is a foundational early step. A PHA, required by OSHA 1910.119, is part of the first stage of the safety lifecycle and is a structured method for identifying process hazards, understanding risk, and defining safeguards. HAZOP (Hazard and Operability Study) is one of the most common PHA techniques but other methods include Checklists, What-Ifs, HazIDs, and LOPAs. (Layers of Protection Analysis). PHAs are typically performed for new projects, major modifications (management of change), and legacy systems—then revalidated every five (5) years to confirm safeguards still match real plant conditions.