What HAZOP Is For

A hazard and operability study examines a process design systematically for deviations from design intent, using guidewords applied to process parameters at each node. It answers two questions for every credible deviation: what could cause it, and what would happen.

Prerequisites

HAZOP is a detailed study and it cannot be done on incomplete information. Before starting you need:

• Frozen P&IDs at a defined revision — studying drawings that change mid-study invalidates the work.
• Process description, heat and mass balance, and design intent for each line and vessel.
• Material safety data, relief philosophy, and the control and interlock schedule.
• Layout drawings and an understanding of what is nearby.

Hazard and operability

The second half of the name matters. A deviation that cannot hurt anyone but shuts the plant down for three days is a legitimate HAZOP finding, and operability findings are frequently where the study repays its cost.