HAZOP Deviation Matrix: Find Process Deviations Systematically
What is HAZOP?
HAZOP (Hazard and Operability Analysis) identifies process deviations by systematically combining guide words with process parameters, such as more flow, high pressure or reverse temperature. For each deviation it analyzes causes, consequences and existing protections, assesses risk and proposes recommendations. It is the most widely used hazard analysis method in the chemical and process industries and follows IEC 61882. Analysis records should be kept and linked to change management so modified nodes are re-evaluated.
When to Use It
Use it during the design phase of new plants, for revalidation after process modifications, in incident investigation and safety reviews, and as the prerequisite analysis for LOPA and SIL rating. The depth and frequency of analysis should match the risk level of the unit to avoid both over-analysis and missed deviations.
How to Use It (Step by Step)
Divide the P&ID into nodes, then let the tool expand the deviation matrix by combining guide words (no, more, less, reverse, phase change, etc.) with parameters (flow, pressure, temperature, level, concentration, composition, etc.). For each deviation record the cause, consequence, existing protection, risk level and recommendation, then track recommended actions to closure.
Key Formulas / Example
An example matrix cell: Parameter Flow × guide word No gives "No flow"; More gives "High flow"; Less gives "Low flow"; Reverse gives "Reverse flow". A HAZOP team should include process, equipment, instrumentation, operations and safety specialists, led by a qualified facilitator. Deviations that recur should be linked to root cause analysis so the same risk does not reappear.