Hazard and Operability (HAZOP) studies are the gold standard for identifying potential hazards and operability problems in chemical and process facilities. A successful HAZOP relies on a multi-disciplinary team systematically examining the Piping and Instrumentation Diagrams (P&IDs) using a set of guide words.

The Role of Node Selection

To keep the HAZOP workshop efficient, the study facilitator must carefully divide the process into logical “nodes” (e.g., a feed line, separator vessel, or discharge line). A node represents a section of the process with clear boundaries where process parameters (flow, pressure, temperature) are expected to remain consistent.

Applying Guide Words & Deviations

For each node, the team applies combinations of process parameters and guide words to create deviations:

• No Flow / Reverse Flow: What happens if a control valve fails closed or a check valve leaks?
• More Pressure / Less Pressure: What if a cooling utility is lost, or a vacuum breaker fails?
• More Temperature: Can chemical runaway reactions occur?

The team then identifies the causes, consequences, existing safeguards (like alarms or interlocks), and recommends action items if the risk exceeds acceptable thresholds. Keeping a detailed record of the workshop in safety study reports ensures traceability and compliance with safety standards.