HAZOP is short for Hazard and Operability Analysis. HAZOP is one of the most comprehensive yet most tedious of the hazard and operability identification methods. The underlying premise of HAZOP is that a team of experts can, more effectively than a single person, collectively use a systematic method to identify hazard and operability issues in any process or operation. A team of subject matter experts as mentioned in the PHA protocol is assembled to do a systematic evaluation of a process or operation using a guideword approach.
IDENTIFICATION OF RISK
Guidewords denote loss of intended function for a segment of a process or operation which is called a node. Guidewords are applied to every vessel, line, process step, and other process components. The team derives the nodes to examine at the outset of the study. Acceptable and unacceptable risk is employed as a decision-making tool to determine when a hazard or operation must be addressed further and to what degree it must be addressed. Individuals responsible for follow-up and timing of the response are assigned as part of the examination technique. Should unknown phenomena or conditions be discovered, the guidewords application is postponed until adequate descriptions of the phenomena are presented. The investigation of such unknowns is started immediately so resolution may become possible in the course of the study.
The deliverable from the HAZOP process is the identification of scenarios that require mitigation. As with any study of hazards, a HAZOP can be performed on new processes or operations or on existing ones. The outcomes may differ since it is at times more difficult to change processes or operations of a plant that is already built.
For each hazard or operability issue the causes and safeguards are examined. Safeguards are called Independent Protection Layers (IPL) in Layer of Protection Analysis (LOPA), but the meaning in HAZOP is the same. Safeguards are independent protection layers that are auditable and do not rely upon the process or operation controls to function. Also safeguards by definition will totally mitigate the hazard or operating issue relying on no other system interaction.