HAZOPKey WordProcess Parameters and DeviationsBack

The hazard and operability tool (HAZOP)

What is HAZOP

The incidence of major industrial accidents around the world led to the innovation of various hazard identification techniques. Potential hazards and accidents for personnel, equipments and the environment can be recognized and prevented by special process. HAZOP, as a multidisciplinary team effort, was initially developed since 1960 for analysis of risk factors and safety measures and can be considered as one of the most accurate methods for identifying hazards in the various industries, especially chemical plants. In this approach, members use their innovation and initiative according to the basis of simulation and brain storming for identification of deviations from the main process design, their relative causes, effects and finally to present the method of control. To determine the deviation of parameters from the main aim of process design, guide words including temperature, pressure, conductivity, water flow, services failure, utilization of instruments and others are also applied. The qualitative matrix methods, as an instrument for adopting a logical decision, have also been used for determining of any relative risk level.

The special role of the HAZOP is hazard analysis of completely new operations. In these situations, traditional intuitive and experiential hazard ID procedures are especially weak. Because they are totally new, no one has any experience and there is little basis for intuition. This lack of experience hobbles tools such as the what if and scenario process tools which rely heavily on experienced operational personnel. The HAZOP deliberately maximizes structure and minimizes the need for experience to increase its usefulness in these novel situations.

As indicated above, the HAZOP should be considered when a completely new process or procedure is going to be undertaken. The issue should be one where there is significant risk because the HAZOP does demand significant expenditure of effort and may not be cost effective if used against low risk issues. The HAZOP is also useful when an operator or leader senses that “something is wrong” but they can’t identify it. The process of the HAZOP will dig very deep into the operation and is very likely to identify what the “something” is.

The HAZOP is certainly the most highly structured of the hazard ID procedures. It uses a standard set of guide terms which are then linked in every possible way with a tailored set of process terms (for example “flow”). The process terms are developed directly from the actual process or from the operations analysis. The two words together, for example “no” (a guide word) and “flow” (a process term) will describe a deviation. These are then evaluated to see if a meaningful hazard is indicated. If so, the hazard is entered in the hazard inventory for further evaluation. Because of its rigid process, the HAZOP is especially suitable for one person hazard ID efforts.

The HAZOP is highly structured, one could say “rigid,” and often quite timeconsuming. Nevertheless, in its special role, this tool works very effectively. It was selected by OSHA for inclusion in the set of six mandated procedures of the OSHA process safety standard.

Key Word

No: Negation of the design intent
More than: Quantitative increase
Less than: Quantitative decrease
As Well As: Qualitative increase
Part of: Qualitative decrease
Reverse: Logical opposite of the intent
Other than: Other than Complete substitution or the operational procedures occur abnormally

Process Parameters and Deviations

Pressure: More or low or no pressure
Flow: No flow, reversed flow, more & low flow
Temperature: More or low Temperature
Opacity: More & low opacity
Conductivity: More Conductivity
Pollution: Route blockage
Abnormal operation: Valve, pump and etc failure
Corrosion: More corrosion
Contaminants: Increase or decrease CL or oil in water
PH: More PH
Recovery: Low Recovery
Level: More or low Level
Concentration: More or low concentration