PT Notes
Addressing Weaknesses in HAZOP Studies
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Most practitioners view the Hazard and Operability (HAZOP) study as the most thorough and comprehensive of the traditional process hazard analysis (PHA) methods. On face value, the method appears to offer a thorough and comprehensive identification of hazard scenarios. However, while theoretically it may be capable of achieving this goal, practically it is unlikely to do so for various reasons. Despite its popularity, the HAZOP study suffers from numerous inherent weaknesses, many of which are not generally recognized.
Weaknesses include those related to:
- Coupling of vulnerabilities of the HAZOP method with the human limitations of practitioners
- Deceptive sense of security provided by the apparent structure of the HAZOP study
- Counterintuitive inductive / deductive starting point for scenario identification
- Multiple aspects of design intent that must be considered for a complete study and the difficulty of identifying them
- Meaning and identification of parameters
- Difficulty in identifying important deviations
- Consideration of multiple, compound and repeated deviations
- Propagation of deviations and the focus on deviations
- Limitations of guide words
- Lack of guidance on the identification of causes of deviations and initiating events
- Difficulty in focusing on specific hazard types
- Challenges in addressing chemical reactivity hazards and process changes
Knowledge of these weaknesses can assist study teams in compensating for them to the extent possible and can help guide the development of improved PHA methods.
These and other issues in the performance of HAZOP studies, together with guidance on addressing them, are covered in the paper:
A critique of the Hazard and Operability (HAZOP) study, Journal of Loss Prevention in the Process Industries, Vol. 33, pages 52–58, 2015.
The paper can be accessed for free on ScienceDirect until January 11, 2015 by clicking on the link below. No sign up or registration is needed.
http://www.sciencedirect.com/science/article/pii/S0950423014001983
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