This paper considers changes in Hazard and Operability (HAZOP) methodology since its introduction 40 years ago. HAZOP is a team-based activity for identifying process hazards and operability concerns. The intent is to review process design and identify hazardous deviations through facilitated application of guidewords, then evaluate safeguards and (where necessary) recommend improvements.
HAZOP’s origins are well documented, originally in the UK at Imperial Chemical Industries (ICI) and Chemical Industries Association (CIA) and then codified within the Institution of Chemical Engineers (IChemE) guidelines. The technique was subsequently adopted by the American Institute of Chemical Engineers (AIChE) and endorsed within US Occupational Safety and Health Administration (OSHA) Process Safety Management Regulations, where HAZOP is identified as a preferred method of Process Hazard Analysis (PHA).
The original HAZOP concept was comparatively simple, comprising structured brainstorming of high-hazard processes within the chemical industry. HAZOP activities were generally in-house, operator-led and largely collaborative team activities. Discussion and recording of identified hazards was often ‘by exception’, with only notable issues identified and recorded.
By contrast, HAZOP now has near-universal application within process, energy, transport and utilities industries. HAZOP methodology and content have also increased significantly. HAZOP is now typically independently facilitated with multiple participant stakeholders (e.g. project or process owner, operator, contractor, consultant, etc.). Discussion and full recording, based on a complete set of guide words, is universally required.
Another significant change is the extent to which risk assessment is applied within HAZOP. Starting with simple classification of findings and recommendations, this methodology has progressed through generalised risk ranking of all HAZOP recommendations and latterly to using risk-based decision criteria.
Where dedicated Safety Instrumented Systems (SIS) are included for process safeguarding, their functional integrity is also studied more formally using Layer of Protection Analysis (LOPA) and Safety Integrity Level (SIL) classification. These activities are often performed in conjunction with, or immediately following, a HAZOP.
Other practical and logistical challenges result from the introduction of computer and projection technology and bespoke HAZOP software applications. Although these bring undoubted real and potential benefits in terms of transparency, consistency and team engagement, they can become a distraction if not properly managed.
Finally, the increasing demands of methodology, stakeholder engagement and embedded risk analysis are not always recognised within project schedules. This can lead to commercial and technical pressures and conflicts. Careful balancing of technical, quality and commercial goals has therefore become increasingly important.
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