The technique is based on breaking the overall complex design of the process into a number of simpler sections called nodes which are then individually reviewed.
The HAZOP technique is qualitative and aims to stimulate the imagination of participants to identify potential hazards and operability problems.
Recently, it has been used in domains other than or only loosely related to the process industries, namely: software applications including programmable electronic systems; software and code development; systems involving the movement of people by transport modes such as road, rail, and air; assessing administrative procedures in different industries; assessing medical devices; etc.
In 1974 a one-week safety course including this procedure was offered by the Institution of Chemical Engineers (IChemE) at Teesside Polytechnic.
[2] By this time, hazard and operability studies had become an expected part of chemical engineering degree courses in the UK.
[2] Nowadays, regulators and the process industry at large (including operators and contractors) consider HAZOP a strictly necessary step of project development, at the very least during the detailed design phase.
For each node, in turn, the HAZOP team uses a list of standardized guidewords and process parameters to identify potential deviations from the design intent.
For a medium-sized chemical plant, where the total number of items to be considered is around 1200 pieces of equipment and piping, about 40 such meetings would be needed.
To prompt discussion, or to ensure completeness, appropriate process parameters are considered in turn, which apply to the design intent.
The IEC standard notes guidewords should be chosen that are appropriate to the study, neither too specific (limiting ideas and discussion) nor too general (allowing loss of focus).
In a large process there will be many HAZOP meetings and the individuals within the team may change, as different specialists and deputies will be required for the various roles.
Specialist software is now available from several suppliers to support the recording of meeting minutes and tracking the completion of recommended actions.