Hazop
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Hazop is an abbreviation for a Hazard and Operability Study. Originally developed for use at manufacturing facilities such as oil refineries, offshore oil platforms, petrochemical and chemical plants, natural gas processing plants and power plants, its application has expanded to other areas as well. It is a systematic method for examining complex facilites or processes to find actual or potentially hazardous procedures and operations so that they may be eliminated or mitigated. Hazop Studies are performed by a team consisting of plant operators, engineers, managers and others, some of whom should be intimately familiar with the facility being studied.
The origins of Hazop Studies are in the British chemical industry and its adoption was driven by the 1974 Flixborough explosion, where lack of a systematic review of modifications by appropriately qualified personnel was identified as a contributing factor.
[edit] Methodology
The methodology may be applied to any process or project although most practitioners and expertise originate in the chemical and offshore industries. Depending on the application, a Hazop uses guide words (e.g. "more", "less", "as well as") and parameters (e.g. "temperature", "control", "ventilation") to consider process intent, possible deviations from the intended process, the consequences of any deviations, and the hazards presented by these consequences.[1][2][3] The following table gives an overview of the most used keywords and parameters and a common interpretation.
| Keyword | More | Less | None | Reverse | As well as | Partly | Other than |
|---|---|---|---|---|---|---|---|
| Flow | high flow | low flow | no flow | reverse flow | deviating concentration | contamination | deviating material |
| Pressure | high pressure | low pressure | vacuum | delta-p | explosion | ||
| Temperature | high temperature | low temperature | |||||
| Level | high level | low level | no level | different level | |||
| Time | too long / too late | too short / too soon | sequence step skipped | backwards | missing actions | extra actions | wrong time |
| Agitation | fast mixing | slow mixing | no mixing | ||||
| Reaction | fast reaction / runaway | slow reaction | no reaction | unwanted reaction | |||
| Start-up / Shut-down | too fast | too slow | actions missed | wrong recipe | |||
| Draining / Venting | too long | too short | none | deviating pressure | wrong timing | ||
| Inertising | high pressure | low pressure | none | contamination | wrong material | ||
| Utility failure (instrument air, power) | failure | ||||||
| DCS failure | failure | ||||||
| Maintenance | none | ||||||
| Vibrations | too low | too high | none | wrong frequency |
Once the causes and effects of any potential hazards have been established, the system being studied can then be modified to improve its safety.
[edit] See also
[edit] References
- ^ Center for Chemical Process Safety (1992). Guidelines for Hazard Evaluation Procedures, with Worked Examples, 2nd Edition, Wiley-AIChE. ISBN 0-8169-0491-X.
- ^ Vesely, W.E., Goldberg, F.F., Roberts, N.H. and Haasl, D.F. (1981). Fault Tree Handbook. U.S. Nuclear Regulatory Commission. NUREG-0492. Nuclear Regulatory Commission (Pdf file)
- ^ Kletz, Trevor (1999). Hazop and Hazan, 4th Edition, Taylor & Francis. ISBN 0-85295-421-2.
