A HAZOP survey is one of the most common and widely accepted methods of systematic qualitative hazard analysis. It is used for both new or existing facilities and can be applied to a whole plant, a production unit, or a piece of equipment It uses as its database the usual sort of plant and process information and relies on the judgment of engineering and safety experts in the areas with which they are most familiar. The end result is, therefore reliable in terms of engineering and operational expectations, but it is not quantitative and may not consider the consequences of complex sequences of human errors.
The objectives of a HAZOP study can be summarized as follows:
1) To identify (areas of the design that may possess a significant hazard potential.
2) To identify and study features of the design that influence the probability of a hazardous incident occurring.
3) To familiarize the study team with the design information available.
4) To ensure that a systematic study is made of the areas of significant hazard potential.
5) To identify pertinent design information not currently available to the team.
6) To provide a mechanism for feedback to the client of the study team's detailed comments.
A HAZOP study is conducted in the following steps:
1) Specify the purpose, objective, and scope of the study. The purpose may he the analysis of a yet to be built plant or a review of the risk of un existing unit. Given the purpose and the circumstances of the study, the objectives listed above can he made more specific. The scope of the study is the boundaries of the physical unit, and also the range of events and variables considered. For example, at one time HAZOP's were mainly focused on fire and explosion endpoints, while now the scope usually includes toxic release, offensive odor, and environmental end-points. The initial establishment of purpose, objectives, and scope is very important and should be precisely set down so that it will be clear, now and in the future, what was and was not included in the study. These decisions need to be made by an appropriate level of responsible management.
2) Select the HAZOP study team. The team leader should be skilled in HAZOP and in interpersonal techniques to facilitate successful group interaction. As many other experts should be included in the team to cover all aspects of design, operation, process chemistry, and safety. The team leader should instruct the team in the HAZOP procedure and should emphasize that the end objective of a HAZOP survey is hazard identification; solutions to problems are a separate effort.
3) Collect data. Theodore16 has listed the following materials that are usually needed:
➢ Process description
➢ Process flow sheets
➢ Data on the chemical, physical and toxicological properties of all raw materials,, intermediates, and products. ➢ Piping and instrument diagrams (P&IDs)
➢ Equipment, piping, and instrument specifications ➢ Process control logic diagrams
➢ Layout drawings
➢ Operating procedures
➢ Maintenance procedures
➢ Emergency response procedures
➢ Safety and training manuals
Table-11.2: HAZOP Guide Words and Meanings
|Guide Words |Meaning | |No |Negation of design intent | |Less |Quantitative decrease | |More |Quantitative increase | |Part of |Qualitative decrease | |As well as |Qualitative Increase...
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