Hazard　and　Operability　Study　(HAZOP)--大智的blog

Hazard and Operability Study (HAZOP)

HAZOP addresses each element in a process. The elements must first be identified. The expected way each element operates is determined. Deviations from the intended or expected operations and element parameters are identified using guide words. The consequences from the deviating element are estimated. Causes of the deviations, currently planned (or used) hazard controls, and inadequate controls are identified.

The study is conducted by a team made up of five or six persons usually including a team leader familiar with HAZOP, a safety and health expert, a manager/supervisor, a technical person, a senior process operator, a maintenance person, a chemist, etc, The quality of the results will depend upon the quality of the team selected.

The team will start by collecting process information from piping and instrumentation diagrams (P & ID), written operating instructions, material safety data sheets, plant models, Safety Analysis Reports ( SARs), etc. They then review each element step by step through each line or process. At each element they apply key words or guide words to tease out the potential deviations from normal expectations of a design parameter. The guidewords are shown in Table 15-2.

The hazard and operability consequences, if any, for each deviation are determined and documented. The actions or changes in plant methods which will prevent the deviation or reduce the consequences are identified. If the const of the changes can be justified, the team then must agree on the change and who will be responsible for the action. The team then must follow up to make sure that the action has been taken. If the cost is not considered to be justifiable, the team must agree to accept the risk. One or more reports of the evaluation are made, usually including tabular representations of the results. Team decision making is at the heart of this methodology.

This technique as well as the others in this chapter is supported by software. The reader is advised to “surf the net” for the latest. Arthur D. Little Company is one source.

TABLE 1-2 HAZOP Guide Words

Key word	Meaning	Comment
No/Not	Complete negation of design intention	No part of the design intention happens, e.g., “No flow”, “No pressure”, etc
More, Less	Quantitative increase of decrease	Refers to quantities, properties, and duration of design parameters, such as flow rate, temperature, etc.
As well as	Something else occurs in addition to design intention	Design intentions are achieved, plus additional things occur.
Part of	Only part of design is achieved	Partial addition or removal of material occurs. Activities are incomplete.
Reverse	The opposite of the design intention	Reverse flow of material, electrical current, and voltage polarity. Backward installation (e.g., check valve), opposite chemical reaction (e.g., decomposition).
Other than	Complete substitution	Original design intention is not accomplished; a different activity occurs-e.g., leak, rupture.