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Guide Word Meaning
Standard guidewords
No Negation of the design intent
More Quantitative increase
Less Quantitative decrease
As Well As Qualitative increase
Part of Qualitative decrease
Reverse Logical opposite of the intent
Other Than Complete Substitution
Auxiliary guidewords
How How is the step to be accomplished
Why Is the step or operation really needed
When Is timing of the step or operation important
Where Is it important where the step is performed

TABLE 12.3 Standard and Auxiliary Guidewords Used to Conduct HAZOP Studies

Plant components (pumps, compressors, exchangers) are found
within nodes. In the same fashion, a parameter is an aspect of the
process that describes it physically, chemically, or in terms of what is
happening (flow, level, temperature). Parameters are usually
classified as specific or general to respectively describe aspects of the

Begin study
Select a node
Define the design intention
Select a parameter
Specify the intention
Select a guideword
Investigate deviation
Identify credible causes
Note significant consequences for each cause
Note existing safeguards
Document recommendations, if any
Assign responsibility for recommendation
Any other deviation? (Yes)
Any other guide word? (Yes)
Any other parameter? (Yes)
Any other node? (Yes)
Study complete
FIGURE 12.8 HAZOP process iterative loops.