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Page Title:
Table 4.14 Guide Words for HAZOP Studies |
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|  DOE-HDBK-1100-2004
parameters. Process deviations are determined by combining guide words with the
important process parameters. The established set of guide words is shown in Table 4.14.
Table 4.14 Guide Words for HAZOP Studies
GUIDE WORD
MEANING
EXAMPLES
None of
Negation of Intention
No forward flow when there should be.
Sequential process step omitted.
More of
Quantitative Increase
More of any relevant physical parameter than
there should be, such as more flow (rate,
quantity), more pressure, higher temperature, or
higher viscosity.
Batch step allowed to proceed for too long.
Less of
Quantitative Decrease
Opposite of "MORE OF"
Part of
Qualitative Decrease
System composition different from what it
should be (in multi-component stream).
As well as
Qualitative Increase
More things present than should be (extra
phases, impurities).
Transfer from more than one source or to more
than one destination.
Reverse
Logical Opposite
Reverse flow.
Sequential process steps performed in reverse
order.
Other than
Complete Substitution
What may happen other than normal continuous
operation (start-up, normal shutdown,
emergency shutdown, maintenance, testing,
sampling).
Transfer from wrong source or to wrong
destination.
The process parameters and example deviations typically used in a HAZOP study are
shown in Table 4.15. Additional process parameters can be added if warranted. One
purpose of the guide words is to assure that all relevant deviations of process parameters
are evaluated.
The following are examples of deviations created using guide words and process
parameters.
Guide Word
Parameter
Deviation
No
+
Flow
=
No flow
More
+
Temperature
=
High temperature
Other than
+
Location
=
Wrong location
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