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Is it necessary to install a downhole safety valve in a subsea oil/gas well?
Table 6-1 Advantages and disadvantages with the HAZOP analysis [9] (with some supplements of the
author.)
Advantages and disadvantages with the HAZOP analysis
Advantages Disadvantages
Identifies potential hazards before they become
built into the system
The systematic method covers all the
potential hazards for of system
Provides a basis for a list of “actions” in order to
prevent or rectify problems
People with different fields of profession are
working together.
The different parties included in the process or
procedure get an insight to the other areas of the
work or process.
Requires a mixed team of engineers and personnel
from all fields in order to cover all aspects of the
system
Human factors may sometimes be set as the reason
for hazards rather than looking at the underlying
reasons
The study will generate extensive information.
This must be recorded by someone responsible
The study takes long time to complete depending
on the extent of the investigation.
The HAZOP only reveals component weaknesses
and is not an in-depth review of the causes and
consequences.
6.2.2 HAZOP methodology
Essentially the HAZOP procedures involve taking a full description of a process or a procedure
and systematically question every part of it. A number of “brain-storming” sessions help
finding deviations from the design intent. Once identified, an assessment is made as to whether
such deviations and their consequences may have a negative effect on the safe and efficient
operation of the analysed system. If considered necessary, action is then taken to remedy the
situation. The outcome of a HAZOP may be a recommendation of actions that are to be taken
in order to address the concerns found during the analysis. The different steps of the HAZOP
procedure is presented in appendix D
An essential feature in the process of systematically questioning is the use of guide-words in
combination with different parameters in order to focus the attention on deviations and their
possible causes. The entire technique of HAZOP revolves around the effective use of these
guide-words, so their meaning and use must be clearly understood. A HAZOP study is in
principle qualitative, there is no quantification of risk. However, the hazards identified form
the basis for further quantitative risk or reliability analysis.
After finding appropriate the guide-words the procedure may begin by accessing each of the
different elements of the study. By making use of the flow diagram in Figure 6-2 the potential
problems can be identified.
The output of the study consists of a set of recommendations on how to approach a better
solution.
A HAZOP study is a team effort. The success is very much dependent on the team. To gain the
relevant information and a successful HAZOP analysis a reasonable composition by
experienced and contributing members must be established. Representatives of all disciplines
involved in the operations should be included in the team. Input based on their responsibility in
the performance of the operations is essential. The diversities in background help the different
members identifying all the important issues of the study and provide an ability to see the
scenario from different angles. A study will generally involve at least four and rarely more than
seven persons. The larger the team, the slower the process.
Diploma thesis, NTNU 2002
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