It is impossible to compare hazard identification techniques and come to any conclusion as to which is the best. Each technique has been developed for a specific range of circumstances taking many factors into account including the resources required to undertake the analysis, expertise available and stage of the process. This project has attempted to classify the resources required for each technique on a scale of 1 to 3 with one being quick and inexpensive and three being time consuming and expensive. Further comparisons of their applicability to SME’s, COMAH, offshore and nuclear installations have been made using a four point scale with one not being applicable and four very applicable. Table 3 gives the results of the comparisons.
HEALTH AND SAFETY LABORATORY
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43
Table 4, Hazard identification applicability to several industries.
Applicability to
Ref Hazard Identification Techniques Nature of results
Process life cycle phase
Time/Cost COMAH Sites
SME's OSD Nuclear
Industry
1 Concept Hazard Analysis Qualitative Concept 2 3 2 2 3
2 Concept Safety Review Qualitative Concept 2 3 2 2 2
3 Preliminary Hazard Analysis Qualitative Design/operation 2 3 2 2 2
4 Pre-HAZOP Qualitative Design stage 1 3 2 2 3
5 HAZOP Qualitative Any phase 3 4 2 4 4
6 "What if?" Analysis Qualitative Any phase 2 4 3 3 3
7 Checklists Qualitative Concept/design 2 2 4 2 2
8 Standards/Codes of practice Qualitative Concept/design 1 3 4 3 3
9 FMEA Qualitative Design/operation/mods 3 3 2 3 4
10 Functional FMEA Qualitative Design/operation/mods 3 3 2 3 4
11 FMECA Qualitative Design/operation/mods 3 3 1 2 4
12 Safety Audit Qualitative Any phase 3 4 3 4 4
13 CHAZOP Qualitative Design/mods 3 3 1 3 4
14 Critical Examination of System Safety Qualitative Design/operation 2 2 2 1 1
15 Cause-Consequences Analysis Both Design/operation/mods 3 3 1 3 3
16 Fault Tree Analysis Both Design/operation/mods 3 3 1 3 4
17 Structured methods Qualitative Design stage 2 2 1 2 2
18 PETRI NETS Qualitative Design stage 2 2 1 1 1
19 Sneak Analysis Qualitative Design/operation 2 3 2 2 2
20 Structural Reliability Analysis Quantitative Design/construction 2 2 1 2 2
21 Reliability Block diagram Quantitative Design/mods 2 2 2 2 2
22 Human reliability Analysis Semi-qualitative Operation/mods 3 3 2 3 3
23 Action Error Analysis Both Operation/mods 2 3 1 3 3
24 Task Analysis Both Design/operation/mods 2 3 2 3 4
HEALTH AND SAFETY LABORATORY
An agency of the Health and Safety Executive
44 Table 4, Continued
Applicability to
Ref Hazard Identification Techniques Nature of results
Process life cycle phase
Time/Cost COMAH Sites
SME's OSD Nuclear
Industry
25 Maintenance and Operability study Qualitative Design/operation/mods 3 3 2 3 2
26 Predictive Human Error Analysis Semi-qualitative Design/operation/mods 3 2 1 2 3
27 Pattern Search method Qualitative Operation/mods 2 2 1 2 2
28 Vulnerability Assessment Qualitative Design/mods 2 2 1 2 2
29 DEFI method Quantitative Design stage 2 1 1 2 2
30 Maintenance Analysis Both Operation/mods 3 3 2 3 3
31 Matrices Qualitative Design stages 2 2 1 1 1
32 GOFA Semi-qualitative Design/operation/mods 2 2 1 2 2
33 MOSAR Semi-qualitative Operation/mods 2 2 1 2 1
34 FIHI Qualitative Design/operation 2 2 1 2 2
35 State-Transition Diagrams Qualitative Design stage 2 2 1 1 2
36 GRAFCET Qualitative Design stage 2 1 1 1 1
37 Inherent Hazard Analysis Qualitative Design stage 2 2 2 2 2
38 Hierarchical Task Analysis Qualitative Operation/mods 3 3 1 3 4
Note:
COMAH = Control Of Major Accident Hazards SME = Small Medium Enterprises
OSD = Offshore Safety Division
Both = The nature of the results are qualitative and quantitative
HEALTH AND SAFETY LABORATORY
An agency of the Health and Safety Executive
45 8 DISCUSSION
The literature review has provided an overwhelming source of information on hazard identification techniques. Many of the references are themselves a comparison of hazard assessment schemes to a particular application. Whilst there is a wealth of information on examples of applying hazard identification techniques, there is little guidance available on how to apply them.
Whilst the literature was wide ranging it is impossible to claim that every technique has been listed. Many of the techniques have been developed for particular applications and renamed.
No attempt has been made to sort out this ‘family tree’ of techniques but where they are obviously similar they have been grouped together as a single technique.
The most difficult aspect of this review was deciding on the amount of detail to be included for each technique: too little and the review becomes little more that a list, too much and it becomes an unreadable tome. A subjective assessment of the advantages and disadvantages is given, but the real question about hazard identification is related to its ability to carry out the task of identifying all the relevant hazards. This question can only be answered on a case by case basis. Most techniques can be applied in any circumstances provided enough resources and expertise is available. The most suitable technique will not only depend on the
application but also the available resources. It would be nonsensical to embark upon a HAZOP without access to an experienced chairman. Other less applicable techniques could probably be undertaken with more chance of success by utilising available expertise.
The comparison has attempted to match techniques with various types of installations taking into account not only the probable availability of resources to carry out the assessment but also the magnitude of the hazards present.
9 CONCLUSIONS
This report has provided a useful overview of the majority of the hazard identification techniques that will be found in COMAH reports and other high hazard industries. It also gives an indication of the applicability of each technique for SME’s, offshore and nuclear facilities.
There are a wide range of hazard identification techniques available most of which have many examples published. With the notable exception of HAZOP there are few formal guidance documents on the application of such techniques. The most common method of learning to apply a technique is attendance at one of the many training courses or working with a more experienced colleague.
The lack of formal guidance is to be expected with a range of techniques that need to be very flexible to allow their application to a wide range of circumstances without discouraging free thinking. The guidance available appears to concentrate on providing a description of the technique rather than setting any standards of quality for applying the technique.
10 RECOMMENDATIONS
HEALTH AND SAFETY LABORATORY
An agency of the Health and Safety Executive
46 (i) Feedback on this work should be sought from both industry and the regulators of experience gained from applying hazard analysis to satisfy the COMAH Regulations. This report should be updated to take into account ant significant comments.
(ii) A small number of techniques that are most commonly used on COMAH installations should be reviewed in greater detail. This detailed review should provide guidance on the information required for COMAH reports and assessment criteria
11 REFERENCES
1. Agerwala 1979, PUTTING PETRI NETS TO WORK, T.Agerwala, Computer, v12, n12, p85-94, 1979.
2. Andow 1991, GUIDANCE ON HAZOP PROCEDURES FOR COMPUTER -
CONTROLLED PLANTS, HSE contract research report No. 26/1991, P.Andow, Her Majesty’s Stationary Office, 1991.
3. Balemans 1974, CHECK-LIST. GUIDE LINES FOR SAFE DESIGN OF PROCESS PLANTS, A.W.M.Balemans, 1st International Loss Prevention Symposium, p7-33, 1974.
4. BSEN1050 1997, SAFETY OF MACHINERY - PRINCIPLES FOR RISK