A review of HSE's risk analysis and protection-based analysis ...

2.2.3 ASSURANCE Project Findings
The study found that the participants used several different techniques for
identifying hazards. Some participants used a combination of complementary
approaches. The participants used broadly similar techniques (known as risk
ranking) to whittle down the initial list of events produced by the hazard
identification exercise and to select those that should be included in the
subsequent steps of the risk analysis.
The overall finding was that the events selected by the participants differed
substantially in terms of the details, but that there was good agreement as to
which events were considered the most important. Hence it appears that,
with regard to the most important events at least, HSE’s approach is
comparable to those used by other practitioners.
2.2.4 Conclusions – Hazard Identification
The review of research comparing QRA approaches with accident experience
as reported in this Section indicates that the approach used by HSE is
generally adequate for the relatively simple installations for which HSE
currently performs QRAs.
Comparison with accident experience at UK COMAH establishments (1)
shows that the majority of incidents detailed in the accident records would
have either been identified in a QRA, or would have been similar to or less
onerous in magnitude than the event(s) considered in a protection-based
analysis. However, there are a four recommendations arising out of this part
of the review. The recommendations are:
1. that HSE consider supplementing the ‘top down’ (see Section 1.3.2)
approach to the identification of hazards with other methods, if in the
future HSE seeks to apply QRA to types of plants more complex than
those currently analysed using QRA;
2. that HSE considers whether events resulting in unintended releases
from vents (such as vessel overfill during transfers from road tankers)
should be included in risk analyses for sites storing chlorine or other
pressurised liquefied gases;
3. that in the case of sites storing or using water reactive materials (such
as sulphur trioxide), HSE considers whether the risk analysis should
include scenarios where water is inadvertently added to the dangerous
substance (for example, where water may be used for cleaning of tanks
or equipment); and,
4. that HSE performs further investigations into the significance of
hazards arising from undesired chemical reactions and, if necessary,
develops a means of including such hazards in a risk analysis.
(1) Establishments covered by the Control of Major Accident Hazards Regulations 1999 (COMAH).
ENVIRONMENTAL RESOURCES MANAGEMENT HSE 0016072 AUGUST 2004
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