The safe isolation of plant and equipment (HSG253) - Health and ...

135 For work on pumps, typical short-duration tasks include:
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packing of glands;
removal of couplings;
replacement of mechanical seals; and
change of lubricant.
136 For variations involving short-duration work:
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Health and Safety
Executive
completion of the intrusive work (ie entire process from installation of isolation
to recommissioning) should take less time than is needed to install and remove
the final (positive) isolation;
the work should not extend beyond one operating shift;
the work instruction should specify the required contingency action if
unforeseen difficulties cause intrusive work to overrun the single shift (reinstate
the plant or install a positive isolation);
you should prove each isolation point/valve before starting the work, and
monitor for leakage during the work activity;
the worksite should not be left unattended. This allows prompt remedial action
if a leak develops; and
mitigating action to bring any leak under control should be understood and
necessary equipment available.
Modification considerations
137 When a variation from the normal level of isolation is authorised for work on
a plant, you should consider improving the isolation facilities at the first available
opportunity.
138 Where plant modification will reduce risk, it should be carried out unless the
costs would be grossly disproportionate to the risk reduction. Where work will be
carried out on a repeated basis, this will shift the balance of risk reduction and cost
towards plant modification.
139 Remember that no modification should be carried out until you have assessed
the potential consequences (looking at the wider implications for the plant as a
whole, not just at the specific isolation activity). Modifications should not reduce the
inherent safety of the plant. For example, you should assess with great care any
proposed modification to permit isolation of protective devices, where no isolation
was previously permitted.
140 Previous authorisation of a variation does not justify its use for future
interventions. Repeated use of a variation is acceptable only where your decision
not to upgrade to the required standard is justified by risk assessment and risk
reduction to ALARP criteria. Record the basis for such decisions. You should review
the assessment each time the variation is proposed, taking into account changes
on the plant and in available technology to control the residual risk.
Monitoring the use of variations
141 The use of variations from company standards on a plant should be regularly
monitored and audited. Relevant matters to scrutinise include:
for variations:
■ the proportion of isolations carried out at lesser security than company policy;
■ full compliance with a variation approval process;
■ whether an alternative system of work could avoid the use of a less secure
isolation method; and
■ whether costs/circumstances have altered the validity of the original ALARP
decision; and
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