Eliminating human error
“Relevant
personnel
should always be
aware of why
certain critical
operations must
be done in a
particular order.
If they fully
appreciate the
significance of
their actions,
then potential
excursions should
be reduced
How can you be sure you that you have done everything that is reasonably
practicable to avoid a potential disaster? Dr Julian Hought explains
MAINTENANCE ON SAFETY CRITICAL PLANT AND
equipment should really be one of the safest jobs
undertaken on a site. Given the nature of the working
environment, it is generally well planned: checks and
sign-offs abound (the permit-to-work system); risk
assessments are done; senior engineering staff are
involved; and dangerous substances are removed,
flushed out and cleaned from the plant.
Many of the potential hazards are eliminated and, for
those left, very tight controls are employed. This focus on
the occupational safety of the maintenance personnel
is highly admirable. But it should not be forgotten that for
safety critical plant, it is vital to ensure that the plant or
equipment following maintenance is once again meeting
the design intent.
It is vital that the plant, process or equipment remains
compliant with the design following maintenance – and
the maintenance personnel must understand the
criticality of the process, so that they are aware of the
consequences of not doing a job properly.
For the routine changing of a pump, for instance, most
maintenance personnel would ensure that the new
pump gives the same rate of flow, the motor is the same
size and so forth. However, dependent on the properties
of the material, the most important criterion might
actually be the construction of the pump internals. If
replaced incorrectly, then a loss of containment event
may ensue.
This is a clear demonstration of human error – most
likely unintentional. The equipment was designed to
have particular materials of construction and without
these the design is compromised. Whilst this may not
prove critical if the loss of containment is of an
innocuous material, it is a far more serious matter if the
substance released is toxic or flammable.
To guard against human error during maintenance
operations, companies must first determine which
equipment within the plant will have the greatest
overall impact were it to fail. A full risk-based
analysis covering all aspects of the plant should
then be undertaken, taking historic reliability
data and operating experience into consideration
where possible. Based on the results of this analysis,
planned maintenance should be scheduled for all
safety critical equipment.
Personnel involved in the maintenance of these
SAFETY
PLANT MAINTENANCE
safety-critical areas need to fully understand the
importance of regular maintenance and inspection of
this equipment, rather than waiting until the situation
reaches a near-critical level. Liaison between
engineers, production operatives, maintenance
personnel and procurement departments is also
important to ensure that the correct levels of spare
parts to the correct specification are kept in stock for
maintenance purposes.
Relevant personnel should always be aware of why
certain critical operations must be done in a particular
order. If they fully appreciate the significance of their
To guard against
human error
during maintenance
operations, companies
must first determine
which equipment within
the plant will have the greatest
overall impact were it to fail
Dr Julian Hought“
actions, then potential excursions should be reduced.
Training goes some way towards avoiding mistakes
and system violations, but is unlikely to eliminate
unintended omissions where the person has simply
forgotten to do something that relates to a critical
maintenance activity.
Educating personnel in the importance of doing tasks
in a specified order or a particular manner is an essential
element of the process safety management regime.
The degree to which a team or individual employee
feels they have ownership of an area of plant or piece
of equipment, the more reliable it is and the more likely
it is to be operated and maintained in the correct
manner. Again, the correct manner needs to be clear,
unambiguous and understood; and related to the design
intent, rather than based on picking up the historical
practices of the old-hand operatives.
PE
Dr Julian Hought is managing director,
HFL Risk Services Ltd
PROCESS ENGINEERING : MAY/JUNE 2009
37
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