The work instruction is a detailed step-by-step
specification for intrusive maintenance, containing the
threshold limits required for each routine test during
in-service conditions.
Where tests are within specification, no further action
is required. However, where routine results are out of
spec, an investigation is necessary. This investigation
may be simple, where the field operator has noted that
re-building of the mechanism is required, or moving
contacts may need to be replaced at the next
intervention. A corrective action is required.
There are rare cases where equipment can be
energised if one of the routine tests has exceeded the
limits. This decision requires careful consideration
and is often the decision taken by the specialist in
consultation with relevant staff. The customer supply
is restored but, a follow-up action is planned
immediately. Often, abnormal spare or replacement
parts may be needed, and the repair time for the
defect, may be longer.