Page 422 - Offshore Electrical Engineering Manual

Maintenance Scheduling Software 409

5. Abseiling may be used instead of scaffolding where maintenance intervals are
infrequent and the maintenance required is within the capabilities of abseiling
personnel. Poor access location jobs such as painting, testing or replacing small
devices (e.g., gas detectors) are often carried out by abseiling, and the cost-
saving can be very substantial.

TRANSPORT, ACCOMMODATION AND PEOPLE ONBOARD
PROBLEMS
When planning an offshore construction project, the limitations of helicopter trans-
port and accommodation for personnel, crane lifting capacity and storage/laydown
space for equipment play a large part in deciding the sequence of events.
Cranes are limited in lift capability by two main variables, namely, radius of
operation and sea state. If the crane is working near its maximum lift capacity, it is
unlikely that the wave height in winter will allow lifting to be accomplished safely.
Wind speed is also likely to affect the proceedings, but this will also depend on the
wind direction and the location of the lifting operation.
Ever since the sinking of the Titanic in 1912, it has been a statutory requirement that
there are sufficient lifeboats for the number of people onboard (POB). This applies just
as much to fixed offshore installations as it does to the Queen Elizabeth 2 and must be
borne in mind when planning a large offshore construction project. If necessary, because
of a shortfall in lifeboat capacity, a floatel type accommodation vessel will need to be
provided during project peak manning levels to comply with POB restrictions. This prob-
lem is often exacerbated by the need to send lifeboats ashore for maintenance during the
summer months, when peak manning for platform maintenance is likely to occur. It can
be overcome, however, by keeping a spare lifeboat of the same type onshore, which can
be shipped out in advance, ready to replace the one being serviced.
In general, the more detailed the installation procedures are documented during
the design phase, the less likely it is that logistical problems similar to those outlined
earlier will occur during construction.

MAINTENANCE SCHEDULING SOFTWARE

A good reliability-centred maintenance scheduling system is essential offshore.
However, the system has to take many other issues into account, for example,

1. availability of spares for the targeted equipment
2. safety criticality of the equipment
3. when the equipment will be available for maintenance
4. consequences of downtime

a. other plant affected

b. emergency shutdown logic affected
c. fire and gas logic affected