Page 421 - Offshore Electrical Engineering Manual

408 CHAPTER 2 Maintenance & Logistics

When estimating travel time for such an offshore visit, some time should be
allowed for weather delays. This is often worse in the summer months when fog is
more likely.
Telephone communications are by line-of-sight and/or satellite links, and access
is usually available when major platform construction work is not in progress. On
some of the nearer platforms, cell net telephones have been put to good use to supple-
ment normal communications.

MAINTENANCE INTERVALS AND EQUIPMENT SPECIFICATION

When specifying and procuring offshore electrical equipment and, in particular, gen-
erator prime movers, manufacturer’s recommended maintenance intervals should be
carefully studied. Excessively short maintenance intervals will very quickly wipe
out any savings in first cost because of the high costs of offshore servicing by manu-
facturer’s or agent’s servicing departments. Short intervals may also indicate poor
reliability or unsuitability for the particular package, orientation or offshore environ-
ment in general.

SCAFFOLDING AND ABSEILING (RAPPELLING)
It is a common misconception that equipment or cabling may be accessed by scaf-
folding, almost invariably without a major impact on cost or completion date. In some
areas such as a platform cellar deck or flare stack, the cost of erecting, maintaining
and dismantling scaffolding may be the most significant cost in a small project.
Locating equipment and cables in inaccessible places, necessitating heavy use of
scaffolding, has the following penalties:

1. Heavy scaffolding requirements will discourage frequent maintenance, par-
ticularly if it is going to obstruct an accessway where traffic is heavy or an area
which is already congested.
2. The handling of scaffolding poles is well known in both on- and offshore petro-
chemical installations for causing accidents or damage to process equipment.
3. Scaffolding will also need to be erected each time it is necessary to inspect the
equipment.
4. Scaffolding offshore can be very costly. Costs in excess of £300,000 for a
single access structure are not unknown. Because of the need to access high-
routed cable installations along their whole length in order to complete the
installation, they are particularly expensive to install and should be avoided
where possible. If an elevated or inaccessible location is unavoidable, consid-
eration should be given to installing some form of permanent access structure,
bearing in mind, of course, that this will itself need routine inspection, main-
tenance, painting, etc.