Page 211 - Offshore Electrical Engineering Manual

198 CHAPTER 1 Notes on Design Project Organization and Documentation

increased load. Small-project cable schedules may be produced manually using
draughting blanks. However, a more practical medium is the computer database,
especially during a large project when large numbers of cables are continually
being added. For ease of identification, cables should be grouped into service
and area. Insertion of extra cables into a schedule would be extremely laborious
on a manual schedule but is relatively easy on a database. Other advantages are
that duplicate cable numbers cannot exist and that most database programs have
powerful sorting and search facilities. An (manually produced) example is given
in Fig. 3.1.10A and B. The cable schedule should also contain a list of cable
types giving a full description of each type, a type code that can be referred to
in the main schedule and the total length for each type. Drum/cutting schedules
should also be produced to minimise cable wastage during installation. The
cable schedule must state how the individual cable lengths were derived. For
example, do they already contain a margin for drawing inaccuracy, cutting wast-
age, installation errors, etc.?
2. Electrical equipment schedule: As an aid to draughting and ensuring that every
node in the electrical distribution is catered for in the design, an electrical
equipment schedule should be produced. This may be combined with a master
equipment list later on in the project. Every item should be allocated a client
tag number and the information presented should include the service, location,
manufacturer, type and environmental details such as ingress protection num-
ber and suitability for hazardous areas. Motor schedules will give details of the
controls and instrumentation required at the motor, at the starter and any other
point of control. It should also indicate the motor full-load current and the fuse
size and indicate any special requirements, such as earth fault relays or thermis-
tors. The schedule may be split into types of equipment such as motors, junction
boxes and luminaires, and in some cases, it will only be beneficial to produce
schedules for particular types of equipment, depending on their populations
and whether the same information has been produced on another document.
An example of this type of schedule is shown in Fig. 3.1.11. Again, a computer
database is recommended for the production of these schedules.
3. Plug and socket schedule: These schedules are often required for diving and
subsea equipment, as they tend to be a prolific user of special underwater con-
nectors. Each connector may have over a hundred connections. Pin current
ratings may not all be identical on the same plug, and it may also be necessary
to parallel several pins in one circuit to obtain the required rating. It may be
necessary to monitor circuits for continuity as well as for earth leakage. To fur-
ther complicate the matter, every socket of identical size will require a different
orientation to prevent plugs being mated with the wrong sockets. Some form of
schedule is essential to keep track of circuit routing through the various connec-
tors. Each connector should be provided with a separate page (or pages) in the
schedule and this will need to identify the service, the plug and socket manufac-
turer and the catalogue number and the orientation between the plug and socket.
Each circuit should then be listed, with details of cable cores terminated in the
plug and socket, circuit rating, purpose, etc.