Page 143 - Offshore Electrical Engineering Manual

130 CHAPTER 12 Process Drives and Starting Requirements

this arrangement is that the motor starts with the generator, effectively providing
a reduced voltage start characteristic. If the motor were started from a switching
device, then a generator of lower rating than that required can be used. Another
benefit of this arrangement is that a generator voltage can then be specified which
minimises the stilling tube cable diameter, i.e., copper and insulation cross sec-
tions can be traded off. The fire pump diesel generator module is designed to be
as independent as possible from other platform systems, and if using cooling
water bled from the fire pump system itself, it only requires to obtain combustion
air from its surroundings. The photograph in Fig. 2.12.5 shows a typical diesel
generator of the current design.

FIRE PUMP DIESEL ENGINE STARTING REQUIREMENTS

The starting requirements for fire pump diesel engines are laid down in the (American)
National Fire Protection Association (NFPA) Specification No. 20. This requires that
the engine be provided with two batteries each capable of 12 start attempts, specified
both for minimum cranking duration and interval between each cranking. The engine
must also have an independent means of starting, such as a hydraulic or compressed
air device complete with some form of accumulator.

FIGURE 2.12.5
A typical fire pump/emergency generator module designed for fire survivability and inde-
pendent operation.
Courtesy SPP Offshore, a division of SPP Ltd.