Page 145 - Introduction to Marine Engineering

Pumps and pumping systems 131

The emergency bilge suction or bilge injection valve is used to prevent
flooding of the ship. It is a direct suction from the machinery space bilge
which is connected to the largest capacity pump or pumps. An
emergency bilge pump is required for passenger ships but may also be
fitted as an extra on cargo ships. It must be a completely independent
unit capable of operating even if submerged. A centrifugal pump with a
priming device is usually used, driven by an electric motor housed in an
air bell. The power supply is arranged from the emergency generator.
A typical system is shown in Figure 6.19. The various pumps and lines
are interconnected to some extent so that each pump can act as an
alternative or standby for another.

Ballast systems

The ballast system is arranged to ensure that water can be drawn from
any tank or the sea and discharged to any other tank or the sea as
required to trim the vessel. Combined or separate mains for suction and
discharge may be provided. Where a tank or cargo space can be used for
ballast or dry cargo then either a ballast or bilge connection will be
required. The system must therefore be arranged so that only the
appropriate pipeline is in service; the other must be securely blanked or

Overboard
discharge
Suction or discharge
fore peak and double
bottom tanks
onward port
bilge well
Aft port
From port
hold bilges

I From starboard
7 hold bilges
;**-J
Forward starboard
bilge well
Suction or discharge
double bottom tanks

Figure 6.19 Bilge and ballast systems