Figure 4-6.—Typical service system pump-room piping arrangement.
The service pump discharge header is common to
all four service pumps. Like the suction header, it is
divided into port and starboard headers by a set of
crossover valves. The cross-connection to the transfer
pump discharge header is used with, and for the
same purpose as, the cross-connection between the
respective suction headers of the transfer and service
pumps. They are also used to drain back the service
piping for maintenance.
From the service pump common discharge
header (on the seventh deck), the distribution riser
extends directly to the filter room (on the third deck).
JP-5 enters the service filter through the inlet section
and leaves the filter through the discharge line
attached to the clearwell chamber and the automatic
shutoff valve. Both inlet and discharge have shutoff
valves.
The filters are also provided with a bypass line.
This line fitted with a shutoff valve (locked closed), is
installed between the filter inlet and discharge lines.
The bypass line is primarily used for draining back
the distribution piping for maintenance.
As the distribution piping leaves the discharge
side of the service filter, it is divided into two sections
(commonly called “legs”). Each leg extends outboard;
one goes forward to supply all the service stations in
the forward section of the quadrant, and the other
goes aft to supply all the service stations in the aft
section of the quadrant. This piping may or may not
run outside the skin of the ship and is known as the
outboard distribution main.
The aft leg of the forward quadrant and the
forward leg of the aft quadrant are connected by a set
of
cross-over valves. Additionally, port and starboard
quadrants are connected by cross-over valves. With
the correct alignment, this allows fuel to be pumped
4-9
