spring-loaded valve will fail in the open position
and almost all of the secondary drain system
if a diaphragm rupture occurs.
valves are equipped with remote operating gears.
You can operate these valves locally, or in an
emergency, you can operate them from remote
REMOTE-OPERATED VALVES.--Remote
stations. Remote operating gear also includes a
operating gear is installed to provide a means of
operating certain valves from distant stations.
valve position indicator to show whether the valve
is open or closed.
Remote operating gear may be mechanical,
hydraulic, pneumatic, or electric.
PRESSURE-REDUCING VALVES.--Pres-
Some remote operating gear for valves is
sure-reducing valves are automatic valves that
used in the normal operation of valves. For
example, the main drain system manual valves are
provide a steady pressure into a system that is at
a lower pressure than the supply system. Reducing
opened and closed by a reach rod or a series of
valves of one type or another are found, for
reach rods and gears. Reach rods may be used to
operate engine-room valves in instances where the
example, in firemain, seawater, and other systems.
A reducing valve can normally be set for any
valves are difficult to reach from the operating
desired downstream pressure within the design
stations.
Other remote operating gear is installed as
limits of the va1ve. Once the valve is set, the
reduced pressure will be maintained regardless of
emergency equipment. Some of the main drain
Figure 6-9.--Air-operated control pilot.
6-6
