MAGAZINE SPRINKLER CONTROL
rooms are equipped with drains that limit the maximum
water level to a few inches. Magazines are completely
VALVES
enclosed; if flooded, they would be exposed to the full
firemain pressure. The firemain pressure on most ships
Magazine sprinkler control valves (commonly
is considerably higher than the pressure magazine
referred to as main valves) are globe-type valves,
bulkheads could withstand; therefore, magazines are
normally closed but designed to open wide when
equipped with exhaust ventilators located in the
actuated, to supply seawater to the sprinkler system.
bulkhead near the overhead. An exhaust ventilator is a
They are diaphragm operated and open at a minimum
pipe with a check valve that permits pressure release
system operating pressure of 40 psi.
(usually to topside). Since the diameter of the pipe is
The diaphragm-operated control valve (fig. 1-4) is
large enough to allow water to flow out as fast as it flows
held closed by the combination of firemain pressure
in, no excess pressure can build up in the magazine
acting against the valve disk and valve spring force
compartment. On newer ships, magazines are also
equipped with small, capped drainpipes located in the
acting against the upper diaphragm washer. When the
bulkhead near the deck. The caps may be removed in
hydraulic control system is actuated, pressurized
the adjacent compartment to drain flooded magazines.
seawater from the firemain enters the diaphragm
chamber and pushes (via the diaphragm) against the
Shipboard magazine sprinkler systems are
bottom of the upper diaphragm washer. The bottom
hydraulically- controlled saltwater/seawater-operated
surface area of the upper diaphragm washer is larger
systems. There are two basic types of sprinkler
than the surface area of the valve disk. This difference
systems--the dry-type and the wet-type. In the dry-
type system, water is not delivered to the sprinkler
in surface areas allows the water pressure in the
heads until the system is activated. In the wet-type
diaphragm chamber to create a lifting force greater than
system, water is continually available at the sprinkler
the closing force created by the spring and pressure on
heads and is sprayed in the magazine when heat
the valve disk. As a result, the valve disk is lifted and
activates the sprinkler head. Both types may be found
water is allowed to flow through the valve. When the
on some ships. However, the wet-type system is being
control system is secured, the operating pressure is bled
discontinued. Therefore, we will cover only the dry
from the diaphragm chamber and the valve is closed by
type. Technical information on both types is contained
the force of the valve spring.
in Magazine Sprinkler System, NAVSEA S9522-AA-
The control valve may be actuated either
HBK-010.
automatically or manually. We will discuss automatic
A dry-type magazine sprinkler system consists
actuating first, followed by manual actuation.
basically of three subsystems. The first subsystem is the
loop of piping and valves that delivers firemain water to
the sprinkler heads. The second subsystem is the
AUTOMATIC (THERMOPNEUMATIC)
hydraulic control system. This system uses firemain
CONTROL SYSTEM
water, through smaller piping, to operate the control
The automatic control system is designed to actuate
valves in the first subsystem. The third subsystem is the
the magazine sprinkler system in response to both a
thermopneumatic system. This system provides
rapid rise in temperature (caused by an active fire) and
automatic control of the hydraulic control system. A
the reaching of a preset temperature (caused by a
manual valve is installed in the hydraulic control system
smoldering fire). The thermopneumatic elements,
to activate the main sprinkler control valve in case the
which monitor the temperature of the magazine and
automatic system is inoperative or slow to respond. We
activate the sprinkler system, generate a pneumatic
discuss all of these subsystems, along with the
signal in response to thermal action. The pneumatic
magazine sprinkler control valve and the alarm system,
signal can be either a sudden increase or decrease in air
below.
pressure.
As you read about each area of the sprinkler system,
The automatic control system consists of heat-
the system components are related. Pay particular note
sensing devices (HSDs), transmission lines
to the legend list for the symbols. In addition to the
(Rockbestos- or Rockhide-covered copper tubing),
orifices and valves, this figure also identifies the OPEN
circle seal check valves, and a pneumatically released
and CLOSE loops of the operating pressure circuit.
pilot (PRP) valve.
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