Figure 1-11.--Hydraulically-operated check valve.
control valve is returned to the NEUTRAL position, the
Hydraulically-Operated Check Valve
operating pressure is vented from the CLOSE loop via
The hydraulically-operated check valve (fig. 1-11)
orifice/drain line No. 2, thereby permitting the
is a normally closed, diaphragm-operated, globe-type
hydraulically-operated check valve to close.
check valve that is opened by operating pressure in the
MAGAZINE ALARM SYSTEMS
CLOSE loop acting against the underside of the
diaphragm. This valve permits the operating pressure to
Several
Several types of warning devices or systems are
be vented from the diaphragm chamber of the magazine
used on board ship. One of them is the alarm system
sprinkler valve, thereby permitting that valve to close
activated by the water switch (fig. 1-12) on the dry side
rapidly and completely.
of the sprinkler system main (group) control valves.
This alarm is designated FH and indicates by sound or
Orifices
light that the main control valve is open or leaking.
Two 0.098-inch orifices are installed in the control
system piping to prevent a buildup of pressure in the
piping due to leakage past a control system component.
The orifices also vent operating pressure from the
control system piping when the manual control valve is
returned to the NEUTRAL position. Orifice No. 1 is
installed in the OPEN loop upstream from the
hydraulically- operated check valve. Orifice No. 2 is
installed in the CLOSE loop adjacent to the operating
pressure connection of the hydraulically-operated
check valve. When the control system is actuated, there
will be a steady flow of water from orifice/drain line
No. 1 and no flow from orifice/drain line No. 2. When
the control system is secured, there will be a steady flow
of water from orifice/drain line No. 2 and a diminishing
flow from orifice/drain line No. 1. When the manual
Figure 1-12.--FH alarm sensor.
1-12
