balances the firemain pressure on the bottom of the
diaphragm and allows the spring to close the valve.
NOTE: LOWER SPRING IS
REMOVED ON POWERCHECK
VALVES INSTALLED ON
AFFF BALANCED PRESSURE
Figure 6-9. Powercheck valve.
P O W E R T R O L VA LV E W I T H T E S T
CONNECTION.-- The powertrol valve with test
Figure 6-10. Hytrol valve.
connection is a diaphragm-type, hydraulically
operated, globe control valve. It is essentially a
H Y C H E C K VA LV E . -- T h e h y c h e c k va l ve
powertrol valve with test capabilities. This valve is
(fig. 6-11) is a diaphragm type, fail open, seawater
normally used as a sprinkler group control valve. It
pressure-operated control valve, which allows the
would be impractical to test a sprinkler group unless
flow of seawater from the firemain system to be mixed
the fluid flow could be diverted before it is discharged
through the sprinkler heads. To perform a test, remove
with AFFF concentrate. The hycheck is equipped
the test connection cap from the bottom of the valve
with a sliding lift check feature like the powercheck
and insert the test fitting. The test fitting has an O ring
valve. When the AFFF system is in standby, the
to provide a seal between the fitting and the valve seat.
hycheck is held closed by firemain pressure from the
Connect a drain hose to the fitting and place the outlet
master SOPV on top of the diaphragm. When
end of the hose in a suitable location. When the
firemain pressure on the diaphragm is relieved by the
operating chamber is pressurized, the valve opens.
master SOPV, the hycheck is forced open by firemain
Fluid is routed over the top of the seat, diverted
pressure. If foam demand stops and the
through the test fitting and out the drain hose. The
AFFF/seawater solution pressure equals or exceeds
valve is successfully tested and the sprinkler groups
the firemain pressure, the lower spring closes the
are dry. When the test is complete, vent the operating
valve disk. This prevents the AFFF pump from
chamber, remove the test fitting, and reinstall the test
pumping concentrate back into the firemain.
S O L E N O I D - O P E R AT E D P I L OT VA LV E
HYTROL VALVE.-- The hytrol valve (fig. 6-10)
(SOPV).-- Solenoid-operated pilot valves (fig. 6-12)
is a diaphragm type, fail open, seawater
are electrically operated pilot valves that control the
pressure-operated control valve which controls the
activation of many AFFF fire-extinguishing systems.
flow of AFFF solution to systems. When in ready
All SOPVs (master and service) have four control line
status, the top of the diaphragm is subject to spring
ports; one port is always connected to supply pressure
pressure and control line pressure. When the control
(firemain), and a second port is the valve drain (which
line pressure is removed, the firemain pressure
should be piped to discharge within the coaming of
overcomes the spring pressure and opens the valve.
the AFFF station). The other two control ports are
When an SOPV directs firemain pressure to the
connected by control lines to diaphragm-operated
control valves on master SOPVs. Service SOPVs
control line, the pressure on top of the diaphragm