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APPENDIX A
TM 07661B-14/1
for the AFFF system. This quick opening valve is mounted on the outlet of the nitrogen N2 cylinder. Lifting the handle
up 90 degrees completely opens the valve and pressurizes the AFFF system, provided the charging valve in the system
is in the stand-by or open position. Pushing the handle down shuts off the nitrogen supply to the system.
b.
Nitrogen Cylinder Pressure Gage. The 0-3000 psi pressure gage (2, figure 2-4) installed on the quick-
opening valve attached to the outlet of the nitrogen cylinder is on the cylinder side of the cutoff. The gage gives a
continual reading of cylinder pressure, regardless of valve position. Normal reading on the gage when cylinder is fully
charged is 2400 psi at 700F. Minimum pressure indication for fire extinguisher operation is 1700 psi at 70°F.
c.
Nitrogen Pressure Regulator. The pressure regulator (3, figure 2-4) is mounted under the hose reel frame
and connected by high pressure hoses to the nitrogen cylinder and to the AFFF system piping. The function of the
regulator is to reduce the high pressure nitrogen supply to system working pressure 230 psi. The pressure regulator is
pre-set at 230 psig and should not require readjustment in normal operation.
d.
Charge Valve. The charge valve (4, figure 2-4) controls the pressurization of the AFFF tank. This valve is
kept in a normally open position to ensure the "ready" status of the extinguisher in event of fire. Normally, the valve
should be closed only when it is necessary to purge the AFFF discharge and dispensing lines with nitrogen directly from
the nitrogen cylinder. With the charge valve closed, the lines can be purged without pressurizing the tank.
e.
Purge Valve. The purge valve (5, figure 2-4), controls the tank bypass line and permits purging of the
discharge lines and dispensing hose with nitrogen directly from the nitrogen cylinder. This valve is normally closed
except when necessary to apply additional nitrogen pressure if tank top pressure is insufficient to purge the lines.
f.
AFFF Control Rod. Located at the front of the unit, the AFFF control rod (6, figure 2-4) puts the AFFF
shutoff valve within easy reach for quick actuation of the AFFF system. The rod connects through a u-joint to the AFFF
shutoff valve on the outlet of the AFFF tank. Turning the control rod 90 degrees counterclockwise fully opens the
discharge line of the AFFF tank. To stop the product discharge, the valve rod is returned to the closed position.
g.
Twin Agent Nozzle. The nozzle (7, figure 2-4) is quick coupled to the dispensing hose for the AFFF system.
As viewed from the hand grips the AFFF nozzle is the left nozzle of the twin nozzle assembly. Squeezing the nozzle
lever opens the shutoff valve in the nozzle. The AFFF nozzle is an air aspirating type which provides an approximate
reach of 50 feet, with 8. 5-foot spray pattern and a foam expansion ratio of five to one under normal operating
conditions. The nozzle places final control of the AFFF discharge in the operator's hand after the system is activated.
When not in use, the nozzle is stored as part of the twin nozzle assembly on a nozzle bracket.
A 2-8
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