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TM 07661B-14/1
APPENDIX A
failure or proximity to fire. The temperature relief plug also acts as a drain plug. The tank's plumbing also contains an
adjustable, self-resetting pressure relief valve, preset to 250 psig, which protects the tank against pressures in excess of
250 psi.
c.
Nitrogen Cylinder. Two nitrogen cylinder assemblies (3, figure 1-2),are provided, one for pressurizing each fire-
fighting agent container. Each cylinder, fully charged, contains 300 cubic feet of nitrogen (N2) at 2400 psi. Quick-
opening lever operated valves requiring only 90 degrees rotation of the handles to be fully open, are installed in the
cylinder inlet-outlet opening. A 0-3000 psi gage is installed in the valve, on the cylinder side of the cutoff. Thus the gage
continually reads cylinder pressure, regardless of the valve position. Protective covers are installed over the valve and
gage during shipment. The cylinder assemblies are installed horizontally, one on either side of the extinguisher, in racks
provided for that purpose. They are held in place by hold-down brackets. The cylinder valves are attached to regulators
leading to their respective chemical agent container when ready for use.
d.
Nitrogen Regulators. A high volume pressure regulator (4, figure 1-2) is connected to each nitrogen cylinder by a
high pressure hose. The regulators are preset at the factory to reduce nitrogen pressure to 220-240 psig working
pressure. Equipment is protected from pressure build-up, or failure of, the pressure regulator by a non-adjustable, self-
resetting pressure relief valve installed in one of the regulators outlet ports.
e.
Shutoff Valves. The shutoff valves are located in the chemical agent discharge plumbing. The dry chemical
valve (7, figure 1-2) is located next to the dry chemical tank and the AFFF valve (8, figure 1-2) is located next to the
AFFF tank. Each valve is connected to a valve rod that extends to the front of the fire extinguisher and is used to
operate the valve. Each valve has an identification plate, located on the skid frame next to each valve rod handle, to
indicate the chemical agent it controls. The purposes of the valve is to prevent discharge of chemical agents when it is
desired to pressurize tanks without discharging chemicals into reel or handline, and prevent moisture from entering tanks.
The valve also allows hose blowdown without pressurizing tanks.
f.
Charge Valves. Two one-half inch ball valves are used on this fire extinguisher to control nitrogen flow to the
agent tanks. When the charge valve (5, figure 1-2) is open, nitrogen pressurizes the dry chemical tanks. When the
charge valve (6, figure 1-2) is open, nitrogen pressurizes the AFFF tank.
g.
Purge Valves. Two one-half inch ball valves are used on this fire extinguisher to clean the dry chemical and
AFFF hand lines of agent. The dry chemical purge valve is shown as item 9 in figure 1-2. The AFFF dry chemical purge
valve is shown as item 10 in figure 1-2.
A 1-10
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