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Pressure regulator valve and test fixture
valve(s) should be left in the closed position
when not in use. Leaving valves open could
result in damage to unit diaphragms.
2-4. TIME CYCLES.
a.
Maintenance personnel will purge and charge tank
fire control items every 180 days and artillery fire control
items every 90 days or when condensation is evident in the
instrument.
b.
NOTE
The 180-day cycle does not apply to rangefinders
which are purged and charged once a year. How-
ever, a visual inspection is required every 90 days
for evidence of moisture. The electrical compo-
nents of M21 Ballistic Computer System to in-
clude the Ammo Select Unit, Cant Angle Sensor,
Computer Unit, Output Unit and Rate Tachome-
ter and the Laser Rangefinder, AN/VVG–2, Elec-
tronics Unit require purging every 180 days,
when unit is opened for maintenance, or when ev-
idence of moisture is present.
Maintenance personnel will purge and charge fire
control materiel being repaired whenever the repair func-
tion affects internal sealing.
c.
For maintenance of material in storage refer to appli-
cable equipment manuals.
d. NSN’s 4820-01-384-9005 and 4730-00-277-9615
are mandatory for purging artillery fire control.
2-5. PURGING
DURES.
TM 750-116
AND CHARGING PROCE-
a. Purge and Charge: Inlet Port Entry, Relief
Valve Exit. This procedure is used when instrument is
designed to hold a charge.
HANDLE WITH CARE. IN THE EVENT
THE RADIOLUMINOUS SOURCE IS
BROKEN, CRACKED, OR SUDDENLY
LOSES ILLUMINATION, DO NOT AT-
TEMPT TO REPAIR. IMMEDIATELY
WRAP DEVICE IN PLASTIC AND
NOTIFY THE LOCAL RADIATION PRO-
TECTION OFFICER (RPO).
(1) Remove inlet port cap of instrument to be purged
and charged.
(2) Inspect inlet port for cleanliness and presence of
valve core. Remove any dirt or foreign matter.
Ensure regulator valve is closed (counter-
clockwise - CCW) or damage may occur to
regulator.
To avoid damage to instruments being
purged and charged, do not exceed maxi-
mum pressure. Unless otherwise noted for
specific instrument, maximum pressure is 10
psi.
(3) Connect hose assembly to inlet pert on instrument.
(4) Open main valve on nitrogen tank (CCW).
(5) Open regulator valve (clockwise - CW) until spe-
cified purge pressure is indicated on low pressure gage.
(6) Watch low pressure gage and listen for purge relief
valve to open.
(a) Relief valve should open between specified
pressures.
(b) If relief valve does not open before pressure
reaches maximum range, immediately turn off regulator
valve (CCW). Replace pressure relief valve on instrument.
Repeat procedure.
Change 1 2-3
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