TM-9-6920-430-14
COOLANT RECHARGING UNIT, TRAINING GUIDED MISSILE SYSTEM M80 AND CHARGER, BATTERY PP-7309/T
TECHNICAL MANUAL; OPERATOR’S AND ORGANIZATIONAL DIRECT SUPPORT, AND GENERAL SUPPORT MAINTENANCE MANUAL
AUGUST 1980
TM-9-6920-430-14 - Page 15 of 180
TM 9-6920-430-14
Section III. GPU PRINCIPLES OF OPERATION
1-8. GENERAL.
The Gas Pumping Unit is comprised of an electrically-driven
compressor, in-line desiccant filters, relief valve, two pressure switches and various control
valves. The GPU is basically a combined gas cleaning and pumping unit used to fill the
internal trainer argon gas bottle up to 6000 ± 200 psig within a maximum period of 45
minutes. A 6000 psi in-line pressure switch automatically shuts off the pump when the
outlet pressure gage reaches between 5800 and 6200 psig. The relief valve functions as a
secondary safety valve by immediately releasing high pressure in the event the pressure
switch fails. When the GPU is operated in the high proof pressure mode, the second
pressure switch shuts off the pump at 7750 ± 250 psig.
1-9. GPU HIGH PRESSURE PUMPING SYSTEM OPERATION (Figures 1-1 and 1-2).
Argon gas is routed to the GPU through the inlet flexible hose interconnecting the argon
gas bottle to the inlet connector port on the left side of the GPU. The inlet pressure gage,
located down line from the inlet shutoff valve, indicates gas pressure available from the
argon gas bottle at the input of the pump. The argon gas enters the pump from the inlet
side via the inlet port and in-line particle filter (1). The gas is pumped down line from
compressor, past the relief valve and pressure switches, through molecular filters (1) and
(2), where impurities such as water or oil are filtered from the gas. The pressurized argon
gas is then routed through in-line particle filter (3) and to the trainer fill port via the outlet
flexible hose. The outlet pressure gage indicates THT bottle pressure. The GPU has two
primary electrical controls, OFF (Red pushbutton) and ON (Green pushbutton). When
depressed, the ON switch S3 applies 115 V AC to one side of the Starter Relay K1 Coil via
J1-1, S1 and S2. The other side of the Starter Relay Coil is connected to the supply source
via J1-2. This energizes Starter Relay K1. AC power is applied to the compressor via
contacts A and B, and terminals 2, 3, 5 and 6 of the Starter Relay K1. The starter Relay is
self latched ON through contact C or K1 and S4, S2 and S1. Thus maintaining AC power
to the compressor after the ON switch S3 is released. Timer M1 (running time meter) is
connected in parallel with AC power applied to the compressor motor and records the
compressor running time. Once activated, the compressor motor remains on until pressure
switch S4 senses 5800 to 6200 psig at which time S4 opens, unlatching starter relay K1,
removing AC power from the compressor. Momentarily depressing the OFF switch will
also de-energize the starter relay. A safety switch S1 located in the cabinet will auto-
matically shut down the system if the cover is opened during operation.
1-10. PROOF PRESSURE TEST OPERATION (Figure 1-3 and 1-4).
Connector J2
permits connection of the proof test remote control cable to the GPU when performing
proof test. The hand held control unit contains a RELIEF VALVE OVERRIDE switch and
a COMPRESSOR RUN switch. Depressing the RELIEF VALVE OVERRIDE switch
energizes the solenoid valve L3, closing the relief valve exhaust. The COMPRESSOR
RUN switch is connected through S5 across the ON switch and provides for remote start
capability of the GPU. Both switches are momentary type controls and must be held down
to keep on. During the Proof Pressure Test, Pressure Switch S4 is bypassed by the
COMPRESSOR RUN Switch S6 through Pressure Switch S5 allowing the compressor to
pump above the normal 6000 ± 200 psig cutoff. When the pressure reaches 6900 ± 350
psig the relief valve will open, verifying its operation. Pressing the RELIEF VALVE
OVERRIDE switch S7 closes the exhaust port of the relief valve and allows the compressor
to continue pumping until the pressure switch S5 opens at 7750 ± 250 psig and stops the
compressor motor. A remote digital readout device provides the operator with a constant
pressure reading during the proof pressure test. The digital readout device connects to the
pressure transducer unit via a 100 foot cable. A test hose connected in line with the closed
system by means of a T connector permits pressure sensing by the transducer.
Change 3 1-7
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