TM 5-4220-233-14
SECTION III. PRINCIPLES OF OPERATION
Paragraph
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Principles of Operation .......................................................................................1-11
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PRINCIPLES OF OPERATION.
NOTE
Reference desiginators are used for clarification purposes
only; however, they are not Identified on the equipment
The mobile compressed gas Servicing Unit is used to fill SCUBA cylinders with breathing air. The Servicing
Unit consists of a trailer assembly and a body assembly.
a.
Body Assembly. The body assembly is bolted to the trailer and can function while mounted on the trailer
or can be removed from the trailer and operated independently. The body assembly consists of an aluminum
frame which provides the mounting provisions for the Compressed Gas System storage cylinders and control
panel and accessory components including a trough, and a tool box/
(1) Compressed Gas System. The Compressed Gas System consists of eight large storage cylinders
(Cylinders #1 through #8) capable of storing breathing air at 5000 psig. Figure 1-4 depicts an operational
schematic of the system air flow described in the following paragraphs. Each storage cylinder has a shutoff
valve (MV100 through MV107) connected to its outlet port that isolates the pressure in each cylinder from the
rest of the system. Flexible hoses connect the storage cylinders to a high pressure manifold (MAN 100)
mounted on the control panel. The high pressure manifold directs the flow of air to the storage cylinders when
filling the Servicing Unit or to the low pressure manifold (MAN 200) when filling SCUBA tanks.
(a) Each of the eight flow paths from the storage cylinders to the high pressure manifold also contain a 1/4-turn
ball valve (MV108 through 115) and a 0-6000 psig cylinder pressure gauge (Pl100 through PI107). A recharge
station is connected at the Inlet to the manifold with a recharge valve (MV116) and a connection port. This
station Is used when refilling the storage cylinders.
(b) At the outlet of the high pressure manifold, the manifold valve (MV117) Is provided to Isolate high and low
pressure portions of the system. Down stream of this valve, air passes through a 90 micron particulate filter
(F100). The air is, then, diverted to the high pressure valve (MV119) or to a pressure regulator (PR100). The
pressure regulator(PR100) is used to control the fill pressure of the SCUBA cylinders. Two 0-6000 psig
pressure gauges (PI108) manifold pressure gauge and (P1109) servicing pressure gauge are connected to the
pressure regulator for monitoring the inlet and outlet pressure. Downstream of the pressure regulator the
servicing valve, (MV118) isolates pressure to the low pressure manifold.
(c) The low pressure manifold directs pressure to four fill stations (#1 through #4). The fill stations can be used
independently or simultaneously. Each fill station contains a fill station valve (MV200 through MV203) and
a outlet port that connects to 15 foot long flexible fill hoses. The fill hoses have a yoke adaptor (YFA200
through YFA203) at the outlet that can be connected to SCUBA cylinders with either "J" or "K" type
connections. The low pressure manifold is also connected to the bleed off valve (MV204) that is used to
bleed pressure from the system once the SCUBA cylinders are filled. Each manifold contains a relief valve
(RV100 and RV200). The storage cylinder valves, also, contain relief devices to vent excess pressure
overboard, if the air pressure exceeds safe levels.
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