Automatic Combustible Gas Alarm and Air-Purging Systems

TM 5-6640-213-14

(a) Close the air tabletop-mounted

stopcock (8).

(b) Close the valve to the manometer (9).

position.

(d) Allow time for pressure buildup in the

air surge tank.

(e) Connect the RVP gage to the fitting.

(f) Open the valve (3) to the

manometer (9).

(g) Adjust the air pressure regulator (2)

until the manometer with the gage reading.

(h) Compare the pressure indicated on the

manometer indicates the desired pressure.

Automatic Combustible Gas Alarm and Air-Purging Systems.

(1) Purpose and General Description.

(a) The automatic combustible gas alarm is a cali-

brated instrument designed to continuously monitor for combustible

gas/air mixtures.

It alerts personnel of combustible mixtures that

could cause explosions and fires, and it automatically activates an

air-purging system.

(b) The alarm system consists of a main control unit

and a remote detector assembly. The main control unit (2, fig. 1-4)

and 10, fig. 1-5) is in a protected nonhazardous area and connects

electrically to the detector assembly (21, fig. 1-4). The alarm can

operate using 115/230 volts ac, 50/60 cycles, or 12 volts dc, with 15

watts of power. The alarm is calibrated for propane and has a set-

ting of 20 to 40 percent of the lower explosive limit (lel) of gas-

oline. The remote detector voltage is 5.5 volts dc. An indicating

meter shows the concentration level of a sample being monitored, and

adjustable dual level alarm circuits are triggered whenever a concen-

tration exceeds the preset level or lower explosive limit (lel).

(2) Cabinet Assembly of the Alarm System. The cabinet

assembly houses the electronics and control circuits necessary for

instrument operation.

Incoming power and detector leads enter the

cabinet through 3/4 inch conduit fittings. The controls, fittings

and connections are discussed below.

(a) Green Pilot Light. When the instrument power is

on and the detector circuit is energized, the green pilot light comes

on.

(b) Blue Fail Light. When there is equipment failure

or malfunction, the blue fail light comes on.

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