(a) Close the air tabletop-mounted
(b) Close the valve to the manometer (9).
(c) Place the ON-OFF switch in the ON
(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
(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
It alerts personnel of combustible mixtures that
could cause explosions and fires, and it automatically activates an
(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
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
(b) Blue Fail Light. When there is equipment failure
or malfunction, the blue fail light comes on.