Low Pressure Steam Boiler

TM 5-6640-212-14

b. Operation.

2-21. Automatic Combustible Gas Alarm and Air

Purging System. Description.

(1) Set thermostatic control to desired temperature.

The automatic combustible gas alarm is a

CAUTION

calibrated instrument designed to continuously monitor

for combustible gas air mixtures. It alerts personnel of

Do not allow high pressure steam

combustible mixtures that could cause explosions and

boiler to operate when steam flow is

fires, and it automatically activates an air purging system.

interrupted.

b. The alarm system consists of a main control unit

(2) Turn AUX switch on the gum bath to the ON

(cabinet assembly) (fig. 2-16) and a remote detector

position.

assembly (fig. 2-17). The main control unit is wall

mounted in a protected nonhazardous area and

NOTE

connects electrically to the detector assembly. The

Do not exceed service-pressure

alarm can operate using 115/230 vac, 50/60 Hz, or 12

temperature rating.

vac, with 15 watts of power. The alarm is calibrated for

propane and has a setting of 20 to 40 percent of the

(3) To shut down the high pressure steam boiler, set

lower explosive limit (lel) of gasoline. The remote

the AUX switch on the gum bath to the OFF position.

detector voltag voltage is 5.5 vdc. An indicating meter

shows the concentration level of a sample being

2-20. Low Pressure Steam Boiler. Description. The

monitored, and adjustable dual-level alarm circuits are

low pressure steam boiler (fig. 2-12) is located in the

triggered whenever a concentration exceeds the preset

front compartment of the semitrailer, on the left side as

level (lel).

you enter the compartment. The low pressure steam

boiler is used to preheat water from the water tank to the

c. The cabinet assembly houses the electronics and

high pressure steam boiler which is used with the gum

control circuits necessary for instrument operation.

bath. The low pressure steam boiler has its own

Incoming power and detector leads enter the cabinet

circulator pump (fig. 2-13) which can be used to draw

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

water from the water tank, or external water supply; if

and connections are discussed below.

tank or external water supply is under pressure,

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

circulator pump need not be turned on. The boiler is

on and the detector circuit is energized, the green pilot

equipped with an automatic water fill system (fig. 2-14),

light comes on.

and glass sight glass. The automatic water feeder

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

system (fig. 2-15) will automatically fill boiler to proper

or malfunction, the blue fail light comes on.

level and shut off the water when an internal float valve

(3) Amber Warn Light. The amber warn light comes

closes when proper water level is reached. The low

on when a combustible gas condition exceeding the low

pressure boiler also contains a pressure gage, pressure

alarm setting exists at the remote detector, or when the

cut-off switch and a pressure release valve to protect the

alarm test switch ((e) below) has been actuated.

boiler from damage if boiler pressure is too high, or water

(4) Red Alarm Light. The red alarm light comes on

level is too low. Circuit breakers for the pressure steam

when a combustible gas condition exceeding the high

boiler, high pressure steam boiler and gum bath must be

alarm setting exists at the remote detector, or when the

turned on for use. After tests are completed, open drain

alarm test switch has been actuated.

valve (fig. 2-11) on low pressure boiler and drain off

(5) Alarm Test Switch. The alarm test switch is a

water from boiler then close valve. Turn off circuit

momentary contact pushbutton switch incorporated with

breakers.

the warn light. When it is depressed electrically, there is

a simulation of an alarm level of gas concentration at the

CAUTION

remote detector. This switch provides a functional check

If trailer is to be stored in an area

of the analyzer and remote alarm circuit.

where the temperature will be below

freezing and no heat supplied, be

sure to drain all water from system to

prevent damage to boiler.

2-26