TM 55-203
CHAPTER 11
HEATING
11-3. Pressure-Reducing Valve
11-1. General
The pressure-reducing valve (fig 11-2) located in the
locomotive provides a means of maintaining a
a. Modern passenger cars are heated almost
predetermined reduced pressure on the train steam-heat
universally by finned-copper, floor-mounted, steam
line. Outside temperatures and the number of cars in the
radiation systems supplied from the locomotive. A well-
train are the factors which govern the pressure desired
constructed and insulated car will use from 250 to 350
Steam is admitted to two chambers in the valve. It
pounds of steam per car per hour. In some cases,
passes an open or unseated auxiliary valve, which is held
passenger cars are heated by a split system which
includes an overhead air circulating system provided with
heating and cooling coils and floor-mounted standing
radiation along the car sides Some electric trains and
motorcars use electric heat in which resistance coils
usually are placed beneath the seats or along the walls.
b. The systems most generally used today include
the steam vapor, the vapor zone, the straight vapor, and
the direct steam (or pressure heating) systems The vapor
zone system uses steam at high pressure; the others use
steam at low pressure. The steam vapor system is
controlled manually. In other systems, automatic control
is furnished by thermostats and electrically energized
valves. The steam vapor system is used on most Army-
owned passenger cars.
11-2. Steam Line Connections
The steam line of each car has a flexible metallic conduit
to the line of an adjacent car. One end of the conduit
connects to the car steam heat line, and the other end,
which is equipped with a steam coupler, connects to a
similar coupler on the flexible metallic conduit on the
adjoining car. A steam coupler includes a body, a spring-
loaded locking lever, and a gasket which is held in place
by a spring Flanges and lugs provide a means of
interlocking connections so that the couplers are
steamtight. The end trainpipe valve provides a means of
shutting off the steam in the main steam line at each end
of a car. A conduit includes an end-valve connector, an
upper body, an intermediate casting, a lower body, and a
coupler adapter The coupler adapter is joined to the lower
body by means of a sleevetype joint. All these parts are
connected to form ,a complete unit by use of steamtight
Figure 11-1. Flexible metallic conduit.
ball-type joints which permit the conduit to adjust to any
irregularity.
11-1
Previous Page
