together at the overlapped seams. Tanks vary in design
in relation to commodity transported Some, like Army-
owned tank cars used for the transportation of petroleum
products, are constructed to provide one large
compartment (fig 2-6), other types are divided into
several compartments so as to carry different kinds of
liquids at the same time.
9-33. Construction Features
a. General. The superstructures of tank cars
(shells) must be constructed of materials which resist
corrosion, or be lined with corrosion-resistant material.
For this reason, tank shells are built of alloyed steel,
nickel steel, or aluminum. Insulation is sometimes
required to maintain an even temperature for certain
Some viscous liquids require the
application of heat to facilitate unloading. This normally
is accomplished by steam coils installed inside the tank
Figure 9-5. Arrangement of dome and, bottom
b. Dome. Most tank cars are equipped with
domes (fig 2-6). These are cylindrical chambers affixed
Tank Cars in Theaters of Operations.
to the top of the tank to provide a means of filling the
Petroleum products are the principal commodities
tank to its full cubic capacity. Domes also serve as
moved in tank cars in oversea theaters of operations.
reservoirs for the accumulation of gases and fumes that
Tank cars of AAR, DOT, and CONUS specifications,
develop in the transportation of some liquids. The size
modified by emergency austerity demands, are standard
of the dome is governed by the size and class of the
for oversea theaters. The United States type center-sill
tank to which affixed. In multiple-compartment tanks,
construction between bolsters is incorporated in car
each compartment is equipped with a separate dome.
designs, and side buffing is provided for In designs
Domes are provided with vents or safety valves to
where hook-and-link couplers are used as shown in
exhaust accumulated gases or vapors. The details of
dome and outlet valve arrangement are shown in figure
applied to the bolster center-sill connection; this is
preferable to the conventional European use of side sills
for buff resistance Standard bottom outlet valves and
dome safety valves are incorporated in tank car
installed on the underside of the tank and provide a
specifications, which are available from the US Army
means of emptying the contents of the car. They must
Mobility Equipment Command, St. Louis, Mo.
be constructed in such a manner that they will be
capable of passing the type of lading carried, whether it
9-34. Maintenance and Repair
be free-flowing liquid (aviation gasoline) or heavy
viscous materials (crude oil, molasses). The outlet
a. General. A leaky tank is one of the more
valve must be able to pass the contents without blocking
common defects encountered in tank car maintenance.
or stopping. It must also be made of materials which
The first and most vital tank car maintenance principle
resist corrosive action. Outlet valves extend downward
is: CAUTION-NEVER APPROACH A L,EAKING TANK
from the bottom of the tank to a point below the
CAR WITH AN OPEN LIGHT. This is applicable
underframe members, providing a ready access. These
whether or not the inspector knows what the lading
valves are opened and closed by a mechanism housed
consists of. In fact and in practice, an open light
in the valve and activated by a rod which passes from
(match, torch, candle, or lantern) must NEVER be used
the valve upward into and through the tank body, and is
in the inspection of tank cars, empty or loaded.
affixed to the inside of the dome housing.