Method of forming a composite foam insulated jacket for a railroad tank car

A railroad tank car includes a tank body and means for applying generally uniform heat to the lower portion of the body. There are a plurality of spaced generally semicircular rings attached to the body with each pair of adjacent rings defining a heat chamber which extends laterally about the lower portion of the tank body. There are longitudinal channels having ports which open into each of the heat chambers. There is a cover for the tank which includes a longitudinally extending generally semicircular metal jacket. A layer of insulation is positioned about the jacket and a layer of plastic foam overlies and adheres to the insulation. The structure is completed by a plastic exterior coat, preferably fiberglass, which overlies and adheres to the plastic foam.

SUMMARY OF THE INVENTION 
The present invention relates to railroad tank cars and in particular to a 
combination insulation and cover which encloses the tank and heater. 
Another purpose is a tank car having a simply constructed reliable 
one-piece exterior coat. 
Another purpose is a method of applying a one-piece laminated jacket to a 
railroad tank car which uses the tank body as a mold. 
Another purpose is a laminated jacket for a railroad tank car body which 
provides built-in expansion control and is air tight. 
Another purpose is an improved jacket for a railroad tank car body which 
eliminates the heretofore used sliding anchors. 
Another purpose is a jacket formed of sprayed-on laminations for use on a 
railroad tank car body. 
Another purpose is a jacket construction for a railroad tank car body which 
eliminates the requirement for painting. 
Another purpose is a laminated jacket for use on railroad tank car bodies 
having substantially less weight than heretofore used constructions. 
Another purpose is a laminated jacket for use on railroad tank car bodies 
which provides considerable savings in manufacturing costs and maintenance 
over the life of the car. 
In the disclosed embodiment the one-piece exterior jacket of this invention 
is used in a tank car which includes an annular heater, which heater can 
be applied to all types and sizes of tanks with no design modifications. 
The disclosed tank car heater provides more efficient and uniform heating 
over the entire heater area and it makes more efficient use of heating 
steam. The disclosed tank car heater provides a heating space at 
substantially less cost than previous designs and in addition, provides 
stiffening for the tank itself. The disclosed tank car heater provides 
uniform heat and uniform pressure to the heat chambers. 
Other purposes will appear in the ensuing specification, drawings and 
claims.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Railroad tank car exterior heaters presently in use generally consist of 
longitudinally extending half oval sections, six or eight inches wide, 
which cover the lower portion of the tank with spaces in between. The ends 
of the heaters are connected with the steam supply and return line so that 
steam is circulated through each half section, thereby transferring heat 
to the commodity within the tank. The areas between the half oval sections 
generally receive heat from a fin construction. The principal drawback 
with this type of construction is that it does not provide a uniform heat 
for the contents of the tank. In addition, each different design of tank, 
whether it be a straight shell, scalene cone, opposed frustoconic or plain 
sloping bottom, must have a different design for the half oval heaters and 
a different design to facilitate drainage of the condensate. The present 
invention overcomes the above disadvantages as will appear in more detail 
hereinafter. 
In FIG. 1 a tank car indicated generally at 10 includes a tank 11 (see FIG. 
2) which has a cover 12 over generally the lower portion thereof. The tank 
car 10 is mounted in the conventional manner upon trucks 14 and there are 
the usual couplers 16. The conventional ladder and inlet and outlet 
connections are fixed on the tank in the normal manner. 
Looking at FIG. 2 the tank has positioned thereupon a series of generally 
uniformly spaced semicircular rings or channels 18 which may be termed 
stiffening rings and divide the lower half of the tank exterior into heat 
chambers 20, generally uniform in size. The rings, which are each formed 
by two generally equal sections, are positioned along generally the entire 
length of the tank and thus will divide the exterior lower portion of the 
tank into a series of annular heat chambers. There are two, although only 
one is shown herein, longitudinally extending channels 22 which are 
positioned upon the upper ends of the rings 18 and form the upper closures 
for each of the heat chambers 20. There is a port in each longitudinal 
channel 22 opening downwardly into each chamber 20. The ports are shown in 
detail in FIG. 4 at 24. Ports 24 are graduated in size with the smallest 
port being adjacent the center of the tank and the largest ports being 
adjacent the opposite ends of the tank. For example, the ports may vary in 
size from 3/8 inch to 3/4 inch, with such variation being uniform between 
the center and outer ends. 
It is customary in the heating of tank cars to use steam as the heat medium 
although the invention should not be limited to this application. In the 
event steam is used, the center stiffening ring 26 forms the steam inlet 
and there is a pressure reducing valve 28 at the inlet so as to provide 
generally constant steam pressure within the heat chambers. The steam 
flows into ring 26 (FIG. 3) and then through an opening 25 into 
longitudinal channels 22 and then downwardly into each of the heat 
chambers 20 through the described ports. 
Directly adjacent inlet ring 26 there is a condensate drain 30 which is 
illustrated particularly in FIG. 4. Drain 30, which may have a steam trap 
32 associated therewith (FIG. 2) so as to drain only condensate, extends 
inwardly through the outer jacket to be described hereinafter and is in 
communication with interior space 34, illustrated in FIG. 4, which 
represents one of the steam or heat chambers. In order to connect the 
various heat chambers so that the condensate from all such chambers will 
drain through outlet 30, each of the stiffening rings 18 is formed in two 
sections defining a notch 36, which notches are at the bottom of each ring 
and are in longitudinal alignment so that the condensate from each of the 
heat chambers 20 will drain toward the center of the car. 
Steam is applied to inlet ring 26 with pressure reducing valve 28 insuring 
that the pressure at the inlet is always a predetermined value, for 
example 53 psi, so as to provide a generally constant temperature within 
the various heat chambers. At a value of 53 psi inlet pressure the heat 
chamber temperature will be a generally constant 300.degree. F. The steam 
flows into the longitudinal channels 22 and then through the variably 
sized ports 24 into each of the heat chambers 20. The condensate from the 
steam drains along the bottom of the various heat chambers through the 
spaced stiffening rings 18 to condensate outlet 30. 
Because the steam is applied at uniform pressure and temperature to 
generally the entire bottom half of tank 10, the heat will be uniform. All 
parts of the tank bottom will be in contact with the steam chambers and 
thus there will be no intermittent heat as in the previously-described 
half oval type of system. By utilizing a pressure reducing valve and a 
steam trap, more efficient use of the steam is provided. In addition to 
defining the heat chambers it should also be understood that the 
stiffening rings 18 do provide a certain degree of support to the tank. 
Because the stiffening rings are positioned on the tank exterior in 
longitudinal spaced relation to each other, the same design may be 
utilized regardless of the shape and size of the tank. For example, a 
straight shell, scalene cone, opposed frustoconic or plain sloping bottom 
tanks all may utilize the same design with only the actual size of the 
rings being varied. 
It is essential to maintain even pressure to secure the maximum and most 
efficient use of the steam in heating the contents of the tank. This 
result is provided by the pressure reducing valve situated at the heater 
inlet. A steam trap positioned at the heater outlet limits the discharge 
to condensate and there is no steam lost from the heat chambers. 
Tank cars with heaters of necessity must have some form of insulation and 
the insulation is conventionally covered with a metal jacket so as to 
protect it from the weather. The jacket normally adds nothing to the 
strength of the car structure as it is free to move with the expansion and 
contraction of the tank during the heating cycle. Conventionally, sliding 
anchors are positioned at each end of the car and sliding sections are 
positioned at each body bolster to accomodate expansion and contraction. 
Such sliding sections are neither watertight nor airtight and so a degree 
of the protection for the insulation is lost. 
The present invention provides a laminated jacket and insulation combined 
to form a one-piece cover for the car with built-in expansion control as 
well as providing an airtight cover. This is accomplished by using the 
tank as a mold over which the various layers to be described hereinafter 
are formed. 
Looking at FIGS. 3, 4 and 5, the heater spaces 20 are covered by a steel 
jacket 40 which will be secured to the stiffening rings by welding or the 
like. The entire tank including jacket 40 forms the mold for the laminated 
cover. First, an absorbing insulation material, indicated at 42, is formed 
about the entire tank. This insulation may be sprayed on or applied in any 
suitable manner and it may be similar to the Pittsburgh Corning product 
known as TEMP-MAT made of glass fibers and put in mat form by a needling 
process. Other manufacturers make a similar insulation such as the 
Johns-Manville SPIN GLASS. The insulation will absorb tank expansion and 
will act as a heat barrier between the tank which will be heated to 
approximately 325.degree. F. and second layer of insulation to be 
described which normally will accept heat only up to about 275.degree. F. 
Formed about the insulation layer 42 is a layer of foam, for example a 
urethane foam, of approximately 2 lb. density and preferably having a 
thickness of approximately two inches. The foam layer is indicated at 44 
and again may be sprayed or otherwise formed upon insulating layer 42. 
Positioned about the urethane foam layer 44 is the final cover 46 which 
may be a polyester or epoxy reinforced fiberglass having a minimum tensile 
strength of approximately 38,000 psi. The fiberglass cover can be sprayed 
on so that the entire structure is a unitary one-piece outer cover or 
jacket for the entire tank. It is important that the materials, as sprayed 
or otherwise applied, adhere to the previously-deposited layer so as to 
form a unitary structure. Normally the various layers will be applied, one 
at a time, thus permitting one layer to cure before the succeeding 
material is applied to it. 
By utilizing a fiberglass exterior, the resin may be mixed with a suitable 
color or pigment so that the desired coloring may be applied to the tank 
with elimination of painting which is conventionally a process which must 
be repeated as the car remains in service. In addition, the paint or 
pigment may have an ultraviolet inhibitor added thereto so as to lengthen 
the life of the color. It is possible to provide a 15-year life to the 
exterior as compared to the current five-year period for a normal paint 
coating. 
An additional advantage of using the described laminated structure which 
includes the foam layer 42 is that the foam itself provides a seal at the 
body bolsters and sills, thus making the entire structure airtight to 
provide better insulation and a more weatherproof structure. 
It is conventional practice in the manufacture of a fiberglass product to 
mold the fiberglass and auxiliary layers about a particular shape and then 
to apply the molded laminated product to its ultimate structure. The 
construction herein works the process in reverse in that the laminate is 
formed about the structure it is intended to cover. Thus, it is not 
necessary to have various size molds to accomodate different sizes and 
configurations of tanks. 
In addition to the above-described advantages, the conventional steel outer 
jacket of the tank has been eliminated with a savings of approximately 
6,000 lb. of weight. The insulation is more efficient, for example as much 
as 30 percent more efficient. This provides a substantial saving in energy 
in applying the heat necessary to unload the tank. 
Whereas the preferred form of the invention has been shown and described 
herein, it should be realized that there may be many modifications, 
substitutions and alterations thereto.