TM 5-810-15
belt size larger than recommended i.e. if a conveyor
and 80 ton capacity cars which are more popular at
is sized at 30 inches wide to handle a certain
smaller sized plants.
capacity, then use a 36-inch wide belt. Conveyor
speeds in excess of 700 fpm are not recommended
5-7. Railcar unloading system components.
for western type coal.
a. Railcar scales. Railcar scales are optional for
large plants if their use can be justified. These
5-6. Coal delivery.
scales are usually not installed in a coal handling
a. General. The method of delivering coal to the
system.
b. Railcar haulage. The designer can select from
plant can be a significant cost in the delivered price
of the coal and will affect the design, operation and
capstan type, drum type, or hydraulic type car
cost of the coal receiving system. The delivery
pullers. Cost is dependent upon the type of car
mode depends on such factors as, plant location,
puller arrangement and accessories provided. The
distance from mine to plant, daily "burnrate" under
capstan type puller is the cheapest, and is used
full load conditions, available coal storage area and
where one or two cars have to be moved. The
the cost of competitive transportation methods.
capstan puller can only be used on level track, and
The ability to receive coal by either truck or rail can
has very limited capabilities. An alternative for very
be advantageous and create a competitive pricing
small systems where three to four cars are moved
atmosphere. The ability to accommodate 10-15
per week, a front end loader fitted with a railcar
railcars or higher multiple car shipments can enable
moving device should be considered. Drum or
the user to obtain lower shipping rates and reduce
reversible type railcar pullers provide more
demurrage on the railcars due to the amount of
versatility and are becoming the most commonly
time a car spends at the plant. Enough track must
selected units. The operator makes one connection
be provided at the plant site to allow for the loaded
to a "string" of railcars and pulls them backward or
and empty railcars and the unloading area. The
forward, up or down grades, and around curves
economic justification for a loop track or spur track
with a car puller. The designer will ensure that the
rail storage system can be made as a result of
operator and control panel is well protected from
savings in freight rates, if space permits.
the railcar pulling rope. A railcar string is usually
b. Truck delivery. Trucks are an extremely con-
one to twelve fully loaded cars. Hydraulic car
venient form of coal transportation, but due to the
pullers are usually the most expensive. They are
high manpower and fuel costs, this type of trans-
used at larger plants where high volume railcar
portation has become expensive. Over-the-road
moving is required. In making a selection, the
trucks vary in net carrying capacity from 10 to 40
designer must take number of loaded railcars, track
tons. Trucking coal more than 150 to 200 miles to
grade, radius of curvature of track (straight
a plant site usually increases the delivered price of
preferred), track condition (new or old), operating
coal to a cost that is financially unacceptable for
temperature, and amount of travel distance re-
efficient operation. Truck delivery of coal can
quired into consideration. The designer should
usually be incorporated into the design of a railcar
consult a railcar manufacturer for final equipment
unloading hopper. If trucks are the sole method of
selection.
c. Railcar shaker. Railcar shakers are used to
coal delivery, the designer should investigate the
economics of a covered shed over the unloading
vibrate the railcar for fast removal of coal from the
hopper. Truck hopper should be a minimum of 12
railcar without the operator having to get inside the
feet by 12 feet with a steel grating covering the
car and manually clear the material out, thus
dump area. Maximum grating opening should be 6
reducing unloading time and manpower
inches square. Grating should be designed to
requirements. Car shakers can be the overhead or
withstand the loads imposed by the fully loaded
side mounted type. Side mounted car shakers
truck. Truck weighing scales are optional subject to
require a foundation outside of the rails, and this
both economics and justification.
becomes a problem if there are two or more
c. Railroad car delivery. This is the most com-
railroad tracks spaced close together. This type of
mon form of coal delivery to the boiler plant. If a
shaker is more expensive than the overhead type.
plant has good access to a rail network, the
The overhead shaker is the more common of the
delivery of coal in 70-100 ton railcars is usually
two types of shaker, having been in proven use for
more efficient and economical than delivery by
many years. The designer must ensure that suitable
trucks. The most common size of railcar is the 100
electrical interlocks are provided for the hoist and
ton capacity car. The designer should also take into
shaker to prevent incorrect use.
consideration any requirements for the smaller 50
5-3
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