Design of a 500 Ton Biti
Coal Washing Plai
Design of a 500 ton
bituminous coal washing
For Use in Library Only
500 TON BITUMINOUS
COAL. WASHING PLANT
PRESIDENT AND FACULTY
ARMOUR INSTITUTE OF TECHNOLOGY
FOR THE DEGREE OF
BACHELOR OF SCIENCE IN MECHANICAL ENGINEERING
HAVING COMPLETED THE PRESCRIBED COURSE OF STUDY IN
June I. 1906
ILLINOIS INSTITUTE OF TECHNOLOGY
PAUL V. GALVI-N LIBRARY
35 WEST 33RD STREET
CHICAGO IL 60616
DESIGN OF A 50G TON BITUMINOUS COAL WASHING PLANT.
HENRY JACOB SAWTELL,
PRESENTED JUNE 19C6.
To make the operation of the plant more easily under-
stood, and to show the development reached in this work. a
short account of the action of the machines is here given
with a short history tracing the development from the crude
early machines to those now in use. The descriptions are
By coal washing is meant the process of separating the
impurities with which the coal is mixed as it comes from
the mine by means of special machines which use water as
The coal as it comes from the mine consists of coal
proper^ jand impurities, such as slate, sulphur in the form
of pyrites or calcium, 'and magnesium sulphate, bone coal,
and fire clay. With some exceptions these substances have
a higher specific gravity than the pure coal, which is about
1.28 or 1.30, and it is this fact that makes their separa-
The principle of the washer is demonstrated when two
substances of different specific gravities are shaken to-
gether in a box. The heavier substance will settle in a
flayer on the bottom, while the lighter substance will re-
main in a layer on top. This would not occur in a
vacuum; water is a better medium than air.
The method of washing to separate materials of diffe-
rent specific gravities is a very old one. It has been
used in mining operations for a long time. In its use with
precious metals the process is reversed, it being desired to
save the heavier substance and get rid of the lighter.
Almost every conceivable arrangement has been used;
the process has been developed from the simple trough washer
to the senfcative jigs. Some have tried air as the medium,
others use centrifugal force, but none have proved as satis-
factory as the jigging method.
The simplest washer is known as a trough washer, and
consists of an inclined trough with cross riffles at regul-
ar intervals. The coal is fed at the top and is given suf-
ficient force by the water flowing down the trough to carry
the coal over the riffles with it, leaving the slate on the
recesses. At the bottom is a draining screen which sep-
arates the coal from the water. The slate is removed at
intervals by an attendant with a rake. This is a very
crude and imperfect method, and requires an excessive amount
An improvement on the simple trough washer is the
Elliott trough washer. This consists of an inclined trough
in which a flight conveyor operates. The coal and impur-
ities are fed at the center of the trough. Water enters
at the top. The flights on the conveyor act as the riffles,
the water washing the coal over the flights. The
impurities are carried up the trough and are discharged
at the top end. The coal passes down the trough to a re-
ceiving car, passing over a draining screen before it enters
the car. The process is thus continuous and requires but
little attention. Its marked simplicity is a feature, but
a large quantity of water is required and the work, rather
expensive because of its imperfect separation.
Another washer along this line is known as the Scaife
trough washer. This consists of an inclined semi-circular
trough, about two feet in diameter, and twenty-four feet
long, provided at intervals with riffles. Running along
the center of the trough is a shaft provided with fingers
which act as stirrers. The shaft is given a reciprocating
motion. The raw coal is fed at the upper end. The im-
purities remain on the riffles, the washed coal being dis-
charged at the lower end. When the riffles are full the
supply of coal is shut off, the good coal remaining in the
trough is washed off and the trough cleared by dumping the
refuse into a box below. The process in intermittent, but
the advantages claimed for it are its simplicity and the
lack of a screen to wear out. The fingers or stirrers
which are the only parts subject to much wear being easily
The Campbell bumping table consists of a shallow
trough 2 l/2 x 8 f t . x about 6 or 8 inches deep, open at
both ends. It is hung in an inclined position, and by
means of a cam is thrown against a bumping post at the
upper end. The coal is sluiced on with water and as the
bumping table is thrown against the post the impurities are
thrown off the upper end while the pure coal is washed off
the lower end with the water.
The Robinson washer is of different construction. The
coal and refuse are fed at the top of the vessel which is of
the shape of an inverted cone. Water enters at the bottom
with sufficient force to carry the coal over one side with
it. The impurities settle in the bottom. A vertical shaft
with stirring fingers attached keep;'the mass agitated thus
allowing a better separation.
An arrangement of German origin drops the raw coal
past a blast of air which is of sufficient strength to force
the pure coal to one side allowing it to drop into a bin.
The impurities drop past into a refuse bin.
A separation by means of centrifugal force has been
used in the anthracite fields. A spiral trough is revolved
to throw the slate in the coal, which is fed at the upper
end, off the trough allowing the pure coal to slide down
into a bin at the bottom. This is merely a rough separation.
Jigs have to a large extent replaced the older methods
of washing, being more economical and thorough.
The Luhrig jig is typical and is widely used, giving
excellent results with economical working. The two cross-
sections here shown are for nut and fine coal treatment.
The nut coal jig consists of a box or chamber separated
LUHRir. NUT i OAL
LUHRIG FELDSPAR JIG
- at about the center by a partition extending about half
way down from the top. On one side is a plunger which is
actuated by an eccentric through a connecting rod. On the
other side is a screen on which the raw coal is fed. The
screen is inclined, the coal being fed at the upper end.
The plunger imparts a pulsating motion to the water which
fills the entire box and this motion agitates the body of
coal. The impurities being heavier settle in a layer on
the bottom on the screen. The mass gradually works to the
lower end where the coal is washed over the sill with the
water. The impurities pass through an opening under the
sill which is known as the slate valve. Below this slate
valve is a conveyor trough into which the impurities fall
and are carried by the screw conveyor to an elevator boot.
The elevator raises the impurities to a trough or conveyor
which leads to the refuse heap. This slate valve opening
can be regulated so as to keep a uniform bed of impurities
on the screen and thus prevent good coal from passing through
the slate valve and being wasted. The coal is sized before
being fed to the jig so that very little passes through the
screen. Most of the material that does pass through the
screen is very fine and is refuse, so a draining valve is
placed in the bottom of the box to allow this waste material
to be run off. This draining valve is connected to a sluice
way which leads to the refuse settling tank. A continuous
supply of water is fed at the rear of the jig through the
The fine coal jig is of about the same construction
and operation, but differs in the manner of handling the
waste materials. In these jigs it is necessary to handle
coal from that which will pass through a 3/4 inch round
perforation down to a fine dust. The box is divided as
in the previous case with the plunger on one side and screen
on the other. Cn the screen is placed a layer of feldspar
which has a specific gravity higher than the coal, but lower
that the impurities. The pieces have a diameter larger
than the openings in the screen. The coal is fed in the
same manner and works its way across the screen to the sill
where it overflows with the water into the sluiceway in front.
The refuse works its way through the layer of feldspar into
the hoppered bottom of the jig box from where it passes through
the refuse gate into a sluiceway by gravity and is carried to
the refuse settling tank. These jigs can be placed in a
battery up to twelve, so that one shaft and sluiceway will
serve the entire battery. In the operation of these jigs
it is very important that the coal treated in each jig be of
The Hartz jig is about the same as the above in general
operation. It differs in construction, being made of sheet
steel with semi-circular bottom.
Berard's machine is another of similar operation.
This machine was introduced as early as 1851 in London.
It was used in Pennsylvania for a few years s» 1873.
The Stutz jig has a few special appliances, the bottom
Till: STEWART TYPE UP J
THE STEWART TYPE OF JIG
being of special shape. In the improved machine the
pulsating mechanism is placed directly under the screen on
which the coal rests. A plant with this machinery capable
of handling 6C0 tons per day of 1C hours has been estimated
to cost $16C00.0C. The cost of washing has been given as
2 cents per ton, but this does not include interest and de-
The Stein jig has a special method of arrangement and
handling the coal. The jigs, which resemble the others,
are double. Coal is fed at the side of one jig. It passes
over this bed to the next jig from which it is discharged in-
to a sluiceway. There is thus obtained a long path and a
thorough separation is accomplished. One result gives a
reduction from 35^ to 1C$ ash and Z% to 1.35# sulphur.
The Stewart jig operates a little differently than the
others. This jig consists of a box with a perforated bot-
tom which is suspended in a tank of water from eccentric rods
by means of which it is given the pulsating motion. The
bottom is inclined. The coal is fed at the upper end and
works its way across the screen where it is washed over the
sill with the water. The refuse passes through a valve in
the front of the jig into the hoppered bottom of the jig
from which it is discharged by an elevator. The coal that
is fed to the jig is not sized. The capacity of each jig
is higher than that of the Luhrig jigs, but with small size
coal the operation is not as economical.
The Diescher washer is similar to the Stewart. The
N'KW I'EXTUKY" N'UT COAL JIG
jig has a different shaped bed and has some variations
in the mechanical construction.
The special feature of the New Century jig is the
plunger. By means of a spring a quick stroke is accomplish-
ed which seems to be very effective in separating fine coals.
Luhrig, New Century, and Stewart type jigs are common-
ly used in the Illinois coal fields. In the selection of
jigs for this plant the Luhrig type were selected because
of the economical construction, operation and high efficiency
The entire plant, in fact, has been equipped with Luhrig ap-
The elevators with the exception of the raw coal, are
Luhrig type. A cut here given shows the type of bucket
and method of discharge. The buckets are perforated to
allow as much water as possible to drain off before the
coal is placed in the storage bin. This moisture remain-
ing in the coal is a serious problem, and will be mention-
ed later. The head wheels are cast iron. The elevator
is driven from the head-end by means of a chain-drive from
a jack shaft. The speed reduction is accomplished by re-
ducing from the jack shaft to a counter shaft and again by
means of a spur and pinion from the counter to the head
shaft. The head and counter shaft are supported on a
Luhrig take-up which facilitates the fitting of the chain
when construction or repairing. This take-up consists of
a sole plate on which the bearings rest. They are spaced
to accommodate the gears and are held thus by a spacing
rod. By means of a take-up screw both bearings are moved
at the same time, thus allowing adjustment of the head wheel
without disturbing the gears.
The raw coal screen is shown by the sketch. It forms
a compact and efficient method of grading the coal. Shaking
screens are sometimes used, but they require more room and
seem to have no greater advantages, altnough claimed by some
to have. The screens are driven by means of gears and
pinions. The jackets are supported by spider arms. The
rinsing and resizing screens are all single jacketed.
An important feature in coal washing is to have coal of
uniform size fed to each jig. This is especially true of
fine coal. The separation of the different sizes is nicely
accomplished in the hydraulic grading box. This consists
of a long box with honpered divisions across the bottom.
The coal is sluiced into the box at one end, the larger
sizes being heaviest settle in the first compartment and
are sluiced to the first jig. The next size collects in
the next compartment, and so on through the six grades.
In this manner each jig can be regulated to a nicety to
wash its product, and excellent results are obtained.
An important feature of tne Luhrig system is the re-
covery of the sludge. In the older style washers the
water used in the jigs was allowed to run off carrying with
it much fine coal in the form of dust. Mr. Karl Luhrig
saved this by allowing the water with the fine coal to pass
into a large settling tank, known as the sludge tank.
The fine coal is here allowed to settle. A slowly
moving conveyor then carries it to an elevator pit located
at one end of the tank.
At the end opposite to that at which the elevator is
located is the suction pipe for the centrifugal circulating
pump. The water at this end is clear enough to allow its
use in the jigs. The water is thus used over and over
again. The only water that is lost is that which is used
in sluicing away the refuse. Enough fresh water is added
as rinsing water to counteract this loss and keep the quant-
ity constant. Tie fjji-tf
He. s /'? i.
" In the design of this plant the following conditions are
to be met. 5CC tons of raw coal are to be washed in 8 hours,
washing the product from the mine that passes through a 3"
round perforation producing 5 sizes of washed coal as follows:
Size Percent Thro. Cver
Sized according to Illinois Coal Operators' Association
standard. All perforations in screens to be round.
It is assumed that the mine will produce from 800 to
100 tons of raw coal per day, and that 50^ will pass through
the 3" perforations.
The following is an analysis of the coal which is from
the Illinois coal field and is taken as a basis for the
design of the plant.
In the raw coal there is 25$ ash, that is, in the coal
passing through the 3" perforations. The coal analysed in
specific gravity solution gives the following results:
66 $ A.
Cr 12.8$ raw coal lies between 1.35 and 1.45, and
carries 19$ ash.
OPERATIC*! AND OUTLINE OF PLANT.
The coal will be taken from the mine tipple where it
will pass through a 3" round perforated screen and be carried
to the raw coal bin by an inclined flight conveyor which will
be operated independent of the washery machinery to allow the
bin to be filled in case the washeniis shut down.
From the raw coal bin coal will be fed to a continuous
bucket conveyor by means of a Link Belt revolving feeder
which will put a uniform load on the elevators and keep a
uniform amount fed to the jigs. The coal will be lifted
by this elevator to a triple jacketed revolving sizing
screen which will separate ,'1, 2, and 3, which will pass
to their respective jigs while 4 and 5 will pass through
into the hydraulic grading box.
Each size of coal will be washed separately, two
jigs being provided for #1, three for #2, two for #3, and
six for #4 and 5.
After passing through their respective jigs #1, 2, and
3 washed coal will be sluiced to draining screens located
directly over bins for their storage. These draining
screens will also act as resizing screens so that any coal
that has been broken and is undersize will be separated
here and pass with the water to a redraining screen where
sizes over #4 will be separated and returned to the boot of
the raw coal elevator. It will thus be allowed to take its
proper place in the rewashing. The fine coal and water
passing through the redraining screen will pass into the
hydraulic grading box. From the grading box the uniform
sizes will pass into the fine coal jigs, six in number, and be
washed separately. The washed coal will pass over the
sill of the jig and be sluiced to a large revolving screen.
#4 will pass over A into a sluiceway leading to the boot of
the Luhrig elevator which will carry it to the top and empty
it into the bin. #5 which consists of much dust and fine
particles will pass through A with the water into the sludge
recovery tank located directly beneath the screen. As the
fine coal settles it will be carried to the elevator pit by
a flight conveyor. A Luhrig elevator will lift the coal
to the #5 bin.
The nut coal will be rinsed by a spray of water on the
draining screens; #4 by a spray on the separating screen,
and #5 by a spray on the coal as it is being lifted to the
bin from the sludge tank.
The refuse passing through the slate valves of the nut
coal j^gs will be carried by a screw conveyor to the boot of
a Luhrig elevator which will lift the slate to a sluiceway and
by which it will be sluiced to the refuse heap. The impur-
ities from the fine coal jigs will pass to a settling tank
from which it will be elevated by a Luhrig elevator to the
The nut coal jigs will be connected with the refuse
settling tank so that the fine particles passing with the
impurities through the screen and settling in the bottom of
the jigs can be run off when necessary.
The water for the nut coal jigs will be taken from
the end of the sludge tank opposite to that at which the
elevator is located. It will be lifted by a centrifugal
pump to the jigs. The pump will be belted to a pulley
on the engine crank shaft.
Fresh water for rinsing the coal will be supplied
from an outside source and will be supplied to the screens
by a steam pump.
The sludge and settling tanks will be provided with
large size drain pipes so that the water could be run out
in case of a shut-down in winter.
The building will be heated by steam. The various
gates and valves will be provided with steam connections
to prevent their freezing in winter.
The building will be lighted with electricity to
allow night work. The raw coal storage bins will have a
capacity of 200 tons, and the washed coal storage bins a
capacity of 270 tons.
Revolving feeder and gate for raw coal bin.
1 Link-Belt revolving feeder, complete.
Also 1 "Spellman" gate complete with levers, etc.
for delivery of raw coal from bin to raw coal elevator.
Raw Coal Elevator.
One continuous bucket elevator 60 ft.
centers for lifting coal from raw coal bin to raw coal
sizing screen. This elevator is to be made up of 16"
x 12" x 18" #10 steel continuous buckets, carried by double
strand of 18" pitch bar link rolling chain, complete with
necessary head, counter, and foot shafts, bearings, collars
sprocket wheels, patent spur equalizing gears, driving pul-
ley on countershaft, and sprocket wheel on foot shaft for
driving revolving feeder, also flat steel track for chain.
Raw Coal Screen.
One triple jacketed revolving screen for raw coal,
inner jacket 12 ft. long; middle jacket 11 ft. long, and
outer jacket 10 ft. long, complete, with 5 15/16" rough
turned screen shaft, spiders, rings, steel cone, and
covering of l/4" plate with 3/4" round perforations, and
1" round perforations for outer anil middle jacket,
respectively, and of 3/8" plate with 1 3/4" round perfor-
ations for the inner jacket, also bearing and countershaft
with bevel gear drive.
Nut Coal Jigs.
Seven Luhrig nut coal jigs, complete with shafts, ec-
centrics, etc. These jigs to be in one battery.
Refuse Elevator from Kut Coal Jigs.
One #5 Luhrig elevator, 15 ft. centers, complete, with
all necessary head, and foot mechanism, chain and buckets,
angle guides, back lining, and driving countershaft with
Nut Coal Draining Screens.
Five 31''t. diameter x 6ft. long nut coal draining
screens, complete, with bearings, spiders, and coverings
of #10 plate - two to have 1 3/4" perforations, two to have
1" perforations, and one to have 3/4" perforations.
Also one 3'C" x 6'C" screen with covering of #10 plate
and 3/4" perforations for over size coal in redraining.
These screens to be complete with counter shaft, etc.
Fine Coal Jigs.
Six Luhrig fine coal jigs, complete, with shafts,
eccentrics, feldspar beds, etc. These jigs to be in one
Fine Coal Draining Screen.
One 4'0" x 10*0" revolving screen, complete, with
shaft, bearings, spiders, rings, and covering of f/-lC steel
plate with l/4" round perforations.
#4 Fine Coal Elevator.
One ,;'l Luhrig elevator, 38 ft. centers, complete,
with all necessary head and foot mechanism, chain and bucket
angle guides, back lining, and driving countershaft with fit-
One conveyor, about 46 ft. horizontal centers, and 1C
ft. vertical centers, complete , with necessary head, counter
and corner shafts, bearings, collars, sprocket wheels, gears,
and Sstrands of £730 chain, each 122 ft. long, fitted with
3/16" steel flights, having reinforcing angles and wearing
shoes ;also necessary steel tracking.
#5 Coal Elevator.
One #4 Luhrig elevator, 55 ft. centers, complete, with
head and foot mechanism, chain and buckets, angle guides,
back lining, and driving countershaft with fittings.
Fine Coal Refuse Elevator.
One #4 Luhrig elevator, 43 ft. centers, complete,
wit$i head and foot mechanism, chain and buckets, angle
guides, back lining, and driving countershaft with fittings.
Gates for Washed Coal Bins.
Five Link^Belt steam- jacketed gates, complete.
Bin and Sluice Lining.
Necessary #12 steel plate linings for bottoms of raw
and washed coal bins; #12 steel lining for chutes, and #14
steel lining for sluiceways.
One #8 Morris Imperial standard double suction
horizontal pump, complete, with pulley, for circulat-
ing water for jigs.
Cne #25 - 7" x 5" x 10" "Gardner" low service duplex
steam pump for fresh water.
Necessary piping, with valves and fittings, from
sludge recovery to pump, and to jigs, grading box and
Necessary piping from fresh water pump to sludge
recovery, draining screens, and to refuse sluice.
Steam piping to steam gates from steam lire in engine
room. Also steam piping to steam coils for heating build-
Necessary 12" vitrified sewer pipe for draining sludge
and refuse pits .
Engine, Line Shaft, etc.
Cne 13" x 18" double class "A" H. S. & G. #122
horizontal engine, 160 R.P.M., 130 H.P., with 80 lbs.
steam pressure, complete, with usual fittings, and a
90" 4-groove split flywheel, sheave for 1 3/8" manila
rope, also pulley for driving centrifugal pump.
Necessary line shafting, jack shafting and counter-
shafting, with rope transmission to main shaft, rubber
belt to jack shafts and chain connection to the various
appurtenances, elevators, conveyors, screens, etc.
The lumber used for the building will be #1 common
yellow pine, and for hart tc.i lumber of suitable quality.
All lumber to be surfaced four sides. The building, with
the exception of the bins, and sludge tank, will be cover-
ed with drop siding and complete with corner fc>oar<ls,window
casing, frieze, etc. The roofing will be 2-ply composition,
and necessary gutters will be provided. The building to be
complete with all necessary doors, windows, and stairways,
the windows being glazed. All exposed wood work is to be
With the building are to be provided all necessary
timber supports for machinery, and all necessary tanks,
chutes, sluiceways, elevator casings, etc.
Foundations are to be concrete.
Many coals of poor quality in the raw state are made
excellent fuel coals be washing, others of low quality and
value are relatively increased. The substances that go to
make up the ash in the furnace are removed by washing. It
is thus that the quality is increased. As coal is now
bought to a large extent on the heat unit basis it behooves
the coal operators to have as small a percent of ash as
By the removal of the impurities which to a large
extent form the clinker in the furnace, such as pyrites
and clay, the capacity of the furnace is often increased.
Another advantage of washed coal is that it is of uniform
size when delivered, which is also condusive toward an in-
creased furnace capacity by giving a uniform fire bed.
In the manufacture of coke the treatment of the coal is
an important matter. Coal of excellent coking qualities,
but which contains too much ash or an excess of sulphur can
often be improved by washing to make a very high-class coke.
In the design of this plant the coal has been treated only
with reference to boiler fuel.
One disadvantage encountered in the treatment of coal
is the amount of water that is retained by the coal, especial-
ly by the #5 size. It is very difficult to lower the per-
cent of water which is often as high as lC^jwhere the coal
has plenty a chance to drain, as in being transported quite
a distance the coal drains quite thoroughly in the large
sizes. The percentage of water above given includes the
water that is contained in the pores of the coal as it comes
from the mine. Often this runs as high as &fo . The water
added from washing remains on the outside and drains off
quite readily in the large sizes, but the #5 size contains
so much fine stuff that it packs very close and holds the
moisture. Attempts have been made to reduce the moisture
but have as yet been unsuccessful in most cases, the treat-
ment being too expensive.
In the preparation of this paper much valuable inform-
ation has been obtained from Mr. A. J. Sayers, of the Link-
Belt Machinery Company, Chicago; John Fulton's book on Coke
has been found to be very instructive, as well as
Richards' on Cre Dressing. The plant and mine of the
Consolidated Coal Company, at Collinsville , Illinois, was
visited. This plant is of about the same capacity and gen-
eral arrangement as the one given in this design, employing
Luhrig apparatus. At East St. Louis, Illinois, the plant
of the Bessemer Washed Coal Company was inspected. This
plant washes coal which the operators buy from the mines in
the Illinois coal fields. The mine owners .often glad to get
rid of the slack which can be washed and sold at a profit.
This plant uses the Stewart type jig with Luhrig recovery.
From the descriptions here given the importance of coal wash-
ing can be seen, as also the magnitude to which it has now
developed. As the better beds of coal are used up the treat-
ment of the poorer grades to make them fit for market b© wash-
ing is bound to occur.
In prepairing the design of this plant it was first at-
tempted to have the machinery arranged to allow for expansion.
As an entirely new equipment would be necessary, and also
alterations in the entire plant, it was thought that it would
be better to have a nearly independent plant than to try to
arrange any additions. As the Stewart jigs have a larger
capacity than Luhrig, and with large size coal they are
quite as economical as the Luhrig, it was thought at first
to install a fewer number of nut coal jigs by using the
Stewart type. It was found, however, that this had been
tried, but had not been particularly successful, so this
500 Ton uiTumnous COAL
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was dropped and the entire plant equipped with Luhrig
apparatus. The plant of the Consolidated Coal Company has
been operating for about a year, running sixteen hours per
day, and is giving excellent satisfaction. No results are
obtainable as to the efficiency of the plant as yet, but the
fact that it was installed by the Link-Belt Machinery Company
will insure a high mark.
In the design of this plant the speed of the screen and
elevators, and sizes of jigs, tanks, etc, were determined as
far as possible from results found to be satisfactory in
Raw Coal Elevator.
This elevator will be required to lii't about 6C tons of
coal per hour, or 1 ton per minute. Each bucket will hold
about 4C lbs. 2000 . 50 buckets per minute.
Each bucket is 18" deep. 50 x 18 = 75 ft. per minute =
speed required. Assuming this as 80^ of capacity, for full
capacity a speed of about 100 ft. per minute will be required
The head wheels being 36 inches in diameter, about 11
R.P.M. will be necessary. With the arrangement of shafting
as shown there are 3 reductions between the line shaft at
150 R.P.M. and the head shaft at 11 R.P.M.
With equalizing gears of 46.75" and 8" diameter the
With 24" and 36" sprockets on chain drive from jack
shaft to countershaft the speed will be raised to 9S E.P.M.
36 x 66 = 99 R.P.M.
With 48" and 32" pulleys froir jack to line shaft the
speed of 150 R.P.M. on line shaft will be met.
48 x 99 = 148.5
The belt could be counted on to slip enough to give
about 11 R.P.M. at head shaft.
Raw Coal Screen.
80^ of coal will pass through first screen, which
equals 48 tons, allowing 4.3 sq.ft. per ton hour;
48 x 4.3 = 2C6 sq.ft. required.
Screen is 12 ft. long.
2C6 = 5.5 ft. = diameter.
TT x 12
57% will pass through next screen;
.57 x 120CCC . 684GC lbs = 34.2 tons per hour.
Allowing 6 l/2 sq.ft. per ton hour.
34.2 x 6.5 = 222 sq . ft. of screen;
second screen 11 ft. long. 222 . 6.5 ft. diameter.
11 x 3.14
48/£ will pass through third screen.
.48 x 1200CC = 576CC lbs. = 28.8 tons per hour.
Allowing 8.7 sq . ft. per ton hour
28.8 x 8.7 = 25C sq . ft. screen.
Screen is 10 ft. long. 250 = 8 f t . diameter.
10 x 3.14
With screen running at 9 R.P.M. a peripheral speed of
226 ft. per minute is reached.
To obtain 9 R.P.M. at screen three reductions are used:
66_i52_x_9_ =52.5 R.P.M. speed of countershaft.
66.52 and 11.38 = diameters of gear and pinion respectively.
Belt to jack shaft. 52. 5 x 38 = 100 R.P.M. speed of jack
shaft - 38 and 20 = diameters of pulleys.
Eelt to line shaft: 48_x_ 1CC_ = 150 R.P.M. - speed of line
shaft. 48" and 32" - diameters of pulleys.
Nut Refuse Elevators.
From 100 R.P.M. on jack shaft to 6 R.P.M. of head shaft
through two reductions: 24 x 48 = 11.5" diameter of the
sprocket on jack shaft. 2 4 x 9.55 = 39.63" diameter of
spur gear on head shaft.
Fine Coal Elevators.
Using same gears as above. Then it is necessary to
reduce from 150 to 24 through two reductions.
150 on line shaft to 81 on jack shaft -
81 on jack to 24 on counter shaft.
24 x 48 = 14 l/4" diameter of jack shaft sprocket.
150 x 24 = 45" = diameter of pulley on line shaft.
Nut Goal Jigs.
75 R.P.M. of eccentric shaft frorr 150 on line shaft.
150 = ratio 2 to 1, which can be had by using 26 and 18
Fine Goal Jigs.
125 R.P.M. of eccentric from 150 R.P.M. of line shaft.
150 - ratio of 6 to 5, which is given by 36 and 30 inch
150 R.P.M. on line shaft to 22.5 through two reductions
150 x 22 = 69 R.P.M.
69 = ratio of 3 to 1 for bevel gears, which is obtained
15.28 and 5.09 inch diameters resp.
#4 and #5 Screens.
150 R.P.M. to 15.7 R.P.M. through two reductions:
16 x 150 = 60 R.P.M.; 16 and 40 inch.* diameters of
1 1.75 x 60 = 15.7 R.P.M.; 11.75 and 45 inch. = the di-
ameters of sprockets.
4 x 3.14 x 15.7 = 197 ft. per minute peripheral velocity of
60 R.P.M. of jack shaft to 4 R.P.M. of scraper shaft
through two reductions.
60 x 11 . 14 = 26.7 R.P.M.; 11.14 and 25 inch. = diameters of
7.24 x 26.7 = 4 R.P.M. ; 7.24 and 47.9 = diameters of pinion
and spur gear.
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At 11 R.P.M. 66 buckets will be filled per minute.
With three divisions on feeder 66/3 r 22 R.P.M. necessary.
Foot shaft runs at 11 R.P.M. , which gives a ratio of 2 to 1.
With 30 and 15 teeth on sprockets this ratio is obtained;
sprockets are 24 3/4" and 12 l/2" in diameter resp.
The horse power supplied is very liberal, but as fuel
is a small item it was deemed best to allow plenty of power.
The power will be used as follows :
Each jig has been allowed 1.75 B.P.
13 jigs will require 15 x 1.75 = 22.75 H.P.
Each small elevator has been allowed 5 H.P.
4 elevators require 20 H.P.
For the centrifugal pump 1 H.P. has been allowed for
each foot lifted, which is 30.
For the raw coal elevator 10 H.P. has been allowed.
Then allowing 20 H.P. for the screens, shafting and scraper
conveyor a total of 103 H.P. is reached.
The H. S. & G. Company's nearest size would be 50 H.P.
which when placed double would give 100 H.P. It would be
necessary to run overload with this size so the next size
was selected which is 65 H.P. giving 130 H.P. when placed
double. The engine is not protected by placing it in an
enclosed room so that it is subjected to quite rough treat-
ment; thus an excess of power at the start is not unreasonable.