Charles George Warnford Lock.

Economic mining: a practical handbook for the miner, the metallurgist and ... online

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the large ram, constituting the delivery valves ; and another similar
system of valves at the bottom of the large barrel, which constitute
the suction valves.

The action of the pump is as follows :— As the plunger rises, the



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DRAINING. 77

water follows it into the lower barrel ; and at tbe same time the water
in the hollow plungers is forced into the rising main. On the down
stroke, the water m the lower barrel is forced through the lower
plnnger and valves into the npper barrels and plungers, and thence
into the rising main. Thus there is a continuous delivery on the up
ind down strokes. One of the upper plungers was open at the top
u)d formed the discharge orifice for the water, and the other was
sloeed, to form an air-vessel. On the later type of pump, both the
boUow plungers are connected with pipes passing up each side of
the steam cylinder and joining together above, wim the rising main,
[nside each of these pipes is a lesser tube, air-tight at the top, leaving
m annular space which forms an air-vessel. The steam cylinder is
)f the Davidson type, which is found to give excellent results in
nrork. There is practically no dead point, with small movement in
the reversing eccentric lever ; and the steam valve is actuated by
iirect steam pressure as well as a positive movement, should sticking
Mxmr, communicated from the reversing lever. The first pump oIh
tained was guaranteed to lift 50,000 gal. water per hour 300 ft. high
iritii 80 lb. boiler pressure of steam. This quantity was obtained
ifhen running at about 35 strokes per minute, but on emergency, for
nany days together, a speed of 45 strokes per minute was maintained.

A telescopic suction-pipe of steel, with cast-steel snore, was pro-
rided, by means of which the sinking proceeded about 6 ft., without
leoessitatins the lowering of the pump. This slide pipe was cased
yatside with strips of deal 3 in. thick, secured with iron clamps, to
prevent bulging by shot firing. The whole was suspended from the
ntrfaoe on two old winding ropes passing from suitable eye-bolts on the
ibor connecting-rods of the pumps, up the shaft, over pulleys carried
m long beams laid on packs over a considerable area of ground, and
thence to the drums of a capstan engine. After the pump was placed
n position it was further secured by means of wooden clkmps on the
rope resting against the pulley framing. The supply, steam, exhaust,
uiid water pipes were secured to the hanging ropes by iron stretchers,
placed about 9 ft apart, provided with staples. Steam was conducted
to the pit-top through 6 in. cast-iron pipes, connected with a length
nispended in the head gear, provided with a stuffing-box at the lower
m^ wherein the 3^ in. steel shaft-pipes were free to slide.

As the sinking progressed, after the suction-pipe was drawn out
o its fiill extent, the pump with the columns of pipes was lowered
>y running the ropes off the capstan, and exhaust- and water-pipes
vere built as required on the top ; the steam-pipe, after being drawn
ts full length out of the stuffing-box, was pushed back and another
^wa inserted. A stop-valve and a lubricator were placed in the fixed
iteam-pipe on the surface. A lad was in charge to regulate the supply
>f steam as required, he being in communication with the sinkers in
Jie shaft bottom by means of a signal bell. The speed of the pump
vas thus controlled and lubrication effected without any one being in
the shaft for these purposes. This was a great advantage when more
[mmps were put in, as the same lad looked after the whole of them.

(^ reaching a depth of 55 yd., the influx of water increased so
li to necessitate the use of another pump, which was of the same



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78 ECONOMIC MINING.

ooDstmotion, except tHat the stroke was increased to 36 in. This
pump was guaranteed to lift 70,000 gal. an hour while mnnbg
35 strokes per minute. But this, on getting down a few inch^
farther, was still inadequate to deal with the amount of incoming
water, and another similar pump was obtained and put to work. The
sinking progressed to a depth of 57 yd., and was then stopped on
account of the inability of the pumps to drain the shaft In the
meantime the No. 2 shaft was following down comparatively dry, and
it was decided to continue it until it reached the same stratum as in
No. 1, and put additional pumps in that shaft. The first, or No. 4
pump, was put to work at a depth of 45 yd., and No. 5 was placed in
No. 1 shaft, making four pumps in that pit. Both shafts were sunk
simultaneously to sandstone 73 yd. deep in No. 1, and 62 yd. deep in
No. 2 shaft. Another pump, No. 6, was put in No. 2 shaft, and the
sinking was carried on untU the first wedging crib was laid in No. 1
shaft at a depth of 72 yd. 2 ft. The tubbing was now built up to
the surface and wedged. Before this was fixed, the quantity of water
lifted out of both shafts exceeded 400,000 gal. per hour, as tested in a
tank and over a sill. This quantity had to be dealt with for 3 months
until the tubbing was wedged.

The first wedging crib was laid in No. 2 shaft at 78 yd. 2 fL, and
the tubbing was built thereon up to the surface. Both shafts were
afterwards sunk to a depth of 100 yd., wedging cribs being laid and
the tubbing joined up in short lengths, so as to lay open as few fissures
as possible to bring the water. At this depth the limit of the pumps
was reached and two more were procured, making a total of eight
They were then re-arranged, two being placed in the bottom of each
shaft delivering into a cistern fixed 70 yd. from the surface, and two
lifting from the cistern to the surface. These latter pumps were hung
by similar means to the lowering ones, but the ropes were attach^
to beams on the surface. The sinking was continued by this means
until the whole of the feeders were stopped by tubbing at depths
of 131 yd. 2 ft in No. 1 shaft and 123 yd. in No. 2 shaft The tub-
bing was continued to obtain a solid and hard bed, to cribs laid at
137 yd. 2 ft in No. 1 shaft, and 129 yd. in No. 2 shaft

The capstan consists of six drums connected to a pair of 13-in«
cylinder by 26-in. stroke engines geared on the third motion 25 to 1.
These are arranged so as to hang sca£folds in both shafts for putting
in the tubbing, and afterwards bricking. The pump-ropes were pro-
vided with couplings to attach to the capstan ropes, and were changed
as required. Eight Lancashire boilers, 30 ft. by 7 ft 6 in., were
required to provide steam for all purposes, which included two pairs of
24-in. cylinder by 48-in. stroke sinking engines, three steam winches,
one 16-in. cylinder by 42-in. stroke fan engine, which also drives an
electric dynamo for lighting, mortar mill, shop engine, &c. These
boilers were worked at a pressure of 80 lb. per sq. in.

It will be noticed that the pumps have not been designed for
economy of steam, but for the following advantages: — Comparative
small &:st cost; no firm, stable, or expensive foundation required;
taking up little room in the shaft; working independently of each
other ; requiring no staying in the shaft ; having few working parts.



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DRAINING. 79

«nd these of Bimple constraction ; easily repaired in case of accident ;
freely controlled from the surface ; capability of working in case of
sabmersion and with wet steam ; quickly raised or lowered ; and they
can be tied out of the perpendicular, a great advantage in putting in
tubbing, d^c. All these points were practically proved to have been
attained in a degree beyond anticipation, and, as before stated, the
quantity of water lifted was far in excess of the calculated capacity.

Electricity in its application to pumping machinery is attracting
much attention, and at the Andrews House Colliery, Durham, is a
good instance of a plant for driving pumps inbye. This colliery
is noted for the large quantity of water that must be handled ; at
one time 40 tons of water were raised for each ton of coal. The
electrical plant was put up in June 1889, and has been enlarged
and extended. A dynamo, with armature 10 by 10 in., shunt wound,
was located about 300 ft. from the shaft-mouth, and connected, on the
third motion, through two leather belts and a counter shaft, ratio 24
to 1. The engine has one cylinder 12 in. diam. and 24 in. stroke. At
980 ley. the dynamo gave 17 amperes at 245 volts, equivalent to
5-5 h.p. The motor was in the workings 4800 ft. from the dynamo,
and was of 1*8 h.p., 175 volts, 10 amperes, 850 rev,, 10 by 4 in.
Immature, series wound. It was connected by means of a leather link
belt, 4 in. wide, with a treble ram pump, to lift 30 gal. a minute 44 ft.
high, the rams being 3 in. diam. and 7^ in. stroke. The ratio of speed
between the motor-shaft and the crank-shaft of the pump was 15 to 1.

The cable, as first put in, was of 7 copper wires 18 W.G., insulated
with the Fowler- Waring patent lead covering, which has proved very
satisfactory. For the return current, old rope was at first and is stiU
used nearly all the way, and is allowed to lie on the ground, or is
attached roughly to the side of the way by nails. Only 250 yd. of
the return conductor is insulated cable. A test gave the total resist-
ance of the cable as 5 ohms ; that of the 4800 ft. lead cable may be
reckoned at 3 • 05 ohms, and of the 750 ft. return cable • 47 ohm, leaving
1*48 ohms as the resistance of the 1350 yd. of old rope. The first
motor and pump replaced a horse crank pump, which was employing
8 hones, and then could not drain the feeder of water. As the water
increased, it was soon found necessary to add a second motor and pump.
I'his motor is of the same size and type as the other, and the pump has
three rams 3 in. diam. by 8^ in. stroke, the ratio of speed between the
motor-«haft and crank-shaft of the pump being 17 to 1. A test
showed that the motors utilised 34 per cent, of the power given by the
driving engipe. The total cost of ^e installation, including dynamo,
two motors, two pumps, cable, and labour of fixing, was about 5001.
More recently it was found that the two motors and pumps were not
sufficient to cope with the water, which had more than doubled in
quantity. A larger dynamo was therefore got, armature 12 by 12 in.,
compound wound, yielding at its normal speed 38 amperes at 270 volts,
but it has been run up to 50 amperes and 300 volts. It is connected
with the same driving engine, on the second motion, by a leather link
belt, the ratio of speed being 1 to 11. The field of the old dynamo
was rewound, and it was utilised as a motor to drive a third pump, at
a distance of about 6000 ft. from the dynamo. This pump has three



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8o ECONOMIC MINING.

rams 5 in. diam. and lifts 60 gal. a minnte a height of 84 ft. A new
cable was got For 250 yd, it is 19-18, i. e. 19 wires of 18 W.G.,
and for the rest of the distance to the first motor there are two cables,
one 7-18 and the other 7-16 ; from the first motor to the second, ^which
is 900 ft. farther inbye, the cable is 7-16, and from the second motor
to the third 7-18.

Fig. 17 shows the form of support used for the insulated cable.
The cable a is fastened by wire to the earthenware insulator h ; the
cups c are intended for holding a little oil« so as
to break a continuous surface of moisture, which
might allow the current to get to earth ; d is
an iron rod fixed into a timber balk or plug in
the roof or side. Old ropes are still used for
the return current, as before. Considering the
resistance in the pipes, the average work done
„ ,^ o by the pumps is as follows: Ist, 0*57 h.p. ;

C]^^"^""" 2nd, 0-89 h'J.; 3rd. 1-78 h.p.T a total of
3 • 24 h.p. The normal current required at the
third or farthest inbye motor is 19 amperes and 172 volts. Between
the motor and the dynamo there is a loss of electrdmotive foroe of
100 volts. The efficiency of transmission of the present plant has
been oedculated to be 45 per cent., as follows : Brake h.p. of driving
engine at 75 rev., 16 • 60 h.p. ; the dynamo gives 85 per cent, of this
= 13 '17; the cables give 69 per cent. = 9 '08; the motors give 80
per cent. = 7 • 27 ; the total being, 46 • 02 per cent. The pumps are
kept at work constantly, resting only 40 to 60 minutes in 24 hours,
and one man attends to them, the motors and the pumps, llie speed
of the motors is regulated by resistance coils in the usual manner.
The installation is giving complete satisfaction.

In slate formations, or where junctions of slate and sandstone, for
example, occur, there is likely to be considerable leakage of suiiiEu^e
water into the workings, and unless great care is taken the storage
reservoir for the mill, Ac, may add very largely to the amount of
pumping required.

In limestone formations particularly the quantity of underground
water is so great that no pumping machinery has yet been devised
to cope with it ; and where drainage cannot oe effected by tunnels,
the mineral deposits have to be abandoned.

In copper mines the decomposition liberates so much sulphuric
acid that tne pump pipes and valves become very rapidly corroded.
So much is this the case, for instance, at the Oagrion mine, Montana,
tiiat Superintendent Goodale proposes lining the iron pipes with wood.



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8i



MINING AND WINNING.

Except in the oase of simple open qnarries, where the whole oper-
ation IB carried on in daylight, the extraction of ores and other mineral
snbstaDces is conducted by means of horizontal passages, which bear
Ter^ various names, acoording to the precise manner and object with
which they are constructed.

When the deposit to be worked lies beneath a level or flat surface,
tlie first preliminary is to sink a shaft down to the bed. But when
the ooantry is mountainous or hilly it is generally possible to attack
the mineral by means of a tunnel or adit driven directly in from
the face of the slope. This latter method possesses numerous ad-
TantageSy among which may be specially mentioned that the cost of
pnmpmg out the natural drainage water from the workings is avoided,
and that the expense of bringing the product to surface is very greatly
Tedoced. These considerations render mining by adit immeasurably
preferable to the shaft system wherever circumstances allow it to be
done.

Obviously many points arise in determining how the adit shall be
driven, firstly with regard to its location and secondly with regard
to its construction. The aim of the miner is to reach the ore body as
qxiickly and economically as possible, to attack the maximum of
mineral by one expenditure, and to ensure continuous and safe work-
ing at a minimum cost.

Two of the most vital conditions in all minine are drainage of
the workings and cheap transport of the mineral boui inside and out-
side the mine. Therefore the adit must be so driven that it shall
discharge its water where it can readily flow away, and deliver the
mineral at a spot handy for further treatment. In vein mining, the
adit is generally driven on the vein, but there are cases where it is
advantageous to run the adit in the country rock at one side, and tap
the mineral by occasional cross cuts. The annexed illustrations show
various forms of adit.

Fig. 18 is the simplest, the whole tunnel being in the vein matter,
which is sufficiently firm to render timbering unnecessary. The
tramway or barrow road is laid along the middle of the gallery, and,
the mine being dry, a small gutter on the footway side suffices to
cany away the drainage water.

in Fig. 19 the tunnel is driven entirely in the country rock,
which, being firm on all sides, requires no timber ; but the drainage
water is so abundant that a larger gutter has to be provided under
the roadway, and the latter is supported on timber.

In Fig. 20 the adit is run entirely in the vein. The walls of
ooantry rock being firm and the bedding flat, no timber is needed at



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82 ECONOMIC MINING.

the sides ; but the veinstuff affords a bad roof, and timbers have
therefore to be run across, their ends being secured in the conntiy
rock at each side, and smaller timbers laid across them.

In Fig. 21, the country rock is flat bedded, and stands well in the
wall and roof, but the veinstuff requires the support of timbers let in
as shown.

In Fig. 22, it is the veinstuff which stands firm, while the conntry
rock is not flat bedded, and timbering becomes necessary on that side
of the adit.




Fio. 19. -=sgBd Bit Fig. 18.



Fig. 21. .^ I ffl "- Fig. 20.




Fig. 23. Fig. 22.




Fig. 25. ^^sm W^ Fio- 24.



Examples or Tuknels.

In Fig. 23 the dip of the country rock makes it necessary to
timber the roof as well as one wall, while the veinstuff stands alone.

In Fig. 24, the country rock is firm despite its dip, but the vein-
stuff is weak, and on that side of the adit double timbering is neces-
sary, the adit being run entirely in the country rock.

In Fig. 25 the ground is weak on all sides, and there is no alter-
native but to make a complete timber framework.

Levels are run at varying distances apart. When the vein is
steep it is best to have the levels far apart, up to 150 ft., thus effect-



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MINING AND WINNING. Zi

mg a greater saving in tibe dead-work of cntting out stations and of
nmning drifts to open up the ground. Flatter veins demand that
the levels shall be nearer.

When the levels have been run, the ground is ready for mining
proper, or *' stoping/' as it is called. This operation may be oonducted
m either of two ways, known respectively as " overhead "and " under-
hand."

Overhead stopine aims at removing a block of ground by oom-
mencine at one of we lower comers. Ihiring the progress of the
vrork, the solid ground, as seen from the stopes, resembles a series of
Btain»8e steps. It is by far the more generally adopted system, and
is started from a raise which was previously made to the level above
to obtain a current of air.

In this ^stem, the " deads " or waste is piled back as the stopes
progress. When the ore has been extracted, the block of lode is thus
replaced by a block of waste occupying entirely or in part the same
space. ^ Mills " or '* shutes " are carried up as stoping advances, and
shoot the ore to the level below, where it is drawn into the cars.
Sometimes the shutes are lined on the sides and bottom with lumber ;
sometimes only on the bottom with lumber, while the sides are lined
with small poles or with piled up rock.

As from 12 to 15 ft. is about the extreme distance to which a man
can shovel the material broken in the vein, in order to avoid the
XDore expensive method of using wheelbarrows, the shutes must oome
within about 30 feet. Where the vein is wide (40 ft. or more for
instance) the shutes are carried near the middle of the stopes. In
Teins of greater width than 40 to 50 ft. there is usually one shute
near the hanging and another near the foot wall of the stopes.

Where the material to be shovelled is very heavy, as in lead mines,
the shutes are kept verv close. An angle of 45° is necessary to have
Ae ore carried down the shutes by gravitation. Where the shutes
are flatter, owing to the flat character of the vein, more or less
fihoTelling is necessary. In some flat veins this is an item of consider-
ahle expense. Where the shutes are flat, a chain fastened at the
upper end may be used to start the ore. On the other hand, where
the yein is very steep, " set-offs " are required to prevent undue wear
and tear of the shute in case the levels are very far apart.

An example of overhead mining on a vein which does not exceed
2 fathoms thick is shown in Fig. 26. The main adit or level a 6 is
first driven, and from this at intervals the winzes or shafts are made
*p«ar(2f as at c, and from these again other levels d are driven.
Similar operations are extended downwards as at e / ^, the bottom of
the shaft e forming a '' sumpf " or sump at A, into which the mine
water will drain and from which it must be pumped.

The process of excavating one of the square masses t of ore is
hettor seen in Fig. 27, where a 6 is the adit ; c d, shafts or mills or
fihutes; «, timbering which forms the roof of the adit, and at the
same time the floor of the chamber being excavated ; /, a heap of ore
hroken down from overhead ready for running out of the adit ; ^, that
portion of the mineral which has no value — the " deads," — and which
^^^cumnlates under the feet of the miners as their work progresses ;

a 2

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84 ECONOMIC MINING,

A, a substantial wall forming one side of the shaft or shute c, some-
times built of the larger pieces of rock broken down from t, but more
often timbered ; », the unworked portion of the vein ; k, space in which
the miners wield their tools.

The advantages of this system are that less timber is needed, and
the ore is more easily brought to bank. Its disadvantages are that
the miner has to reach upward to his work, and that some ore must
necessarily get mixed with the waste g and be lost.

Underhand stoping consists in beginning the removal of the block
of ground at one of its upper comers. In this method the waste is
piled on stages or " stulls," one of which is generally required for
every stope. The workings resemble steps of stairs seen from above,
and the stulls on which the waste is stored look like a staircase seen
from below, the arrangement being just the reverse in appearance of
overhead stoping.




Figs. 26, 27.-— Ovkrhbad Minino.

Overhead stoping is started from a raise, while underhand stoping
is started from a winze. From the raise or winze, as the case may be,
the stopes extend in both directions, forming two wings, which re-
semble an inverted fan in the case of overhead and a fan in ordinary
position in case of underhand stoping.

In underhand stoping more timber is used than in overhead
stoping. In overhead stoping one line of stulls is necessary just
above the roof of the level, whereas each stope, which represents a
height of 6 to 8 ft. in underhand stoping, requires a line of stulls.
The expense of timber for underhand stoping increases greatly with
width of the vein and with the lack of solidity of the walls. Conse-
quently, this method is of economical application only in narrow veins,
say, as a rule, 2 to 4 ft. wide, though for short depths where the walls
and vein are solid, greater widths may be worked.

On the contrary, overhead stoping may be worked sometimes
30 ft. or more in width, depending upon the character of the ground.
Also, overhead stoping possesses facilities for breaking down the
stuff, for stowing away the waste, and convej^ng the air to the levels.
It is also much safer than underhand stoping, where the walls are
bad, but not so safe where there is much loosened ground in the vein.
Underhand stoping is sometimes preferably adopted where the ore is



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MINING AND WINNING. 85

rery friable and very rich, because there is less loss of rich pieces in
)r^king the ore, as the broken ore falls on solid ground in this
aethod, while it falls upon waste in the method of overhead stoping,
ind may get lost. But this loss may, to a great extent, be obviated
)y laying boards near the face to be blasted.

An example of underhand mining when the vein does not exceed
I £Bithoms thick is shown in Fig. 28. From the main adit a 6 a shaft
t is sunk on the vein. Then, commencing at d, miners standing on

he ore in the vein excavate it in a ^ .

eries of steps d ef g^ the ore having n C-Cf"^*^ ' *'-*^-f *'g**°=^ r~

be raised by windlass or other con- E>Vi5>>^ . ,— a — I

livance through openings in the

loor timbers of the adit a 6, whilst

.he waste or deads is thrown back

m strong timber shelves h built

igainst the wall of the shaft c. Pio. 28.— Undkbhand Mining.

The advantages of this syst^em
ire, that the miner has easier access to the ore and can apply more
power, while the loss of ore is less. The disadvantages are extra cost
for timbering and for transporting ore to bank, and increasing diffi-
cnlties in ventilation and removal of water.

With very thick veins, e. g. those over 2 fathoms thick, it is
necessary to modify either of ^e systems described, so as to deal
irith the width of the vein in successive sections. This is illustrated
in Pigs. 29, 30. A main gangway a is first driven
along either wall 6 c of the vein r, and substan-
tially timbered. From it a series of breasts or
cross-cuts d efg h % are driven at right angles
through the vein till they rpach the opposite wall



Online LibraryCharles George Warnford LockEconomic mining: a practical handbook for the miner, the metallurgist and ... → online text (page 10 of 76)