June 6, 1913.

THE COLLIERY GUARDIAN.

1221

UNDERGROUND CONVEYING.*

By Sam Mayor, M.I.E.E.

(Continued from page 1115).

Applications.

The author next gives examples at machine-cut and
hand-cut faces, and referred to the diagrams. (See
Colliery Guardian, May 30, 1114). A few examples
of special applications of conveyors in Continental
collieries, where the seems generally are inclined and
where the shaker type is most favoured, are also given.

Conveying Debris.—At many Continental collieries
where full packing of the goaf is compulsory, conveyors,
especially in inclined seams, serve the important
function of delivering debris to the goaf. In Germany
two conveyors alongside of each other are frequently
employed at the same face, one for coal, the other for
dirt, and they may be operated by the same motor. The
coal conveyor is within 2 or 3 feet from the face and
discharges at the bottom level; the dirt conveyor,
which is parallel with it and a short distance in arrear,
is loaded at its upper end in the top level and, by means
of a baffle plate deflecting the material through opened
gates in the side of the trough, delivers the material
where required. This arragement permits of simultaneous
clearing of coal and packing of dirt on two consecutive
shifts. Where only one conveyor is used coal is filled
out in the morning shift and the goaf is packed in the
afternoon.

Conveyors in Rise Workings.—The method illustrated
.by fig. 4 is in use in Holland in a friable coalseam 3 ft.

Fig 4.

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thick, under a roof which is so tender that only short
faces can be worked, and these must be rapidly
advanced. The levels are 50 yards apart, and faces
about 8 yards long are advanced to the rise. Two
shaker conveyors are used as shown, one for coal and
the other for dirt. Coal is worked in the morning and
is passed by one conveyor to the lower level, between
30 and 40 tons per shift being got. In the afternoon,
dirt is tipped into the end of the other conveyor at the
upper level, and is delivered at the short face, where it
is packed in the space from which coal was extracted in
Hie morning shift. As the face progresses towards the
rise, sections about 6 ft. long are detached from the
upper conveyor and added to the lower one.

Conveyor with Two Discharging Stations.—In Austria
the full length scraper has been used to deliver at two
loading roads, one in the centre and the other at the
end of the face; a gap, formed in the floor of the
trough where it crosses the centre road, permits
discharge at this position. A single engine thus serves

in effect for two conveyor faces. In seams thick enough
to yield considerable daily output from a conveyor face,
the dividing of the coal between two loading-roads
avoids congestion of tram traffic at the discharging
position. On the other hand, interruption of loading at
either road necessitates stoppage of the conveyor and
cessation of loading in both roads.

* From a paper read before the South Wales Institute
of Engineers and published in the Proceedings.

Conveyors in Gates.—Fig. 5 illustrates a method in
vogue in Austria in seams where the roof is too bad to
permit the use • of conveyors along the line of face.
Narrow gates are formed at right angles with the face,
and in each of these a light jigger conveyor is
suspended. In the shorter gates (under 25 yards) the
conveyors are operated by boys through a crank handle,
and for jigging the troughs in the longer gates a
compressed-air punching-machine cylinder, with piston
acting directly by a link, is used. Prior to the applica-
tion of the conveyors, two men were allotted to each
place and they delivered the trams to the crossgate;
now two places are stripped by each pair of men, who
have their own punching-machine cylinder and piston.
The puncher is connected to the first conveyor to be
used, and when the first place is cleared the puncher is
quickly moved to the second conveyor, so that one
puncher serves two conveyors. In order to avoid any
expense in maintaining the gates, they are cut off by
mother gates at intervals of about 65 yards. Where the
height in the gate is less than 2 ft., chain suspension
cannot be suitably used, and the troughs are mounted
on small wheels or rollers and reciprocated through a
range of about 12 in.

Jigger Conveyors on Low Inclination.—In Belgium
the jigger is the only conveyor which has gained a
footing, and this type is used on inclinations of only a
few degrees ; the jigger is, however, sometimes unsatis-
factory on inclinations under 10 degs. Two parallel
conveyors are frequently in use at the same face, as in
Westphalia, for dealing respectively with coal and with
debris for packing.

Conveyors in Highly Inclined Seams.—In the steep
seam districts of Austria, where the inclinations are
frequently much above the angle of rest of loose coal,
conveyors are used in the intermediate levels to pass the
coal from the faces to the chutes. Fig. 6 illustrates the

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arrangement. Formerly side-tipping trams were used
in the intermediate levels to transport the coal from the
faces to the chutes, but the increased output produced
by longwall coal-cutters led to the application of con-
veyors as described.

Capacity and Limitations.

It is impossible to fix a generally applicable lower
limit of output which would warrant the use of a
mechanical conveyor or, on the other hand, to state the
maximum attainable output from a conveyor.

In recent years the problem of stripping the machine-
cut faces has been enlarged by the progressive improve-
ments in strength, power, cutting capacity and reliability
of coal-cutters and by increment of experience in the
management of machine-worked sections.

When the quantity delivered by a conveyor exceeds
100 tons per shift, and often with much smaller
quantities, the traffic problem asserts itself and imposes
the limit of available capacity of the conveyor, whereas
individual coal-cutters in seams about 3 ft. thick are
undercutting nightly 220 to 250 tons of coal. Where
the holing is easy the productive capacity of the coal-
cutter is often greater than that of the conveyor.

In many seams of sufficient height to permit filling of
trams at the face, much advantage might be derived
from extension of the system by which auxiliary haulage

gears are used to haul sets of empty trams along the
face, and the loaded trams to the roadways.

The labour costs for marshalling trams, attendance at
loading end, and shifting the conveyor, amount in their
seams to a relatively large charge per ton, and are
nearly constant for daily outputs of between 45 tons
and 90 tons. Increase of output above the lower figure
named adds to only one item of cost, i.e., that of filling
on to the conveyor, and a substantial reduction in the
total costs is effected. There is thus a strong induce-
ment in thin seams to make an undercut of such depth
as will yield a paying output from the conveyor face.
In hard holing it may often be good policy to make
sacrifice of lineal distance undercut per shift by a coal-
cutter, and to double shift the machine to enable it to
cross the face with a deep cut; on the other hand,
double shifting the coal-cutter increases the difficulties
of conducting all the operations concerned in conveying.

Shifting Conveyors.

In the shifting of full-length conveyors with rigid
trough or frame, either of two methods may be
adopted:—1. Removing the whole line of props along
the face side of the conveyor, and dragging the conveyor
bodily by prop-withdrawers or other appliances to its
new position. 2. Detaching the conveyor into such
lengths as can be passed for rebuilding to the new
position, without disturbance of the props. The choice
is generally determined by the character of the roof.

Shifting bodily under favourable conditions is the
less expensive, but with ordinary vertical propping it
can only be practised under a very good roof. A usual
method of shifting a full-length conveyor under a good
roof is illustrated by figs. 7 and 8.

B

The cost of shifting differs as the roof conditions, and
under similar roof conditions as the interest and
guidance of the officials in the method and manner of
the operation. The total time occupied in shifting
rigid full-length conveyors varies between 24 hours and
60 hours. The time required to shift the traveller and
carriage types varies between 16 hours and 30 hours.
Where the roof conditions permit of two webs of coal
being taken off the face for each shift of the conveyor,
the cost of shifting as a charge per ton output is, of
course, halved.

Under many roofs which will not stand temporary
complete withdrawal of a line of props, the bodily
shifting of the conveyor may be rendered practicable by
the use of horizontal bars at right angles with the face,



Fig. 9.

and at such intervals as the nature of the roof requires.
Fig. 9 illustrates a method frequently used in this
country.

The shifting of a conveyor of the traveller type is a
simple operation. The turn-pulleys and rope are moved
to the new line; one length of turn-rails guides th*
tubs to the new track; only two or three props require
to be disturbed. At some collieries the detaching of
the tubs from each other and passing them indepen-
dently between the props to the new position is
preferred.

In shifting the carriage type the turn-pulley is first
shifted, then a few props are withdrawn at the strongest
part of the face, the roof being strapped if necessary,
and the flexible carriage is drawn by the haulage gear
in a slanting direction from the old run to the new one.

Appliances.

In operations involving so much manual labour as the
filling, discharging, and shifting of a conveyor, and the
incidental work of timbering, ripping, &c., efficiency in
application of physical labour is substantially affected
by the number and character of the appliances provided