September 24, 1915.

THE COLLIERY GUARDIAN.

619

=—SB

constantly delivered by the air compression. Mr. Price
Abell thought that a great step had been made by the
introduction of turbine motors, driven by compressed
air, such as the “ Spiro ” turbine, which appeared to
lend itself to an auxiliary motor being fixed alongside
the main one for use when chokes occurred. One of the
main causes of neglect of the loss in compressed air
was, that users did not realise that compressed air had
the opposite characteristics of steam, in the fact that,
the lower the air pressure, the higher the efficiency to
be got from the use of compressed air—this resulting
mostly through there being no efficient way of utilising
the heat that it was necessary to extract, and dissipate
from the air during compression. For greater efficiency,
three points deserved attention :—Pipe leaks; a coal
cutter capable of running, and getting through jams, at
a constant low pressure; and a compressor that could
utilise the heat now dissipated during compression.

Mr. A. Lupton thought the loss by leakage was, as
a general rule, controllable. There were other Sources
of loss not so readily controllable, to which the attention
of mining and mechanical engineers was being given.
Of course, electricity threw compressed air into the shade
for a time, and people had forgotten the discussions in
which their fathers took part.

Mr. G. Blake Walker thought that one moral which
might be drawn from the figures which Mr. Mavor had
brought before them—which, he must confess, were
somewhat startling and unexpected in their intensity—
was that if they were to use compressed air largely in
fiery mines in the future they must get that compressed
air very cheaply. Possibly they might, within reason-
able limits of time, have means of producing it by using
turbo-compressors, generated by either exhaust steam or
by electric motors, which might enable them to give
a much larger supply than any of the reciprocating con-
veyors with which they were familiar. If it was desir-
able that the fall of pressure should be minimised, then
in the turbo-compressor they had a more efficient
machine at a low pressure than they had at a high
pressure. Of course, it was obvious that there were
means of minimising the losses which mining engineers
were accustomed to—by the use of pipes of very large
area, and reducing the speed of the compressed air
current; and he understood that Mr. Mavor stated in
his paper that so far as the main junctions in-by were
concerned, where these large pipes went to, there was
a very much less loss than there was when they got
beyond that point, and got into the workings, where the
strata were more or less in a constant state of movement.
It was largely a question of attention to maintaining
their mains in as complete a state of efficiency as they
could. He thought that there was very vast scope for
getting better results from compressed air than they
were obtaining at present.

Mr. Gervase Cook said that as far as compressed air
working coal cutters was concerned, 20 lb. pressure
might be serviceable, but when it came to rock channels,
where they had 30, 40, or 60 machines going at the same
time, they could not do with less than 60 lb. There was
no doubt' that there was a great loss from the leakage
of pipes, rqore than anything else, in conveying it a
long distance.

Prof. Louis said Mr. Mavor had left out a method of
compressed air measurement which he (the speaker) pre-
ferred, which was the diaphragm method. He would
like to draw attention to the Taylor compressor, one of
which, he believed, was working in this country, and
which promised to give an exceedingly cheap source of
compressed air. He would also like to allude to the
possibility of recovering a large amount of the energy
lost in compression by reheating. He thought it was
quite possible that electric re-heaters might be used,
working inside the compressed air pipes. They might
possibly be employed even in fiery mines.

Gas Producers at Collieries.

Mr. Mansfeldt Henry Mills presented a paper on
“ Gas Producers at Collieries for Obtaining Power and
By-products from Unsaleable Fuel,” which was taken
as read. He remarked that owing to the war he had
not been able to complete the paper, and he would add
something to it before it appeared in the Transactions,
(See p. 617.)

Mr. Wild suggested that the author should deal with
the question of the use of producers in connection with
coke ovens. The producer plant would be able to act as
a stand-by for keeping the ovens heated. In cases where
a high value gas was required, possibly for house heating
or anything of that kind, they would be able to fire
their ovens by the producer gas, and so save rich gas, or
have a larger quantity available for resale. The pro-
ducer at the same time could be run with small coke, or
waste, if they had any extra. Mr. Mills mentioned in
his paper an engine for Denaby Main. It had been
started up. that week, in connection with a 750-horse
power engine and a producer plant. There had been
a lot of troubles in the past with gas engines and pro-
ducers, and in his opinion these were attributable to
Hirty gas. At Denaby Main they had made exception-
ally good arrangements for cleaning the gas, and he
anticipated very little trouble there in consequence of
that.

Mr. G. Blake Walker thought Mr. Mills was abso-
lutely and entirely right in saying that at collieries an
immense amount of valuable material for the production
of producer gas was wasted. If that material were
turned to effect, as Mr. Mills suggested it should be, they

would get their colliery consumptions down to 1 per
cent, of the output. It would probably cost as little to
put this wasted material into the producer as it did to put
it over the tip. He thought that in these days they
should turn all their output to better use than that of
producing power. Moreover, there was the question of
the recovery of by-products, to which many of them now
looked almost more for their profits than they did to
the coal itself. The great drawback to the introduction
of large producer plants was their very considerable
first cost. Whatever might be the case with a few
large and flourishing concerns, the majority of collieries
were generally rather hard put to it to raise a few
thousand pounds for improvements that were very
obvious and full of promise. A Leeds gentlemen said to
him “ There’s money waiting for you to pick up; why
don’t you pick it up? ” and the answer to that, in the
case of producer plants, was that most of them had not
got money for everything that they would like to do.
But he was certain that in both Mr. Mavor’s and Mr.
Mill’s papers the institution had before it subjects which
would lead to the saving of a great deal of money; but
whether all the savings that they could achieve by
chemical and mechanical means would be sufficient to
keep them afloat in these days of constantly rising
wages, he could not say.

Mr. A. Lupton said he entirely agreed with the writer
that it was a great pity that batty and carbonaceous
shales should be thrown away to waste on the top,
because they were probably burnt there, and the burning
did no good to anybody, but as a rule did a great deal
of harm by sending forth nasty smoke. But, in leaving
inferior coal underground, because it was not profitable
to wind it to the surface, there was no waste of our
national resources. They could not have a better keep-
ing place than the pit, except in those comparatively
small places where there was spontaneous combustion of
the stuff that was left below. All the slack and car-
bonaceous material that was left in the pit would be a
great boon and blessing to their remote descendants
500 years hence, who would get it all out. They knew
what could be done if they only had so much per ton.
Supposing it cost them 8s. a ton to get an ordinary seam
of coal 3 ft. thick into their railway truck, then, if they
had a coal only 2 ft. thick, it would very likely cost
them 16s. per ton, and if it was only 6 in. thick it
would probably cost 30s. or 40s. a ton. But at the price
that coal would be 500 years hence, that would be a very
small matter to consider. Therefore all the coal left
below ground, and said to be wasted, was coal that was
saved.

Votes of Thanks.

Prof. Louis proposed a vote of thanks to the president
and council of the Midland Institute of Mining
Engineers for the admirable arrangements they had
made for the meeting. He said it was, of course, no
fault of the Midland Institute that they were in the
middle of a terrible war, which had prevented the usual
festive side of the gathering, and in so far they had had
a certain difficulty. They had had a still greater diffi-
culty in the sad and sudden death of Mr. Fryar, which
they all deplored as a loss to the mining profession.

Mr. Ashworth seconded, and the resolution was
carried unanimously.

Mr. Walter Hargreaves in reply said it had been a
great pleasure to the council and members of the insti-
tute to contemplate the visit of the association to Leeds.
It was their first visit to that city, although they had
been in Yorkshire before.

Votes of thanks were also accorded to the owners
of Maltby Main and Bentley collieries for granting per-
mission to the members to visit their collieries on the
following day, and providing refreshments, and to Sir
Thomas Holland for presiding.

On Thursday, September 16, visits were paid to
Maltby Main and Bentley collieries. The following
descriptions of these collieries were compiled by Mr.
Alfred Thompson and Mr. Robert Clive, respectively.

Maltby Main Colliery.

The colliery is situated eight miles east of Rotherham
and seven miles south of Doncaster. The area con-
trolled by the company consists of about 9,000 acres of
the Barnsley seam. The colliery is equipped to deal
with 6,000 tons per day in two shifts. The sinking of
No. 2 shaft was commenced on March 30, 1908, and
the Barnsley seam was reached on June 18, 1910, at a
depth of 2,460 ft. The last 1,200 ft. of sinking and
bricking in No. 2 pit was accomplished at an average
rate of 36 ft. per week. The quantity of water met
with was 21,000 gals, per hour, which came from several
springs, the bulk being within 200 yds. of the surface.
During the sinking operations, the marine bands, which
have occurred in each of the deep sinkings in South
Yorkshire with remarkable regularity, were passed
through. The workable thickness at No. 2 shaft bottom
is 5 ft. 2 in., excluding the Bright coal, which is divided
from the Main seam by 6 in. of dirt.

The empty wagons are delivered by the South York-
shire Joint Railway at the top of the empty sidings, and
from there gravitate through screens into the stock
sidings at an average gradient of 1 in 65, and thence into
the railway company’s labelled sidings, which are not
yet constructed.

Winding Plant.—The winding engines for the upcast
pit have cylinders 36 in. in diameter by 6 ft. stroke.
The admission valves are 11 in. in diameter, and are
of the Cornish double-beat type. The exhaust valves are
9 in. in diameter, and are of the Corliss type. These
engines were erected for use in completing the last
1,200 ft. of the sinking, and for this purpose were fitted
with a temporary flat drum. This drum has now been

replaced by one of the semi-conical type, the small
diameter being 13J ft., taking 5| laps of 1| in. rope, 3| of
which laps are dead. The conical part consists of six
laps rising to the parallel portion of the drum, which
is 22 ft. in diameter and 7| ft. wide. The engine makes
37 revolutions per wind in 55 seconds. The downcast
pit serves as the main coal-winding shaft. The engines
have cylinders 44 in. in diameter by 7 ft. stroke. The
admission valves are 14 in. in diameter, and are of the
Cornish double-beat type. The exhaust valves are 9 in.
in diameter, and are of the Corliss type. The drum is
of the semi-conical type, and is of steel throughout.
The smaller diameter is 17 ft., grooved to take six laps of
2 in. diameter locked-coil rope, three of which laps can
be made live. The conical part rises in 14 laps to the
parallel portion, which is 33 ft. in diameter and 7| ft.
wide. The total weight of these engines and drum is
320 tons.

King hooks are in use at both shafts, those at No. 1
pit being fitted with Barker secondary catches. The
Wallace depth-indicator and overwinding safety gear
have the advantage of being directly in view of the
engineman, and have few working parts to get out of
order. The machine is driven by means of a drag-crank
on the horizontal shaft through the vertical shaft and the
gear wheels. The cams are fixed to levers, which close
the throttle and operate the steam brake, and are brought
into line with the pins on the bicycle chain by the speed
governor. The travel of this chain, in proportion,
represents the travel of the cage. If the engineman
should not reduce speed at the proper point, the cams
remain in line of travel of the pins in the upward motion
of the chain. The pins are placed at fixed points on
the chain, so as to trip the gear at any number of revolu-
tions from the flat sheets. If the engines should be
started in the wrong direction, the gear is at once
tripped, and the cage prevented from going more than
2| ft. above the flat sheets.

In both cases steel rail guides across the centre of the
shaft have been adopted in preference to rope guides.
The cost of the guides in the upcast shaft was as under :

Cost

Total cost, per yard.
£ s. d. £ s. d.
Labour in building wall-boxes in
the shaft; fitting up the guides
complete on the surface, and their

erection in the shaft ......... 1,885	15 8 ... 2 5 11

Material, including cement, mortar,

wall-boxes, and guides, complete 3,758 19 0 ... 4 11 9

£5,644 14 8	£6 17 8

The conductors weigh 1101b. per yd., the web being
thickened to allow for extra wear. The rails were cold-
straightened by the makers, and were specified to be
dead straight in lengths of 40 ft. The buntons, which
measure 9 by 7|in., are of rolled steel joists, and are
fixed across the centre of the pit at 10-ft. centres. The
advantages which arise from fixing the buntons in the
centre of the pit, as against a set of buntons on each
side of the pit, are that it is impossible for the cages to
collide, and a better bond is obtained in building the
wall boxes in the shaft. The wall boxes are of cast
iron, and of two sizes, the larger one being made with
extra depth to allow of the insertion of the bunton and
its withdrawal into the smaller box on the opposite
side. These boxes are placed alternately on either side
of the shaft, and are filled with cement concrete. The
joint straps consist of a cast steel slipper, which
embraces the flange of the rail. One side of -the slipper
is cut away, and a machine-tapered wedge is inserted.
This wedge is a driving fit, and is further held in posi-
tion by two bolts on each side of the joint. The inner
bearing surface of the joint strap is milled out so as to
make a perfect fit for the rail flange. The sole plates
consist of a drop forging, machined to take the flange of
the rail and the bunton, both of which are punched
to receive the four securing gib bolts. The pocket bolts
are to secure the bunton in the pockets, the former being
slotted so as to allow of a lateral movement, and the
latter to allow of an end movement. The cage slippers
were in the first instance of phosphor bronze, but the
wear was much too rapid, and a cast steel slipper is now
being adopted, with a renewable lining of slightly softer
material than the guides themselves.

The air lock is constructed of brickwork. The roofing
is made of railway sleepers laid on girders, the whole
being covered with concrete. The air lock doors are
of the balanced type, both deck doors working on the
same shaft. The top deck door, being smaller, opens
inwards, and the larger door on the bottom deck out-
wards. The extra area on the bottom deck door keeps
both closed, and as the door on the -top deck opens with
the pressure, very little power is required to open them.
When the fitting-up is complete, levers will be so
arranged that both sets of doors can be operated from
one point by means of a small engine. After leaving the
air lock, the full tubs gravitate to the tippler, and the
empties run back to the creeper, which lifts them suffi-
ciently high to allow them to gravitate on to each deck
of the cage.

The cages are fitted with 2 decks with tilting bottoms,
each deck carrying three tubs. The decking, both top
and bottom, is simultaneous; at the top the full tubs
are lowered to the bottom deck by a drop cage, while
the empties are separated for each deck at the top of
the elevating creeper. At the empty side of the pit at
the surface, tilting cradles to hold three tubs are fixed
at each deck. These will be operated by small hydraulic
cylinders fixed below. As the cages drop on the fallers,
the bottoms are tilted and the catches released.

At No. 2 shaft bottom simultaneous decking is accom-
plished by drop cages worked by hydraulic power. For
the full-tub decking cage, the power pipes are connected
to the lodge at the 368-yd. level, by which sufficient
pressure is obtained to lift the empty cage to the top
deck level. Three full tubs give sufficient extra weight
to force the water used in this lift back to the same
lodge, and also to lower the loaded cage to the bottom