1298

THE COLLIERY GUARDIAN.

June 12 1914.

clear from the paper whether the Durham Power Com-
pany had a special motor generator for the winding
engines. He was exceedingly interested to find that
the company were using electric lighting for their
cottages. Some years ago he considered the problem,
desiring very much to introduce electric lighting into the
miners’ cottages, but he gave it up because he could not
hear of a sufficiently good and cheap meter. Mr. Prest
and his company had taken the bull by the horns, and
had dispensed with the meter altogether, exactly in the
same way as had been done at Wednesbury in Stafford-
shire, where they were lighting a great number of work-
men’s dwellings by electricity at a charge of 7-Jd. per
week. He believed they charged the men for breakages
of electric lamps. He would also like to know whether
the light given by the electric lamp was equal to that
from an incandescent gas burner, what was the so-called
candle power of the electric lamps, what kind they were,
and how many were allowed in a large living room.

Mr. A. E. du Pasquier (Manchester) thought the paper
was a very modest record of a very considerable achieve-
ment. One figure had impressed him very much, viz.,
the quantity of water they had to deal with in the North
Pit, namely 21,586 gallons per minute. It would not be
too much to say that a few years ago, or even to-day
in less capable hands, the shareholders might have lost
their money. With reference to the type of winding
engine adopted, there was no question of any equalising
being necessary, owing to the favourable situation of the
colliery, and therefore once electrical winding had been
decided upon there were two systems to choose from,
the simple alternating current winder, taking power
direct from the mains, and the Ward-Leonard, necessi-
tating the interposition of the motor generator. It was
not generally sufficiently appreciated that with an alter-
nating current winder there were no stand-by losses of
any description. It took a certain number of units to
make one wind, and it took no more with 3,000 tons of
coal a day than with 300. The figures given in the paper
worked out at 2'2 units per ton raised from a depth of
450 yds., which, if the cost of power were at anything
like a reasonable figure, would give a remarkably low
winding cost. The Ward-Leonard system had, of
course, always the advantage of the very delicate and
perfect control obtained by its use; on the other hand
the prevailing conditions were exceptionally suited to the
alternating current control, namely single deck cages and
keps, which did not necessitate lifting the down-going
cage at the commencement of the winding. It would
also be seen from the diagrams that there was no
negative torque during the retardation period, and con-
sequently the control operations were very simple. With
reference to the large gear winding engines on the Rand,
it might interest the members to know that there were
winding engines there which had been worked for several
years, dealing with net loads of 6,000 lb. from a vertical
depth of 2,500 ft., the maximum horse power transmitted
through the gearing being 2,000.

Mr. Harry Rhodes (Rotherham) asked Mr. Prest to
state from his valuable experience whether, assum-
ing he knew the conditions that he was going to
encounter, and that he had no existing plant to be
transferred from one colliery to another, he would adopt
the method he did, namely pumping the water and
tubbing it, and supplementing it by cement injection
when the difficulty became too great, or whether he
would go in for one of the newer methods of either
cementation or sinking?

Mr. W. C. Mountain (Newcastle-on-Tyne) thought it
would add very much to the interest and value of the
paper if the authors would give some idea as to how
much of the power was produced from the exhaust steam
plant from the other pits, and how much was taken
from the power company, and also the price which was
being paid for current. In an investigation, in which he
had recently been engaged, he had come to the conclu-
sion that with coal under the boilers costing 10s. per
ton, it was necessary for electric winding to compete on
even lines as regards the cost of coal wound per 100 tons
from the shaft bottom to the shaft top, that the price to
be paid for the current must not exceed 0*25d. per unit,
and for ventilating purposes, when driving large fans, the
cost of current must not exceed 0’2d. per unit, and even
at these figures no credit had been taken for the value of
the exhaust steam from the winding engine and fan
engine, which, however, actually possess a very con-
siderable value. At a colliery in the Barnsley district,
in which he (Mr. Mountain) had recently acted as
consultant in the installation of a mixed pressure turbo-
generator of 750 kw., the capital outlay was 425,000, and
the total running and maintenance charge, 422,304 per
annum. The rate of power consumption was 3,770,000
units per annum, and the cost per unit, 0’146d. The
offer of a power company for the same consumption
would amount to 427,413 per annum, or 0*471d. per unit.
The saving effected by the installation of the exhaust
turbo was, therefore, 0-325d. per unit at present, or a
saving of £5,109 per annum. It would, of course, be
necessary at some time to instal another turbo-generator
as a stand-by, as this one cannot go on indefinitely. This
would add about £3,000 to the capital outlay. It would
not be necessary to duplicate the circulating pumps,
condenser, accumulators, etc. The cost per unit in that
case would be 0’175d. with the increased capital. Deal-
ing with the type of winding engine installed, he fully
endorsed Mr. Brest’s selection of the plant. He had
found in actual working, and also from calculations,
that for winders of moderate size, a simple induction
motor driving the winding drum through machine cut
helical gearing, with the gearing running in oil, was a
much less expensive plant than either driving through
a motor generator or an “ Ilgner ” balancer, and it had
the advantage also that there was less risk of breakdown.

As regards the consumption of current there was really
little to choose between the two systems, because with
the motor generator or balancer there was a considerable
loss in conversion. Considering for a moment the cost of
winding electrically, and without any figures as regards
the cost of current, it became necessary to assume the
price per unit, which were taken at 0'5d., 0*33d., and
0-25d. respectively. They were informed by Mr. Prest
that the winder consumed seven units per wind, and
that there were 60 winds per hour, so that the consump-
tion of the winder was equivalent to 420 units when
winding 200 tons per hour, or 210 units per 100 tons.
The cost per 100 tons at the different prices per unit
would therefore be 8s. 9d., 5s. 10d., and 4s. 4Jd.
respectively. In considering the above figures as
compared with steam winding it was only necessary to
ascertain the weight of coal burnt under the boilers per
100 tons of coal raised, and to add to this the cost of
firemen’s wages and depreciation on boiler plant. An
adjustment might also be necessary for the difference in
interest and depreciation between the cost of a steam
winder and an electric winder. The problem of ventila-
tion by fans driven electrically, or alternatively by
economical steam engines, depended very largely upon
the size of fan, and taking the examples before them,
namely, the electrically-driven fan requiring 800-horse
power to drive, it was necessary to consider the cost for
current, and the following figures might be of interest :—
The fan would require for 800-horse power, say,
680 units per hour, or for 8,760 hours per
annum, say, 6,000,000 units, and this would cost—
At 0-5d. per unit, say £12,500 per annum; at 0-33d. per
unit, say £8,000 per annum; at 0-25d. per unit, say
£6,300 per annum; at 0-2d. per unit, say £5,000 per
annum. In practice the fan would probably not be
running to its full capacity for the whole year, but the
cost would very nearly approach the above figures, and,
therefore, the view that electrically-driven fans of large
capacity were not economically possible unless the
current was supplied at an exceedingly low rate, was
clearly demonstrated. The same view might be taken
as regards the compressors, and this was borne out by
the fact that supply companies had to sell current at an
exceedingly low figure to consumers who were driving
compressors at collieries.

Prof. Arnold Lupton (London) asked why the authors
adopted wooden guides.

Mr. J. J. Prest (Horden, co. Durham), in reply, said
that so far as the comparative cost of concrete and brick-
work was concerned, labour and material in that par-
ticular spot was 15s. per cubic yard. They had all the
aggregate, the sand, and everything on the spot to make
concrete with; it was there as part of their own property,
and that cost 6s. per cubic yard. On the other hand
they, would have to pay 45s. per 1,000 for the bricks
required for the work. It would have cost 2j- times as
much. As to the lighting the colliers’ houses, they
charged 6d., 7d. and 8d. a week, depending upon the
number of rooms in the house and the number of lamps.
The lamps ranged from 8-candle power to 16-candle
power, ordinary Edis wan lamps. In addition, the men
were charged for all repairs and breakages. They could
burn the lamps for 24 hours if they liked, but they had
to renew the lamps themselves and pay for repairs. So
far, the men were exceedingly pleased with the installa-
tion. With men difficult to obtain, it was rather an
inducement to them to have the electric light in their
houses, and one got a choice of men in consequence.
The provision of the electric light was not a county
custom, and, therefore, by doing that they could steal a
march occasionally on their neighbours. As to the
method of sinking, he could not express an opinion at
the present time. He had promised to write a paper
on that particular subject for the Engineering Congress
next year, and it would be rather premature to discuss
the matter now. He would do his best to answer Mr.
Rhodes’s question then. So far as Mr. Mountain's
criticism was concerned, he agreed that the whole
question as to the adoption of electric energy versus
steam was one of cost per unit, and how little one could
get it at. At the present time they had about 600 kw.
spare energy over their consumption at the collieries, and
by and by in the course of development there would be
sufficient space energy to run the whole colliery by waste
heat; and although at the present time they were
purchasing energy from the power company, the scheme
they intended to carry out, and which would be carried
out in due course, would provide all the energy they
required at the least common multiple, and what that
least common multiple was, Mr. Mountain knew as much
about as most people. It depended upon how low one
put it to say whether it was going to pay to have steam
or electric energy. Personally, he had not the least
doubt as to the commercial results of the entire instal-
lation of electric energy. It took seven units to wind
three and a-third tons. One could put the energy at
anything one liked, 0’10d., 0*17d., 0*2d., 0’25d., 0‘275d.,
and so on, and it brought it down to 3s. 6d. or 4s. per
100 tons raised.

Mr. J. Leggat (Middlesbrough), in reply, said it was
very difficult to make the electrical part of the paper
interesting, because one could not give the price; it
depended on a long and complicated agreement with the
power company, which took into account the payments
for waste heat and so on; in fact, the actual cost
depended on a lot of things. With reference to getting
heat from coke ovens, the whole of the energy needed
for the colliery would be got, as far as kilowatt capacity
went, from these ovens. The advantage of the arrange-
ment with the power company was that they took it
all the time the collieries did not need it. They only
needed the maximum at certain times, but they got heat
from the ovens all the time, and the scheme worked out
well, because the power company could take it all the

time. That was one of the reasons why the price came
out so low. Without it one could not do it. Mr.
Abell had mentioned the question of ram pumps. They
had gone most carefully into that. As a matter of fact
it was difficult to get pumps capable of dealing with 1,500
gallons per minute. The best results were obtained from
the duplex. They had quotations from one of the best
makers of the large pumps, and their efficiency was 80
per cent., and at that it did not, by any means, work out
as the best thing to do. As to the question of upkeep,
Mr. Abell mentioned the pumps at the Thorne Colliery,
but was apparently referring to sinking pumps, which
were a totally different proposition. When one came to
main pumping and could get clean water and make
arrangements for water without that grit which one
generally gets in sinking, the upkeep was not tremendous
at all. Mr. Lupton had asked about the gearing. The
Citroen gear was quite noiseless; it was entirely enclosed,
and ran in an oil bath, so that one could hardly hear it
running. In the winder itself the clank of the drum
going round was much greater. The power company
kept a motor generator running specially for the winder.
The power at 3,000 volts went direct on to the winder.
The reason they could take these large peaks was that it
was right on their main system. They supplied current
at 20,000 volts, and it was reduced to 3,000 in the sub-
station. That was one of their reasons for adopting that
type of winder. Mr. du Pasquier’s remarks did not call
for any comment. Each case must be considered on its
merits. If the thing had been a little larger or the
current had been more costly, it might have been worth
while to go to the other type of winder. With regard to
Mr. Mountain’s remarks, there were about 800 kw.
available at present, and the rest came from the power
company. So far, the kilowatt demand amounted to
something like 2,400 kw. Even at the present time the
consumption was coming out very favourably. The
winder had only been in operation for three months, and
the prices were only just about to be properly analysed,
but it appeared that even without the addition of the
extra waste heat, which was coming on, it was quite the
right thing to do.

Gas Engines at Collieries.

Mr. John Davidson’s paper on the “ Development of
the Internal Combustion Engine for Power Generation at
Collieries,”* was next read and discussed.

The President, in moving a hearty vote of thanks to
the author for his valuable and suggestive paper, said
that the question raised was one which was every day
becoming of great advantage to collieries.

Mr. Maurice Deacon, in seconding the resolution, said
the subject was of very great importance, although, no
doubt, it had not been taken into very serious considera-
tion to a large extent by colliery owners. It was now
20 years since he put down a gas engine for the utilisa-
tion of waste gases from blast furnaces, and he had had
very many difficulties to contend with. Gradually,
however, the type of engine had been so greatly improved
that now he ran high-speed 4-cylinder tandem engines
with very great satisfaction; there was hardly ever any
breakdown, repairs were extremely moderate, and the
stores consumption was infinitesimal as compared with
the old class of engine. He thought that those high
speed engines might be applied with equal advantage to
coke oven gas as to blast furnace gas, but a lot of
technical points would have to be got over before the
result was as satisfactory.

The resolution was carried by acclamation.

Mr. W. Price Abell (Duffield, Derby) took exception
to the author’s statement that economy in fuel at
collieries did not appear to have been considered of any
importance. He would rather say that colliery manage-
ment, having cheap freightless fuel, found it a sound
commercial proposition to wait until expensive experi-
ments establishing safe engineering practice had been
made by concerns where dear fuel warranted that
expenditure. The author had not mentioned that one
great point which had caused the success of the small
gas engine was the absence of pressure on piping joints
or anything outside the cylinder itself. The author had
given some of the weak points of the gas engine, but
one not mentioned was the difficulty so often
experienced in starting a large engine. It would be
interesting to know what system the author considered
the best. Doubtless the thing that would make the
internal combustion engine successful and reliable would
be the greater get-at-ability of its parts. Another weak
point which the author did not mention was that the
gas engine power plant did not offer that reservoir or
storage of power which was so necessary for the inter-
mittent work of the colliery winding engine.

Prof. Arnold Lupton (London) thought that the
reliability of the steam turbine would have been much
greater than that of the steam reciprocating engine, and
very much greater than that of the reciprocating gas
engine.

Mr. E. Kilburn Scott (London) remarked on the fact
that the power which the author had taken in each case
in his estimate was 2,000-brake horse power. If the
author had gone a little lower than that, he thought
the figures for the recovery plant would not have shown
at all well. He believed that was just about the margin
at which it paid to put down recovery plant for taking
out sulphate and so on. With larger powers the steam
turbine showed up very much more favourably. It
would be interesting if the author would say into how
many units that 2,000-brake horse power in steam engine
and in gas engine plants was divided. There was no

* See Colliery Guardian, June 5, 1914, p. 1253.