January 28, 1916.

THE COLLIERY GUARDIAN.

169

electricity on the spot, taking it in wires into the towns,
and supplying it for lighting, power, heating, and any-
thing else there was.

Mr. Laverick said it was only due to Middlesbrough
to say that that town was partly lighted by gas from
by-product coke ovens. He read in one of the technical
papers some months ago that the rates of Middlesbrough
benefited to the tune of somewhere between ,£20,000 and
£30,000.

Mr. M. W. Waterhouse (Bawtry) said Leeds also
derived a considerable amount of gas from the by-product
ovens of a neighbouring colliery. Mr. Chambers’
remarks reminded him of a meeting of the Institution of
Civil Engineers which he attended in London some 25
years ago. A member there ventured, even at that date,
to prophesy that the time would come when coal would
bo burned at the collieries, and the power and heat
would be transmitted to the towns by means of wires.

Prof. Fearnsides said the installation of tire
Skinningrove works was of great interest in this, con-
nection. Only a few years ago they used to bring their
coke, already made, from Durham, for use in the blast
furnace. He had it (on the authority, he thought, of.
Prof. Bone) that they now paid approximately the same'
amount of money for fuel which they bought as coal—
they brought it to Skinningrove, coked it there, and the
power they got from the coke oven gas enabled them to
sell their pig iron, not as pig iron at all, but as already
converted into steel, without any extra outlay for power.

Mr. George Blake Walker (Tankersley) wrote that
it appeared from the discussion that some of the
speakers were not aware to what extent coke oven gas
was being utilised in Germany for town lighting and
power purposes. In The Times for January 1911 one or
two interesting articles on this subject were to be found,
and he had already on another occasion quoted the
following from this source :—

“ In the colliery district around Essen there are 92
coke works. In 1905 only four produced gas for light-
ing purposes, the output being 631- million cu. ft. In
1909 the number was eight (out of 96), and their pro-
duction was 896 millions. The fact that as yet only one
in 12 of the coke works in the Dortmund district dispcses
of its surplus gas as an iliumin ant indicates the vast
resources that are still untapped. Obviously only a
small proportion of this gas could be used with advan-
tage for lighting, but its conversion into electrical energy
opens out boundless perspectives.

“ Arrangements for supplying lighting gas from coke
ovens were first made with the towns of Essen and
Mulheim. To the former, gas will be supplied in bulk
at 8-J-d. per 1,000 cu. ft. Bochum has agreed to take its
gas from Krupp’s Collieries, and Gelsenkirchen is doing
similarly. At Barmen . on April .1 the municipal
works will be closed down, and under the new arrange-
ment for a supply of- coke oven gas, the town secures
an immediate gain in two ways — it is to receive a
minimum profit of £5,000 a year, while it is saved
£100,000, which would otherwise have had to be spent
in re-building the works. The contract at Barmen,
which is 30 miles away from the coke works supplying
the gas, ranges from Is. 3d. to Is. per 1,000 cu. ft.
Negotiations are in progress with a number of towns and
villages in the country beyond Barmen, including
Solingen and Remscheid,'and a big scheme is being pro-
moted for the establishment of a large station, from
which, if needful, the whole of the industrial district of
Westphalia would be supplied.”

The Association of Colliery Managers in India.—By the
kind invitation of the general manager of the Bengal Iron
and Steel.Company Limited, the members of the Association
of Colliery Managers in India paid a visit to the Kulti
Iron Works, near Barakar, on Monday, December 20, 1915.
The .various coal fields were fully represented, members
attending from the Jherria, Rannegunge, the Central
Provinces, and the Palmow coal fields, and there were also
representatives of the British Westinghouse, Simon Carves,
and Parsons. The members inspected the various depart-
ments under the guidance of the general manager, Mr.
G. H. Fairhurst, and his staff, the processes pursued in the
manufacture of iron being lucidly explained. The works
are equipped with the most modern machinery, three blast
furnaces are now in blast, and a fourth is being budt; besides
this there -are two batteries of 34 each of Simon Carves coke
ovens, from which the by-products, tar, and ammonia, are
recovered. A sulphuric acid making plant has also been
at work for about 12 months, sulphur for the purpose being
imported from Japan. After the inspection, which was both
interesting and instructive,' the members were entertained at
luncheon by the Bengal Iron and Steel Company. After this
repast, the president, Mr. C. H. McCale, moved a vote of
thanks to the company and their general manager, both for
their hospitality and "for the most enjoyable morning the
members had spent in inspecting the works; also to the staff,
who had so ably assisted the visit by -explaining the different
methods of work in the various departments. Mr. G. Miller
also addressed the meeting, and reviewed the various
improvements that had been effected since Mr. Fairhurst
assumed the management of the works. In reply, Mr.
Fairhurst expressed his appreciation of all that had been
said, and while thanking the association, he wished it everj7
success. Mr. Charteris reviewed the introduction of turbines
and their success in India. Capt. Nixon, Adjutant of the
Chota Nagpur Light Horse, who was'one of the guests, and
who is leaving the corps to re-join his regiment, bale good-
bye to the members of the squadron, who largely consisted
of the members of the Association of Colliery Managers,
some of them also being attached to the staff of the Kulti
Iron Works. .

USE OF ELECTRICITY IN MINES.

At the invitation of the Nottingham Society of
Engineers, a joint meeting with the Nottnghamshiire and
Derbyshire Branch of the Association of Mining
Electrical Engineers was held at the Welbeck Hotel,
Nottingham, on January 19, when Mr. R. A. Sheldon,
A.M.I.E.E., who is a member of both organisations,
read an interesting and instructive paper on “ The Use
of Electricity in the Conveyance of Coal from the
Working Face to the Pit Head.” In the absence of
Mr. AV. Ralp Bates, president of the engineers’ society,
the chair was taken by Mr. A. Beeston, manager of the
Clifton Colliery,-Nottingham. There was a good attend-
ance of members from the two oiganisations, the
representatives of the local branch of the Association of
Mining Electrical Engineers including Air. E. E.
Beadsmoore (vice-president), and Mr. E. R. Hudson
(hon. secretary).

Mr. Beeston, in opening the meeting, stated that that
was the first joint meeting held of the two societies, and
on behalf of the engineers he extended a hearty welcome
to the electrical engineers. Some of those present were
members of both organisations, and they recognised the
benefit to be derived through them from an educational
point of view. The application of electricity to colliery
work was now on an extensive scale. During the short
time ho had had any tiring to do- with electricity in con-
nection 'with coal mining, he had seen rapid develop-
ments. In his paper, Mr. Sheldon would deal with only
a part of the use of electricity in mines, but it was a
subject of importance, and no doubt Mr. Sheldon would
prove conclusively how economies could be effected by
the use of electricity in connection with the conveyance
of coal underground.

Air. Sheldon, who is a lecturer on electrical engineer-
ing at the Nottingham University College, prefaced his
remarks by stating that in a pit completely worked by
electricity, the coal might be cut by electrical coal
cutters, conveyed to the gate ends by electrical con-
veyors, taken by electrical haulage to the pit bottom,
and drawn up the shaft by electrical winders. In con-
sidering the suitability of the use of electricity under-
ground, they must take into consideration the special
conditions which generally obtained there. These were
the possible presence of gas, and the consequent risk of
explosion, the extreme danger incidental to a fire occur-
ring underground, the presence of dust and damp, the
special danger to life from,shocks, and the very confined
spaces and headroom sometimes available for working.
With regard to danger from shock, the rules insisted on
a continuous earthing system. With few exceptions,
all cables had to be armoured, and the armour had to
have a section 50 per cent, the conductivity of the con-
ductors. The greatest care was taken to preserve ample
metallic continuity over joint boxes, and to extend this
continuity right up to the ultimate confines of the
system, that was to say, past the gate end box, along the
trailing cable, and to the coal cutter motor frame itself.
Of 86 deaths occurring below ground due to electricity
in the nine years ending December 1913, 40 were due to
contact with the outer coverings of apparatus through
absence of an efficient earth connection, 12 were due to
contact with uninsulated live parts, 32 to defective cable
insulation, and two to misadventure and other causes.
Thus, they would note that defective earthing and acci-
dental contact accounted for 60 per cent, of the fatalities.
Since the new code of 1911, earthing being more
general, the figures were much more conclusive. In
the years 1910-1914, 10 fatal accidents had occurred in
the Scottish group; only two were on armoured systems,
and in both cases the armouring was defective. At least
four of the 10 accidents would not have occurred in a
properly armoured and earthed system. To be fully
protected against shocks, all apparatus should be con-
structed so that no live part was accessible. All
switches, etc., should be enclosed in earthed metal cases,
so arranged that the lid could not be opened unless the
switch was in the off position; and when open, the switch
ought to be locked off. Fire underground was, as every-
one knew, a dreadful occurrence, and every precaution
should be taken to make pump rooms, engine houses,
switchboards, etc., as fireproof as possible. In some
cases fires might be started by short circuits and defects
in the electrical machinery, as they might be started bv
other agencies' apart from electricity. In the Hem
Heath disaster last February, which involved the loss of
11 lives, the fire was due to oil lamps, kept to prevent
the freezing of exhaust pipes from the compressed air
engine. The new rules provided for non-inflammable
materials in the construction of switchboards.

Coming to the question of danger from gas and
■explosions, Air. Sheldon said that, contrary to what
might at first sight appear desirable, it was not useful,
necessary, or advisable to make all underground motors
fireproof. A safety lamp to indicate gas was required to
be kept near each motor where inflammable gas was
likely to be present, and the motor must be switched
off, if If- per cent, of gas was present. As this is well
below the danger point, even when dust is present,
the provision of explosion-proof motors was not
demanded by the Regulations; but motors must be so
constructed as to prevent open sparking. Where, hpw-
ever, gas was likely to be found, an explosion-proof
motor was, of course, an additional precaution, for
although open sparking was not present, it was obvious
that in an explosive atmosphere, if some of the explosive
mixture gained admittance to the interior of the motor
it might be fired there, and this local explosion be com-

municated to the air around the motor. To avoid this
danger, the first idea was to try and exclude the entry
of gas to the interior of the motor by joints made with
rubber gaskets -and stuffing boxes. This was quite
useless, as the motor “ breathed ” and sucked in air
despite every care, Then again, the gasket was liable
to be carelessly replaced and a space left, and finally, if
an explosion did take place inside the motor, the more
gastight it was the higher the resulting pressure, and
the motor might be wrecked by this internal pressure,
the flame spurting out and Kring the surrounding gas.
It was usual, therefore, to make no attempt at a gasproof
or gastight- motor, but the motor was made strong enough
to stand any internal explosion, and arranged so that
the issuing gases were cooled sufficiently to prevent
the explosion spreading. Several methods had been
tried, for example, gauze protection. One or two layers
of gauze were placed over the openings, after the manner
of ia safety lamp. It was, however, of very little use.
After the internal explosion more inflammable air was
drawn through and ignited, with the result that what
was called “ after burning ” was set up, and this pro-
bably raised the gauze to a dangerous temperature.
Cooling by means of long tubes and labyrinth protection
was not now used.

AVith regard to plate protection, the efficiency was
completely destroyed if any single fault occurred, such
as too large a gap between any of the plates. Hence
the advisability of testing the plant before installing.
In some United States (Bureau of Alines, 1913) explo-
sions the plate protection failed when a fan was fitted
to the motor. Flames were discharged through the holes
in all cases, when the fan was used, but -never when
the fan was not running. That was to say, as long
as the fan kept drawing into the motor fresh gas to be
-ignited, it was impossible, with a reasonable size, to
have sufficient cooling effect at the plates. The most
usual method applicable to all kinds of apparatus was
that known as flange protection. Broad flanges were
used at each joint, and these were only roughly
machined so as to allow awoo O1’ ToUo ^n- clearance for
■ the escape of gas; otherwise, relief valves had to be
fitted. The flanges must bo wide enough to cool the
gases below 650 degs. Cent., even if “ after burning”
occurred. The apparatus must have groat mechanical
strength and be able stand at least 100 lb. of internal
pressure.

AVith regard to the mechanical side of the transporta-
tion problem, an obvious method of getting the coal
from the face to the shaft- bottom was in tubs on -rails,
and where head room allowed, this was the usual method ;
but in the thin seams there was no room for the tubs
in the actual stalls, and so conveyors came to be used.
A conveyor could effectively remove all the coal along
a face of from 60 to 100 yds. The- fewer gate roads
were a great advantage, as the cost of maintaining
headings was great. Air. Sheldon then went into details
as to various typos of conveyors, and made a brief
reference to certain advantages of the use of under-
ground locomotives, which were restricted in this
country, adding that the overhead trolley system had
been developed abroad. For the rapid conveyance of
coal along the main roads to the shaft bottom, some
kind of mechanical haulage was required. Steam and
compressed air -had long been used for haulage pur-
poses underground. The disadvantages of steam pipes
in the shaft or boilers underground had caused attempts
to be made to work from surface machinery by band
ropes on guide pulleys in the .shaft. Compressed air
was inefficient, and could only be used for comparatively
small powers. It still had, however, a useful vogue
in fiery places. Electricity, although more expensive
in prime cost, was fast displacing all other methods,
•and was much cheaper in working than steam. After
referring to -different types of haulages, Air. Sheldon
mentioned that there had been a development recently
■in the use of small portable hauliers to draw the coal
out of the gates, and to do away with ponies.

Coming to electrical winding, this, he said, was,
after all, only an extension of the haulage problem,
many large haulage plants being actually bigger than
small winders. Up to very recently the steam winder,
even though non-condensing and not even compounded,
had held the field, and the advent of the exhaust steam
turbine seemed likely to make its position still more
secure. Notwithstanding this, electrical winding had
made great strides in the last few years, especially in
new pits 'adjacent to large power stations. Electrical
winding gave great reliability, and very exact control
was possible, both at the winding speeds and at the
low speeds necessary for the extension of shafts and
ropes. In addition, it gave every possible safeguard to
life. The emergency brakes were usually actuated by
a weight- held off by compressed air,’ the compressor
being driven by a small motor. The stop valve of the
compressed air supply was kept closed by a solenoid,
and thus any failure of the current or air applied the
brakes. Overwinding was prevented by the depth-
indicator releasing the brakes, and any increase of speed
above the safe limit could also be made to apply the
brakes by means of ia centrifugal switch. The use of a
balance rope was much more possible with an electrical
winder. Then the total output of the pit was limited
by the winding capacity. The problem, therefore, was
to accelerate a heavy mass, consisting of cages, trucks,
ropes, pulleys, and coal, to a speed of some 40 miles
per hour, in perhaps 20 seconds, to maintain this speed
for a very few seconds, and then to reduce the whole
mass to rest in a few seconds more. The power neces-
sary to do this was very great during the acceleration
period, less than half the amount during the free running
period, and zero during the breaking period. If this
power were taken directly from the supply station to
the winding motor, the station must be of enormous
size, otherwise serious in convenience would arise. In
conclusion, Air. Sheldon described in detail various
kinds of electrical winders,