1232

THE COLLIERY GUARDIAN.

December 11, 1914.

ELECTRIC LAMPS IN COAL MINES.

Discussion at Manchester.

At a meeting of the Manchester Geological and
Mining Society, on Tuesday last, Mr. Leonard
Fletcher in the chair, a general discussion took place
on the use of electric lamps in coal mines.

Mr. Percy Lee Wood said they could not discuss
the merits of electric lamps without, at the same time,
discussing the merits or demerits of flame lamps; one
must go with the other. Dealing with the question of
lights, he observed that, even when an electric lamp was
new they seldom got more than a candle-power out of
it, and with many of the modern flame lamps it was
possible to get much more than a candle-power, which
was maintained to the end of the shift. The new electric
lamp did remarkably well for a time, but the experi-
ence of his firm was that when, four or five months after, it
came to be taken underground it gave very considerable
trouble after four or five hours. The batteries them-
selves would not last more than six or seven months;
after that period they had to be replenished. The bulbs
were also far from satisfactory, and the cost of repairs
to them was enormous. The figures quoted by Mr.
Hargreaves, at Sheffield, were most astounding. He
said that the cost of maintenance in his case was Ijd.
per week, a figure which, to him, seemed extraordinary,
and for this reason. One very large electric lamp
making firm had quoted for maintenance alone 4|d. per
week, and from actual statistics he had taken out that
would seem to be very near the mark. Their costs ran
to 4’7d. per week as compared with the IJd. mentioned
by Mr. Hargreaves, who went on to say that his cost for
oil lamps was 2Jd. a week. That again was very extra-
ordinary, because Messrs. Ackroyd and Best, who were
very large lamp makers, let lamps out on hire for Ifd.
per lamp per week for an ordinary lamp, and 2d. for
the new lamp with the inner combustion tube. He
made enquiries the other day at one colliery, and was
told that one-half the lamps were out of commission
through bad cells and bad bulbs. In view of those facts,
although he was very much impressed with the new type
of electric lamp with its beautiful light, he thought it
was a mistake to praise the electric lamp as some
of them were doing at the present time. They were
very far from being perfect, but he hoped further
improvements would be made, and there was no doubt
they would be, ultimately, infinitely better than the oil
lamp. The new Hailwood lamp, with the combustion
tube, he considered, was a vast improvement on the old
Marsaut lamp, to say nothing of the old Davy lamp,
though the Hailwood lamp was itself still far from perfect.
His firm had had a fairly large experience of them, and
they found in regard to the first lot of lamps sent out
that the hole in the middle of the inner tube through
which the flame passed was made so small that the
inner glass was always smoking. In another lot which
had been sent to them quite recently the hole was made
considerably larger, but he was afraid in removing the
defect of the smoking they had diminished the light
very considerably. Of course one hoped for great
things with the electric lamp, but it was just as
conceivable that great improvements would be made
with the oil lamp. He had one brought to him three or
four weeks ago which gave quite half as much candle
power again as the latest Hailwood. That particular
lamp would soon be on the market, and his view was
that it would certainly be as good or better than any
electric lamp at present invented.

One great advantage of the electric lamp over the oil
lamp was in connection with coal cutters. His firm
had some high speed coal cutters, and if an ordinary
flame lamp was near them when they were cutting, the
flame immediately ran up to sometimes three or four
times its normal size; it almost filled the gauze. In
cases like that the electric lamp was a great advantage,
and it was also useful in connection with coal cutters
for this reason, that it could be turned on its side when
it was necessary to examine the machinery to see if
there was any defect.

Mr. H. Stephenson asked if the enlarged aperture
through which the flame went in the latest design of
the Hailwood lamp was an improvement. The original
lamp had an oblong hole, but now it was circular, and
he should like to know if it gave every satisfaction.

Mr. Wood replied that personally he did not think
it would be a change for the better, because the light
was rather worse, though the glass did not smoke quite
as easily.

Mr. Wordsworth agreed with Mr. Wood that it
must not be taken for granted that by having an
electric lamp in the pit they had got something which
was miles in front of any oil lamp yet made. Still they
had to thank the electric lamp people for giving them a
start; he did not think they would have got the oil
lamps which were on the market, or were about to be put
on the market, if the electric lamp had not been invented.
Everyone, he thought, would agree with Mr. Wood that
they did not always get from the electric lamp the
candle-power it was credited with, especially after it had
been worked for a few months. At the collieries he
was interested in they had had a small number working
for some time. The first lot were tried in July 1911,
they lasted 17 months and the total cost was 4d. per
week. Then they were scrapped entirely so that the
cost of the lamps themselves bad to be added on to the
cost of maintenance. Since then they had had a further
108, and taking repairs only, without reckoning anything
for labour, they cost £51 4s. 6d. Allowing 25 per cent,
for those which were out of commission, which was
about the average they generally found stopped for

batteries, &c., it worked out at 2’4d. per week for material
only, in addition to which there was something expended
on labour, which ought to be added to the cost of the
upkeep. The second lot were put to work in June 1913,
and some in November 1913, so that they had been in
use practically more than a year, and in that time 82
cells had been renewed out of the 108 lamps. The new
type of flame lamp they had experimented with had
certain disadvantages, one being that when they tried to
examine the roof it immediately began to smoke up the
combustion tube. They had also found that in cases where
a fireman reported gas, another man following with
a combustion tube lamp could not find any at all, but if
he borrowed one of the ordinary lamps he could find as
much as 1J to If per cent. It would appear therefore
that in the pit the new combustion tube lamp was
not as sensitive in the detection of gas as the older type
of lamp. What the other lamp, which they heard was
going to be put on the market, would do they could not
say, but from the information he had it would go a step
further than the Hailwood lamp had gone. There was
another advantage about the electric lamp. Some
months ago on a working face they were getting coal
with a conveyor where half the men were using electric
lamps and half were using flame lamps. A small out-
burst of gas caused all the flame lamps to be put out on
the face, and the electric lamps were most useful in
preventing any panic among the men, because they were
able to leave the face with a proper light, and to get out
without being any the worse for what had happened.
If they had been entirely in the dark, some of those men
might have sustained, at any rate, minor injuries
through knocking one another down, and there might
have been a terrible panic. Therefore it was a point to
be considered whether they should not have both types
of lamp in a pit, at all events on the working face.
Even if the flame lamps were improved so that they got
an increased light, which no doubt would be done, the
electric lamps would still be of use in such cases as he
had just mentioned.

Mr. Harrison (H.M.I.M.) pointed out that Mr.
Wordsworth’s story might be taken as a testimony to
the value of the oil lamps, because if the men had had
nothing but electric lamps they would have gone on
working and not known there was any outburst of gas
until they had succumbed to its effects. On the other
hand, he knew of two cases where the men had had to
come from the working face in the dark, and no doubt
if they had had electric lamps they would get away a
great deal quicker and easier. In the instance Mr.
Wordsworth had referred to, the men were certainly
much better placed through having an electric light;
it was a thin mine and with a big conveyor it would be
easy for a man to get a knock, and a little knock
sometimes meant a big compensation bill. There was
no doubt the electric lamp required more skilled
attention than the ordinary lamp. If they were put
under the charge of a man without skilled knowledge
ht did not keep them up to the mark and they were out
of commission in about 12 months—everything about
them went wrong. The cases got eaten with acid and
the whole thing had to be renewed before it got its
second year over. If a man who had followed the history
of electric lamps, and knew all about them, was engaged
to give a certain amount of attention to them he could
keep them right and then the maintenance cost might
compare not unfavourably with the other.

Mr. H. Stephenson remarked that his experience of
the Hailwood lamp was slightly different from Mr.
Wordsworth’s. Only last week he had one in a testing
chamber, and found that it was quite as good a tester
of gas as the ordinary Marsaut lamp ; it was even better
with certain percentages. However, that was only in a
testing chamber, and he intended to try it in a mine.

Mr. Orchard said that in naked-light mines it was
the common practice to have candles at the face and
an oil lamp hung at the gate end. It seemed to him
some similar combination was desirable with the electric
lamp ; that was to have an electric light on the face
and an oil lamp at the end to test with. Besides fire-
damp, the possible presence of blackdamp had. to be
provided for, and, of course, with an oil lamp they
could test for either. The gauze lamp, properly handled,
so far as his experience went, was a very safe lamp ;
the danger arose when it got into unskilled hands.
Whatever kind of detector was adopted, it must be very
pimple—something which could be handled by fairly
ignorant men. His firm had been using electric lamps
for the last three or four years, experimenting with
them, and he was strongly inclined to approve of their
use mainly on the ground of safety, in preference to
gauze lamps, in unskilled hands.

Mr. W. H. Murray (H.M.I.M.) said one point in favour
of the electric lamp had not yet been touched upon—
namely, its ability to stand rougher usage below ground
than the oil lamp.

Mr. W. Maurice said in taking part in the dis-
cussion he was more or less in the position of replying
to a discussion of his own paper. The question raised
by Mr. Wood as to the relative candle power was neces-
sarily a difficult question. A lead accumulator of any type
had a limited and pretty well defined life; from the
first day it was put in until it dropped out of commis-
sion, say, after nine or 12 months, it was gradually
losing its storage capacity. But there was no particular
reason why that should be troublesome to the colliery,
because in a well organised electric lamp room there
would be systematic treatment of accumulators and
systematic scrapping of bulbs at such points as would

ensure a fairly good average constant value of light at
all times. Of course, there were always slight variations
of candle-power due to bad contacts. That was prac-
tically always a matter of the management of the lamp
cabin. The defects arose from want of proper care and
attention. Another difficulty was the bulb. At the
present moment there were no English makers producing
lamp bulbs equal to those which came from the Continent
a few months ago. He did not suggest that was due to
lack of technical skill in this country. The reason was
that the Continental manufacturers had a much longer
time to specialise in this branch and the manufacturers
at home were now buying their experience very largely
at the expense of the lamp users. With regard to the
amount of candle-power, they might take it that
generally there was going to be a race between the two
types; it was not at all likely that either would be able
to reach the top and stay there permanently, at all
events, not for some time to come. Taking the small
incandescent bulb, there were at the present time small
metal filament bulbs taking anything from 1J to 1^
watts. The members knew about the commercial
advent of the |-watt lamps. There were some in
existence to-day for use on a miner’s safety lamp; he
had used them himself experimentally and could assure
the members that they would come into the market in
time, providing they were prepared to use a lamp not
made in this country. So far as he knew, there was
not a |-watt l|-candle power 2-volt lamp in this
country to-day, but at any rate, there were the pos-
sibilities. He did not risk very much in the way of
prophecy when he told them that within 18 months they
would have the choice of running their present lamps for
two shifts with one charge, or running them for the
same length of time and getting double candle-power,
and possibly even more.

He thought it would be generally agreed, if the
matter was looked at impartially, that notwithstanding
all the improvements in construction one did not get in
practice a much better light to-day than was got 30
years ago. He did not mean in that observation to
make any reference to the flame combustion tube lamp.
Without the slightest intention of disparaging it, he
thought he was justified in saying that it had not yet
been accepted as one which would come into permanent
use in the mining industry. In no very long time there
would be 5 candle-power lamps, and probably after that
10 candle-power, so that the question of the amount
of light had not yet got near its final stage.

Mr. Hargreaves’ figures of maintenance cost, Mr.
Maurice continued, were not at all extraordinary. It
was perfectly possible for a colliery company to run its
lamps for about IJd. per lamp per week, excluding, of
course, any possible abnormal costs which might be
ruling at the present moment, A charge for maintenance
of 4Jd. was considerably in excess of what could be
obtained in the market. The natural life of a lead
accumulator in a miner’s lamp varied from 8 to 12 or
even 16 months; it was entirely a question of the
skill and attention of the users. Some speakers had
referred to the ability of the electric lamp to withstand
rough usage. He was sorry to say that property was
working out much to its disadvantage, and was the
reason why in some places it was acquiring a bad
reputation, because it was very badly treated. In some
Midland collieries it was a common practice for men
holing in a thin seam to lay the lamp on its side and
work with it like that all day. Also when doing a bit
of work in an awkward place they would suspend the
lamp upside down if that would give them a little more
light. That sort of thing was possible with a metal-
cased accumulator, the contents of which was nermeti-
cally sealed, but in the case of a lead accumulator fitted
with a valve of some kind it went without saying there
would be leakage ; the sulphuric acid would get out and
damage the terminals, and it would also create that
evidence which prompted the statement that one could
always tell where electric lamps were being used because
the men had red trousers.

Mr. Rothwell said the flame lamp had an
advantage over the electric lamp, in detecting the
presence of gas, but in other respects, in safety and
economy, the advantage was with the electric lamp.
There were many component parts of the flame lamp
which might go wrong—damage to the gauze or the
glass might be a serious thing. With the electric lamp
it did not matter if the glass was defective. Then as
to the light, he had noticed in the few mines which he
had been down that there was a variety of light wfith
the flame lamp. On the intake it got bright, in the
return airway it went down. It occurred to him
whether the flame lamp would be safe with the flame
increased as had been suggested. He had one out of
which he could get two-candle power, but it became
very hot. With the increased heat, would it be as safe
on a return airway as an ordinary lamp ? Would it
withstand the same test ? He believed the ordinary
lamp had withstood a test of 35 ft. velocity. He should
like someone to investigate this point and let them
know the result. On the whole it was his opinion that
with an electric lamp one got a better light and a
more constant light down the mine, and as Mr. Maurice
said, the time was coming when they would get a
greater candle-power.

Mr. Lincoln stated that the patent rights of the
Ceag lamp were acquired by a British company about
six months ago ; it was now made entirely in this
country, every part manufactured here, and nothing
but British labour employed. Both Mr. Wordsworth
and Mr. Wood had commented on the short life of the
accumulator, but that was the fault of the people
using the lamps. After they had been put in, the
lampman sometimes said, “ They are all right, they do
not want anything doing to them.” That was true for