652

THE COLLIERY GUARDIAN

October 6, 1916.

both sinking and bricking was about 4 yds. per week of
11 shifts. Generally five men and one chargeman were
working in the shaft at one time.

Cost.

The contract price for the widening was .£10 per yd.,
and £15 per yd. for the special work at the High Hazel
Level, which included taking out the old tubbing and
inserting 18in. brickwork with concrete filling at the
back. The total cost, including the new brickwork at
the various insets, worked out approximately to £20 per
yard for labour and materials.

Results.

So far as the ventilation is concerned, there is a small
increase in the amount of air passing, accompanied by a
slight decrease in the water gauge of 0-2 in., which for
a few years will be satisfactory. A larger enginehouse
is now in course of construction to contain a more
modern pair of winding engines, and a permanent head-
gear will also be erected in the near future with guides,
etc., to run two chains.

SOUTH WALES INSTITUTE OF
ENGINEERS.

Stone Dusting in Steam Coal Collieries.

At an ordinary general meeting of the South Wales
Institute of Engineers, held at the Royal Jubilee Metal
Exchange, Swansea, on Tuesday, September 26, dis-
cussion was resumed on the paper of Mr. G. D. Budge
(Aberaman) : “ Notes on the Stone Dusting of Steam
Coal Collieries.”*

The President of the institute (Mr. William Stewart)
said it had been suggested—and he thought it probable
—that before long there would be legislation on the
question of stone dust in collieries. It was true that
in the Swansea district, with its large anthracite
industry, the problem might not appeal to them with
that urgency which applied to it in the eastern part of
the coal field, but it was an important point where the
dividing line began and the particular collieries in which
stone dust was more or less applicable in that area.

Mr. L. G. Hill (Birmingham) said at the Cardiff
meeting Mr. W. W. Hood declared he would not accept
the recommendations of the Explosions in Mines Com-
mittee as being of any value. What did they find inde-
pendently of the Explosions in Mines Committee?
Within three weeks of the issue of No. 5 Report an
explosion occurred at Senghenydd, by which over 400
lives were lost; but, on the other hand, 500 lives were
saved by the accidental presence of stone dust in a tract
of roadway separating the two areas. This was not
disputed. Again, in July 1914, an explosion began at
the Denaby and Cadeby pit in the same conditions,
except in one important respect, as those existing at the
disastrous explosion at the same colliery two years
previously. On the second occasion, however, owing to
five months’ stone dusting with Griffin ground dust, the
initial explosion was extinguished, and no one was hurt.
A question was asked at the last meeting as to the
effects of stone dusting on survivors after an explosion.
He heard of no inconvenience on this score at the Denaby
and Cadeby pit. He submitted that these facts estab-
lished the value of the stone dust recommendation of
the Explosions in Mines Committee. Mr. Hood was
an advocate of watering and water zones; but damp
walls and roofs would not attract coal dust, and there
remained a floating dust in the atmosphere which was
dangerous. Of this they had had two examples during
the past 12 months, namely, nine lives lost at Rowley
Regis by an explosion of dust in a damp mine, and early
in August 13 lives lost by an explosion at Ashington
Colliery, which he was told 18 months ago was a damp
mine and did not need stone dusting. Stone dusting
should be done carefully and economically; and he was
inclined to think Mr. Hood’s chief motive in his oppo-
sition was to ensure that stone dusting should receive
skilled and intelligent attention. Without disinterested
opposition, all reforms would be slipshod. To revert to
the recommendation of the Explosions in Mines Com-
mittee, Mr. Clive, of Brodsworth, said it was impossible
to increase the natural ash content of 35 per cent, up to
50 per cent., and consequently quite impossible to
increase South Wales dust up to 50 per cent. ash.
United States practice said 75 per cent, was necessary.
The Explosions in Mines Committee said efficiency was
a matter of degree. Mr. Budge, as a result of 12
months’ practical work on a fairly large scale, had
increased his South Wales ash content up to an average
of 63 per cent.; and this with a very small expenditure
of dust. He (the speaker) ventured to predict that,
with a continuous automatic distribution of stone dust
slightly in excess of Mr. Budge’s practice, the 75 per
cent, of the United States could be attained without
inconvenience to anyone. Anyway, Mr. Budge’s
actual results were a complete answer to Mr. Clive and
Mr. Hood to the degree of 63 per cent, ash content.
Five or six years ago it was expected that a mixture of
14 to 1 would be necessary.

Mr. Guy de Gruchy Warren (Pantyffynon) said Mr.
Budge had done the colliery community and the insti-
tute a great service in undertaking an investigation that
had obviously entailed upon him a long-continued task
of an exacting and arduous character. As the president
had said, the coal dust problem did not appeal to those
in the western district with the urgency that it did in the
steam coal area. In comforting themselves that anthra-

* Colliery Guardian, Sept. 22, 1916, p. 548.

cite dust was not dangerous, however, they might be
living in a fool’s paradise. Two experiments were made
at Altofts with anthracite dust, but neither was satisfac-
tory, and there was a recommendation for further trials.
He believed that in the American tests numerous
attempts were made to fire anthracite, and in all cases
they were unsuccessful, which was comforting to those
engaged in the Welsh anthracite industry. He con-
curred with Mr. Budge's remark that the key to all stone
dusting operations was given by the Explosions in Mines
Committee in the conclusions to the Fifth Report, and
that incombustible dust was more effective in preventing
the ignition of coal dust than in checking an inflamma-
tion that had started. He (the speaker) believed that M.
Taffanel declared that 75 per cent, of stone dust was
insufficient to stop the propagation of an explosion, and
he did not think there was any colliery with that average.
After the care Mr. Budge took to make Ifis roads safe, it
was disappointing to read that there remained in the
colliery two danger zones—the coal face and cavities. He
did not know if Mr. Budge had made experiments at
the coal face; perhaps he would let them know. He did
not profess to have intimate knowledge of the subject,
but it struck him that something in the form of a barrier,
either of stone dust or water suspended—something after
the arrangement that Mr. George Hann had designed—
might be erected in the faces, to be tilted immediately
a small explosion occurred—similarly to the practice in
the French experiments—and produce an atmosphere
which would extinguish the flame. He had had the
privilege of seeing some of Mr. Budge’s experiments, and
of seeing the ejector at work. It was extremely simple
and, apparently, extremely effective. It seemed to cover
the roadway in a very short time with a thick film of
stone dust. Mr. Budge informed them he had, so far,
been unable to obtain a good collector. Had he tried
reversing the operation of his ejector to form an injector
in order to collect the coal dust, which apparently blew
away, before he started dusting with the ejector? He
would also like to know whether Mr. Budge considered
it the best practice to blow away the coal dust film before
starting to stone dust, because he told them in the paper
he obtained an immunity in one part of the mine at the
expense of another part. Perhaps the better practice
would be to apply the stone dust to the coal dust film and
make a harmless mixture, to be collected as opportunity
arose. With regard to the analyses, had Mr. Budge
formed an opinion as to the value of natural ash in the
coal in preventing explosions, and in his analyses had he
taken the natural ash into consideration? His reply
might be that the Powell Duffryn coal contained no
natural ash, and therefore the ash given was inert dust
only. In trials of several Aberaman coals at Altofts, he
believed it was found that the efficacy of natural ash was
very similar to coal dust in which an artificial mixture of
inert dust had been put. In regard to the French experi-
ments, M. Taffanel stated he did not think that, given
equal proportions, the natural ash of coal was as
efficacious as an artificial mixture. Mr. Budge’s paper
gave a valuable record of the varying conditions in coal
mines, and pointed to the necessity of doing something
more than the Coal Mines Act required. Coal mines
must be treated as were patients in a hospital. Outward
appearances were no good; each mine, like each patient,
must be dealt with according to its own particular condi-
tions, and after a careful diagnose or analysis, the proper
remedy applied in the shape of a proportion of stone dust
suited to its case. He was sure Mr. Budge would con-
tinue to give them the benefit of his experience in stone "
dusting, and perhaps in the course of time they might be
privileged to learn that he was able to make a colliery
safe.

Mr. George Roblings (Llanelly) said while he was
now one of those who might be “ living in a fool’s
paradise,” yet many years ago he assisted in collecting
coal dusts for Dr. Galloway’s experiments, and saw very
forcibly how very dangerous these dusts were. With
these early and abiding recollections, he had read with
keen interest Mr. Budge’s paper, which was of a highly
important character in the facts which it contained of
the results of actual practice.

Mr. Sidney L. Gregor (Swansea) also spoke of early
practical tests of the explosibility of South Wales coal
dust with which he was associated.

Mr. John Standidge (Ystalyfera) said they must all
agree with Mr. Budge that the first thing to be done
was, as far as possible, to prevent the accumulation of
coal dust, and then deal with what was left as efficiently
and economically as possible. The author told them
that machine mining tended to increase the proportion
of the finest dust, the inference from which was that
machine mining tended to make the face more dan-
gerous. Of course, it depended a good deal upon the
mode of cutting. It was, however, the general practice,
where possible, to cut in the dirt under the coal, or
under any small band of dirt available. Dealing with
the work of the injector in cleaning and stone dusting
610yds. of main haulage road, the author had said two
men carried out the work in L:{ shifts, and samples were
taken after three days had elapsed and after 300 tons of
coal had passed over the road. He (Mr. Standidge)
understood it was near the pit bottom. If that was so,
the cost would be rather a serious matter. The work
would have to be done again in 15 da vs’ time to keep the
50 per cent, stone dust. As to Mr. George Hann’s
distributor, it seemed to be a kind of hopper arrange-
ment above the trams, and as each tram came 0'72 oz.
of dust was liberated. A good deal depended in whether
the road was single or double.

The President said the old trams in the South Wales
district tended to spread coal dust. They were designed
before they fully realised the danger of the dust: before
Dr. Galloway’s experiments opened their eyes to the

peril. In practice, it was necessary in their steam coal
collieries, where extensive repairs were needed, that
trams should be provided with doors to facilitate the
loading of rubbish. In the Midlands, where repairing
was not on the same scale as in South Wales, trams
with doors were not essential. There was no doubt, of
course, that the trams in South Wales caused a great
deal of coal dust to get on the roads. Much could be
done by the workman, in loading the trams, to mitigate
the evil. The watering of trams as they came on to
the double parting was also essential, as Mr. Budge had
pointed out. A feature to which he did not think Mr.
Budge had referred was the filling up of all cavities by
means of stone or brick archings or girder arching. In
recent years he had had considerable experience of the
work of securing roadways with girder arching, and
had proved that this method was financially advan-
tageous, as well as getting rid of the dangers of overhead
cavities. In one instance, there were immense cavities
in a return, which was heavily timbered the whole of
its length. All the cavities were filled up, and the work
of securing that return with girders was done without
sending out a ton of rubbish, all the rubbish being
deposited in the cavities. He thought it was very neces-
sary, whether they were watering or stone dusting, that
the cavities in the roadways should, as far as practicable,
be filled up. Mr. Budge had told them that* it was
impossible to get cavities stone dusted to the same
degree of efficiency as the roadways. It was true they
might have cavities near the working face, where the
ground was not sufficiently settled for arching, but the
bulk of the cavities were on the intakes and returns.
As to the quality of anthracitic dust, whilst the
Eskmeals experiments, as far as they had gone, had not
succeeded in exploding that dust, he did not think it
was desirable to take that as sufficient evidence of the
inexplosiveness of anthracite. There was no doubt that
they were likely to see legislation soon introduced bear-
ing upon this matter, and probably the mining engineers
in the western part of the coal field would be asked to
express their views and relate their practical experience.
Meanwhile, they might take it that the results of the
experiments at Eskmeals would be taken as a basis of
enquiry and possibly legislation.

Danger at the Coal Face.

Mr. G. D. Budge, replying to part of bhe discussion,
said there were some points with which he preferred to
deal in writing. The safety of anthracite dust depended
on the difficulty of igniting it. In certain other parts
of the coal field they were trying to make a coal dust
mixture difficult to ignite. With regard to the coal face,
he had not yet made any considerable experiments with
stone dust in the face. They had recently been making
experiments for the Home Office with treacle and
colloid, and they had also tried a certain proportion of
stone dust. At the present time he saw no clear way to
make the coal face safe. The coal face was undoubtedly
the most dangerous place, if the pit was stone dusted. In
the face at a steam coal colliery they might have dust
which would not yield, on incineration, more than 5 per
cent, of ash; they might have 15 times as much dust in
the coal face as was necessary to propagate an explosion.
In the old days a large accumulation of dust was known
to be a safeguard, to a certain extent. He knew of one
explosion which, from all accounts, seemed to have been
choked by too much dust at or near the coal face; but
there was sufficient of the finest dust of low ash content
in all steam coal faces to generate a very violent explo-
sion, and if an explosion started in the coal face it was
not at all certain that a 50 per cent, incombustible coal
dust mixture on the roadways throughout the colliery
would stop that explosion. The coal face must certainly
be dealt with, and he intended to study the matter very
carefully. He hoped other people would also do so, in
order that a very difficult problem might be solved. The
question of barriers of stone dust tilting into the atmo-
sphere in the coal face presented difficulty. Supposing a
piece of coal face was isolated by those barriers, they
would have to arrive at the length of coal face which each
barrier would have to deal with, and the barriers would
have to be not only frequent, but also of considerable
length. It would mean cutting up the coal face very
considerably; so that he was afraid it would interfere
with the continuity of the face-—a very serious matter in
South Wales. As to the question of cleaning before
stone dusting, he did not believe in using the ejector for
cleaning. He had tried it several times, and had opened
the doors leading from the main intake to the main
return, blowing the coal dust up the upcast pit, and he
then got into considerable trouble with residents near the
pit top, owing to the quantity of coal dust coming up the
shaft. A tremendous cloud of coal dust was raised in the
atmosphere, and it certainly came up the pit, but that
could only be done for a short distance near the bottom.
Unless they could collect the coal dust after raising it
into the atmosphere, and taking it out of the colliery in
trams, there was no object in disturbing it at all. It was
far better to leave it than to allow it to be carried to
some other part of the mine and perhaps deposited in
high cavities and places where there might be gas. The
question of reversing the ejector and using it as a
vacuum cleaner had been mentioned. He had tried it,
and for cleaning electric cables underground the method
was very satisfactory. It had been tried for cleaning
cavities, but as there might be gas at any time in a
cavity, say, 20ft. or 30 ft. above the haulage road, one
was somewhat chary of the mixture that this vacuum
cleaner was handling. All that could be said about the
vacuum cleaner was this : it was certainly efficacious, but
it was too costly to be practicable. It was suitable for
taking coal dust off a length of electric cable, which, of
course, was necessary, but beyond that it was not practi-
cable. With regard to the analyses, the natural ash of
the coal was included in all instances, and in the figures
that he had given, this was of considerable effect. The
general variation of the dust in South Wales steam coal