256

THE COLLIERY GUARDIAN

August 11, 1916.

while to controvert the paper in detail, for one would
have' to begin at the very ABC, and go through with it.

The New President.

The scrutineers reported that the ballot for the elec-
tion of officers for the year 1916-17 had resulted as
follows: President, Mr. Frank Coulson; vice-presidents,
Messrs. A. M. Hedley, C. C. Leach, Henry Louis, John
Simpson, F. R. Simpson, and R. L. Weeks; and mem-
bers of council, Messrs. R. S. Anderson, Sidney Bates,
R. C. Brown, C. S. Carnes, Benjamin Dodd, Mark
Ford, Tom Hall, Austin Kirkup, F. O. Kirkup, J. P.
Kirkup, W. C. Mountain, R. F. Spence, Simon Tate,
W. 0. Tate, R. J. Weeks, J. R. R. Wilson, E. S. Wood,
and T. 0. Wood.

Mr. Greener vacated the presidential chair in favour
of Mr. Coulson, and, doing so, thanked the council and
members of the institute for the very great kindness and
courtesy they had shown to him during his term of
office. The period had been rather unfortunate. No
sooner was he elected president than the European war
broke out. He hoped Mr. Coulson would be president
when peace was declared.

Mr. Coulson, who was greeted with applause, returned
thanks for his election. He hoped that, notwithstand-
ing the war and the absence of so many members, they
might have many interesting and useful papers and dis-
cussions, for there was much good to be derived from
these. We talked a great deal of a trade war to follow
this war. He trusted that we would be in a better posi-
tion to undertake the trade war than we were to under-
take the military operations two years ago. He had no
doubt, in view of the numerous committees that had
been appointed, and the eminent men that were on those
committees, that we should be able to undertake that
trade war; but we wrere a long way behind in that
matter. In Germany, for example, almost every colliery
—at any rate, every group of collieries—had a number
of research chemists, men who could tell them not only
that there was so much sulphur and so much ash in the
coal, but could find things in coal of the existence of
which they had never dreamed. He thought that it was
very desirable that such research should be carried on in
this country. The colliery manager had enough to do,
and, besides, he was not a chemist. The men whom we
wanted for that work were chemists. It was not that we
had not the men. We had as good men as the Germans
—better men, and more scientific men. We had not
sufficient of them, however, and we did not make enough
use of them. In this country there was a certain
amount of coal free from sulphur and ash—coal that
was very useful in the manufacture of high-class steel.
He thought that that coal should not be allowed to go out
of the country, but should be utilised here entirely. In
the speech of the first president of that institute occurred
the passage : “We must each act as if we were indi-
vidually responsible for the success of the institute ”—
a sentiment he (Mr. Coulson) commended for their
adoption.

Votes of thanks to the retiring president, vice-presi-
dents, members of council, and representatives on the
council of the Institution of Mining Engineers, concluded
the meeting.

ELECTROLYSIS IN UNDERGROUND PIPES.

Some important considerations relating to the mitiga-
tion of the electrolytic corrosion of underground pipes
by stray currents are embodied in a report of the United
States Bureau of Standards

It is found that paints, dips, wrappings, etc., are not
of much avail in themselves, although useful in a
secondary way. Even insulating points offer but an
imperfect guard. The Dressem coupling is commonly
used in gas mains. A sleeve rests with rubber packing
on the two pipe ends, and is sub-divided by rubber insu-
lations. Through the use of this coupling high insula-
tion resistances have decreased to a few ohms. In
leadite joints the decrease occurred in a very short time.
In this case the leadite, which is poured like lead,
contains sulphur, resulting in sulphuric acid when the
ground is wet.

Wood stave joints, as used by the Pennsylvania Water
Company, do well in an area where jointings are few,
and appear to be preferable to wood stavings wrapped in
asphalted spiral steel tape.

The Metropolitan Water Board, Boston, has recourse
to a plain sort of joint, consisting of planed and shaped
overlapping sections of white pinewood built up to form
a | in. lining, encased in paraffin impregnated
canvas. The ring thus formed and driven in prevents
the pipe ends coming into contact, and stops leaks up to
a pressure of about 75 lb. A higher pressure is overcome
by closing the pores of the wood in a bath of red lead.
The spigot end of the pipe may be banded with iron.

Another type is a cement joint with a packing of
rubber or fibre between the ends of the pipes. After a
hempen ring is driven in, cement is added, and then
another ring of hemp binds the joint. The report recom-
mends that tarred paper or a coating of pitch may be
used on the exterior. Another point which compels
attention is that of the danger to electric pipe drainage
system by negative boosters. The bureau opposed the
system of pipe drainage in a complicated area.

A warning is issued against uninsulated negative feeders
accompanied by the following suggestions : (1) Limit the
actual potential drops on the earth or on pipe network;
(2) limit the over-all voltage drop to 2 or 4 volts, and the
gradients to 0’3 or 0-4 volt per 1,000 ft.; (3) instal
permanent potential 'wires to determine drop period
values. The bureau deprecates metallic connection
between underground metallic structures and the track,
and recommends inter-connection of intersecting or
parallel tracks as well as good bonding and cross bonding.

SOUTH WALES COAL DUST
EXPERIMENTS.*

By W. W. Hood, G. Knox, and E. C. Evans.

In a letter accompanying their report on the experi-
ments, the authors state that the results, although
obtained empirically, are distinctly alarming, and, they
believe, are less dangerous than the conditions actually
pertaining in the mine. They are more than ever con-
vinced that a strong case has been made out for the
erection of an experimental mine somewhere in the
South Wales coal field, and under the direction of men
with practical and technical knowledge, so that research
wTork may be carried out in conjunction with the micro-
scopical investigation already in operation in the coal
field. Although they admit that they have no cut and
dried scheme so far as the details of the suggested
experiments are concerned, they are strongly of the
opinion that an experimental gallery on lines approxi-
mating to actual working conditions, would permit of a
series of investigations being made, which would be of
the utmost value. Up to the present they are of the
opinion that neither watering, nor stone dusting, nor
both combined, are sufficient to prevent the initiation,
or propagation of explosions, although either or both
may mitigate the effect, or lessen the chances of initia-
tion; still, something may be found which will give a
greater immunity than the methods now known to,, and
adopted by, mining men.

Report on Experiments.

These experiments were carried out with a view to
determining, as far as possible, the conditions of coal
dust deposition in the collieries of South Wales and
Monmouthshire. The method of procedure adopted was
to place unplaned wooden boards of 1 sq. ft. in area in a
horizontal position at the point examined, allowing the
dust to be deposited on them for a period of six days.

Intake Dust

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Chart 1.—Average Dust Deposits in Intakes, Returns and Faces, of Collieries Examined.
Arranged in descending order of magnitude of dust deposits in intakes.

At the end of this time the board was covered over to
prevent any loss of the dust deposited, and was carried
to a manhole or other sheltered position, and the dust
carefully brushed, off. The weight of the dust thus
obtained, multiplied by the perimeter of the roadway at
that spot, and divided by the area, gave an idea of the
amount of dust per cubic foot of space at that position.

Degree of Accuracy of Method.

The method itself is only an empirical one, and several
factors would arise to vitiate the results. In the first
place, it was found at Bargoed Colliery that when the
shelves were placed in such a position that they were
sheltered from the air current, the amount of dust depo-
sited was considerably greater on the sheltered boards
than on boards horizontally placed in the same position,
but exposed to the air current. Generally, the amount
was at least twice as great.

Secondly, the innumerable crevices of the walls and
timbers with the immeasurable area of surface thus
exposed would offer far greater facilities for dust collec-
tion than would be given by a comparatively smooth
board.

Thirdly, there would always be some unavoidable loss
in the collection of the dust. This could, in certain
circumstances, be exceedingly great. In some of the
earlier work on this point it was found that, unless
special precautions were taken, the loss in this way could
quite easily amount to 75 per -cent, of the dust deposited.
The dust was so exceedingly fine that the air current
carried it away whilst it was being brushed off. Some
of the results obtained are anomalous owing to this
reason.

The results obtained therefore must be regarded as
being considerably lower than the actual amount of dust
deposited at the positions chosen; and probably the total
amount of dust per cubuc foot in any position would be-
at least very much greater than the amount calculated.
The results, however, serve excellently for comparative
purposes, and from a detailed study of the figures a
number of important facts have been ascertained.

Distribution of Dust.

(a)	Intake Airways. (1) Main Haulage Roads.—A
considerable amount of work on this point has been done

*From Journal and Proceedings of the South Wales
Colliery Officials’ Association.

at the Lewis Merthyr Collieries, which can be regarded
on the whole as being typical steam coal collieries. It
was found by far the greatest deposit took place at the
pit bottom, owing to the dust coming from the screens
and from the trams passing up the shaft. The amounts
of dust deposited in this way vary considerably with the
direction of the wind. At the Hafod pit, for example,
two series of experiments were made at different times.
The dust deposited at the pit bottom in the second case,
and up to the point influenced by the shaft dust, was
considerably greater in the second series than in the
first. This was due to the fact that in the second case
the wind was blowing directly from the screens to the
shaft, and a considerable quantity of dust thus carried
entered the downcast. It was found in both collieries,
and in both series at the Hafod pit, that the amount of
dust decreased fairly rapidly from the pit bottom to about
300 yds. inbye. Beyond that point the direct influence
of the shaft dust was inappreciable. From this 300 yds.
limit to the end of the main haulage road the dust deposit
(allowing for the local variations wffiich were unavoidable
owing to the experimental method) can be regarded as
fairly constant. As far as could be seen, the velocity of
the air current had no appreciable effect, but this can be
easily gathered from the fact that the air velocity at any
position is continually varying, by the passage of men,
horses, journeys, etc. In the case of Chart II., the dus-t
deposits in the main intake have therefore been repre-
sented as a straight line once the 300 yds. limit has been
passed.

It has been found that, with the exception of the
Monmouthshire collieries, together with a few Rhondda
collieries, the dust deposit in a week‘is on the whole con-
siderably greater than the limit of propagation obtained
by Taffanel. If the contention previously put forward
that the actual dust deposit is considerably greater than
the results obtained, then it will be seen that such a
deposit is obtained in practically all the Rhondda
collieries in the course of one or twro days.

(2) Horse Haulage Roads—Intake.—As a general rule,
once the limit of the main haulage is passed, the dust
deposit undergoes a rapid decrease, and, in the horse
roads on the intake side of the face, it is exceedingly
small; and, comparatively speaking, a dangerous amount
would not be formed for a considerable period of time.

(b)	The Coal Face.—Once, however, the coal face is
entered, an extremely rapid increase in the dust deposits
occurs, and in most cases enormous deposits have been
obtained. With very few exceptions a sufficient quan-
tity of dust is deposited in one day to cause the initiation
or propagation of an explosion. In many cases several
times that amount is deposited in the course of a day,
and the point is emphasised far more seriously when the
low results given by the method adopted are taken into
consideration. Generally speaking, the dust deposit
increases as the return end of the face is approached, the
maximum being at the return end. As a general rule,
also, the face dust is the most dangerous, both in
regard to the low ash content, and also in respect to
its degree of fineness.

(c)	Horse Roads—Return End of Face.—These again
show exceedingly high deposits, due to the dust being
carried from the face by the ventilating current. The
quantity of deposit is greatest near the face, and
diminishes gradually as the face is receded from.

(d)	The Main Return.—This as a rule is comparatively
free from dust. In the few cases in which compara-
tively high results 'were obtained, the estimations were
made fairly near the face. The influence of the face
dust does not extend further than 200 to 300 yds., and
beyond that point results are consistently low.

Character of Dust Deposit.

The experimental method adopted allows of the esti-
mation only of the exceedingly fine dust floating in the
atmosphere. In practically all cases the dust was sifted
through a lamp gauze before weighing, so that it was
not contaminated by pieces of timber, larger pieces of
coal, etc. In some instances, estimations were made
of the degree of fineness of the dust, and an average of
well over 80 per cent, passed through a 200 mesh, i.e.,
a mesh of 40,000 holes to a square inch, while in many
cases over 90 per cent, of the dust passed through this
mesh. The ash content also of the dust is exceedingly
low.