1060

THE COLLIERY GUARDIAN.

May 23, 1913.

continue it. The supply of gas was exhausted, and the dust
was too intermixed with stonedust to allow of its con-
tinuing the explosion. For an analysis of the sample taken
(when an entry was made to the recovered workings) in 19’s
crossgate below 19’s landing, showed it to contain 80*81
per cent, of ash*, and the dust was very coarse, only 10*52
per cent, passing through a 100-mesh sieve.

Probably the same explanation holds good in respect of
the dying out of the blast coming out by 14 level. A sample
of dust from this level at the foot of 19’s crossgate was
shown to contain 48 31 per cent, of ash.

As to the cause of the explosion. I think the fire which
originated some years ago in the neighbourhood of the
fault had never been completely eradicated, but gave
occasional evidence of its existence, and that as the coal
was worked off against the fault a great cavity formed, both
fire and cavity keeping pace with the extraction of the coal,
that an incipient explosion had occurred previously—viz.,
on January 20, 1912, and that the condition of affairs on
Monday night provided just the combination of circum-
stances necessary to cause an explosion on a more extended
scale—viz., the effective sealing off of the exit from the fire
area, but the failure to seal off the inlet, allowing of the
accumulation of an explosive mixture, and a vent for the
consequent explosion. That Mr. Chambers’ instructions
were well conceived for effectually sealing off the affected
area and were of the nature set out in an earlier part of
this report, I believe to be the case, but I do not believe
these instructions were carried out in their entirety. Who
blundered I do not know. Mr. Bury, being dead, cannot
appear in his defence. I refrain from attaching blame to
anyone in particular.

The Second Explosion.

The second explosion seems to have travelled wholly
along the face—not to have divided—as there were no signs
of force or burning out of 64’s or 19’s gates, or along 19’s
level or 19’s crossgate other than were occasioned by the
first explcsion.

The injury from supposed burning thought to have been
occasioned in respect of one of the men, Birch, who was
rescued after the second explosion—he said he had been
burnt on the back—I found to have been due to the heat of
the breathing apparatus (the injury was about the size of a
florin). Birch was with Mr. Pickering’s party, none of
whom showed signs of burning.

As to the exact route taken by the explosion south of 19’s
gate there is no evidence. Mr. Robinson did not find it
possible to travel the part of the face south of 19’s gate;
Fisher and Hulley traversed this part but did not notice
anything of particular importance, and all that it is
possible to be positive about is that the explosion took a
southerly direction, and came out by 14’s level. Hulley
informed Mr. Bobinson that the force of the explosion
spent itself in 14’s level and did not go along the crossgate
for 131’s and 153’s, neither did it go along 13’s.

It may be that there was a large accumulation of gas on
the “ rise ” side of the district after the first explosion,
which, igniting at the fire, burnt more or less quietly up
and down the face until an explosive mixture was formed at
about 14’s level, when it detonated. The force in 14 level
was very much greater than in the first explosion. The
greatest evidence of burning was along the face also. The
flame in the second explosion extended nearly to the end of
14 level, or it may be that, seeing that the purest and
consequently the most dangerous coaldust undoubtedly
existed at the face, the explosion followed that route in
consequence.

Had it actually extended far on to the plane, I think it is
probable that the whole colliery would have been wrecked
by a great explosion, as the analyses of the samples of dust
marked A, B, taken by Mr. Mottram—B from the south
plane, 14 yards top of south side of 14’s level; and A, from
south plane, just below 33 level—point to a dangerous
condition of dust. See also report on samples submitted for
test on July 31.

I consider that the facts which I have stated above are
eloquent testimony to the value of an inert dust—acting,
as it does, as an adulterant to the coal dust—as a pre-
ventative to the spread of a colliery explosion.

The Rescue Operations.

I have formed a decided opinion in respect of the rescue
operations. Whilst there was provided at the colliery
as fine a body of men trained in rescue work as one
could wish to see, the organisation at the mine on the
occasion of these explosions was most defective. When
Mr. Witty made his arrangements at the surface, he
should have issued instructions prohibiting the descent
into the mine of all persons unprovided with a written
authorisation to do so. He should also have placed a
guard at the outbye end of the south plane to prevent the
entry into that district of unauthorised persons from other
parts of the mine. Had this been done the loss of life
occasioned by the second explosion would, I am sure, have
been much less heavy.

The further question as to whether the work of recovering
and bringing out the bodies should have been undertaken

* These samples were analysed by Dr. Wheeler, the chief
chemist at the Home Office Experimental Station at
Eskmeals, Cumberland.

at this stage is one in respect of which there will doubtless
be differences of opinion. I have no doubt on the point*
I know that sentiment weighs heavily in the consideration
of a problem of this nature, and that there is an intense
desire on the part of relatives of the dead to see and bury
the bodies. I do not think, however, that the management
of a colliery is justified in allowing persons to risk their
lives in order to recover and bring out dead bodies, for that
such a procedure is always attended by the great risk of a
second explosion when a fire is known to exist underground
after an explosion is evidenced by case after case. Instances
may be cited in which the bodies have been recovered after
an explosion of this nature (e.g, Jamage Colliery). I agree,
but it is a race with death. It is hard, however, to make
people realise this, and so strong may feeling run on these
occasions that it sometimes requires a higher moral courage
to resist a natural impulse and prohibit persons from
undertaking (and undertaking oneself) a risk of this nature,
than to allow the risk to be undertaken.

I should also remark that great difficulty was experienced
in obtaining a correct number of the casualties; this was
not definitely ascertained for three days after the disaster
owing to the indiscriminate issue of lamps after the first
explosion. This was a very regrettable incident, and one
which emphasises the necessity of strict discipline on these
occasions.

Should the Persons in the District have been Withdrawn
pending the Complete Isolation of the Fire Area during
the Week-end and on Monday Morning ?

I have arrived at the conclusion that pending the com-
plete isolation by stowage and stoppings, all the men not
engaged in combatting the fire should have been with-
drawn from the district in which it occurred. It was stated
that to do this would be dangerous, for, it was stated, if the
face is allowed to stand fires break out. I cannot accept
this, and, in my opinion, no reason which will bear investiga-
tion has been advanced in support of this contention.

The Cause of Spontaneous Combustion at the Cadeby
Colliery.

Valuable evidence was given by Mr. W. H. Chambersand
Mr. J. E. B. Wilson, on the subject of the cause of spon-
taneous combustion at the Cadeby Main Colliery, and I
give in the Appendix a precis of their opinions. On the
general question, however, of spontaneous combustion and
the precautions which should be taken in the interests of
safety when combatting gob fires, I forbear to express any
opinion pending the results of the enquiry now being con-
ducted by the Departmental Committee on Spontaneous
Combustion in Mines.

Extinguishing Fire by the Application of Inert Gases.

The credit of carrying into practical effect the idea of
extinguishing gob fires by forcing an inert gas into an
isolated fire area belongs to Mr. Chambers, and its further
application is worthy of the serious consideration of mining
engineers.

Breaches of the Coal Mines Act.

I am glad not to have to report any breaches of the Coal
Mines Act as contributing to the cause of any of the
explosions.

I should like to state that the management of the colliery
did all that they could to assist me in my enquiry, and that
in the examination of witnesses I was ably assisted by the
representatives of the workmen.

I cannot conclude this report without recording my sense
of the magnitude of the loss which the Mines Department
has sustained in the death of three of its inspectors. Mr*
Tickle was a most promising junior inspector, and was, I
know, held in high esteem by Mr. Pickering. Mr. Hewitt
was a careful and experienced inspector. By Mr. Pickering’s
death the country is deprived of one of its most capable
and devoted public servants, and I personally have to mourn
the loss of a most able colleague and a loyal and valued
friend.

There are appendices to the report containing a list
of the killed, samples of the atmosphere taken between
the explosions, analyses of dust samples by Dr. Wheeler,
an account of the organisation of rescue brigades at the
colliery, and the summary of Mr. Chambers’ and Mr.
Wilson’s evidence with reference to spontaneous com-
bustion and gob fires. These are held over until next
week.

(To be continued.}

Hull Coal Exports.—The official return of the exports of
coal from Hull for the week ending Tuesday, May 13,1913
is as follows:—Antwerp, 944 tons ; Amsterdam, 856;
Alexandria, 8,419; Bremen, 1,717; Bombay, 163; Copen-
hagen, 567; Calais, 1,716; Cronstadt, 8,452; Gothenburg.
1,973; Ghent, 489; Hamburg, 2,420; Harlingen, 1,385*
Harburg, 2,619; Kalmar, 1,257; Kiel, 1,094; Karachi, 268;
Libau, 2,918; Newfairwater, 200; Norrkoping, 595; Odense,
1,587; Oxelosund, 831; Palermo, 5,016; Pernau, 2,793;
Reval, 4,326; Rotterdam, 4,616 ; Reykjavik, 1,156; Rouen,
8,712; Biga, 7,841; St. Petersburg, 7,557; Stockholm, 601;
Stettin, 3,036 ; Windau, 1,165; total, 87,289 tons. Corre-
sponding period 1912, 77,883 tons; 1911, 91,246 tons; 1910,
87,056 tons.

COMPRESSED-AIR PIT LOCOMOTIVES *

By T. Giller.

During the past few years considerable progress has
been made in the construction of compressed-air loco-
motives for use in mines, especially in connection with
the pressure at which the air tanks are charged, it
having been recognised that the use of increased pres-
sure enlarges the radius of action of the locomotive, or
enables the same duty to be performed with much
smaller tanks, besides affording greatei* security in the
event of the driver neglecting to have the tanks recharged
at the proper time. The early locomotives were con-
structed for a charging pressure of 30 atmospheres,
which was gradually increased in course of time to
60 atmospheres; and quite recently it has been found
practicable to employ charging pressures of 100 to 150
atmospheres, by using seamless steel tanks. In Germany,
tanks of this type have been approved by the Mines
Department, for standing a charging pressure of 150
atmospheres in a number of instances where the loco-
motives have been compounded on reconstruction (fig. 1),
with ihe result that the engines have been enabled to
make, for instance, three double trips, instead of two as
formerly, before recharging.

Against this advantage must be set the drawback that
increasing the pressure in the compressor from 115 to
165 atmospheres (these pressures corresponding to
charging pressures of 100 and 150 atmospheres respec-
tively) entails an increased consumption of power
amounting to 9*6 per cent. On the other hand, the
author has ascertained that only a fraction of this
increased consumption of power is actually lost, because
the relatively high temperature of pit air largely
counteracts the lowering of temperature and diminution
in volume caused by the throttling action of the reducing
valve. He is therefore of opinion that the charging
pressure for compound locomotives should be at least
130 atmospheres, whilst 150 atmospheres is still better.

Before proceeding further with the question of the
locomotive itself, it may be well to devote a few words
to the compressors and air mains, as forming an integral
part of the system of locomotive haulage by compressed
air. Even at the time the charging pressure did not
exceed 60 atmospheres, multiple-stage compressors were
already known, three stages being used for pressures up
to 60 atmospheres, four stages for up to 100 atmospheres,
and five stages for still higher pressures. Although
some makers consider four-stage compressors suitable
for 130 atmospheres pressure, it is really not desirable to
exceed the ratio of 1 : 2*8 to 1.3 in each stage, since
when these conditions are observed the air temperature
is not unduly raised, and the air valves have a much
longer working life ; and, besides, in the event of any
one stage getting out of order, the work can still be
safely carried on with the others. In addition, the
leakage losses between the several stages are smaller.
In comparison with these great advantages, the small
cylinder diameter (2 to 3| inches) of the fifth stage, and
its two small valves are of no moment with reference to
the mechanical efficiency. Finally, the floor space
occupied by a five-stage compressor is not very much
greater than in the case of one of the four-stage type.
One of these compressors, operated by live steam, is
illustrated in fig. 2, and they may also be direct-coupled
to an electromotor, or driven from the latter by belting
as shown in fig. 3. In the absence of steam, or where
cheap current is available, one or other of the two latter
methods is indicated, provided the plant is in fairly
constant work, and there is therefore no risk of setting
up rushes of current in the main circuit through frequent
stopping and restarting the motor.

When steam is available this is the best form of
motive power under normal working conditions, because
the speed, and therefore the output, can be varied to
suit the needs of the case in a highly simple manner,.
free from any complications. Exhaust steam is the
cheapest form, and experience has amply demonstrated
the reliable working of compressors operated in this
way. In some cases three-stage compressors have been
installed for high pressures, the air being drawn from
the ordinary compressed air mains of the pit (five to six
atmospheres pressure) ; but this is not an advisable
practice, since the pressure in these mains is liable to
fluctuation according to the demands of the ordinary
service, and consequently the output of the high-pressure
compressor varies, and any stoppage of the low-pressure
plant will interrupt the haulage. It is far preferable to
incur the additional outlay and keep the high-pressure
plant entirely separate from the low-pressure plant.

With regard to spare sets, a complete unit is desirable,
but if economy has to be observed increased security of
working can be attained by employing a double cylinder

* From a paper read before the Ruhr District Section of
the Society of German Engineers.