368

THE COLLIERY GUARDIAN.

February 13, 1914.

BOOK NOTICES.

Application of Electric Power to Mines and Heavy
Industries. By W. H. Patchell. 5J in. by 9 in.
xiii. + 333 pp. ; numerous illustrations. London :
Constable and Co. Limited. Price 10s. 6d. net.

This book is the outcome of a course of special
advanced lectures delivered at the University of London,
King’s College, and is evidently designed for the use of
electrical engineers interested in the application of
electricity to mines and the heavy industries. It is,
however, without doubt the best practical contribution
on these subjects we have as yet come across, though we
rather question the advisability of introducing rolling
mills, heavy machine tools and cranes, and electric
welding into a work of twelve chapters, nine of which
deal solely with mining.

In Chapter 1 the author deals with legislation, and
rather pertinently asks, why should there be special
rules for the use of electricity in mines ? We might
go further and ask, “ Why should there be a Coal
Mines Act ? ” To Mr. Patchell, an experienced
electrical engineer, special rules are doubtless
unnecessary, but to the colliery manager without any
special knowledge or experience in electrical engineering,
we think the Special Electricity Rules are probably more
necessary than the Coal Mines Act. He can work his
pit without the latter, but the former fixes a standard,
and checks any tendency on the part of electrical con-
tractors to persuade the owner or manager into accepting
a jerry job. Probably electrical contractors were more
to blame for the introduction of the Electricity Rules
than the mineowners.

We are glad to note that the author has a kind word
to say for direct current; we have always been of the
opinion that the wholesale condemnation of the con-
tinuous current motor was an error based upon a very
inadequate knowledge of the conditions of colliery work,
and it is quite refreshing to read Mr. Patchell’s state-
ment that “ such machines as ventilating fans, stone
crushers, conveyors, screens, saw and motor mills,
motors, locomotives, &c., can be driven better by con-
tinuous motors,” and recommends the adoption of a
mixed system. In regard to electric shocks, too, the
author shows that one may stand a higher voltage from
direct current than from alternating current.

Chapter 2 deals with cables and switchgear and their
installation, with a few notes on “ earthing,” and, con-
sidering the very great importance of £his fquestion, it
would certainly have been useful to the colliery engineer
if this had been dealt with in greater detail. We are
rather surprised, too, to read “ Sometimes an old haul-
age rope is used as an earth connection ”—in view of
the numerous failures of “ old ropes ” in this respect.
The proper way to “ earth ” a mine is to run an entirely
separate conductor.

Chapter 3 deals with coal-cutters, in which it is
pointed out that a compressed-air longwall machine will
take from three to four times more power than one
electrically driven. Electric drills, conveyors, shot-
firing, lighting, electric safety lamps and signalling are
also shortly dealt with. We note, however, that “ low-
tension fuses consist of small platinum wires embedded
in fulminate of mercury,” which is not quite correct, as
the fulminate of mercury is contained in the “ detonator,”
which is quite separate from the electric fuse.

Chapters 4 to 7 inclusive deal with haulage and
winding, and, for the colliery engineer, form the most
valuable portion of the book, as Mr. Patchell speaks
with the authority^of one who has had actual experience.
It is, however, scarcely correct to say, “ On the
Continent fibre ropes are largely employed,” as we
know of no case where fibre ropes are applied to
“ haulage,” and we believe that, for winding purposes
their use is confined to the north of France and a few
mines in Belgium. Further, we scarcely agree that
there is no scientific distinction between hauling and
winding. The accepted meaning of the term “hauling”
is to pull a “ set ” or train of wagons resting on their
own wheels which are attached to each other by
couplings. “ Winding,” on the other hand, involves the
use of a “ cage ” or “ carriage ” upon which the wagon
is at rest. Moreover, in dealing with any “ winding ”
due consideration must be given to the best means of
effecting the “ decking ” or changing of the wagons on
the cage. The distinction may not be of much
importance; still, it is just as well to be quite clear on
such points. The various types of gearing are dealt
with; “ Patchell’s ” system of operating controllers is
described, the “rating” of motors, and the different
systems of electric winding are discussed in an eminently
practical way. We would draw the author’s attention,
however, to the diagram of the “ Whiting ” system of
winding, which appears to us to be not quite correct.

Chapters 8 and 9 deal respectively with ventilation
and air-compression, and pumping. Of the two,

probably the former is the most interesting, as the
question of speed regulation of the fan and the various
methods of securing this is dealt with.

The remainder of the work deals with the application
of electricity to the driving of rolling mills—the
problem of which is somewhat analogous to “ winding ”
—heavy machine tools and cranes, and electric welding,
all of which will be found of interest to those engaged
in these industries. However, on page 306, “ Benardos ”
is spelt “ Bernados,” and we believe “ Crepelet ” should
be “ Creplet.” The book is well illustrated with several
folding plates, is printed in clear type, and well bound,
and we have no hesitation in thoroughly recommending
it to engineers seeking for reliable information on these
very important electrical subjects.

SPONTANEOUS COMBUSTION IN COALMINES.

A Digest of Evidence before the Committee.

(Continued from page 317.)

Dr. W. N. ATKINSON.

On July 31,1913,. evidence was given by Dr. William
Nicholas Atkinson, the senior divisional inspector
for South Wales. He said he had had a very long
experience of gob fires in North and South Staffordshire.
In considering the conditions under which men should
be withdrawn, witness thought it would be necessary to
classify the mines in some way. He would define a fiery
mine as a mine producing firedamp in an appreciable
quantity, but it was difficult to define an appreciable
quantity. If they took all mines as fiery in which safety
lamps had to be used to conform to the Act, that would
include all the mines that ought to be included as fiery.
Another difficulty was to define a dusty mine. He
referred more particularly to the composition of the
dust. In all cases on the outbreak of heating or fire, he
would recommend that the place should be either stone-
dusted or watered, and maintained watered and stone-
dusted continuously until the fire is either extinguished
or built off. Watering would be effectual for more than
one day in some cases; but on the whole, probably
stonedusting would be preferable in almost all cases.
Witness added that he had taken a number of samples
of dust and had them analysed at places where explosions
actually did stop in mines. The general result of that
was that 50 per cent, of ash in the analysis showed a
dust which would not propagate an explosion. Of
course, that was rather different from the proportion of
stonedust. That was the usual contents of the samples ;
but to be safe he should think 50 per cent, is probably
too low. There would be no difficulty in making it very
much higher, and he thought the Committee ought to
recommend at such places perhaps three or four to one.
He had known a case where, in all probability, an
explosion was stopped from extending by the fact that
the road leading to the fire out of which the explosion
came had been all covered with sand which they were
using for putting out a fire. The sand had been
tipped up near the fire and shovelled in, and the
consequence was that the road near the fire where the
explosion took place was all sand. Otherwise it was a
very dusty pit, and the explosion might have extended.
He had known of the explosion travelling to parts of
the mine with firedamp, where the place was wet or damp.
He did not think he could say anything on the point
as to what extent a dust which of itself was unexplosive
might increase the explosibility of air containing low
percentages of firedamp. He was referring to gas in
the air current itself.

Withdrawals and Reports.

Dr. Atkinson said he could not say that where there
was heating the percentage of gas was very much
reduced near the seat of the fire and the place of the
heating. The amount was often increased by the
operation of shutting a fire off. In collieries with a
mixed system, witness said he would classify that
district where the lamps were required as fiery. In the
case of a fiery and dusty mine the men ought to be
withdrawn very much more quickly and by obligation
than in the other case. Where there was no dust and
no gas, he would allow men to work possibly in other
parts of the mine. In some mines there were always
gob fires going on, and if the men were to be withdrawn
in such a case it would be impossible to work the mine.
Again, the nature of the heating and its situation must
be considered. Spontaneous heating might be anything
from a mere increase of temperature to active combus-
tion. In some cases, the danger might be confined to
the gaseous products of combustion, and, in other cases,
there might also be risk of explosions. When the
site of a spontaneous heating could not be closely
approached, it was not always possible to tell whether it
had arrived at the stage of actual fire. The situation
of the fire had usually an important bearing both on the
question of the withdrawal of men and on the best way
of dealing with the fire. Witness was asked at what
stage he would consider that the managers should report
cases of fire to him, and replied, “ such heating as made
it necessary to take steps to deal with it.” But there
were comparatively very few gob fires in South Wales.
The word “ fire ” being used, be supposed from a legal
point of view that until there was knowledge that there
was fire it would not be necessary to report it, although,
as a matter of fact, they were reported without any fire
having been seen. In practice, he believed, indications
of fire were considered sufficient; at least, he had had
many notices of fires, or suspected fires, where actual
fires had not been seen. He did not see how “ abnormal
heating ” could be defined, except as any case where it was
necessary to take any steps to deal with the fire. A man

would hardly run the risk of having his pit on fire for the
purpose of avoiding reporting anything to the inspector.
A definite increase of temperature might be taken as
one basis. They might fix 10 or 15 degs., or something
of that sort, but even that would be difficult. But there
might be gob stink and increase of temperature without
any actual fire, and to require that all cases of gob stink
should be reported would be a very onerous rule in
South Staffordshire. It would mean an increase of
inspectors in such districts if ail such reports bad to be
investigated, whilst the fact of reporting all small
occurrences of abnormal heating would place the respon-
sibility for dealing with those fires more on the inspec-
tors than on the managers. There really were cases
where it is impracticable to make regulations. Some-
thing must be left to the knowledge and discretion of
the men who have to deal with these things. He agreed
with Mr. Rhodes that if the temperature went up to
120 degs. it would show that there was something
wrong that required attention ; 110 would always indi-
cate some abnormal heating, but where the normal
temperature of a mine was 60 or 70 it would be wrong
to takb a case of 110 in that mine. He was not sure
that Mr. Rigby’s suggestion would not be better, to
take a percentage. Speaking from memory, he thought
cases were known where the temperature had been
reduced 20 degs., or something like that. In the cases
of deep mines, of course, that would not apply to the
actual working face. In most cases the temperature
closely approached to the natural temperature of the
strata.

Carbon Monoxide Dangers.

Continuing, witness said that where the products of
combustion were likely to be considerable, and to be
carried into the workings of the mine, the men should
be withdrawn at once ; and in fiery or dusty mines,
where there was a possibility of explosions, the same
course should be taken ; and in any case there should
be no hesitation, on the discovery of spontaneous com-
bustion, in withdrawing men if their safety was in any
way likely to be affected thereby. When the circum-
stances had been thoroughly investigated it might be
found safe for ordinary work to be carried on more or
less fully while the fire was being dealt with. In the case
of the products of combustion the men should be with-
drawn practically in all cases. Carbon monoxide was
produced before actual fire took place. He would be
inclined to say if any carbon monoxide was going in
with the gas the men should be withdrawn, and then
steps taken to discover what amount there was of it—
on the return side only in the absence of actual fire. In
the case of where there was fire in the working face, the
men ought to be withdrawn at once in some mines.
If there was known to be actual fire they should be
withdrawn on both sides, and be would take smoke as
tantamount to a fire. Cases of actual fire and smoke
should apply to all mines. Where a fire occurred
back from the working face he would also remove
all the men from that district where the fire
broke out if he could not put the fire out at once.
After the place had been investigated, it would depend
on circumstances as to whether the work should go on.
He would stop work altogether in a fiery and dusty
mine ; in that case he would wait until there was no fire
to be seen. The only alternative would be to stop off
the fires, when he would allow the men to go back. Of
course, he knew nothing about the Doncaster pits, and
he would not intentionally prevent all digging out of
fires, and he did not think it was practicable to lay down
positive rules as to what ought to be done in all cases.
There was a point where the only way was to deal with
the circumstances of the case with the knowledge and
experience of the manager and the assistance of the
inspector, and they could not make positive rules to fit
every case. In stopping off fires, the risk of explosion
might continue or increase for some time after the
stoppings were closed, and it might be advisable to with-
draw all men for a time, and afterwards to strengthen
the stoppings so as to enable them to resist any internal
explosion.

Questioned as to the effect on the gate packs of largely
increasing the ventilating pressures,’witness said that
in some cases it would probably increase the liability to
fire, and in others it might reduce it. It might increase
the risk by increasing the pressure on the pack walls,
and inducing currents of air to pass through the gobs,
and in other cases it might reduce the temperature, and
in that way reduce the liability to gob fires.

Gas and Stonedust.

Witness said he would not let men work in a fiery
and dusty mine where fire was coming out of a pack
wall. As regards the presence of gas, Dr. Atkinson
agreed that even if one to one of stonedust made coal-
dust innocuous, gas present to the extent of 2 per cent,
in the atmosphere might make it a dangerous condition
of things, the gas restoring the dangerous condition
which, in the first instance, had been got rid of by the
application of stonedust, but he did not know of any
definite experiments except those of Sir Frederick Abel
some years ago which had really been directed to the
point.

Witness said he had made some observations as to
stoppings which had not been blown out by explosions.
The thickness of the stopping necessary would probably
depend on the area of the road for one thing. The
bigger the road, the longer the stopping should be. He
should say in an ordinary-sized road about 12 yards
would be sufficient. The stanking off depended upon
how tight the stanking could be made and what other
openings there were into the area of the fire. But he
had not the practical knowledge of stopping off to deal
with the particular fires referred to, and as a general
rule they would find that the system of dealing with
fires which was adopted was based upon the conditions
and experience of the. district, and, generally speaking,
was the best one. In a new district, of course, there