152

THE COLLIERY GUARDIAN.

July 17, 1914.

is that separate or non-lead-covered cables may be
allowed to fall into bad condition, but a supply may be
kept up without troubling about low insulation, faults,
districting, or fuses. The insulation of such a network
is so low that it cannot be measured in the ordinary way
as a resistance. Triple concentric mains, which occupy a
minimum of space under a pavement, have never caused
any accidents of this kind, an indirect reason perhaps
being that specially skilled labour is required for joint-
ing them.

Bitumen as a Filling. — Bitumen casing is now no
longer manufactured, but considerable quantities
remain in use in districts where no accident due to
bitumen gas has occurred. Careful subdivision of dis-
tricts and testing for localisation, and repair of faults
in cables drawn into them, seems to account for absence
of trouble. This narrows the matter to the considera-
tion of the filling material used on the solid system,
and the troughs into which it is poured. It must be
admitted that bitumen and pitch-compound are the only
practical materials that can be used to fill the troughs.
The advantages of bitumen are that, since it undergoes
a process of preparation, it can be supplied of a quality
which is claimed to liquefy at a practicable tempera-
ture, to run freely, to weld itself to a subjacent layer,
to adhere firmly to cables and to the right kind of
bridges, to retain at temperatures above freezing point
such viscosity that in case of subsidence of the ground
it will bend slowly without fracture, or if cracked will
re-unite. So long as it is continuous it protects the
cable from moisture. The temperature recommended
for pouring is between 250 degs. and 350 degs. Fahr.
If it is heated above 400 degs. Fahr, hydrocarbons are
driven off, and it becomes brittle, but some engineers
have found it difficult to make a good job unless the
bitumen was run at about 420 degs. Mains to the
value of between two and a-half and three millions ster-
ling are said to have been laid in this way.

Pitch as a Filling. — The alternative to bitumen is
pitch. Blast furnace pitch contains substances which
make it unsuitable. Coal tar pitch by itself is too
brittle, though it has been used successfully for 40 years
for protecting lead pipes. Experiments in tempering
it with oil and afterwards strengthening it with whin-
stone dust were encouraging, and resulted in one case
in a mixture of three tons of pitch to two of stone dust
and 10 galls, of pitch or creosote oil. In another case
10 cwts. of pitch, 10 cwts. of limestone dust, and 10
galls, of tar oil were used; this pitch-compound was
tested in a cement testing machine, and was found to
be as tough as bitumen. The chief advantage claimed
for this over bitumen is cheapness. The melting pcint
is lower; it can be run at 260 degs. Fahr. This lever
temperature, and the fact that the specific heat of pitch
is about 0-5, as against 0-8 for bitumen, have the advan-
tage that the cables over which it is poured are not so
likely to be overheated. On a damp day hot bitumen
froths up, and unless considerable care is taken the
copper core expands, and the cables writhe and buckle.
Pitch-compound holds firmly to unglazed stoneware
bridges; it is apparently not affected by creosote or by
coal gas. While more gas is given off on heating pitch
than on heating bitumen, only two minor explosions
of street boxes have been recorded where pitch has been
used, and it must be remembered that street-box explo-
sions are often due to the sudden expansion of air by
the heat of a heavy short-circuit. Evidence about the
cracking and the self-healing properties of pitch com-
pared with bitumen was directly contradictory.
Perhaps credit may be given to the advocates of each for
understanding the advantages of-their favourite method.

Troughs. — Evidence differed widely about the
material for the troughs. Iron was used at first, wood
was substituted for cheapness, and owing to recent
improvements in troughs with proper socket joints,
earthenware troughs are now much used'. One witness
always uses stoneware troughs, and thinks that only
stoneware or iron should be employed. Earthenware
troughs with separate chases or a separate trough for
each cable is the best method, but it is expensive, and
occupies a good deal of space.

Service Box Faults.—The post-mortem examination
of a burn-out gives but little information about the
proximate causes other than those mentioned. Corners
and impervious pavements and other contributory
causes are also discussed.

Testing and Insulation.—The testing of the insula-
tion of a distributing network of mains has a bearing on
breakdowns and on accidents arising therefrom. The
higher the insulation the more easy it becomes to
measure it, and to detect incipient faults. It is pro-
bable that the object of Regulation 34 was to limit the
current in the earth which might interfere with tele-
graphs, rather than to impose a standard of insulation.
Regarded as an insulation test it has been objected
that the indication is differential, and that a leak from
one outer to earth might balance an equal leak on the
other side, or the instrument may be shunted by a very
heavy leak on the middle wire. To this it may be
replied that in continuous current work leaks to earth
are for the most part on the negatives, but a more effec-
tive answer is found in the evidence given by engineers
of various large undertakings, who rely mainly or
entirely on the indications of middle wire earth
recorders. In some cases the middle wire feeders are
bunched on to one busbar, and the total current is
recorded on one instrument, but by the use of a number
of recorders on different circuits the localisation of
faults is facilitated, and an erratic recqrd suggests that a
fault is on a consumer’s premises, while a steadily
increasing current indicates that it is on the network.
The current which may be neglected as the sum of
inevitable leakages depends on the size of the under-
taking. The one-thousandth permitted by Regulation
34 could not be tolerated on a large network, for with
an output of 8,500 amperes, 8| amperes would be con-
sidered a very serious fault, and if not removed would

result probably in a short-circuit or breakdown. As
soon as three or four amperes is recorded tests would be
immediately undertaken to find the fault. In small
towns if one-fifth of an ampere leakage is found the
engineers proceed to look for it. The fraction one-
thousandth clearly cannot apply to networks of all
sizes, but no suggestion has been made for a test which
can be of general application. If the principle of dis-
tricting, which will be referred to, is carried out, a large
network can be cut up either normally or by the action
of fuses into small ones. These automatic records are
supplemented by other tests, e.g., in one city, the use
of a bank of lamps between middle wire and earth. All
these tests, together with modifications which are some-
times made in them by the use of voltmeters between
outers and earth, and Raphael’s method of a shunted
ammeter, are carried out without breaking the connec-
tion between the middle wire and earth. In another
class of tests the middle wire is disconnected from
earth. It has been suggested that the voltage to earth
after disconnection divided by the current to earth from
the neutral gives the insulation resistance of the net-
work. The true measurement is not so simple as that,
but the Russell test (Journal Inst. Elec. Eng., vol.
xxx., 1900, p. 329) is one of this kind. Another method
is one of observing leakages rather than testing insula-
tion. This is to disconnect the middle wire from earth,
and to earth the positive and the negative alternately
through an adjustable resistance. This gives the com-
bined leakage current of the neutral and the opposite
polarity main. The current varies with the size of the
network. Besides these tests Grove’s method (Journ.
Inst. E. E., vol. xxxiii., 1904, pp. 1030-50) was men-
tioned. In certain small towns where there have been
no explosions of any importance, the leaks are so small
that they would not be recorded on ordinary commercial
instruments, and the practice is to disconnect the
middle wire, and to put the outers alternately to earth
through a lamp.

Where 20 amperes is considered a normal leakage, a
bad fault will pass twice that current or more, and there
is a difference of opinion whether such currents may
injure the cables by developing incipient faults. Some
few engineers hold that it is desirable thus to break
down incipient faults, and put the outer direct to earth
without any controlling resistance. It is difficult to
draw a distinction between this “ test ” and the prac-
tice known as burning out a fault. It is possible by dis-
connection of cables or of links in junction boxes to cut
off part of a network for repair. Such disconnection is
sometimes made for the purpose of localising a fault.
In one large city the engineer prefers to keep no less
than 206 districts electrically separate, connected
neither by fuses nor links. Many large undertakings
have networks interconnected by fuses which normally
carry moderate balancing currents, but two difficulties
prevent a wider use of this system. The fuses should
be placed at points where there is no current, but the
distribution of load in winter may differ so much from
that in summer, that the fuses need constant attention.
The theatre districts need special treatment by double
networks. The other difficulty is that certain kinds of
fuse go off explosively on heavy short-circuits, as when
tested on a large battery.

Conclusions.—(1) The committee finds that the explo-
sions to which its attention has been directed have
occurred in connection with electric supply by con-
tinuous current through separate cables, for the most
part insulated with vulcanised bitumen, and either
drawn into bitumen casing or laid solid in troughs filled
with bitumen. (2) The committee finds that no serious
explosions have occurred where the supply has been by
alternating current, or where concentric or three-core,
or lead covered paper insulated cables have been used,
or where cables have been laid solid in pitch-compound;
but a direct comparison between bitumen and pitch-
compound cannot be made as the former material has
been more extensively used than the latter. (3) In view
of the small number of serious accidents which have
occurred, compared with the large extent to which vul-
canised bitumen cables laid solid in bitumen have been
used, the committee is unable to recommend the Board
of Trade to discontinue to approve of this system. (4)
In view of conflicting opinions of witnesses, the com-
mittee cannot recommend that iron or stoneware trough-
ing should be used to the exclusion of wood, but they
recommend that wood troughing should be used only
where it can be ascertained that the soil is suitable;
that where separate mains are laid in troughing each
cable should be laid in a separate trough, and that
between the troughs there should be a space not less
than 2 in. tightly packed with earth or sand. (5) The
committee recommends (a) that separate mains for con-
tinuous current supply should not be laid on the solid
system below impervious pavements or close to the
walls of houses; (b) that easy bends should be laid at
corners, and the bitumen or pitch-compound should be
poured after the straight lengths have cooled; (c) that
where sharp corners of troughing are suspected to exist
the mains should be opened up and the corners eased;
(d) services should be taken into houses (preferably by
the use of armoured cables) in such a manner that gas
cannot enter. (6) The committee also recommends that
the special attention of engineers of electric supply
undertakings should be called to section 38 of the
schedule to the Electric Lighting (Clauses) Act, 1899,
and to No. 12 of the Regulations made by the Board
of Trade for securing the safety of the public, which
require notification of accidents by explosion or fire, or
any other accident of such kind as to have caused, or to
be likely to have caused, loss of life or personal injury
which have occurred at any part of any electric line or
work, in order that the circumstances may be investi-
gated, and, when necessary, reports made on them.
(7) The committee is strongly of opinion that such
reports should be published for the information of those
concerned.

MINING AND OTHER NOTES.

Bids were recently opened at Washington (D.C.) for
furnishing 600,000 tons of bituminous coal for the Navy
delivery at Hampton Roads or Philadelphia. The bids
received amounted to nearly five million tons, the prices
ranging from 2 dols. to 2 dols. 90 c. at Hampton Roads, and
from 2 dols. 42 c. to 3 dols. at Philadelphia.

The sub-committee appointed by the council of the
Shipping Federation to consider the question of the laying-up
of tonnage to counteract the depression in shipping met in
London last week, when it was agreed to take the opinion
of each individual member of the Federation on the principle
of laying-up, the question of details being left for future
consideration.

Mr. R. Rigby, of The Grove, Lawton, Cheshire, colliery
proprietor, has left 1*39,059, of which £38,741 is net
personalty.

Mr. Robert Pratt Furness, of The Elms, Garstang-road,
Preston, colliery agent and coal merchant, has left estate
valued at £-20,581.

A circular has been issued to the shareholders of the
Pekin Syndicate Limited, giving information regarding the
company’s operations since the annual meeting. The
operations of re-opening pit No. 4 have been proceeding
satisfactorily. The east main level has been recovered for
a distance of 1,660 ft. from the shaft, and the west main
level for a distance of 2,370 ft., while the output has now
reached about 13,000 tons per fortnight; the output
immediately preceding the inundation of water (September
1912) had been 13,367 tons per fortnight. The output from
No. 6 pit is nearly 10,000 tons per fortnight, as against
5,000 tons in September 1912. Coal is now being worked
in the new Machien pit, which it has been decided to call
No. 24 pit. It Was found sufficient to sink one shaft only,
the scheme being to provide ventilation and secondary out-
lets by means of contiguous native pits. The east main
level has been driven 252 ft. and the west main level
310 ft. A considerable output has been produced from the
several shallow pits which are being worked by native-
methods. To provide for the safety of the whole under-
taking it has been decided extensively to increase the
permanent pumping plant by the addition of four electrical
centrifugal pumping units, each capable of dealing with
75,000 gals, of water per hour. The output for the half
year, from December last year to May, was 301,500 tons,
as against 151,000 in the corresponding period of 1912-13.
An arrangement has been made with the Tung Hsing Sino
Foreign Coal Mining Company Limited, for boring at their
mines at Mentakou, near Pekin.

Mr. William Edwin Harvey, Chesterfield, Liberal-
Labour M.P. for North-east Derbyshire from 1907 to 1914,
one of the founders of the Derbyshire Miners’ Association,
left estate of the gross value of £5,052, of which the net
personalty has been sworn at £4,966.

Mr. Hewitson Hall, who has been with Palmers Ship-
building Company for three years, has been appointed
general manager of the company in succession to Mr. A. B.
Gowan.

The course for the college diploma in mining engineering
at the University College, Nottingham, extending over three
years, is recognised by the Home Office as equivalent to two
of the five years’ underground training required from candi-
dates for the colliery managers’ certificate. The course for
the college diploma in mine surveying, extending over two
years, is also recognised by the Home Office. Students are
also prepared for the B.Sc. degree of London University in
mining. Fees, £18 per annum. All information and pros-
pectus from the registrar, Mr. T. P. Black, M.Sc., Ph.D.

Mr. Llewellyn Lewis, of Pentwyn House, Dinas, late
haulage contractor to the Naval Collieries, Penygraig, who
died in April, aged 74, left estate to the gross value of £731,
of which £567 is net personalty.

The University of Liverpool have conferred on Mr. T. F.
Wall, D.Sc., the degree of Doctor of Engineering.

Cakemore Colliery, Blackheath, Staffs, which has been
worked for many years by Messrs. H. S. Pitt and Com-
pany, has been closed for an indefinite period. The closure
is said to be due to the bad state of trade and heavy work-
ing expenses. Over 100 men will be thrown out of employ-
ment.

OBITUARY.

The Earl of Ellesmere, whose death occurred on Monday
morning after a rather lengthy illness, at his town residence,
Bridgewater House, has for several decades been the largest
private colliery owner in Lancashire, in addition to being a
prominent land and mineral owner, the average output
from his collieries largely exceeding 1,000,000 tons per
annum. The collieries owned and worked by his lordship
are the Bridgewater (Sandhole), Linnyshaw (Berryfield)
and Ellesmere, Walkden; Ashton Field, Farnworth;
Brackley, Middle Hulton; Wharton Hall, Tyldesley; and
Mosley Common, Boothstown. In addition to the collieries
there are modern by-products plant at the Brackley
Collieries, and the whole are linked together by a network
of private railways, which, with sidings and junctions,
cover between 40 and 50 miles. Altogether between
4,000 and 5,000 men and youths—there are no pit brow
lasses engaged at the Ellesmere collieries — are
employed in and about the mines and on the estates in
various other capacities. It is pleasing to be able
to note, too, that the relations between Lord Ellesmere
(through his representatives) and his workpeople have
long been of the most amicable character, strikes and
disputes being few and far between. Many of his lordship’s
miners and other workmen are now enjoying pensions
granted after 50 years’ service in the employ of the Earl of
Ellesmere. Of late years big improvements have been
effected at his lordship’s coalpits, which are amongst the
most up-to-date in the whole country, and in the train of
these developments small villages have grown into important
and populous townships, many thousands of houses having
been built on the Ellesmere estates in the Walkden,
Swinton, Worsley, and Eccles districts alone during the
past 10 or 12 years.

We learn that Mr. James M. Swank, a great authority on
iron and steel in America, died at his home in Philadelphia
on June 21. aged nearly 82 years. Mr. Swank less than
two years ago retired from the position of statistician of
the American Iron and Steel Association. To the duties
of its secretary and general manager Mr. Swank devoted
40 of the best years of his life.