78i

THE COLLIERY GUARDIAN.

Apbil 9, 1914<.

One of the men, feeling he was getting short of
oxygen, turned on his by-pass valve. Finding this of
no avail, he had the presence of mind to feel at his main
valve and found it shut off. This he immediately
turned on. He came to the conclusion that as he had been
working all the time in a stooping position, it had got
shut off by chafing against his thigh. Great credit is
due to him for his presence of mind. But for this, the
result would have been serious, as he was working in
irrespirable atmosphere. .

After some weeks of inactivity at the station—the
instructor being at a colliery attending to brigades—an
apparatus was put on a man, who found himself totally
unable to breathe. Examination showed that the
inhaling valve of the mouthpiece tube had adhered so
tightly to the seating that it could not be opened by the
suction of the wearer, or the pressure in the breathing
bag.

The defect in the apparatus as to the trouble with
the main valve being either accidentally or thoughtlessly
shut off, or the valve withdrawn, has been remedied by
applying a swivel and spring hook. This is attached to
the neck of the tube from the twin cylinders, the hook
being hooked into the wheel of the main-valve spindle,
and when the valve is set it cannot be either opened or
closed more than a quarter turn. This is the idea of
Mr. Clifford, the instructor, and great credit is due to
him for it.

Breathing fumes should not occur if a man with a
moustache takes care, in putting on the mouthpiece,
that all hairs are outside. He should be careful that he
has a firm grip on the mouthpiece with his lips, do as
little talking as possible, and see that the straps are
tightly fastened to his cap. The work at Birchenwood,
Norton, Jammage, Cannock Chase, and Shelton proves
that there is no reason to fear the efficiency of the
mouthpiece if due care is exercised.

The saliva trap falling off shows the advisability of
all screwed joints being in first-class fitting order and
tightly screwed, and put together by one man.

The damaged breathing bag demonstrates that all
men should take the greatest care with the apparatus,
and do everything possible to prevent any portion of it
being damaged in the slightest degree.

The sticking of the valve at the station proves the
danger in using an apparatus that is not in regular use.
I am confident that to have an apparatus out of use
for a period of time at a colliery, and then to put in on
to wear in a mine, is most dangerous; and, if done, is
simply inviting disaster.

Cases of over-exertion prove that the work is limited
in extent.

Turning on a by-pass valve, instead of a gauge valve,
demonstrates the advisability of a captain of a brigade
being selected for his ability, being able to think before
acting, and being able to keep perfectly cool.

For the gallery practice the reducing valve is set to
pass 1^ litres per minute; for actual work down a mine,
from 1J to 2 litres. Caustic soda, 3 lb. for gallery
practice; 41b. for pit work.

The twin cylinders contain about 10 cubic feet of
oxygen compressed up to 120 atmospheres. The amount
of oxygen used varies, some using more than others.
Even the same man doing exactly the same amount of
work on different days also varies the amount. The
average consumption of oxygen per man for gallery
practice is about 70 atmospheres.

The condition of caustic soda after use also varies,
some being much more caked together and carbonised
by one man than another, each doing exactly the same
amount of work.

The varying amount of oxygen used by the same
individual on different dates, when doing the same
amount of work is, I think, caused by his physical
condition.

There is a great difference in the men as regards the
use of the by-pass. You will find that in a team of six
men some will not have used it, and others will have
done so from two to three times. From this I gather
that you cannot fix the exact amount of oxygen
necessary. If it is fixed to suit a man who requires
more oxygen, it will be too much for the man requiring
less, and in the latter case the wearing of the apparatus
will become irksome. One great object is that the
apparatus shall be comfortable; if not, and the man
feels any discomfort, he will have his mind concentrated
on it. Most likely he will become irritable, and the
moment he gets to this condition he is within measurable
distance of trouble. When this happens, he should most
certainly return to the surface, and should not be asked
to go down the pit again.

It is advisable that a man should be perfectly fresh
and in good physical condition before wearing the appa-
ratus in actual rescue work ; also, he should not go down
a mine to work with a full stomach.

I have a case in mind where an intelligent team,
wearing the apparatus, were building off a district of
old workings in an irrespirable atmosphere (the reducing
valves being altered to give an increased supply of
oxygen), complained to me about the supply being
excessive, and that they did not feel at all comfortable.
They said that the work was no more strenuous than
their gallery practice, and they much, preferred the
gallery pressure of oxygen. I explained to them that
it was against all theory. Their answer was that they
knew when they were safe and comfortable without any
theory; they had confidence in themselves, and could
use the by-pass if required.

In training the men, one precaution that has been
drilled into them more than any other is that on no
occasion must they over-exert themselves. They have
been told that, if they do, there is every probability
that they will collapse, and, if in an irrespirable
atmosphere, the result would be death to the man, and
most probably to others of the team.

In actual work down a mine we have proved conclu-
sively that whilst the work accomplished by each
brigade is very limited, very efficient work can be done,
providing every care is taken to follow out the instruc-
tions given to the men at the station. The absolute
necessity of looking to the most minute details should
always be kept in mind, and nothing left to chance.

I am afraid that to increase the supply of oxygen for
the purpose of increasing the amount of work to be
done by each team is a grave mistake, and will most
probably end in disaster to the team.

Unfortunately, the popular idea of rescue apparatus,
and the work that can be accomplised by its use, is not
borne out in practice ; for, in addition to the limitations
before mentioned, you have the fact that a man working
in a dense smoke cannot see and loses all sense of
position, and also that the goggles he must wear in
smoke to protect his eyes have to be strapped so tightly
that severe headache results, which adds to the discom-
fort experienced when wearing the apparatus.

L Mining Institute of Scotland.—The thirty-seventh annual
meeting of the Mining Institute of Scotland will be held in
the rooms of the institute, 39, Elmbank-crescent, Glasgow,
on Saturday, April 11, 1914, at 3 p.m. The president
(Mr. James Hamilton) will be elected, and a ballot for the
election of two vice-presidents and six councillors for 1914-15
will be taken. Mr. Willoughby M. Dunn’s paper on
“ Electric Winding Plant at South Kenmuir Colliery,” and
Prof. D. Burns’s paper on “ Apparatus for the Determina-
tion of Carbon Dioxide and Oxygen in Mine Air” will be
discussed. Mr. Archibald M. Russell will read a paper on
“ Sinking and Equipment of Blairhall Colliery, Fife,” and
Mr. John Gibson a paper on “Mining Economics: Some
Notes and a Suggestion.” The council will meet at the

Fig. 1.—Diagram of Connection of Kotor Circuit with Kapp Vibrator.

close of the meeting. With the object of affording the
members an opportunity of meeting in a less formal way
than is possible at the general meetings of the institute, the
council has made arrangements whereby tea may be had in
the rooms in Elmbank-crescent after the Glasgow meetings.
Members attending the meeting on Saturday, April 11, are
invited to afternoon tea by the council at the close of the
meeting.

Institution of Mechanical Engineers. — As already
announced, the summer meeting of the institution will
be held in Paris, and will begin on Monday, July 6. An
outline programme has been drawn up in conjunction with
Mr. William Hanning (member, president of the British
Chamber of Commerce in Paris), Mr. Henri Gall (president
of the Societe des Ingenieurs Civils de France), and others.
On July 7, the morning will be devoted to the reading and
discussion of papers in the theatre of the Societe des
Ingenieurs Civils; luncheon; and the afternoon to visits
to engineering works and places of interest in Paris. The
institution dinner will be held in the evening. The pro-
gramme for the Wednesday is similar, and in the evening a
conversazione will be given by the Societe des Ingenieurs
Civils. On the Thursday evening visitors proceed to Lille,
where on the following day (July 10) they will visit
locomotive, steel and textile works in Lille, Roubaix,
Valenciennes, &c., returning to Paris in the evening, if
desired. It is intended to arrange for visits to works in
Le Havre, and a visit might be made after the meeting to
the International Exhibition at Lyon. Especially advan-
tageous travelling facilities will be arranged in connection
with the meeting.—An ordinary general meeting will be
held in the Meeting Hall of the institution on Friday
evening, April 24, at 8 o’clock. The following paper is to
be read and discussed : “ Application of Electrical Driving
to Existing Rolling Mills,” by L. Rothera, B Sc. The
anniversary dinner will be held at the Connaught Rooms,
Great Queen-street, London, on Thursday, April 23. The
conversazione will be held at the institution on Thursday,
May 21.

TESTS ON A KAPP VIBRATOR.

In 1913 Dr. Gisbert Kapp read a paper before the
Institution of Electrical Engineers {Journal I.E.E.,
vol. 51, p. 243, 1913), in which he described a new form
of phase advancer invented by him apd called the
“ Kapp Vibrator.”

. Messrs. Sandycroft Limited obtained last year a
licence for the manufacture of these vibrators, and
after devoting a considerable amount of time to their
study, recently received an order for, and successfully
completed the manufacture of, their first vibrator (other
than a purely experimental machine). This vibrator
has since been put into regular commercial service, and,
being the first of its kind, has excited great interest.

The vibrator is working in conjunction with a
330-B.H.P. induction motor built by Siemens Brothers
Dynamo Works Limited, and is installed at the
Chemical Works (late H. and E. Albert), South Bank,
near Middlesbrough. The motor is a 12-pole machine,
operated from the system of Cleveland and Durham
Electric Power Limited, who supply energy at a
pressure of 2,750 volts and a periodicity of 40 cycles per
second.

The vibrator is a phase advancer, or exciter, for use
with induction motors or generators respectively, and
consists of a magnet frame carrying three sets of 2-pole
field magnets, in which revolve three armatures of the
usual continuous-current type. The three armatures are
connected in mesh to the slip-rings of the induction
motor, as shown in the accompanying diagram (fig. 1),
which also shows all the necessary connections, although

in some cases it may be desirable to provide an inter-
locking arrangement to prevent the motor being started
with the vibrator in circuit—that is to say, practically
on short circuit.

The field windings are excited with continuous current.
The low-frequency rotor currents in the armatures cause
the la.tter to rotate first in one direction and then in the
opposite direction with the frequency of slip. This
rotation induces in each armature a voltage which is
opposed to the E.M.F. of self-induction of the motor,
and is greater than the latter by an amount sufficient to
supply, through the resistance of the rotor windings, the
necessary current to produce the magnetic field of the
motor. With normal excitation of the vibrator, no
magnetising current flows in the stator windings, and
consequently the motor operates with a power factor of
unity. If the exciting current be increased, the greater
voltage then induced by the rotation of the armatures
will produce in the rotor windings a magnetising current
greater than that necessary to produce the magnetic
field of the motor, and consequently a leading current
will result in the stator windings.

The photograph (fig. 2) shows the vibrator under
description, which, as will be noticed, is a small and
compact machine. The armatures are only 10 cm. in
diameter, and at full load, with a slip of 2’45 per cent.,
rotate about 3^ revolutions in each direction. Since
the frequency of supply is 40 cycles per second, they
change their direction of rotation every half-second.

The results of the tests made are plotted in the accom-
panying curve (fig. 3), which shows that at half load the
power factor was 0*99 leading, and at full load 0'96
leading. The corresponding power factors without the
vibrator were 0’76 lagging and 0*87 lagging respectively.