536

THE COLLIERY GUARDIAN.

March 14, 1913

portion of the fiery mixture may escape complete com-
bustion within the gauze and continue to burn beyond
it, firing the external atmosphere by a veritable passage
of flame through the gauze. The velocity which the
current should attain in order- that this should take
place will depend on the resistance offered by the gauze
to the passage of the current.

The experiments show that the temperature at which
the gauze enables the external atmosphere to be ignited
increases with the content of methane in the current.
M. Stassart has shown that the percentage most
susceptible to inflammation lies between 7 and 8 per
cent. When the mixture contains an excess of oxygen,
as is the case with mixtures containing 6J per cent, of
methane, the combustible gases that escape from the
wick of a heated lamp are able to burn, by reason of this
excess of oxygen, and as they are not intimately mixed
with the air, they burn with more or less lengthy flames.
When the gauzes reach a certain temperature—825 degs.
for vegetable oil lamps and 700 degs. for spirit lamps—■
these flames are able to pass through the gauze and
ignite the external atmosphere. If the content of
methane in the current be increased, the excess of
oxygen is diminished, and it feeds the benzine flames to
a smaller degree, for the firedamp, which is intimately
mixed with the air, burns first in the interior of the
lamp. The temperature at which the gauzes allow these
flames to pass through them approaches those at which
they allow flame to pass when firedamp alone burns inside
the lamp—namely, 1,000 degs.

On account of the relatively low temperatures at
which they pass through metallic gauzes, it is necessary
to prevent the flames produced by the combustion of
the vapours which escape in abundance from the wick
of a lamp in which firedamp burns from coming in
prolonged contact with the gauze. When the lamp
burns vegetable oil it is sufficient, to prevent the contact
of the oil flames with the gauze, to provide the lamp
with a glass, for the distillation of the oil is never so
active as to allow excessive oil flames to be produced in
the interior of the lamp; but, if the lamp consumes
benzine, large benzine flames may be produced within
the lamp, if the latter be excessively heated in a fiery
current. Therefore, benzine lamps should be very care-
fully shielded to prevent the benzine flames from being
projected against the gauze. Further, it is preferable
to construct them so that in currents of the highest
velocity encountered in the mine, the temperature of
the gauzes cannot reach that at which the benzine
flames are able to pass through them—that is to say,
about 700 degs. In order to do this, it is preferable to
increase, as far as possible, the resistance which the
lamp offers to the entry of the current, so as to reduce
to the minimum the quantity of firedamp that can
penetrate into and burn in the lamp in a unit of time,
and consequently its capacity for heating.

The lamp should be furnished with a double gauze,
and the apertures of the shield and the section of
bottom feeds should be reduced to the strict minimum
requisite. It is equally important not to exaggerate
the breadth or diameter of the lamp wick and, conse-

quently, to demand a corresponding increase in the air
inlets.

In conclusion, M. Lemaire states that in the numerous
tests made at Frameries on shielded benzine lamps
equipped with double gauzes, the passage of the benzine
flames through metallic gauzes raised to a red heat was
only observed in excessively rapid descending currents
(11 m. per second), and only in those types of lamp
in which the apertures of inlets and outlets were of
exaggerated dimensions.

M. Lemaire considers that benzine lamps provided
with shields and double gauzes, if well designed and
constructed, should still be considered, in the actual
state of knowledge, as presenting a degree of security
justifying their employment in fiery mines.

Grimsby] CoaljExports.—The coal exports from Grimsby
during the week ended the 7th inst. to foreign destina-
tions were shown in the official returns returns as follows:—
To Barcelona, 977 tons ; Copenhagen, 1,896; Dieppe, 1,058;
Drammen, 1,624; Gothenburg, 765; Helsingfors, 1,418;
Malmo, 1,006; Reykjavik, 1,125; Rotterdam, 523; and
Ystad, 3,935; total, 14,327 tons. There were no coastwise
shipments.

Partnerships Dissolved.—The London Gazette announces
the dissolution of the following partnerships : — F. H.
Murrell and I. Crocker, carrying on business as shipowners
and coal exporters at Mount Stuart-square, Cardiff, under
the style of Murrell and Crocker; Jos. Clough and Jas.
Clough, carrying on business as iron and steel merchants
and smiths, at Sickle-street Ironworks, Cleckheaton, under
the style of Sam Clough ; J. H. Pybus and T. Pybus,
carrying on business as electrical engineers at Brown-street,
Manchester, and Wilbraham-road, Chorlton-cum-Hardy,
under the style of Pybus Bros.

THE PYRO BOILER-CLEANING APPARATUS. SOUTH STAFFORDSHIRE AND WARWICKSHIRE
INSTITUTE OF MINING ENGINEERS.

If it may be said that the successful transmission of
heat is the greatest problem of boiler design, it is also
true that it is the greatest problem of boiler manage- ;
ment. The presence of scale in a boiler is perhaps ]
the most certain way of losing efficiency in a steam
plant, and if the colliery which obtains its fuel at a low
price has less necessity to economise in the consumption
of coal, the colliery boiler, on the other hand, is excep-
tionally liable to suffer from the incrustation of scale,
owing to the quality of the water supply.

We recently had the opportunity of examining, at the
Army and Navy Stores, an ingenious appliance for
mitigating such evils, that has been invented by Mr.
Adolph Schror, who has already devised several
appliances for removing scale from boilers. This
latest invention is original in design, and differs essen-
tially from the former patents, which were mechanical,
in their action. The “ Pyro ” boiler-cleaner consists,
briefly, in the employment of an oxy-acetylene flame, of
high temperature but moderate pressure, which is
rapidly played upon the scale. The effect is to drive
the moisture to the rear of the layei- and to break down
the deposit. Very thin scale deposits are generally
rather a protection than a danger to a boiler. However,
notwithstanding the high temperature of the flame,
there is, with the “ Pyro ” appliance, apparently “no

!

I

»

Ft'

i

i

■'

The Pyro Boiler-Cleaning Apparatus.





cause for anxiety on the score of undue heating of the
boiler plates, as the apparatus may be used to remove
the thinnest scale, by an accommodation of the working
pressure of oxygen. We have here, indeed, a very striking
illustration of the non-conductive properties of scale. We
saw solid lumps of hard scale, varying from A in. to 1 in.
in thickness, disintegrated in the space of a few seconds
when held upon the hand, protected only by a thin sheet
of paper. Owing to the brilliant light given off by the
flame, which issues from four jets in the head of the
burner, the workman manipulating it is able to observe,
without difficulty, its action upon the scale.

The acetylene generating apparatus itself is equipped
with an ingenious safety fitting, comprising a water vessel
and what is practically a water-gauge glass, the effect
being that any explosion due to obstructions, &c., in the
tubes is rendered practically harmless. The tubes
leading from the apparatus to the burner are supplied
in lengths up to 60 ft., so as to serve a range of boilers.

Contracts under the system are undertaken, on the
“ no cure no pay ” principle, by the Pyro Boiler
Cleaning Company, of 37-39, Essex-street, Strand, W.C.,
who are also the manufacturers of a graphitic paint,
named, “ Corrosanti,” which, it is claimed, will resist
effectually the formation of scale on clean boilers.

Shipments of Bunker Coals.—During February the
quantity of coal, &c., shipped for the use of steamers
engaged in the foreign trade was 1,539,410 tons, as com-
pared with 1,550,319 tons in February 1912 and 1,491,984
tons in February 1911. The aggregate amount so shipped
during the first two completed months of the present year
was 3,297,089 tons, as against 3,066,978 tons and 3,056,722
tons in the corresponding periods of 1912 and 1911
respectively.

A special meeting of this institute was held at the
University, Birmingham, on the 10th inst. In the
unavoidable absence of the president (Dr. J. Cadman)
the chair was taken by Mr. G. M. Cockin (vice-
president).

Mr. Cockin proposed a vote of condolence with
Mr. J. H. Stephen (who was to have been present at
this meeting) on the sad death of his son, news of which
they had just received by telegram. This was passed in
silence, the members standing.

Colliery Development and Surface Support.

Mr. Cockin then called on Mr. H. Bradshaw to
read his paper : “ Suggestions on the Development of
New Colliery Districts, with Special Reference to the
Support of the Surface.”

The author said a paper recently read before the
institute* dealing with the loss of minerals involved
in arranging for the support of surface property,
had prompted him to make some notes on this question
with regard to the future, special reference being
made to its close connection with the development of the
surface of new colliery districts. At the outset he called
attention to the inequity of the law concerning the right of
support. A fair distribution of the liabilities for surface
support would appear tojjbe a third by the colliery pro-





prietor, a third by the royalty owner, and a third by the
owner of the buildings erected on the surface. It was not,
however, the writer’s intention to suggest a campaign
against the existing law, but rather to indicate a means by
which this fruitful source of trouble might in new districts
be minimised. The conditions which would obtain in most
of these new fields would be very different from those of
the past, and the question of subsidence would present
new features. The chief of these would in all probability
be that whilst the number of the pillars left for support
would be less than formerly, this would be counterbalanced
by the great increase in their area, if they were to effect
the object desired.

In considering the development of the new coalfields, the
writer had adopted 420 million tons as the prospective
output in 1961, and in the year mentioned it was probable that
250 million tons of coal would be raised at collieries which
do not exist at the present time. Much, if not all, of this
coal would be derived from the concealed coalfields—that is,
from a considerable depth and in districts which are now
agricultural. The sinking and equipment of most of these
collieries would entail an expenditure of from a quarter to
half a-million pounds, and the output, in order to keep the
capital within reasonable limits (that is, not exceeding
10s. per ton of annual output), must be from 500,000 to
1,000,000 tons per annum. For the present purpose, the
average capital was taken as being .£400,000 and the output
as 800,000 tons. The “ life ” of each of these new under-
takings would doubtless average quite 100 years, and thus
80,000,000 tons would be raised at each colliery during its
“ lifetime.” Assuming a net production of 10,000 tons per
statute acre, the “take” would be 8,000 acres, or 12| square
miles—equivalent to the area of three average country
parishes. The average distance between the collieries
would thus be from 3 to 4 miles. An average output of 250