698

THE COLLIERY GUARDIAN.

Apbil 4, 1913.

furnace. The melting room is of large size and well
ventilated, to prevent inconvenience from the lead
umes.

The large experimental gallery is at present 110 yards
long, in a straight line, but is intended to ultimately
measure about 1,000 ft. It is of circular cross-section
(fig. 2), measuring 6 ft. inside diameter, a flat floor being
provided, made of ferro-concrete, supported by small
angle irons. The shell is of mild steel plate, about f in.
thick, shaped into tube lengths of 33 ft., each tube being
built up of five sections connected together by means of
T-section iron rings, riveted on a (fig. 3), the longitudinal
joints being lapped and fastened by two rows of rivets.
The lengths are connected by angle iron rings b, bolted
together, the joints being packed with flat iron rings
wrapped with graphite asbestos cord. The tubes are
supported on boiler chairs c, 20 ft. apart and resting on
brick foundations. At intervals of 33 ft. connections d
are provided at top and bottom (fig. 2) for the gas,
water and compressed air pipes, and windows e (4J in.
by 9 in., with lin. glass) are arranged along one side of
the gallery at intervals of 12 to 30 feet to facilitate
inspection of the course of an explosion. In the first

Fig. 3.—Section of Large Gallery.



Fig. 5.—Plan of Schondorf Lamp-testing Apparatus.

6 yards of the gallery there are also two windows on the
opposite side.

One end of the gallery is open, whilst the other is
closed by a heavy cover of f in. sheet iron, backed by
two brick pillars 8 ft. high, 4| ft. wide and 10 ft. long,
firmly secured to the foundation by tie rods. A space of
2 ft. is left between the pillars to enable the mortar to
be changed as required. The mortar, which rests on a
wooden foundation in the explosion chamber and close
to the end cover, is 28 in. long, with a 2 in. bore 20 in.
deep. The inner shell is 8 in. and the outer shell 19 in.
thick, and the weight is about 25 cwt. The shots are
fired electrically by a machine operated from the obser-
vation stand.

A fan / driven by hand from outside is used to
distribute coaldust and mix the pit gas and air in the
gallery. The dust is admitted through g and the gas
through a corresponding aperture in the bottom of the
gallery. The explosion chamber v, with a capacity of
about 53 cubic ft., is formed by securing a paper screen
by means of an angle-iron ring h situated 20 ft. from the
end of the gallery. Wooden shelves 5 in. wide and
mounted on brackets so as to stand about 5 in. from the
walls of the gallery, are arranged for a distance of about
90 yards (starting 30 ft. from the end) for the purpose

of supporting coaldust and ensuring uninterrupted
distribution of such dust. As mentioned, it is intended to
extend the gallery to a total length of 1,000 ft., and a
parallel gallery is also projected, a branch connection
having been provided at w (fig. 1) for that purpose.

For ventilation purposes the gallery is connected with
a fan by means of a gallery 100 ft. long starting from
near the end of the explosion chamber. For the first
16 ft. this gallery is of the same diameter as the main
gallery, but then tapers down to 4 ft., and is provided
with three bends (as shown in fig. 1) to protect the fan
from the effects of the explosions. In tests with the
fan at work the escape valves at the bends are merely
covered over with light boards. In ordinary experiments
a heavy sliding door is let down at t between the venti-
lating gallery and the main gallery, and access is afforded
to the former gallery by an iron door k at the end of a
short branch u. The Pelzer fan is 44 in. in diameter,
runs at 580 revolutions per minute and draws in 35,000
cubic feet of air at a depression of 2 in. The maximum
air velocity in the gallery is 20 ft. The fan is belt driven
from a 30 horse-power polyphase motor- (220 volts, 750
revolutions), the speed of which can be reduced to 30
per cent, of the maximum by means of a rheostat. A
reversing valve in the section between the fan and the
gallery enables the ventilating current to be changed in
either direction without reversing the fan.

The gallery for testing explosives is of the German
standard pattern measuring 80 ft. in length, 6 ft. in

i

Fig. 4.—Section of Explosives Testing
Gallery.

height, and 4J ft. in width (elliptical) cross-section
(fig. 4). The walls are constructed of a triple
layer of sound pitchpine boards, each 20 ft. long
and 44 in. wide, the total thickness being 2| in. The
boards, which are laid so that the joints alternate, are
secured by flat iron rings on the inside and rings of
I section outside, and are thickly coated with tar before
being nailed together.

One end of the gallery is open, the other being closed
by a mass of brickwork 12 ft. high and 10 ft. square,
with a cylindrical hole, just above the floor level of the
gallery, for the reception of the mortar. This latter is
34 in. long and has a 2 in. bore 2 ft. in length. It is
pointed slightly upward, so that the prolongation of its
axis strikes the roof of the gallery 11 yards away. The
front end of the gallery, fora length of 17 ft., is formed
into an explosion chamber, in which the explosive
mixtures of firedamp and also the mixtures of air and
coaldust are prepared. The walls in this section are
strengthened by another triple thickness of boarding,
making 4| in. in all, and are also lined with J in. iron
plate. The outer end of the chamber is closed by
packing paper held in position between a fixed
and a detachable iron ring. At intervals of 2| to
3| yards, circular openings 8 in. wide are provided in

the roof of the gallery to serve as safety valves and
relieve the walls of the strains produced by the explo-
sions. They are covered with stout paper.

The air in the explosion chamber is warmed by a
system of pipes carried all the way along same. The
temperature, which for testing explosives is maintained
at 20 to 30 degrees Cent. (68 to 86 degrees Fahr.), is con-
trolled by a thermometer inserted through the roof 5 ft.
away from the end. The pit gas is admitted through a
hole in the middle of the chamber floor, and is uniformly
mixed with the air by means of a two-vane stirrer
operated from outside. Near the mixer is a small hole,
through which coaldust can be poured by the aid of a
funnel.

Fourteen windows, 10J in. by 5^ in. and fitted with
1 in. plate glass, are arranged at intervals of 3 to 10 feet
along one side of the gallery for inspection purposes.
On the opposite side the gallery is backed up by a wall
of earth reaching nearly to the top to assist in taking
up the shock of explosions. No special foundation is
provided for the gallery, which rests on a layer of cinders
in a shallow trench.

Ventilation is effected by a small Pelzer suction fan
driven by belting from a 2J-horse power polyphase
motor, and housed in a shed behind the mass of brick-
work at the end of the gallery. A 12 in. pipe passes
from the fan through the brickwork into the roof of
the gallery, where it can be closed by a conical metal
cover, which is tightly seated against the pipe and can
be operated by a handwheel in the fan shed.

OF SHELVES

^ OFTONAT/OR CHAMFER

HEATING
APPARATUS

EARTHWORK

Fig. 6.—Section and Plan of Explosives
Magazine.

The observation shed, 15 yards from the gallery, has
a long loophole window glazed with thick glass. In this
shed is situated the 100-light gas meter for measuring
the pit gas admitted to the explosion chamber; also the
electric shot-firing machines and two balances for
weighing out explosives.

The small gallery for testing electric motors and
apparatus, and performing sundry tests with firedamp,
is 13 ft. long, 6 ft. high, and 4j ft. wide at the bottom,
which is flat. The foundation is of strong timber and
the walls are constructed of a triple layer of pitch pine
boards held together by channel iron rings. In other
details it resembles the explosives gallery ; and the pit
gas is admitted from the 100-light meter, in the engine
house, which also supplies the large gallery.

Safety lamps are tested in a Schondorf apparatus
(fig. 5) situated in a special room in the main building.
This apparatus is 14 ft. long, and of rectangular cross-
section (10 by 44 inches), the top and bottom walls being
of channel-iron, and the sides of |in. sheet iron, the
joints being riveted and caulked. The gas mixture is
drawn through the apparatus by a Korting injector a,
operated by compressed air, and capable of drawing up
to 950 cubic feet of air per minute when the working
pressure of the compressed air is 44 atmospheres. The
injector is outside the building, and is connected with