May 23, 1913

THE COLLIERY GUARDIAN.

1061

steam engine of the ordinary type, as being unlikely to
get out of order, and providing a multiple stage com-
pressor in combination with each cylinder, the two
compressors being of equal capacity, so that either can
act as a spare. This arrangement can also be adopted
with electric drive. A large number of mine managers,
however, are satisfied, as the result of fairly long
experience, to do without spare compressors for high-
pressure work. As regards the question of horizontal

needed, than down in the pit; and finally, the high-
pressure mains take up very little room in the shaft.

With regard to the high-pressure main, opinions vary
considerably as to the most suitable dimensions. In
America, mains of large diameter (up to 7 in.) are
preferred, without any storage receptacles; but the
pressures employed are relatively low, being only
75 atmospheres at the compressor and 56 atmospheres
in charging the locomotives. Others favour mains up

auxiliary storage receptacles, in the form of weldless
steel cylinders tested to a pressure of 250 atmospheres.
These take up little room, and can be disposed end for
end, side by side, or superimposed, according to the
local conditions. The advantages of this system are
really self-evident. In the first place the pipes are more
easily prevented from leaking, when it is remembered
that the superficial area of a joint in a 3-j in. pipe is
four times as large as that of a 1J in. pipe, and when

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Fig. 1.—The Meyer Compressed-air Pit Locomotive,
1910 Pattern.



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Fig. 2.—Five-stage Compressor Operated by Live Steam,
Compressing to 150 to 175 Atmospheres.

Capacity 200-Horse Power.

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Fig. 3,—Five-stage Compressor, with Belt Drive from Electromotor.

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Fig. 4.—Compressor Plant for High Pressures.

Two compressors, direct-coupled to 200-horse power reciprocating engines operated by exhaust steam.
Initial pressure at intake 4-6 atmospheres, final pressure 150-175 atmospheres.





versus vertical compressors, the former are preferable
as being more readily accessible and less liable to get
out of order, vertical compressors being used only
where the available space is small. It is also more
advisable to have the compressing plant above ground,
as in that situation the plant can receive better attention,
and the interchange of parts is easier, when repairs are



to 3j in. in the case of pressures up to 124 atmospheres,
without any storage vessels; though in such event the
mains must be considerably longer than the position of
the charging station requires, in order to attain the
necessary volume of air. The author’s preference,
based on extensive experience, is for mains of the
smallest practicable diameter, in combination with

the number of such joints is taken into consideration.
Again, these small pipes are more easily shifted, more
flexible and lighter—a 2 in. pipe, for instance, being more
than twice as heavy as one of lj- in. Furthermore,
instances are known where as many as 10 locomotives
are supplied through a single 11 in. main, assisted by
auxiliary cylinders.

The ideal system of distribution is to charge the
locomotives in the vicinity of the pit eye, so that the
high-pressure mains are confined to the shaft and do
not traverse the roads at all. This is feasible where the
haulage road is not more than 3,300 yards in length
(3J miles for the double trip), the locomotive being able
to make this run, and do the necessary shunting, with
a single charge; and in such cases there is no need to
carry the high-pressure main along the road. For
charging locomotives which only work on branch roads,
and do not therefore run to the pit eye, a 11 in. main in
the road will be sufficient. Before leaving the makers,
the separate lengths of pipe are put through an hydraulic
test; but since it is more satisfactory to the user to test
the main when assembled for use, it is advisable to
specify, in ordering the five-stage compressor, that the
latter shall be capable of furnishing compressed up to
225 atmospheres for a short period, so that the main can
be tested to that pressure at the start.

In charging the locomotives, it has been found that
reinforced flexible pipe is suitable for comparatively
low pressures only, the wear being very heavy under
high pressures; but, on the other hand, narrow pipes of
mild coppei- (fig. 5) behave excellently.

Reverting to the locomotive, the simple two-cylinder
pattern has now been practically abandoned, it
having been recognised that the compound type has a
smaller consumption of air by 35-40 per cent. So far as
the exterilal structure is concerned, the forged iron
frame has superseded the cast iron type, being less
liable to fracture. In Germany the air tanks are
arranged on two systems, with three and four tanks
respectively. In the latter type (figs. 6 and 7) the
tanks are mounted in such a way that the space between
the upper and lower pair widens out toward the front
of the locomotive, in order to allow the driver a wider
view of the road and enable him to see the track for
about 70 yards ahead without incurring danger through
leaning out sideways. In roads with a narrow roof
space the three-tank pattern locomotive (fig. 8) has to
be used, and in this case the driver can see along the
sides of the tanks. To do this, however, he is obliged to
lean so far to the side as to run the risk of injury from
projecting portions of the road walls.

As far as possible, all pipe connections between the
tanks should be avoided, the most suitable connection
being afforded by a wrought iron plate, 2| to 3 inches
thick, bored out to fit the necks of the tanks and
connect same together without pipes (fig. 9).

The “motion” or driving mechanism of the loco-
motive should on no account be situated inside the
frame, but on the outside, so as to be completely
accessible (fig. 10). Link-motion gear) should be