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Hay-Stack
boiler
This
boiler is termed the hay-stack boiler from its shape. In some districts
it is called the balloon
boiler, and the kettle boiler. It is a good kind of boiler
up to 10 or 12-horse power, and 10 or 12 Ibs. pressure, where boilers
are required to stand singly. It is strong enough within those limits,
and has the greatest capacity for the least quantity of material employed.
Independent of its economy, which, with inferior fuel, need not be less
than that of any other kind, it has, perhaps, the greatest evaporating
power for its dimensions, and if set up, as it usually is, with a single
wheel draft, it requires only a small chimney.
...
The
Waggon Boiler.
This
boiler is, in principle, the hay-stack boiler just described, only put
into an oblong instead of a
circular form on the ground plan. It therefore permits of facilities
in arranging a number of boilers
side by side without wasting space. It is distinguished in mining districts
as the oblong boiler. In
other places it is sometimes called the caravan boiler, and
by Mr. Wicksteed, the waggon-head boiler. It possesses some advantage
over the hay-stack boiler in its being better adapted for the use of
rich bituminous or flaming fuel, and Newcastle coal generally. It admits
of being made of such a length, that the flame from a well-managed fire
will be generally expended before reaching the end; and it can be easily
varied in its proportions to suit the many varieties of flaming fuel
wood as well as coal. As flaming coal is also smoky coal, the waggon
boiler from its rectangular plan, is suitable for the application of
such coal, because it admits of the ordinary rectangular fire-grate,
with convenient space beyond for any arrangement of the furnace chamber
and bridges, so as to meet almost any requirement for smoke-consuming
purposes.
The
waggon boiler is, except in the direction of its length, nearly as strong
as the hay-stack boiler,
up to 5 feet diameter, and if provided with one, two, or three longitudinal
stays, and 4 such stays of 1 1/2 inch square from end to end if above
that diameter, together with cross stays at every two feet in the length,
it may be safely worked up to 10 Ib. on the square inch. For this pressure
it is usually made of plates to average 3/8 inch thick all round, the
top being never less than 1/4, and the ends ought to be seven-sixteenths
of an inch. Up to 20 or 25 horse-power, boilers which are as many feet
in length by 5 to 5 1/2 feet wide, or equivalent proportions, made in
this way, will weigh 17 or 18 Ib. per square foot of total surface,
inclusive of rivets, overlap of plates, stays, &c. 17 or 18 square
feet of such surface, may be reckoned as equivalent to a horse-power;
from these
data, the weight and cost (at present 25 to 30 shillings per cwt.) is
soon obtained.
Within
the above limits, no boiler ever made can exceed this one in efficiency,
economy, and durability, if well-proportioned to the engine it works,
and to the fuel supplied to it. If required of greater power than 20
or 25 horse, boilers of this kind are made deeper in proportion to their
length, and an internal flue tube is introduced, and such boilers are
then called the Boulton & Watt Boiler. |
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