2·72 _p_
-------- in feet.
56
The preceding values of _p_ and _x_, are,
(16) = 3147; (17) = 203; (18) = 2·44 inches; (19) = 2·33 inches.
The water columns in the highest and lowest situations of the gas-holder
here differ about 0·1 of an inch, and this difference becomes still less
when _p_ has a smaller value, for example, 3 pounds, or when the
diameter of the gas-holder is still greater.
It would thus appear that for coal-gas gasometers, in which the height
of the gas-holder does not exceed its semi-diameter, and especially when
it has a considerable size, neither a compensation chain nor a
counterweight is necessary. The only thing requisite, is to preserve the
vertical motion of the gas-holder by a sufficient number of guide rods
or pillars, placed either within the water cistern, or round about it.
Should the pressure of the gas in the pipe proceeding from the
gasometer, be less than in the gasometer itself, this may be regulated
by the main valve, or by water valves of various kinds. Or a small
intermediate regulating gasometer may be introduced between the great
gas-holder, and the main pipe of distribution. With a diameter of 61
feet in the gas-holder, the pressure in the highest and lowest positions
is the same.
The gasometers employed in storing up gas until required for use,
occupy, upon the old plan, much space, and are attended with
considerable expense in erecting. The water tank, whether sunk in the
ground, or raised, must be of equal dimensions with the gasometer, both
in breadth and depth. The improved construction which we are about to
describe, affords a means of reducing the depth of the tank, dispensing
with the bridge of suspension, and of increasing at pleasure the
capacity of the gasometer, upon a given base; thus rendering a small
apparatus capable, if required, of holding a large quantity of gas, the
first cost of which will be considerably less than even a small
gasometer constructed upon the ordinary plan.
[Illustration: 490]
Mr. Tait, of Mile-End Road, the inventor, has, we believe, been for some
years connected with gas establishments, and is therefore fully aware of
the practical defects or advantages of the different constructions of
gasometers now in use. _Fig._ 490. is a section of Mr. Tait’s improved
contrivance; _a a_ is the tank, occupied with water, _b b_ two iron
columns, with pulley-wheels on the top, _c c_, chains attached to a ring
of iron, _d d_, extending round the gasometer, which chains pass over
the pulley-wheels, and are loaded at their extremities, for the purpose
of balancing the weight of the materials of which the gasometer is
composed.
The gasometer is formed by 2 or 3 cylinders, sliding one within the
other, like the tubes of a telescope; _e_, _e_, _e_, is the first or
outer cylinder, closed at the top, and having the ring of iron _d_,
passing round it, by which the whole is suspended; _f f_, is the second
cylinder, sliding freely within the first, and there may be a third and
fourth within these if necessary.
When there is no gas in the apparatus, all the cylinders are slidden
down, and remain one within the other immersed in the tank of water; but
when the gas rises through the water pressing against the top of the
gasometer, its buoyancy causes the cylinder _e_ to ascend. Round the
lower edge of this cylinder a groove is formed by the turning in of the
plate of iron, and as it rises, the edge takes hold of the top rim of
the cylinder _f_, which is overlapped for that purpose. The groove at
the bottom of the cylinder fills itself with water as it ascends, and by
the rim of the second cylinder falling into it, an air-tight hydraulic
joint is produced.
Thus, several cylinders may be adapted to act in a small tank of water,
by sliding one within the other, with lapped edges forming hydraulic
joints, and by supporting the apparatus in the way shown, the centre of
gravity will always be below the points of suspension. A gasometer may
be made upon this plan of any diameter, as there will be no need of
frame work, or a bridge to support it; and the increasing weight of the
apparatus, as the cylinders are raised one after the other, may be
counterpoised by loading the ends of the chains _c c_.
The water in the gasometer need not be renewed; but merely so much of it
as evaporates or leaks out, is to be replaced. Indeed the surface of the
water in the cistern gets covered with a stratum of coal oil, a few
inches deep, which prevents its evaporation, and allows the gas to be
saturated with this volatile substance, so as to increase its
illuminating powers.
[Illustration: 491]
The gasometer may be separated from the purifier by an intermediate
vessel, such as is represented _fig._ 491., with which the two gas pipes
are connected. A is the cylindrical vessel of cast iron, _a_, the end
of the gas pipe which comes from the purifier, immersed a few inches
deep into the liquid with which the vessel is about two-thirds filled;
_b_ is the gas-pipe which leads into the gasometer, _c_ is a
perpendicular tube, placed over the bottom of the vessel, and reaching
to within one-third of the top, through which the liquid is introduced
into the vessel, and through which it escapes when it overflows the
level _d_. In this tube the liquid stands towards the inner level
higher, in proportion to the pressure of the gas in the gasometer. The
fluid which is condensed in the gas pipe, _b_, and in its prolongation
from the gasometer, runs off into the vessel A; and therefore the latter
must be laid so low that the said tube may have the requisite declivity.
A straight stop-cock may also be attached to the side over the bottom,
to draw off any sediment.