_Gas Metre, or Self-acting Guage, which measures and registers, in the
absence of the observer, the quantity of Gas produced in a given time,
from any given quantity of coal, or consumed during a given period, by
any number of burners or lamps._
For the invention of this machine we are indebted to the ingenuity and
talents of Mr. Clegg, and undoubtedly, of all the improvements with
which the new art of procuring light has been recently enriched, there
is none which has been attended with results more beneficial to the
interest both of the manufacturer and consumer of coal gas.
In this machine we see combined a standard or check on the conduct of
the workmen, which enables the manufacturer of coal gas to assure
himself of obtaining at all times the greatest possible produce from his
establishment; a measure by which he can deal the gas out to his
customers in whatever quantities they may require it, and an index which
registers the exact quantities furnished, and thus serves as an
infallible account of debtor and creditor between the seller and
purchaser of gas.
This machine, therefore, performs at once all the duties of an overseer,
meter, and book-keeper, and performs them all so much more effectually,
that its operation is not dependant on matters so uncertain as the care
or integrity of servants, but on unerring principles which are fixed and
incapable of any hidden misapplication.
The view in which this machine naturally demands our particular
attention is that in which as a standard of the work which ought to be
performed, it enables the manufacturer to make sure of obtaining the
greatest possible produce from his establishment.
The gas metre serves this purpose in the first place by enabling the
proprietors of gas works to know what is the utmost possible quantity of
gas which can economically be obtained from any given portion of coal,
with a given portion of fuel, in any given time.
It is necessary, in every gas light establishment, in order to know
whether as much gas is obtained as might and ought to be produced, that
it be previously ascertained by a series of experiments how much gas the
species of coal used at the works is capable, on an average, of
producing, and such data it is obvious, can only be obtained by means of
an apparatus, which, like this gas metre, shall take measure of the
quantities of gas supplied by the manufactory at all times, and under
all circumstances.
It may, perhaps, be imagined, that assays sufficient for that purpose
might be made by means of a few retorts, or small experimental
apparatus, or by noting down the quantity of gas produced at the works
during the time the valves which convey the gas into the street mains
are shut, and during which time the capacity of the gas holders may
afford a rule for ascertaining the quantity produced. But nothing can be
further from the truth; assays of this description to be practically
useful and to serve as a basis for the operations of a large
establishment, must be made on a scale of magnitude and be continued for
a considerable period of time as well as under every variety of
circumstances.
The quantity of gas obtained from any given quantity of coal, varies so
much with the degree of heat applied, and the circumstances under which
the decomposition of the coal is effected, that the solitary product of
any one period of time can afford no positive criterion for the product
of any other period. A correct general conclusion, in short, can only be
drawn from the result of experiments carried on uninterruptedly through
a succession of days and nights, and such a continuity of experiments
could, previous to the invention of the gas metre, only be affected by
means of two separate gas holders, one for measuring the gas as it is
produced, and the other for receiving the gas after it is thus measured,
in order to its being transferred into the mains. By the aid of a single
gas holder, an admeasurement could obviously be effected only during the
time the valves which transmit the gas into the street mains are shut,
and this, when the days are short, as in the winter season, the most
productive period of the whole year, is only about eight hours out of
the twenty-four, leaving nearly two-thirds of each day, during which, no
account could be taken of the quantity of gas produced at the works.
It deserves further to be observed, that when two gas holders are
employed, the utmost that can be effected by them, is the admeasurement
of the gas produced, while the distinguishing feature of the metre is,
that it not only measures, but by its own action registers the quantity
of gas produced, or expended, in any given time.
Nor does the whole merit of this machine, in an economical point of
view, consist in its thus furnishing the manufacturer with an infallible
criterion of the quantity of gas which ought at all times to be
produced; for, in the second place, it enables him by the several
experiments which have supplied that criterion, to ascertain at what
least possible expenditure of fuel, and in what space of time the
greatest possible quantity of gas can be produced.
The advantage of the gas metre, in these additional respects, will be
sufficiently demonstrated by attending for a moment to the situation of
the manufacturer of coal gas, when without any such protecting register.
Suppose, for example, that the manufacturer desires to know whether his
workmen have made during a given time, (say during the night), the
quantity of gas which they ought to have produced from a given quantity
of coal, or whether they have consumed no greater proportion of fuel for
its production than was absolutely necessary. He may, upon examination,
find all the retorts in an excellent working state, but whether they
have been so during the whole of the night, or whether the requisite
quantity of gas has been really produced during the time that the valves
which convey the gas into the mains have been open, is to him a matter
of uncertainty. The workman may, as has been too often the case, have
neglected the fire during the night, and on every such occasion, in
order to bring back again the retorts to a proper working state, as well
as to redeem the time lost, he may have urged the heat to a degree of
intensity much exceeding the temperature best suited for the most
economical production of the gas. And however injurious such irregular
modes of operating may be for the master’s interest they are altogether
shrouded from his observation. It deserves also to be noticed that the
loss occasioned by this irregularity of operating is not merely a loss
of fuel, for in consequence of it the retorts, (particularly if
cast-iron retorts of the usual forms,) are liable to more injury in one
day than they would be during a whole week, if properly attended.
When the proprietor of the establishment, on the contrary, has recourse
to the gas metre, not one of all these evils can occur without being
liable to certain and instant detection. From the data which preceding
experiments on the productiveness of the species of coal used at the
establishment have furnished, the overseer of the works is always
enabled to determine, from the portion of coal he finds used, how much
gas ought to have been manufactured during any space of time that has
elapsed, and also the portion of carbonizing fuel which was necessary
for the production of that quantity of gas; and comparing these data
with the quantity of gas which the index of the gas metre announces has
been produced, he is enabled to determine by mere inspection, in an
unerring manner, whether the workman has acted with that sedulous
attention to his duty which the economy of the establishment demands.
The many important advantages in short which the manufacturer of coal
gas derives from this machine, considered _as a standard or check on the
conduct of the workmen_, may be summed up in this--that while, without
the aid of the gas metre, no establishment can be possibly more exposed
to suffer from the ignorance of managers or the want of fidelity in
servants, than a gas manufactory, there is none which is more
independent of either than a gas manufactory, possessed of this
important apparatus. Nor can the amount of that possible loss be
regarded as otherwise than extremely serious, when attention is paid to
the difference in profit and loss between conducting the process of
manufacturing coal gas on a system founded on the deductions of
experience, and an assiduous attention to keeping up a regularly
sustained temperature; and conducting the process on a system of random
calculation and irregular working,--a difference, which as appears from
the details already laid before the reader, amounts in respect to the
quantity of gas produced, to from fifty to one hundred per cent.; in
respect to the waste of machinery, to upwards of eighty per cent.; and
in respect to the consumption of fuel and time to a sum in the ratio of
the loss experienced under both these other heads.
The Second General Point of View in which the gas metre claims our
attention, is, its excellence as a standard of fair dealing between the
seller and consumer of gas, by enabling the former to supply the gas in
whatever quantities it may be required, and serving, at the same time,
as a self-acting register of the quantities furnished. It is for this
purpose merely necessary to connect the gas metre with the pipe of
supply, which conveys the gas to any burner, or number of burners, or
lamps, and the index of the instrument will regularly announce the
precise quantity of gas which has passed through the machine during any
period of time, from one day to a number of years, without requiring any
particular sort of care whatever. Every person must have noticed how
shamefully many individuals disregard the terms on which they have
contracted for a supply of gas, some by means of the excessive flame
they keep up, and others suffering the lights to burn hours beyond the
time stipulated and contracted with the gas light company which supplies
them. The latter have officers, it is true, whose duty it is to check
such abuses as far as is in their power, but having no right of access
to the premises of individuals, their vigilance can only extend to shops
and places open to public view and of general access; and to these, of
course, but occasionally. In short in every place where gas is supplied
on contracts to pay for burning it a limited time, by means of certain
sized burners or lamps, instead of according to the quantity actually
furnished, the seller must always be in a greater or less degree, and in
some cases wholly dependent on the care and honesty of the purchaser for
the protection of his commodity from waste and depredation. But when on
the contrary the seller possesses, as he now does, by means of the gas
metre, an infallible check of the exact quantity of gas consumed in a
certain time, and the purchaser is bound to pay for as much as he uses,
the former is relieved from every apprehension or chance of being
defrauded, and the latter is furnished with the same motives for
economizing gas as he would have for economizing oil and candles.
The manufacturer is certain of obtaining what he has a just right to,
value for the whole quantity of gas supplied, and the consumer is
assured that if he wastes the gas unnecessarily, he must as he ought,
pay the price of his own carelessness or profusion. Equal justice is
done both to the consumer and seller, and the public at large are at the
same time most materially benefited, in as much as they are saved from
paying for the expence of that waste of gas by a few, which from the
former impossibility of tracing it to the offending parties, was
necessarily added to the whole cost of the gas, and equally partitioned
upon all the individuals who made use of it. The waste being now
transferred to those who occasioning the waste and ought alone in
justice to bear it, the price of the gas to the equitable and honest
consumer, is thus reduced to an equitable and correct measure of value.
The benefits of this invention have a yet wider range; not only does it
secure full value for the whole of the gas manufactured, but it tends to
make the gas a greatly more marketable article. For in the system of
charging for the supply of gas by the year, half year, or quarter, and
at one common rate, many individuals who are only occasionally in want
of gas lights, or whose demand is irregular and uncertain, such as the
proprietors of public rooms, theatres, &c. are debarred of availing
themselves of this kind of illumination, except at an expence quite
disproportioned to what other more regular customers pay, and out of all
proportion of the value of the quantity of gas consumed by them. The gas
light under such circumstances is not as it ought to be, a light for
all. It is not as oil and candle are, a benefit which every one may
obtain who is in need of it, and in such quantities as may best suit his
means and convenience. One of the capital advantages, of the gas metre,
however, is, that it makes gas a substitute for oil and candles,
applicable under all circumstances, and that it enables the manufacturer
without the least prejudice or chance of prejudice to his interest, to
supply gas in whatever quantities it may be demanded, and at a fair
proportioned price.
In speaking thus of the influence which the gas metre must have in
attending the beneficial application of the new lights, we are not
unaware that situations may present itself where the action of the metre
might be impeded from the want of a sufficient pressure of the gas in
the pipe of supply connected with it. But this can never be the case
except where the pressure of the gas in the pipe of supply is so low as
three-eighths of an inch of a column of water, and in all such cases it
is only necessary to give a greater capacity to the wheel of the
machine, than would be necessary under other circumstances, and this
will at once make up for the inferiority of pressure. In point of fact,
therefore, no situation can occur, where the application of the machine
may not be rendered available.[46]
[46] See directions to workmen, for adapting gas metres, p. 229.
Nor do the various advantages which have now been detailed, form all the
good that this important machine is capable of furnishing. The gas metre
furnishes at its axis a power which has been ingeniously applied to put
in motion the shaft of the lime machine, employed for purifying the gas,
see fig. 3, plate VII.[47] The importance of a power thus certain in its
operation, and obtained free of expence, must at once be obvious, when
it is considered that upon whatever plan the purifying apparatus or lime
machine may be constructed, it is absolutely essential, that its
contents be kept constantly in motion, in order to produce the desired
effect upon the crude gas, which would otherwise pass away in an impure
state.
[47] The upper axis communicates with the agitating shaft of the lime
machine, and the lower axis is a continuation of the shaft of the gas
metre. The two pullies are connected by a strap.
When the charge of keeping the agitating shaft of the lime machine in
action, is intrusted to a workman, there is no positive security against
his occasionally neglecting his duty, whereas by applying the gas metre
to that purpose, the manufacturer is assured beyond the possibility of
deception, that when gas is produced, that gas is as certainly purified,
and a saving is effected in point of labour of the expence of two men,
one during the day, and one during the night.
_Description of the Gas Metre at the Royal Mint Gas Works._
Fig. 4, plate II., represents a perpendicular section of the gas metre.
It is placed between the purifying apparatus or lime machine, and the
gas holder fig. 8, plate III., exhibits a front elevation; fig. 1, plate
III., a perspective view, and fig. 6, plate III., a transverse section
of the machine.
It consists of a hollow wheel or cylinder, made of thin iron plate,
revolving upon an horizontal axis, in the manner of a grindstone; this
wheel is enclosed in a cast iron air tight case containing water.
The cylinder or wheel, is composed of two circular channels, 1 and 2,
fig. 4, plate II., concentric to each other. The larger or outer channel
1, is divided into three equal compartments, by partition plates, marked
_a_, as shewn in the design. The compartments are provided with
hydraulic ducts or valves, made at the upper part of every partition
plate _a_, _a_, _a_, and by means of them a communication is formed
between the larger concentric channel 1, and the outer case in which the
wheel revolves.
Similar valves are also placed at the foot of each partition plate, they
are seen near the letters _a_, _a_, _a_, and by this means, a
communication is established, between each compartment or chamber of the
larger concentric channel 1, and the smaller interior circle 2, of the
wheel.
On inspecting the design, it will be seen that the valves are situated
in opposite directions to each other, hence there can be no
communication either between the inner smaller concentric channel 2, and
the larger compartment of the wheel 1, nor between the latter
compartment, and the exterior case, in which the wheel revolves, except,
through the valves _a_, _a_, _a_, which form the communicating ducts. It
will be seen also, that these valves are carried from one chamber of the
machine into another, but in opposite directions; the entry into one
chamber, being in the opposite direction to the hydraulic duct, placed
in the other chamber.
From these particulars the action of the machine will be obvious.
Let us suppose that the outer case (which is marked in the sketch by a
black tint,) in which the wheel revolves, be filled with water, to about
an inch above the axis of the wheel, and that gas is conveyed into the
interior small channel, by a pipe, passing along the axis, so as to
allow the wheel to turn freely round, and that the pipe is turned up at
right angles in the inner chamber, and projects a little way above the
surface of the water, as shewn in the design. The gas then must enter
into the interior chamber of the wheel above the surface of the water,
and must press against the adjacent partition; it will therefore cause
the wheel to turn round, and in consequence of this motion, the next
partition plate will press the gas against the surface of the water, and
cause it to pass through the hydraulic opening, in an equal quantity to
that, which is introduced into the exterior chamber.
This alternate filling, and discharging, of the contents of each
chamber, will take place once during every revolution of the wheel, and
hence the number of times each particular chamber has been filled, and
emptied of gas, may be known.
In fact this machine performs the office of three revolving gas holders,
fixed on an horizontal axis, and moving in a cistern, which is the outer
case of the machine. One gas holder, or one compartment of the machine,
is always in the act of becoming filled with gas, another is emptying
its contents into the outer case, from which it passes into the
reservoir, where it is to be stored up, or to the lamps, where it is to
be burned, and the third compartment is stationary, or in an
equilibrium. The wheel in any situation will therefore always have one
of its receiving, and one of its discharging valves open, and
consequently it will revolve.
Now to ascertain the quantity of gas discharged by one revolution of the
wheel, we need only to know the capacity of the chambers, and add them
together. Let us for example suppose, that each chamber contains 576
cubic inches, then one revolution of the wheel, discharges a cubic foot
of gas. To register the total number of revolutions which the wheel
makes in a certain time, a train of wheel-work is connected with the
axis of the metre, see fig. 8, plate III.; it consists of a pinion
impelling a common train of wheel-work, composed of any number of
wheels. The pinion on the axis of one wheel, acts into the circumference
of the next wheel, and the circumference of the wheel being as ten to
one, it is obvious whilst the metre makes 100,000 revolutions, if the
series consists of six wheels, the last wheel of the series, will only
have made one revolution. Each axis of the wheels is provided with a
finger and dial plate, divided into ten parts, therefore any number of
revolutions may be read off at any time by inspection betwixt 10,000,000
and one.
The velocity with which the metre acts, is of course in proportion to
the quantity of gas passing through it. Thus suppose there is a burner
or gas lamp connected with the machine, of one foot capacity lighted,
which consumes four cubic feet of gas in an hour, the gas metre performs
four revolutions per hour, and so on for every number of burners or
lamps, not exceeding the number which the machine is calculated to
supply.
To render the construction of the gas metre more obvious, we have at
fig. 6, plate III., exhibited a transverse section of the machine; _a_,
is the outer case of the machine in which the wheel revolves. B, B, the
outer or larger concentric chamber, (marked 1, in fig. 4, plate II.) L,
the inner or smaller concentric chamber, (marked 2, in fig. 4, plate
II.) _d_, the index on the axis which passes through a stuffing box in
front of the machine. 5, 5, 5, 5, are stays or braces for supporting the
wheel; they are likewise seen in fig. 4, plate II. A, is the inlet pipe
for the gas to enter into the machine. The gas passes through the pipe
_h_, and from thence into the curved pipe _i_, into the interior chamber
L, of the metre. The pipe _h_, is surrounded by a second pipe K, which
has a small aperture at _x_, the office of which is, to act as a siphon,
in order to preserve the proper level of the water in the machine. The
water is poured into the machine, through the small funnel at the back
of the entrance pipe A. _y_, is a float, which stops the performance of
the metre altogether, if a fraudulent attempt should be made, to stop
the registering of the metre, by drawing off the water with which it is
charged. In fig. 1, plate III., _a_, is the inlet pipe; _b_, the outlet
pipe of the gas; and fig. 2, shows the interior chamber.
The registering wheel work, may be adapted to any part of the machine,
and the motion may be communicated by a mitre wheel, from the shaft of
the machine to the index.
The gas metre at the Royal Mint measures and registers 30,000 cubic feet
of gas every twenty-four hours.[48]
[48] The gas metre at the Bristol gas works registers 60,000 cubic
feet of gas every twenty-four hours. The metre at the Chester gas
works registers 40,000 cubic feet every twenty-four hours.--One of the
metres at the Birmingham gas works registers 40,000 cubic feet, and
the other (now erecting) will register 100,000 cubic feet every
twenty-four hours.
_Rule for calculating the weight, which a Gas Metre of given dimensions,
will raise to a given height, in a given time._
The following calculation will exemplify the power produced by a gas
metre constructed to register 60,000 cubic feet of gas, in a day. The
diameter of such a metre would be six feet, its depth three feet, and
the depth of its rim eighteen inches.
The section of the rim would therefore contain 648 square inches, and
supposing the pressure of the gas passing into the machine to be equal
to a column of water two inches high, its buoyant power would then be
equal to 1296 cubic inches of water, or forty pounds and a half weight.
The mean diameter of the metre is 4 feet 6 inches, which multiplied by
three, gives the perpendicular height that forty pounds and a half
weight, would be raised by each revolution of the metre. The number of
revolutions, in one hour which the metre makes, is 40, they would raise
forty pounds and a half, 540 feet high in one hour.
Such a power is more therefore than sufficient to keep in motion the
shaft of the lime machine.
_Gas Holder Valve,--Siphon, or Water Reservoir._
This name is given to the principal hydraulic valve, by means of which a
communication is established between the gas holder or gas holders, and
the principal pipe, leading to the mains.
Fig. 7, plate III., exhibits a section of this valve. It is composed of
an air tight box, A, A, A, A, containing a portion of tar, or water;
_d_, is the inlet pipe which communicates with the gas holder, B the
outlet pipe; which conveys the gas into the mains. C, C, is an inverted
cup, furnished with a sliding rod, passing through a stuffing box, so
that by means of the rod, the cup may be raised or depressed. For it is
obvious that a communication will be established between the inlet pipe
_d_, and the outlet _B_, when the cup is raised above the surface of the
tar or water in the box A; and that the communication will be cut off
when the cup is depressed into the tar. In the latter position the cup
is shewn in the design. The sliding rod which raises and depresses the
cup, passes through a frame E, E, affixed to the upper part of the box
A, and which serves as a guard for the rod, so that it may be locked by
means of a cutter passing through the sliding rod, and the frame of the
box.
Fig. 3, plate III., exhibits a similar valve, which at the same time may
be used as a _water reservoir_, commonly called a _siphon_, for
collecting the water that may happen to accumulate in the mains, a
provision which it is essential should be made at the lowest place,
where two or more pipes incline towards each other. For it is obvious,
that if a fluid should happen to accumulate in the angular part, where
two descending pipes meet, to a height sufficient to fill the angular
point, the communication between the two pipes would be completely cut
off, so that the gas could not pass. _x_, _x_, _x_, _x_, fig. 3, is the
reservoir; A, the inlet pipe; B, the outlet pipe; _b_, a short cylinder
communicating with the exit pipe B, it is open at bottom and closed at
top. D, _d_, the hydraulic cup which, when raised by means of the
spindle _e_, closes the exit pipe B, by the open end of the cylinder
_b_, becoming immersed in the tar or water contained in the cup D, _d_.
The darts show the course of the gas when the valve is open: _f_ is a
small pipe furnished at top with a screw and covered with a cap; by
attaching a hand pump to this pipe, the superfluous portion of fluid
that may have accumulated in the reservoir, may be removed. _c_, _c_, is
the _equilibrium_ pipe, it connects the exit pipe B with the inlet pipe
A, when the stop-cock with which it is furnished is opened. This pipe
prevents the tar or water from being blown out of the hydraulic valves
that may be interposed between the different descending mains of a
district, as would otherwise happen, in consequence of the sudden
concussion that takes place when the main or gas holder valves are
opened. Because the gas in the mains, and the gas in the gas holders,
are not in equilibrium. But by means of the small pipe _c_, _c_, the
equilibrium is obtained when the stop-cock of the pipe _c_, _c_, is
opened, and this should always be done before the main or gas holder
valves are opened. For by neglecting this condition, the water or tar is
liable to be blown out of all the hydraulic valves, that may happen to
be interposed in the system of the pipes for conveying the gas, and
communications are thus opened, which were intended to be shut.