_Gas Lamps, and Burners._
The lamps or burners for the combustion of coal gas, may be infinitely
and tastefully varied. The varieties commonly employed, are the Argand
burner, the Cockspur burner, and the Bat’s Wing burner.
The _Argand burner_, fig. 10, and 11, plate V., consists of two
concentric brass tubes, about one and a half inch long, and
seven-eighths of an inch in diameter, (the largest size burner
employed.) The interval between the two tubes is closed at top and
bottom. The upper part is closed with a ring of steel, it is perforated
with fifteen or eighteen holes ¹⁄₃₀ of an inch in diameter. The gas
enters into the cavity between the two tubes, and issues from the
circular row of apertures in the steel ring at the top of the burner
where it is burnt. A double supply of air within and without the flame
is effected by means of the glass which surrounds the flame. The
combustion of the gas is perfect when the admission of air is in due
proportion to the magnitude of the flame. The height of the gas flame
should never exceed three times the diameter of the flame. When the
flame is too large, the light is less brilliant, and it then produces an
odour, because the combustion is imperfect.
The best shape of the glass for surrounding the gas flame of the Argand
lamp, is a straight tube, shown fig. 8, plate V., or a tube enlarged at
the base, shown fig. 9, plate V. Fig. 10, plate V., is called a crutched
argand gas burner, it is used for pillar lamps; fig. 11, is called a
branch argand burner.
It is essential that the apertures for the emission of the gas of the
argand gas lamp, be perfectly round and of an uniform size, without this
condition the flame of the lamp is ragged, and not well defined.
Fig. 15, plate III., exhibits a swing bracket, furnished with a
_cockspur burner_. The burner consists of a hollow flattened globe,
about half an inch in diameter, pierced laterally with three or more
holes, of about ¹⁄₃₀ of an inch in diameter; out of these holes the gas
flame issues in streams as shown in the sketch. With this burner the
combustion of the gas is imperfect, and it is a wasteful mode of burning
coal gas. The surrounding holes of the cockspur burner, was it not for
the upward current of air, would give flames radiating in straight lines
from the centre of the burner, but the ascending current of heated air,
causes them to curve upwards like the spur of a game cock, and hence the
name cockspur burner.
If the gas be made to burn from a series of holes made in the lateral
circumference of a hollow flat cylinder, it will produce a circular
horizontal series of flames curving upwards.
Fig. 12. plate V., is called a _bat’s wing_ burner; it consists of a
small pear-shaped steel burner, about ¹⁄₁₆ of an inch in diameter,
having a perpendicular slit at its upper extremity, about ¹⁄₄₀ of an
inch in diameter. This burner exhibits a tulip-shaped flame, as shown
fig. 13, plate V., it is well adapted for street gas lamps.
The stop-cock for admitting gas into gas burners should always be placed
at least six inches from the burner. The stop-cock in the brackets, fig.
8, or 9, plate V., is placed at _a_. _Pendant gas lamps_, into which the
gas is conveyed from a pipe above, through the ceiling, should be
provided with a mercurial joint, or ball and socket joint. The former
contrivance is preferable, because it can never leak;[51] but the latter
requires occasional repairs. Fig. 14, plate III., shews the mercurial
joint. _a_, is the pipe which brings the gas; it terminates in a sheet
iron cup open at bottom, but closed air tight at the top; this cup is
inverted into a small iron bason, containing mercury. D the iron tube
which communicates with the gas lamp or burner, and the upper extremity
of which projects above the surface of the mercury in the iron bason,
whilst the other extremity proceeds to the burners or lamps.
[51] This contrivance has been adopted throughout the fitting up of
the gas lights at the Royal Mint.
_Swing bracket burners_, fig. 13, plate III., should have the axis of
motion at the joints A, A, A, perforated at right angles to each other,
so as to admit the moveable joints at A, to be left open, without
obstructing the passage of the gas when the bracket assumes different
angular positions. All swing brackets ought to have a double, and not a
single joint, because the latter soon wears oval in the two opposite
edges; this is prevented by the double joint having an uniform bearing
at top and bottom, it therefore can never leak.
Fig. 11, plate VI., exhibits the arrangement usually adopted for a
_pendant perpendicular sliding lamp, or chandelier_, which requires to
be raised or depressed. This contrivance is convenient for lighting
theatres, or public buildings, by means of a large central gas light
chandelier, that may be raised or depressed at pleasure.
The gas enters into the tube _D_, which is firmly fixed in the ceiling,
as shown in the sketch; it passes through a hole near E, into a smaller
tube _j_, which slides perpendicularly within the tube D. This sliding
tube is made air tight by means of two stuffing boxes filled with oil,
placed near B, and C. The sliding tube _j_, together with the chandelier
suspended to it, is counter-balanced by a weight concealed in a box W,
connected with pullies in the usual manner, as shown in the sketch, so
that the chandelier may be raised or lowered at pleasure.
_Directions to Workmen, for adapting Gas Pipes to the interior of
houses._
The adapting gas pipes to the interior of houses, for the supply of gas,
simple and easy as it may appear, has been the means of not a little
contributing to bring the gas light illumination, on many occasions,
into disrepute. It has required years to enable workmen of the best
intention to acquire sufficient practical skill in the proper execution
of a business, which must be pronounced to constitute an art entirely
new, and in which no progress could be made, but after having committed
many errors. A house neatly and judiciously fitted up with gas pipes,
displays to a person experienced in this art, a skill and judgment,
equal to what is established in any other branch of mechanical
employment. It must be obvious, that the art of arranging the pipes and
adapting them, is one of that class of operations in which it is a real
saving to employ the best materials and skilful workmen, to avoid
repairs and subsequent alterations and derangements of the work. The
supply and distribution of the pipes, or the _fitting up_, as it is
called by the workmen, may be done almost at any price with regard to
workmanship and materials, and to bargain for cheapness in the execution
of it, with a faithful, honest, and skilful workman, must naturally be a
losing concern to the person for whom the work is done. The cost of
furnishing and adapting the pipes to one place, cannot serve as a
standard for any other place, every separate place may present
difficulties which could not be foreseen at the commencement of the
work.
The stopping up and corrosion of the gas pipes, which at the
commencement of the introduction of the new lights was complained of in
many places, it is now sufficiently established, originated entirely
from the impurity of the gas, together with a faulty arrangement of the
pipes, in consequence of which, the water of condensation accumulating
in certain parts, exercised a strong chemical action on the copper
pipes, and if the gas was not very pure, ultimately corroded the pipe.
These objections do no longer exist, and it may safely be pronounced,
that pure coal gas produces no action whatever on the copper tubes
through which it is conveyed. In proof of this statement, we need only
refer to the several districts of the metropolis, fitted up with gas
pipes at the first introduction of the new lights, (1809,) all of which
are still in perfect preservation.
It is perhaps unnecessary to add, that no pipe capable of being melted
by a gas flame, should ever be employed for conveying or distributing
gas through the interior of houses, because the facility with which such
pipes might be perforated, could lead to serious consequences, if the
gas issuing from the aperture of the pipe were lighted, the flame in
that case would follow the melted part, through the whole extent of the
pipe, and the hazard by fire would be considerably increased.
Therefore, pewter, lead, and tin pipes, are very improper for
distributing gas through the interior of houses, and should never be
used for that purpose. Hence copper, and iron pipes, are universally
employed.
In order that the pipes for conveying the gas from the mains, and
distributing it through the houses or other buildings to be lighted with
gas, may in the first place not be unnecessarily large, or too small,
the following rule may serve as a guide to workmen:
One gas lamp,--consuming four cubic feet of gas in an hour, if situated
twenty feet distance from the main which supplies the gas, requires a
tube not less than a quarter of an inch in the bore.
Two lamps,--30 feet distance from the main, require a tube ³⁄₈ of an
inch in the bore.
Three lamps,--30 feet distance from the main, require a tube ³⁄₈ of an
inch in the bore.
Four lamps,--40 feet distance from the main, require a tube ¹⁄₂ inch in
the bore.
Six lamps,--50 feet distance from the main, require a tube ⁵⁄₈ of an
inch in the bore.
Ten lamps,--100 feet distance from the main, require a tube ³⁄₄ of an
inch in the bore.
Fifteen lamps,--130 feet distance from the main, require a tube 1 inch
in the bore.
Twenty lamps,--150 feet distance from the main, require a tube 1¹⁄₄ inch
in the bore.
Twenty-five lamps,--180 feet distance from the main, require a tube 1⁵⁄₈
of an inch in the bore.
Thirty lamps,--200 feet distance from the main, require a tube 1¹⁄₂ inch
in the bore.
Thirty-five lamps,--250 feet distance from the main, require a tube 1⁵⁄₈
of an inch in the bore.
All copper pipes employed to convey gas through the interior of houses
should be of the following weight, with regard to a given length of the
pipe:
_Bore of the pipe._ _Weight per foot._
PARTS OF AN INCH. OUNCES.
²⁄₈ 3
³⁄₈ 5
¹⁄₂ 6
⁵⁄₈ 8
³⁄₄ 10
No coppered pipes should be used but such as have wrapt over and brazed
joints. They should be well annealed, to render them pliable without
being liable to break.
All the bends for connecting pipes must be circular, see fig. 22, plate
V.
No branch pipe ought to proceed from a pipe of a quarter of an inch in
the bore, and no more than two branch pipes should proceed from a pipe
three-eighths of an inch in the bore.
All branch pipes before they are fixed for conveying gas, must be proved
by condensing air into them by means of a condensing hand pump. The pipe
should be placed in a trough of water, the leak will then be easily
observed by the air bubbles which rise through the water whilst the air
is condensed in the pipes.
All branch pipes should have a rectilinear course; pipes that are
twisted have an unsightly appearance.
All pipes should have a descent of no less than a quarter of an inch in
four feet.
The seams or brazed part of the pipes must always be out most and not
towards the wall; because if a leak should happen to take place in the
brazed part of the pipe, it may then be easily discovered and more
readily repaired.
When all the pipes have been furnished to a house or place intended to
be lighted, the whole system of the pipes should be examined with the
utmost rigour, to ascertain whether all the junctures are air tight.
This should be done by condensing air into the pipes by means of a
condensing syringe, and if the piston of the syringe lowers after
condensation, it is a sure indication that the pipes are faulty, and
consequently totally unfit for receiving the gas. The leak may be
detected by passing a lighted taper carefully along the whole extent of
the pipe filled with condensed air, when the flame of the taper will be
affected as it passes over the faulty place of the pipe.
The aperture from which the gas can escape may however, be so small, as
to render it a matter of difficulty to discover it in the manner just
stated; but when the pipes are filled with coal gas, the escape of it,
when all the stop-cocks of the lamps and burners are shut, will soon
become obvious, by the peculiar odour of the gas, if the apartment, or
place, where the pipes are placed, is suffered to be closed for about
twenty-four hours. The gas should not be introduced into pipes in which
any defect of this kind is found, until it be completely removed. The
most severe trial to ascertain the air tightness of any system of pipes
is, the trial by exhaustion, by means of an air pump, for the guage of
the pump will discover the minutest leak, which the preceding method of
proving pipes can not discover.
All pipes after being proved should be painted of the same colour as the
surface to which they are affixed.
The whole system of pipes should incline to one or more places, so that
any moisture that may happen to accumulate in the pipes, may collect at
such places, whence it may be readily removed by opening a screw plug
adapted for that purpose.
All the different junctures of mains and branch pipes, should be
effected by means of connecting pieces, so that any part of the system
of the pipes, or any separate branch pipe may readily be detached, and
put up again if occasion should require it; fig. 19, plate V., exhibits
this mode of connecting gas pipes by means of union joints. A, B, C, D,
E, shows a gas pipe with its union or connecting joint, divided into its
separate parts. _D_, is a collar of leather, which passes over the part
C, of the union joint, close up to the shoulder of the joint; the
opposite extremity of the pipe may be inserted into the socket _B_, so
that the shoulder C, comes in contact with the fillet or rim in B, to
prevent it passing over the shoulder C, when B and E are screwed
together. The latter part of the pipe is furnished with a male screw to
correspond with the thread in the collar B. The shoulder piece C, is of
rather a larger diameter than the bore of the tube A, with which it is
to be connected. The short piece E, furnished with a male screw, is of
the same diameter as the part C. The pieces C, and E, of the pipe are
soft soldered, one to the tube A, and the other to the tube E, but
previous to soldering on C, it is necessary that the socket should be
inserted into the tube A, it will then be ready for connecting, as will
become obvious by inspecting fig. 20, which shows the various parts of
the union joint fitted for use. It is evident that if the extremity D,
in the pipe B, be brought close to the pipe E, and if the socket C, be
moved along the pipe A, and screwed upon the male screw at D, as far as
it will go, the face of the part D, must press close against the leather
collar which is placed on E, and render the joint gas tight. These kind
of joints are very convenient for circular bends, fig. 22, and T,
pieces, fig. 21. The T pieces, fig. 21, are very useful for collateral
branch pipes, either for the same or of a less diameter as the pipe,
from which they proceed, so as to branch off at right angles.
Fig. 22, is a quarter circular bend; it is convenient for adapting tubes
along the angular parts of rooms, and to all such situations where the
tube is to have a sudden circular course. Small copper tubes may be
readily bent to the required angle without breaking, but if a tube
should terminate in any angular part of a room, in that case a circular
bend furnished with a male and female screw, is convenient for
connecting the pipes together.
All pipes adapted to the exterior of buildings, should be kept a little
distance off from the wall, to prevent the wet lodging between the pipe
and the surface to which they adapted.
Sheet iron mains for the interior of houses, are preferable to copper
mains, provided the course of the main with regard to the position of
the branch pipes, does not require too many angular directions, or
circular bends.