the top with a flanged seating that exactly fits the parabolic plug.
The outlet pipe is concentric to the inlet pipe, and rises some dis-
tance above the level of the water in the tank. The gas-holder is
balanced by means of an air chamber placed inside the vessel
round its lower curb, so that when the water in the tank is at its
proper level the holder rises, carrying with it the suspended para-
Fig. 21. Station Meter Governor.
bolic plug ; and, supposing all the weights on the top of the holder
to be removed, the holder would ascend to its full limit, carrying
with it the suspended plug, which would ultimately fill the orifice
of the inlet pipe and consequently shut off the gas supply,
reducing the pressure in the shut mains to nil. Since a certain
pressure is always required, however, iron or leaden weights are
placed on the crown of the holder, equivalent to the pressure
needed to supply the district, so that the holder only ascends a
certain distance, while the suspended plug fills the orifice in the
inlet pipe to such an extent as will allow sufficient gas to pass and
give the outlet pressure required, which is rigidly maintained, no
matter what variations may take place in the amount of gas con-
sumed in the district ; for in the event, say, of a sudden demand
on the street mains owing to a fog, or to other causes that would
involve an increased consumption of gas, the pressure in the
COAL GAS FROM RE TOUT TO GAS-HOLDElt. 45
mains would be reduced, and as the governor holder commu-
nicates by means of the outlet pipe with the shut mains, this
reduced pressure would cause the holder to descend ; in doing so,
the parabolic plug would also descend, and thereby increase the
valve opening and allow more gas to pass through, although not in
any way affecting the initial pressure, but only maintaining it at a
constant quantity. Similarly, should the consumption in the
district slacken, the gas-holder would rise and lift up the sus-
pended plug higher into its seating, thus reducing the gas way and
equalising the pressure. Of course, the governor is not intended
to control the initial pressure which is required for supplying the
district ; this is regulated by adding or taking off weights from
the crown of the gas-holder.
GAS SUPPLY FROM GAS-HOLDER TO DOMESTIC METER.
GAS-FITTING is not an exact science in which, for the guidance of
beginners, a complete code of undeviating rules and regula-
tions can be laid down. A gas-fitter requires to be something
more than a mere mechanic. He must be not only able and
willing to employ his hands in various forms of skilled labour,
but must also make use of his wits and exercise his ingenuity.
In these days of competition, bruimvork counts for more than
skilled labour ; and the gas-fitter who can point out correctly
and convincingly the most effective and, at the same time, the
most hygienic methods of lighting a building is much more
likely to succeed in business than the man whose ability is
Gas, even though an old and well-tried servant of the
public, has, for some reason or other not quite clear, been
unfairly disparaged, every conceivable argument against it being
eagerly and incessantly advanced. This state of affairs is mainly
owing, not to the shortcomings of the gas as an illuminant, but
rather to the ignorance of its advocates. The intelligent workman
must be able to prove by argument and to demonstrate in practice
that the case against gas particularly w r ith respect to the allega-
tions as to its unhealthiness has been grossly exaggerated.
A good gas-fitter should not only be thoroughly acquainted
with the minutest details of his own trade, but it is necessary
that he should also possess a sufficient general knowledge of
certain other trades, so that he may be enabled to meet the
requirements or to direct the operations of those workmen
with whom his business brings him in most frequent and most
Houses differ so much in shape and size that, with respect to
fitting them with gas, only general principles can be advanced.
In all cases the number of lights to be fed and the distance from
the supply govern the size of the pipes used. The pipes are of
GAS SUPPLY FROM &A$-HOLDEM TO METER. 47
three kinds wrought-iron barrel, lead, and compo. One of the
advantages of iron is that nails cannot be knocked into it when
it is buried in a wall ; but it is much more difficult, and takes
considerably longer, to fit up a house with iron pipe than with
compo., owing to the fact that with the former material bends
have to be fitted, and the pipes must be cut to the exact length
and threads screwed on. Lead pipe is generally used only for the
connections to the meters.
In laying mains, great care should be taken that all the joints
are sound and well made, in accordance with the instructions
given in this chapter, and that the pipes are of good quality.
The mains should be tested under high pressure, and when
tapped with a hammer should ring ; they should be quite free
from sand-holes, air-holes, scabs, and blisters, and should be of
cast iron, which can be easily tapped and drilled. Where it
happens unavoidably that the pipes are laid in ground containing
ashes or any chemical refuse, they must be properly protected
either with clay or asphalt. Clay should never be put only under
the pipe, as it then stops the water and keeps the pipe wet.
The durability of mains depends greatly on the nature of the
soil in which they are laid, clay being the best subsoil for this
purpose, and ground containing ashes, slag, and clinker the
It is necessary, therefore, to note carefully the description
of soil in which the pipes are to be laid, and if it is of an
injurious character, to imbed the pipes carefully in a good
common soil, or to puddle them round completely with clay,
protecting especially the upper side with a thick covering of the
material. The pipes should have a covering of at least 2 ft. of
soil over them in order to protect them from climatic influences
and from heavy traffic such as steam rollers, etc. The excava-
tion to receive the pipes should be of the least width practicable,
so that the labour of filling in may not be excessive. If the
bottom of the trench on which the pipes rest is not already even
and firm, it should be thoroughly consolidated by pressing. The
soil should be scooped out at the various points in the trench
where the sockets come, so that the body of the pipe may be
laid solid throughout its entire length.
Another subject for early consideration is the size of main
required for delivering a specified quantity of gas. In calcu-
lating the size for a gas main capable of delivering a specified
48 PRACTICAL GAS-FITTING.
quantity of- gas through a given length of main, the following
formula is employed :
(1350)* A, where
d= diameter of pipe in inches.
Q = quantity of gas in cubic feet per hour.
/ = length of pipe in yards.
h = pressure in inches of water.
$ = specific gravity of gas, air being 1.
The above formula can easily be calculated by tbe aid of a table
of logarithms. Thus, log. d = i (2 log. Q + log. s + log. 1 - 2 log.
1 350 -f log. h). Suppose, for example (to take an actual case),
that a gas main is required for a building of somewhat straggling
construction, and situated at about 500 ft. from the company's
main, about 900 burners being required, some in groups of two or
three. The burners may be taken as burning 5 cub. ft. per hour
each ; then the nearest size of main required would be 4 in.
Supposing the reader to be .unacquainted with the use of
logarithms, the following formula, where the size of main is
assumed in the first instance, will probably be found more
/ h fl
f~\ -j oxr* ,72 / *
that is, multiply the pressure in inches of water by the diameter
of the pipe also in inches. Divide this product by the specific
gravity of the gas multiplied by the length of the pipe in yards.
Then find the square root of the quotient and multiply this by
the constant 1,350 and the square of the diameter of the pipe in
inches, and the result will give the number of cubic feet dis-
charged per hour. Using this formula to check the result
obtained by the one first given, the specific gravity of the gas
is assumed to be '4, and the pressure 1 in. or ten-tenths. Then
the query is, to find the number of cubic feet of gas of the specific
gravity "4 capable of being delivered in one hour through a main
4 in. in diameter and 500 ft. or 166 yds. long under a pressure of
1-in. head of water. Then, hd = 4xl=4. while r? 2 = 4x 4 = 16, and
lid 4 T
= '0602, the so. root being
s I '4 x 166
2453. Therefore 1350 d' 2 ^J ~ = 1350 X 16 X '2453 = 5298,
which shows that the main would be amply large ; the next
GAS SUPPLY FROM GAS-HOLDER TO METER. 49
lower size (3 in.) would be too small. It is necessary to .note
that in the case of small service pipes the actual discharge
is less than the calculated quantity, so that it is necessary to
increase the diameter of the pipe by one-third if of lead and by
one-half if of wrought iron.
Yet another important subject for consideration in laying
mains is the way in which ordinary gas lighting is affected by
difference of level between the gasworks and the houses sup-
plied. The specific gravity of coal gas varies with its richness
or illuminating power, but in all cases it is less than that of the
atmosphere. If one portion of a town is below and another
above the works, the gas will rise to the higher parts by reason
of its lightness, but will have to be forced to the lower parts by
the weight of the gas-holder. In other words, for a pressure of
TO or T S O i* 1 a valley the mains
must be so charged as to exert
double or more, or say -} to
-fg in higher places. If a high
building is supplied from one
rising main only, the gas will so
rise to the upper floors as to
necessitate the use there of
burners different from those on
the lower floors ; or, alterna-
tively, gas pressure governors
may be fixed on the various floors. The gas should escape at
a certain pressure to form a solid flame, the burners being
selected in accordance therewith. If the gas escapes feebly,
a flickering flame will be the result, and a quantity of smoke will
be given off.
The general method of making joints in gas mains is illus-
trated by the section shown by Fig. 22. It is called the socket and
spigot joint, and is sometimes known as the open joint system.
In making a joint of this description, the spigot of the pipe
about to be laid is placed in the socket of the pipe already
laid, leaving an annular space between the spigot and the socket.
The inner portion of the annular space is then filled with twine
gasket to about half the depth of the socket, the gasket being
driven well in with the caulking tool. The outside face of the
joint is then tightly closed by means of a belt of plastic clay,
which completely encircles the pipe and presses up against the
Fig. 22. Socket and (Spigot
face of the socket, leaving an opening known as the lip on the
upper side of the pipe. Through this opening molten lead is
poured, filling up the remaining space between the gasket and
the clay, the excess of lead flowing over at the lip. The clay is
then removed, and the joint when cold is set up, as it is termed,
with a blunt caulking tool and hammer, so that the ring of lead
Figs. 23 and 24. Plan and Section of Main Syphon.
is wedged sufficiently tight to prevent any escape of gas. Each
pipe should be laid with the proper inclination or fall (say 1 ft.
in 200 yd.), and there should be a cast-iron syphon or drip-well
at the lowest point of the incline to collect the condensation
water deposited from the gas ; this would eventually clog the
main, if allowed to accumulate. As a rule, gas leaves
the works at a higher temperature than that to which it is
exposed when passing through the mains underground; conse-
GAS /SUPPLY FROM GAS-BOLDER TO ME TEE. 51
quently it holds more vapour in suspension as it leaves the works
than it is capable of carrying with it through the district mains,
the result being that the excess of vapour due to the difference in
temperature deposits in the main and finds its way to the syphons.
Fig. 23 shows plan, and Fig. 24 a section, of a syphon with its
accompanying standpipe, to which the syphon pump is attached
when pumping out the accumulated condensation products. There
is no definite rule with regard to the number of syphons required
for any length of gas main ; the principal factor governing their
Figs. 25 and 26.
Methods .of Drilling
disposition is the inclination of the ground in which the main
is laid. In refilling the trench in which a main has been laid,
shovel in the soil in layers, and ram firmly and equally all
round and above the pipes.
The hole for inserting a service pipe into the main should not
bs cut with a chisel, but should be drilled. The best position
for the hole is at the top of the main ; a bend should be screwed
in the hole drilled, proceeding thence with the ordinary piping,
Only when the main is too high should the wrought-iron tubing
be inserted at the side ; but it is better to lower the main than
to insert pipes at the side. Care should be taken that the
hole drilled in the main is not too large for the size of the main,
52 PRACTICAL GAS-FITTING.
as a disproportionately large hole weakens the pipe, and renders
it more liable to crack.
For drilling mains very simple tools are used, such as the
ratchet-brace with an ordinary flat drill or with a twist .drill ;
the twist drill is preferable, the ratchet being fixed in a bent iron
hook as shown by Fig. 25, p. 51 ; or the apparatus shown by Fig. 26,
p. 52, can be employed. These are the simplest forms of appar-
atus, but in using them the gas can escape when the hole is just
through ; and it is usually then the practice of fitters to close the
Fig. 27. Front Elevation of
Upward's Safety Drill.
space round the drill with a lump of clay or a piece of oily waste,
keeping it pressed down to the main pipe with the left hand
while the right hand works the ratchet handle. The loss of gas
is not the most serious consideration, for it has been a frequent
occurrence that men when working in a small hole excavated in
the ground, with' but little wind stirring, having been overcome
by the fumes of the gas ; and if this should happen when no one
was near to render aid, it is very possible that death might ensue
from asphyxiation. Should a man be overcome by the fumes of
gas, milk should be given at once, as this is the best antidote.
GAS SUPPLY FROM GAS-HOLDER TO METER. 53
In recognition of this danger, many inventions have been brought
out for preventing the escape of gas when drilling and tapping
mains. In some of these the drill passes through a hole in a
sheet of indiarubber that covers the top edge of a cylinder, the
latter being made to fit given sizes of mains by means of india-
rubber rings ; and the whole apparatus is screwed down tightly
to the main by chains with tightening screws affixed being passed
Another type of safety drilling apparatus is that known as
Fig. 28. Side Elevation of Upward's Safety Drill.
Upward's patent safety drill ; this is shown in front and side
elevation by Figs. 27 and 28. For use, it is placed on the pipe in
the required position for drilling the hole, the chain F being
passed round the pipe and secured by the hook H ; this is tight-
ened up on the bridle a until the apparatus is firmly fixed. A
roll of clay is placed around the bottom of the chamber B, to
prevent the escape of gas, and the valve K is then opened with
the handles N N, and the drill piston o, with the proper sized tap
and cutter D in it, is placed in the chamber B. The drill is
54 PRACTICAL GAS-FITTING.
allowed to drop on to the pipe, and the piston o is pushed down
until it touches the spring p, the screw c being then tightened
up. The ratchet handle is put on to the head of the drill at Q,
the feed screw E is screwed lightly down on it, and drilling is
commenced in the usual way, care being taken to feed the drill
gently until it bites properly. As soon as the hole is through, the
set screw c is loosened and the drill pressed down by the screw E
until the tap bites. The completion of the tapping is ascertained
by the tap coming home on the collar at its upper end. When
this is done the drill is drawn up as high as it will go, and
the slide valve K is closed carefully, to prevent the valve being
injured in case the drill should by accident be left too low
in the chamber B. To prevent the escape of gas during the
operation the valve K passes through leather packings LL at
the ends of the valve chamber. By the use of Upward's
Fig. 29. Fig. 30.
Figs. 29 and 30. Correct and Incorrect Positions of Drill.
appliance, the hole is both drilled and tapped at the one
operation ; and it is obvious that, if the above instructions are
carried out, there can be no escape of gas through the hole
made in the main.
Great care should be taken to ensure that the hole is being
drilled in a radial direction from the centre of the pipe that is
to say, if the hole is being drilled in the top of the pipe, the
ratchet and drill must always be kept truly vertical or upright,
whilst if a side hole is being made, the drill must be truly
horizontal. See that the drill invariably points to the centre of
the pipe, as shown in Fig. 29 : then the drill must necessarily
be vertical. If the drill is held incorrectly, as in Fig. 30, the result
will be that when the hole is drilled and tapped, the pipe that
is screwed into it will not point in the proper direction. In
feeding the ratchet-brace with the feed-screw, be careful not to
exert the whole strength upon it, more especially when the drill
is nearly through. The surface of the main being convex, the
GAS SUPPLY FROM GAS-HOLDER TO METER, 55
hole at that time is not exactly round ; hence, if forced too
rapidly, the drill is apt to catch and bind.
When drilling a small main, and a service is required of
nearly the same size, it is advisable to drill a hole some sizes
smaller, putting in a short piece of small-sized pipe and increas-
ing immediately to the size required. The short length of pipe
of small diameter does not sensibly reduce the quantity of gas
passed by the larger pipe.
Fig. 31. Taper Tap.
Hall's patent drilling and tapping machine is a strong and
efficient tool, and its working principle is simple. Under the top
flange of the machine is placed a circular revolving plate, through
which the drill shank and cock carrier shank pass and rest in a
seat, being held in place by a flat ring properly packed and bolted.
The object of this plate is to enable the operator, after having
drilled the hole and backed out the drill, to bring the cock
immediately into position by revolving the plate, the holes in
Fig. 32. Plug Tap.
which are so placed that when it is revolved it brings either the
cock or the drill over the same part of the main.
When a large hole is to be cut in a main a diamond-shaped
chisel is commonly used not, however, when the holes are after-
wards to be tapped.
The taps employed for mains are of two kinds, taper and plug,
as illustrated in Figs. 31 and 32, the taper being used first and
then the plug. Before the tap is put into the hole it is advisable
to see that the hole is cut cleanly through the main, as very often
56 PUAC1TICAL GAS-FITTING.
there remains a portion at the sides that has not been cut away
by the drill : such portion must be cut away with a hammer and
cold chisel before the tap is inserted.
Very great care is necessary to ascertain that the drill used is
of exactly the size necessary for the pipe that is to be inserted,
and the best way of gauging the precise dimensions is to calliper
the thinner end of the taper tap in the part that is of the largest
diameter. The drill should then be made a shade larger than
this, so that the taper tap may be inserted a short way into the
hole, or a combination tool, as shown by Fig. 33, may be used.
When the tap is in, a light blow on the top will cause the
threads upon the tap to slightly enter the iron round it, and
when turned by a key or spanner the tap will gradually force or
cut its way into the hole, making the threads as it enters.
Plenty of oil must be used on the tap, which must not be turned
Fig. 33. Drill Reamer Tap.
steadily in one direction, but must be taken, say, half a turn
forward and then a short way back. Thus the cut is very
gradual, and the metal cut away falls back into the grooves in
the tap, leaving a clear way for that which is to be removed.
Having turned the taper tap until it is as far in as the teeth will
permit (being careful not to allow the tap to pass right through
and drop into the main and so get lost), turn it gradually back
until it is entirely free, and substitute the plug tap. Screwing
this in and out again leaves the hole threaded ready for the pipe
to be inserted.
During the whole of these operations it is usual to keep a
piece of oily waste round the taps, ready to stop the hole when
they are removed. Having plugged the end of the bend, either
with a proper iron plug or cap, or with some of the waste before
mentioned, and painted the thread with red and white lead paint,
screw the bend into the main with the pipe tongs (see p. 68)
until it will turn no further without great force, finishing with
GAR RUrPLY FROM GAR-HOLDER TO METER,
the end of the bend pointing in the direction desired. Lead
paint for gas-fitters' use is prepared by mixing about three parts
of ordinary white-lead in paste with one part of red-lead in
powder. For use as paint for threads of screws, boiled linseed
oil is added to the mixture.
The service pipes should be of the best quality, and be allowed
to fall towards the main. If that inclination is not possible,
they should fall the other way, and a bottle syphon or drip-
well be inserted at the lowest point to receive the condensa-
tion water, which accumulates as explained on p. 51. The
service should be laid with a fall of at least 1 in. in every 12 ft. ;
and where the distance from the main is so great that this fall
cannot be secured without bringing the service pipe too near the
Fig-. 35. Pipe
surface of the ground, it is best to rise from the main as far as
possible, and then start falling again, putting in a syphon-box
(as shown in Fig. 34) where the depth of the pipe is considered to
be too great. In using the syphon- box, the pipes are connected
to the tee shown at A, the upper portion of the tee forming a
portion of the length of the service, the longer vertical pi}De being
carried up to an inch or so below the ground-level and a cap
(not shown) screwed on it. This cap is usually made by using a
plug fixed into a plain socket, the squarehead of the plug giving
greater facility for removal for pumping.
With reference to the slope of the service pipe, it may be well
to point out that, whereas in a wet meter the water condensed
from the gas would help to keep the water in the meter at the
58 PRACTICAL GAS-FITTING.
proper level and be an assistance, in the case of a dry meter its
presence is decidedly objectionable ; consequently, in laying the
service to and the pipes from the meters, note must be taken of
the class of meter which it is intended to fix, and when either
the service or the pipes leading from it to the house happen to
fall in the direction of the meter, a syphon should be used ;
this may be the syphon-box described on the previous page, or
may be a pipe syphon as shown in Fig. 35, the condensation
being removed from the bottom of the syphon from time to
time, merely by turning the tap. These remarks with refer-
ence to meters will be more intelligible if taken in conjunc-
tion with the information given in Chapter V.
In pathways and where traffic is likely to be great, a cast-iron
box with hinged lid should be fitted over the rising pipe of the
syphon to preserve the pipe from damage. The service should
not be allowed to come nearer than 1 ft. 6 in. to the surface of
the road, as a covering of ground less than 18 in. thick is very
porous, letting in sufficient moisture and air to ruin the pipe-
metal within a comparatively short period. Greater depth also
prevents rapid alteration of temperature and consequent con-