Improvements in the Detection and Estimation of Combustible Gas or Vapour Present in Air and Apparatus for that Purpose.
Year: 1893

page_text: Date of Application, 4th Jan., 1893-Accepted, 18th Feb., 1893
COMPLETE SPECIFICATION.
Improvements in the Detection and Estimation of Combustible Gas
or Vapour Present in Air and Apparatus for that Purpose.
We BOVERTON REDWOOD, of No. 4 Bishopsgate Street, Within, in the City of
London, Analytical Chemist, FRANK CLOWES, of The University College,
Nottingham, in the County of Nottingham, Professor of Chemistry, and SIDNEY
WATERS, of No. 24 Ladbrooke Square in the County of Middlesex, Merchant, do
hereby declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement :-
Our invention relates to means of detecting the presence and estimating the
quantity of combustible gas or vapour in air, and is particularly directed to testing
the atmosphere in mines, and in petroleum vessels or receptacles, so as to ascertain
whether such atmosphere can be safely entered by a light or by heated metal such
as rivets employed in repairs.
Our method of testing is founded on the known physical fact that a hydrogen
flame supplied with air containing combustible gas or vapour presents above it a
blueish grey coloured cap of a height depending on the quantity of combustible
present in the air and on the size of the hydrogen flame. We therefore regulate
the hydrogen flame to some standard height, and by measuring the height of the
cap produced above it, we ascertain approximately the percentage of combustible
gas or vapour contaminating the air which supplies the flame.
The hydrogen flame may be thus employed in a safety lamp provided with a
special hydrogen burner and it may be also provided with a reservoir of compressed
hydrogen as described in the Specification No. 6051 of 1892. This lamp which
has the usual provisions for safety, may be taken into the atmosphere which is
suspected to contain combustible, so as to receive its supply of air from that
atmosphere in the usual way.
We may however provide such a lamp with means of closing the usual inlet for
air, and of opening another inlet which can be connected by a flexible or other pipe
to a vessel containing a sample of the atmosphere to be tested.
It is convenient to have a lamp thus arranged, because it may be used in either
way, that is to say, to take its air supply either from the atmosphere surrounding
it or from the sample vessel.
Fig. 1 of the accompanying drawings is a section of a safety lamp arranged to
be employed as above described.
Close beside the wick W is fixed a small tube B which extends down through
the oil reservoir R and out at the side where it is connected to a reservoir H of
compressed hydrogen attached to the side of the lamp.
In the passage from the reservoir H to the tube B there is a screw plug P by
which the flow of hydrogen can be delicately adjusted. The ordinary air supply
to the lamp is from the upper part down through hollow columns C. We provide
a valve by partly turning which the upper mouths of these columns can be
closed, and then on unscrewing a cap U covering a lateral opening into one of the
columns, and connecting to this a tube, which may be flexible, we can admit a
supply of air from a vessel containing it. In testing for inflammable gas or vapour
in the atmosphere of a mine or other space, or in a vessel connected to the lamp
at U, we proceed as follows.
Having, in the first place, kindled the wick in the usual way, in a safe place,
and closed the lamp, we partly turn the screw plug P so as to allow hydrogen to
pass to the tube B, at the top of which it is kindled by the wick flame, which we
then extinguish in the usual way by drawing down the wick by the bent wire or

page_text: pricker. S. We then, by means of the plug P adjust the hydrogen flame to a
standard height which is determined by the bent wire G forming a gauge. Having
observed the cap on the hydrogen flame, we rekindle the wick from this flame,
which we then extinguish by screwing up the plug P.
In cases where samples of air more or less contaminated with combustible can be
conveniently tested in a laboratory or place where there is no danger of explosion,
we employ a lamp having a burner for hydrogen supplied to it from a gas holder or
from a reservoir of the gas compressed, and having under the burner a chamber
containing several wire gauze diaphragms. This chamber being connected by a
pipe with the sample vessel, in which the contaminated air may be kept under more
or less pressure, a portion of this air is allowed to flow, in quantity regulated by a
stop cock or valve, into the chamber of the lamp, an it passes through the gauze
diaphragms to support the hydrogen flame, the diaphragms preventing com-
munication of ignition to the contents of the sample vessel. We prefer to surround
the hydrogen flame with an opaque screen so that its light may not interfere with
observation of the cap above the flame, and this cap is kept steady by its enclosure
in a glass or glazed chimney, which is preferably graduated so that the height of
the cap can at once be observed.
Fig. 2 of the accompanying drawings is a vertical section and Fig. 3 is a plan of
a testing lamp of this kind.
The hydrogen burner supplied by the tube B from a gas holder or reservoir of
compressed hydrogen, is surrounded by an opaque cone G which can be raised or
lowered to determine the height of the flame by moving an external button g along
a graduated scale on the metal chimney E, which may be square, as shewn, with
one side F of glass. The air to be tested is admitted by a pipe A, its flow being
regulated by a screw valve P. In ascending to the flame the air has to pass baffle
plates K and three or more wire gauze diaphragms D. Above these there are
lateral holes covered by a rotating slide valve V which can be moved by an external
button so as to open or close the lateral holes. Before testing, these holes are
opened, allowing the supply of air to the flame to come from the surrounding
atmosphere.
The cap a being removed and the pipe A connected to a vessel containing the
air to be tested, the valve P is opened and is closed, so that the flame is supplied
with a portion of the air to be tested. The lamp is enclosed in a casing L with
hinged doors M in front, which are opened during the testing experiment, the
operator, if necessary, covering his head by a dark cloth extending over the
casing L as in focussing a camera.
For the purpose of obtaining from a tank or other vessel a sample of the con-
taminated air, we employ an apparatus of the following description. It consists of
a cylinder fitted with a piston packed with cup leather or other suitable packing,
the cylinder having an inlet valve at its bottom and an outlet provided with a
stop cock or shut off valve and a suitable nozzle for connecting to it a flexible or
other pipe. The piston is pushed down to the bottom of the cylinder in opposition
In this condition
to a spring or springs and is held in that position by a catch.
the apparatus is lowered into the tank or vessel to be sampled, and, when it meets
the bottom, a trigger is acted on which releases the catch holding the piston.
The piston thereupon ascends, drawing in air which constitutes the sample required,
being retained in the cylinder by the closure of the inlet valve.
Fig. 4 is a vertical section of this apparatus.
C is the cylinder fitted with piston P and having at the bottom an inlet valve V.
The piston is pushed down in opposition to springs S and is held down by a catch H
engaging a collar on the piston rod. The catch is one limb of a bell crank to
the other limb of which is jointed a guided rod R extending below the base of the
apparatus, so that when this reaches the bottom of the tank or vessel into which
the cylinder is lowered, the catch H is disengaged, and the piston P is drawn up
by the springs S, drawing in air past the valve V.
Fig. 5 is a vertical section of a modified form of the apparatus, in which the

page_text: When a
piston rod is fixed to a crosshead having two side rods T bearing on springs S con-
tained in lateral tubes. The piston being pushed down, compressing these springs,
is held by catches H engaging collars on the side rods T. When a central
button M, connected by hent rods R to the catch levers H, meets the bottom,
these catches are withdrawn, and the piston ascends drawing in air.
sample is required in quantity greater than can be conveniently contained in a
cylinder such as that above described, we employ apparatus for obtaining a sample
in compressed condition. This apparatus consists of a strong cylindrical vessel
having the barrel of a hand compressing pump arranged centrally within it; the
suction valve of this pump opens from an inlet provided with a nozzle to which can
be connected a pipe from the space containing the contaminated air, and the
discharge valve opens into the annular space surrounding the pump, which annular
space becomes a reservoir for the gaseous sample charged to such pressure or may
be convenient by a number of strokes of the pump.
Fig. 6 is a vertical section of this apparatus. B is the pump barrel situated
centrally within a strong cylindrical vessel C, which has hinged arms N that can
be folded down to the ground so that the operator can place his feet on them, thus
holding the apparatus down while he works the pump. As the piston P is drawn
up by the handle H, the air to be compressed enters by the nozzle A to which a
flexible tube can be connected, and descends the barrel B, passes through the
piston P, and past the suction valve S into the space of the barrel below the piston;
then, during the down stroke, the air is forced past the discharge valve D into the
annular space surrounding B.
When the apparatus is not in use the arms N are turned up and held by nuts n.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we would have it under-
stood that we make no general claim to detecting the presence of combustible gas
or vapour in air by observing its effect on a hydrogen flame supplied with air so
contaminated, but we declare that what we claim is :-
1. The herein described method of ascertaining approximately the quantity of
combustible gas or vapour in air, by feeding, with air so contaminated, a hydrogen
flame regulated to a definite height and measuring the height of grey cap appearing
above the flame.
2. In a safety lamp arranged as described in the Specification No. 6051 of 1892
for testing the presence of combustible gas or vapour in the atmosphere surrounding
it, the combination of valve V and nozzle U, as and for the purpose set forth
with reference to Fig. 1.
3. The construction and arrangement of testing lamp, substantially as described
with reference to Figs. 2 and 3.
4. The apparatus consisting of cylinder and spring piston and adjuncts for
obtaining a sample of contaminated air, substantially as described with reference to
Fig. 4.
5. The modified apparatus for obtaining a sample of contaminated air, sub-
stantially as described with reference to Fig. 5.
6. The construction and arrangement of compressing pump and reservoir, sub-
stantially as described with reference to Fig. 6.
Dated this 4th day of January 1893.
ABEL & IMRAY,
Agents for the Applicants.