According to the London _Mining Journal_, Mr. W.E. Garforth, of Normanton,
has introduced an ingenious invention, the object of which is to detect
fire-damp in collieries with the least possible degree of risk to those
engaged in the work. Mr. Garforth's invention, which is illustrated in the
diagram given below, consists in the use of a small India rubber hand ball,
without a valve of any description; but by the ordinary action of
compressing the ball, and then allowing it to expand, a sample of the
suspected atmosphere is drawn from the roof, or any part of the mine,
without the great risk which now attends the operation of testing for gas
should the gauze of the lamp be defective. The sample thus obtained is then
forced through a small protected tube on to the flame, when if gas is
present it is shown by the well-known blue cap and elongated flame. From
this description, and from the fact that the ball is so small that it can
be carried in the coat pocket, or, if necessary, in the waistcoat pocket,
it will be apparent what a valuable adjunct Mr. Garforth's invention will
prove to the safety-lamp. It has been supposed by some persons that
explosions have been caused by the fire-trier himself, but owing to his own
death in most cases the cause has remained undiscovered. This danger will
now be altogether avoided. It is well known that the favorite form of lamp
with the firemen is the Davy, because it shows more readily the presence of
small quantities of gas; but the Davy was some years ago condemned, and is
now strictly prohibited in all Belgian and many English mines. Recent
experience, gained by repeated experiments with costly apparatus, has
resulted in not only proving the Davy and some other descriptions of lamps
to be unsafe, but some of our Government Inspectors and our most
experienced mining engineers go so far as to say that "no lamp in a strong
current of explosive gas is safe unless protected by a tin shield."
[Illustration]
If such is the case, Mr. Garforth seems to have struck the key-note when,
in the recent paper read before the Midland Institute of Mining and Civil
Engineers, and which we have now before us, he says: "It would seem from
the foregoing remarks that in any existing safety-lamp where one
qualification is increased another is proportionately reduced; so it is
doubtful whether all the necessary requirements of sensitiveness,
resistance to strong currents, satisfactory light, self-extinction, perfect
combustion, etc., can ever be combined in one lamp."
The nearest approach to Mr. Garforth's invention which we have ever heard
of is that of a workman at a colliery in the north of England, who, more
than twenty years ago, to avoid the trouble of getting to the highest part
of the roof, used a kind of air pump, seven or eight feet long, to extract
the gas from the breaks; and some five years ago Mr. Jones, of Ebbw Vale,
had a similar idea. It appears that these appliances were so cumbersome,
besides requiring too great length or height for most mines, and
necessitating the use of both hands, that they did not come into general
use. The ideas, however, are totally different, and the causes which have
most likely led to the invention of the ball and protected tube were
probably never thought of until recently; indeed, Mr. Garforth writes that
he has only learned about them since his paper was read before the Midland
Institute, and some weeks after his patent was taken out.
No one, says Mr. Garforth, in his paper read before the Midland Institute,
will, I presume, deny that the Davy is more sensitive than the tin shield
lamp, inasmuch as in the former the surrounding atmosphere or explosive
mixture has only one thickness of gauze to pass through, and that on a
level with the flame; while the latter has a number of small holes and two
or three thicknesses of gauze (according to the construction of the lamp),
which the gas must penetrate before it reaches the flame. Moreover, the tin
shield lamp, when inclined to one side, is extinguished (though not so
easily as the Mueseler); and as the inlet holes are 6 inches from the top,
it does not show a thin stratum of fire-damp near the roof as perceptibly
as the Davy, which admits of being put in almost a horizontal position.
Although the Davy lamp was, nearly fifty years ago, pronounced unsafe, by
reason of its inability to resist an ordinary velocity of eight feet per
second, yet it is still kept in use on account of its sensitiveness. Its
advocates maintain that a mine can be kept safer by using the Davy, which
detects small quantities of gas, and thereby shows the real state of the
mine, than by a lamp which, though able to resist a greater velocity, is
not so sensitive, and consequently is apt to deceive. Assuming the Davy
lamp to be condemned (as it has already been in Belgium and in some English
mines), the Stephenson and some of the more recently invented lamps
pronounced unsafe, then if greater shielding is recommended the question
is, what means have we for detecting small quantities of fire-damp?
It would seem from the foregoing remarks that in any existing safety-lamp,
where one qualification is increased another is proportionately reduced; so
it is doubtful whether all the necessary requirements of sensitiveness,
resistance to strong currents, satisfactory light, self-extinction, perfect
combustion, etc., can ever be combined in one lamp. The object of the
present paper is to show that with the assistance of the fire-damp
detecter, the tin shield, or any other description of lamp, is made as
sensitive as the Davy, while its other advantages of resisting velocity,
etc., are not in any way interfered with. As a proof of this I may mention
that a deputy of experience recently visited a working place to make his
inspection. He reported the stall to be free from gas, but when the manager
and steward visited it with the detecter, which they applied to the roof
(where it would have been difficult to put even a small Davy), it drew a
sample of the atmosphere which, on being put to the test tube in the
tin-shield lamp, at once showed the presence of fire-damp. Out of
twenty-eight tests in a mine working a long-wall face the Davy showed gas
only eleven times, while the detecter showed it in every case. The
detecter, as will be perceived from the one exhibited, and the accompanying
sectional drawing, consists simply of an oval-shaped India rubber ball,
fitted with a mouthpiece. The diameter is about 2¼ inches by 3 inches, its
weight is two ounces, and it is so small that it can be carried without any
inconvenience in the coat or even in the waistcoat pocket. Its capacity is
such that all the air within it may be expelled by the compression of one
hand.
The mouthpiece is made to fit a tube in the bottom of the lamp, and when
pressed against the India rubber ring on the ball-flange, a perfectly tight
joint is made, which prevents the admission of any external air. The tube
in the bottom of the lamp is carried within a short distance of the height
of the wick-holder. It is covered at the upper end with gauze, besides
being fitted with other thicknesses of gauze at certain distances within
the tube; and if it be found desirable to further protect the flame against
strong currents of air, a small valve may be placed at the inlet, as shown
in the drawing. This valve is made of sufficient weight to resist the force
of a strong current, and is only lifted from its seat by the pressure of
the hand on the mouthpiece. It will be apparent from the small size and
elasticity of the detecter that the test can easily be made with one hand,
and when the ball is allowed to expand a vacuum is formed within it, and a
sample of the atmosphere drawn from the breaks, cavities, or highest parts
of the roof, or, of course, any portion of the mine. When the sample is
forced through the tube near the flame, gas if present at once reveals
itself by the elongation of the flame in the usual way, at the same time
giving an additional proof by burning with a blue flame on the top of the
test tube. If gas is not present, the distinction is easily seen by the
flame keeping the same size, but burning with somewhat greater brightness,
owing to the increased quality of oxygen forced upon it.
I venture to claim for this method of detecting fire-damp among other
advantages: 1. The detecter, on account of its size, can be placed in a
break in the roof where an ordinary lamp--even a small Davy--could not be
put, and a purer sample of the suspected atmosphere is obtained than would
be the case even a few inches below the level of the roof, 2. The obtaining
and testing of a sample in the manner above described takes away the
possibility of an explosion, which might be the result if a lamp with a
defective gauze were placed in an explosive atmosphere. No one knows how
many explosions have not been caused by the fire-trier himself. This will
now be avoided. (Although lamps fitted with a tin shield will be subjected
to the same strict examination as hitherto, still they do not admit of the
same frequent inspection as those without shields, for in the latter case
each workman can examine his own lamp as an extra precaution; whereas the
examination of the tin shield lamps will rest entirely with the lamp man.)
3. The lamp can be kept in a pure atmosphere while the sample is obtained
by the detecter, and at a greater height than the flame in a safety-lamp
could be properly distinguished. The test can afterward be made in a safe
place, at some distance from the explosive atmosphere; and, owing to the
vacuum formed, the ball (without closing the mouthpiece) has been carried a
mile or more without the gas escaping. 4. The detecter supplies a better
knowledge of the condition of the working places, especially in breaks and
cavities in the roof; which latter, with the help of a nozzle and staff,
may be reached to a height of ten feet or more, by the detecter being
pressed against the roof and sides, or by the use of a special form of
detecter. 5. Being able at will to force the contents of the detecter on to
the flame, the effects of an explosion inside the lamp need not be feared.
(This danger being removed, admits, I think, of the glass cylinder being
made of a larger diameter, whereby a better light is obtained; it may also
be considered quite as strong, when used with the detecter, as a lamp with
a small diameter, when the latter is placed in an explosive atmosphere.) 6.
The use of the detecter will permit the further protection of the present
tin shield lamp, by an extra thickness of gauze, if such addition is found
advantageous in resisting an increased velocity. 7. In the Mueseler,
Stephenson, and other lamps, where the flame is surrounded by glass, there
is no means of using the wire for shot firing. The detecter tube, although
protected by two thicknesses of gauze, admits of this being done by the use
of a special form of valve turned by the mouthpiece of the detecter. The
system of firing shots or using open lamps in the same pit where safety
lamps are used is exceedingly objectionable; still, under certain
conditions shots may be fired without danger. Whether safety lamps or
candles are used, it is thought the use of the detecter will afford such a
ready means of testing that more examinations will be made before firing a
shot, thereby insuring greater safety. 8. In testing for gas with a safety
lamp there is a fear of the light being extinguished, when the lamp is
suddenly placed in a quantity of gas, or in endeavoring to get a very
small light; this is especially the case with some kinds of lamps. With the
detecter this is avoided, as a large flame can be used, which is considered
by some a preferable means of testing for small quantities; and the test
can be made without risk. Where gas is present in large quantities, the
blue flame at the end of the test tube will be found a further proof. This
latter result is produced by the slightest compression of the ball. (I need
not point out the inconvenience and loss of time in having to travel a mile
or more to relight.) As regards the use of the detecter with open lights,
several of the foregoing advantages or modifications of them will apply.
Instead of having to use the safety lamp as at present, it is thought that
the working place will be more frequently examined, for a sample of the
suspected atmosphere can be carried to a safe place and forced on to the
naked light, when, if gas be present, it simply burns at the end of the
mouthpiece like an ordinary gas jet. There are other advantages, such as
examining the return airways without exposing the lamp, etc., which will be
apparent, and become of more or less importance according to the conditions
under which the tests are made.
In conclusion, I wish to paint out that the practice adopted at some
collieries, of having all the men supplied with the most approved lamp
(such as the Mueseler or tin shield lamp) is not a safe one. If the
strength of a chain is only equal to the weakest link, it may be argued
that the safety of a mine is only equal to that of the most careless man or
most unsafe lamp in it. If, therefore, the deputies, whose duty it is to
look for gas and travel the most dangerous parts of the mine, are obliged
to use the Davy on account of its sensitiveness, may it not be said that,
as their lamps are exposed equally with the workmen's to the high
velocities of air, they are the weak links in the safety of the mine? For
the reasons given, I venture to submit that the difficulties and dangers I
have mentioned will be largely reduced, if not wholly overcome, by the use
of the fire-damp detecter.
* * * * *