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THE COAL TRADE BULLETIN. 36
PORTABLE ELECTRIC MINE LAMPS*
By H. H. Clarke. United States Bureau of Mines
Portable electric mine lamps are a comparatively
new development in this country, although
such lamps have been used in European mines for
some time
Wm. Maurice, in a lecture before the University
College of Nottingham, England, stated
that as early as 1SS7, 600 portable electric lamps
were installed in a colliery in South Wales. He
adds that the use of these lamps was eventually
discontinued, but that ten years later portable
electric lamps were used regularly in England
as a substitute for flame lamps, over 1,000 lamps
being in daily use by the latter part of 1899.
E. N. Zern stated in the Coal and Coke Operator
of March 14, 1912, that in 1904 several thousand
portable electric lamps were in use in the mines
of England and Belgium. Portable electric lamps
are now used extensively in European coal mines,
and in a portable electric lamp competition held
recently in England, 195 different lamps were entered.
For at least five years and probably for a
longer time, portable electric lamps have been
used here and there in the mines of this country
in the attempt to develop a satisfactory substitute
for the safety lamp.
Just at present American manufacturers and
mine operators are displaying a great deal of
interest in the development of portable electric
lamps, and the subject is therefore a timely one,
having also the acceptable quality of freshness
because portable electric mine lamps have not
been extensively considered in previous meetings
of this kind.
QUALITIES OF PORTABLE ELECTRIC MINE I.AMI'S.
A widespread knowledge of the qualities of any
new apparatus or device is most essential to its
successful introduction anywhere. In the early
days of any art the manufacturer states the qualities
of his product and the user takes it or leaves
it, as he chooses. As the art develops the user
can pick and choose, and finally a time arrives
when the user defines freely what qualities he
requires. Not until this period is reached can
an apparatus or device be considered as fully
developed The user of a device is the logical one
to specify its qualities If the user is obliged to
adapt his actions, operations, or equipment to the
limitations of the manufacturer the product of
such a manufacturer is not practicable in the fullest
sense of the yvord The measure of practicability
is the ability of the manufacturer to completely
satisfy the requirements of the user.
"Address delivered before the Coal Mining Institute of
America, Pittsburgh. Pa.. December 5, 1913.
Before the manufacturer can undertake to fulfill
his part of the contract the user must clearly
define what he requires, ancl therefore the determination
of the necessary qualities of portable
electric mine lamps is the first step in their consideration
SAFETY.
There are a number of qualities that an electric
lamp must have in order to make it acceptable
for mine use. Chief among these is safety. The
principal reason why the Bureau of Mines advocates
the adoption of the electric lamp is because
fire and explosion hazards yvill be decreased thereby.
It is therefore manifest that the electric
lamp itself must, not be a source of danger. The
Bureau proved by actual tests that the gloyving
filaments of portable electric lamps are capable
of igniting mine gas, but that sparks from portable
electric lamp equipments of not more than
six volts are not capable of igniting mine gas
unless the equipments are unusually large. When,
therefore, the Bureau decided to make tests to
establish the permissibility of lamps for use in
gaseous mines, sparks were ignored as not being
an element of danger, while safeguards were required
for the gloyving filaments.
Schedule 5, which was issued to announce the
Bureau's tests, contained the following paragraph:
"Permissible portable electric lamps shall be
so designed and constructed that under no circumstances
can the bulb of a completely assembled
lamp be broken while the lamp filament is
glowing at a temperature sufficient to ignite explosive
mixture of mine gas and air."
The Schedule gives in detail the requirements
of design, the character of the tests to which the
lamp is to be submitted, and the conditions under
which the tests will be made. Beyond requiring
that the mechanical construction of the lamps
should be rugged, no attempt was made to insure
the capacity, efficiency or practicability of the
lamps tested, although lamps that were manifesly
incomplete or inadequate for mine service yvere
not accepted for test. Therefore, it is clear that
the Bureau's approval of a lamp as permissible
means that the Bureau vouches for the safety of
the lamp but not for its capacity, time of burning,
or expense ancl care of maintenance.
PERMISSIBLE TESTS.
Iii response to the invitation contained in
Schedule 5, six lamps were submitted to the Bureau
for test. Three of these were not accepted
for test, being rejected on account of the inadequate
construction or lack of safety devices. The