AND

JOURNAL OF THE COAL AND IRON TRADES.

Vol. CIX.

FRIDAY, JANUARY 29, 1915.

No. 2822.

The Design and Equipment of Colliery Electric Lamp Rooms
By WM. MAURICE, MJ.E.E., F.G.S.

Until quite recently it could scarcely have been said
that any colliery electric lamp rooms were of such fitness
for their functions as to have been able to lay appre-
ciable claim to design. Even to-day, although it is
coming to be recognised more and more that flame lamps
must give place to their inevitable successors, electric
lamp cabin practice has not settled down in any one
definite direction. The details of lamp room equipment
have latterly been well developed, and there are already
a considerable number of installations, the lay-out and
working of which exhibit a marked advance upon those
which were thought to be fairly good 18 months ago.

When only a limited number of lamps are required, it
is easy to understand that an effort will usually be made
to adapt an existing lamp room rather than build a new
one. But when a supply of 1,000 or 2,000 lamps is
called for, it will be found that the difference in cost
between a first-class equipment and an indifferent one
is not sufficient to justify an inclination towards cheap-
ness—especially when it is remembered (and experience
will certainly provide the remembrance) that an electric
lamp room is the very last place in which experiments
in “ economy ” can be successfully carried out. It is
now possible to post certain general rules, the regular
application of which will go far to promote the econo-
mical and efficient management of this still new system
of lighting the working places of mines.

The general plan upon which a colliery electric lamp
room is to be laid out will depend upon the number of
lamps in daily use. When that number does not exceed,
say, from 200 to 300 lamps, an effort will usually be
made to adapt an existing lamp room in order to avoid
the expense of erecting a special building. In such
cases space is often limited, and the best results are
most likely to be obtained by the selection of internal
fittings which will leave the maximum area of floor
space. Tho two chief space absorbing items in the
lamp room are the lamp racks and the charging stands.
Standard designs have been developed by the writer,
both as wall fittings and as pedestals to stand on the
floor. Roughly, an equipment for up to about 200 lamps
should be of the wall type, and for any higher number
of the floor type. Wall space can only be utilised
between the limits of height and depth within which a
youth can easily reach the cells, otherwise the whole of
the wall space available in any given room could be
used for charging stands, the lamp racks and cleaning
benches being then conveniently disposed on the free
floor space.

Charging Apparatus.

The first step in the design of charging stands was
taken with the object of eliminating the loss of time
involved in connecting up groups of cells one by one.
A solution of the problem was found in so arranging
shelves and contact strips that storage batteries when
placed on the shelves would automatically come in con-
tact with current-carrying strips placed immediately
above them. The use of the insulating trays was first
proposed by the writer in 1911, and early in 1912 he took
out a patent for such a tray, which embodied at the
same time a means of preventing the accidental or
careless reversal of charging current in the accumu-
lators.

Every charging board must be provided with volt-
meter, ammeter, reverse current cut out, switches,
fuses, and regulating resistances, in addition to the
proper complement of insulated shelves and series
contacts. A note may be useful as to providing volt-
meters on these boards. If each board is, say, only of
the 40-cell size, a fixed voltmeter with testing fork
attached to a flexible connection is the most convenient;
but for larger boards the voltmeter is best omitted from
the switch panel, on account of the inconvenience of
taking readings at a distance. For large boards a

* From a paper read before the North Staffordshire
Institute of Mining and Mechanical Engineers,

special portable instrument is usually provided, and it
is desirable that this instrument should be of the best
moving coil type, and fitted with some form of testing
fork. This testing fork is provided with an incandescent
bulb joined in parallel with the prongs. This addition
enables both the voltage and the storage capacity of a
cell to be estimated. A cell which has run down, and
then only been re-charged for a few minutes, may, if
tested with an ordinary voltmeter, indicate its full
voltage, thus suggesting that it is ready for use again,
but by connecting a lamp, or otherwise interposing a

Eleva t/o/v.

Accu/wt atop? Taaaspopt 7aB£.E

TWO DETACHABLE 7aAYS
caapy/a<g 20 Cells

Fig. 2.—Accumulator Transport Table.

(For use on bench., fig. 1.)

E/VD El. E VA 77O/V

? BOO

P/.A/V

W/T/Y	OPLPY TEE) Cq/V YQP,

Fig. L— Steel Cleaning Bench with Conveyor for Storage Cells.

Sect/q/v

relatively low resistance across the terminals, the cell,
if showing a fictitious voltage, will quickly drop to its
true value.

In order to minimise risk of electric shock to lamp
cabin operators, there is a tendency not to exceed—or,
to put it more definitely, to adopt as a standard—a
charging pressure of 110 volts. A pressure of 110 volts
will charge only 40 lead accumulators in series. Con-
sequently, 40 becomes a standard unit, and each series
of 40 requires a separate set of switchgear. Lead-cell
electric lamps should, therefore, whenever practicable,
be purchased in multiples of 40. If the Wolf alkaline
type of cell is in view, then a further consideration of
the voltage question becomes necessary. The reason

for this is that the Wolf alkaline batteries have a
terminal voltage of only 1*3 per cell. The number of
Wolf alkaline cells (using the expression “ cell ” in this
case to mean the two cells in series) which can be
charged in series at 110 volts is 26, after allowing a
margin for possible increases of resistance due to dirty
contacts, etc.

When charging facilities for large installations are
required, the floor or pedestal type of board becomes a
necessity. In the pedestal charging stands developed
by the writer, the main construction consists of tubular
steel columns carrying iron brackets, to which are bolted
steel frames, the said frames forming at the same time
supports for the insulating trays (of pressed glass or
porcelain) and for the series contact springs. These

springs are secured to the angle frame by bolts passing
through ebonite or fibre collars. The switchgear is
mounted upon marble or black enamelled slate panels,
which are disposed in a manner to suit the special
exigencies of each installation. For example, in the
Grassmoor Colliery lamp room the switchgear is detached
entirely from the charging stands, and is mounted upon
the walls of the charging room. At the Sherwood
Colliery, Mansfield, the same design of charging stand
is employed, but the switchgear is mounted for local
convenience overhead. Overhead switchgear has the
advantage of compactness, and the only objection to it
is that the ammeters and switchgear are exposed fully
to the action of the moist gases and corrosive action