by Gavin Chait
Coal mining is hard and unpleasant labour. Worse in a time of burning candles when
invisible firedamp would cause explosions or chokedamp cause asphyxiation.
Miners require two types of light sources: fixed
and mobile. Mobility implies battery technology.
Any light must be intrinsically safe, or explosion
proof. In all cases, lamps must be hardened to
minimise the risk of breakage, should not cause
ignition of volatile gases, and must similarly not
cause harm through radiation to the miners them-
selves. Sodium lamps, for example, will ignite if
they break or if the sodium comes into contact
with water. Colour rendition is also important. Min-
ing environments often contain numerous colour-
coded labels, from different gas mixes, to wiring
and signage. Sodium lamps produce yellow light;
mercury vapour produces bluish white.
The mine lighting industry is now migrating to
LEDs, offering longer operating life, lower energy
requirements and easier heat dissipation. They are
designed in corrosion-resistant metal and operate
from -20°C to 45°C, and at voltage options from
80 V to 240 V.
Some manufacturers, like NL Technologies
S
ir Humphrey Davey invented his safety
lantern in 1815 in which a wick lamp was
enclosed inside a mesh screen. The mesh
acts as a flame arrestor, allowing air through but
preventing the flame from following. The lamp al-
lowed safer mining and detection of the methane
causing firedamp or the carbon dioxide causing
chokedamp.
But, this was only a partial solution. Coal absorbs
light and offers no reflection for the eye to gauge
depth or shape. Nystagmus was a common eye
disease with no cure, causing rapid and uncontrol-
lable oscillation of the eyeballs, with headaches,
dizziness and loss of night vision to follow.
The environment is dirty, hot, damp and ex-
treme. Lighting systems will corrode or fail. Davey
lamps took already dim lanterns and obscured the
light even further. Only with the arrival of bright
electric incandescent lighting did the process to
overcome nystagmus begin, at the turn of the
twentieth century.
Lighting in extremes
27
LiD
08-09/14
