Safety lamp

Miners have traditionally referred to the various gases encountered during mining as damps, from the Middle Low German word dampf (meaning "vapour").

If however the tip turns bluish-gray increasing in height to a thin extended point becoming a deeper blue, then firedamp is present.

[4] When they came into regular use, barometers were used to tell if atmospheric pressure was low, which could lead to more firedamp seeping out of the coal seams into the mine galleries.

This continued to be essential information even after the introduction of safety lamps; at Trimdon Grange there was an accident involving pressure.

Mild nystagmus would self-correct if a miner ceased to perform this work, but if left untreated would force a man to give up mining.

[13] The first safety lamp made by William Reid Clanny used a pair of bellows to pump air through water to a candle burning in a metal case with a glass window.

Early Geordie lamps had a simple pierced copper cap over the chimney to further restrict the flow and to ensure that the vital spent gas did not escape too quickly.

As the lamp burns brighter in dangerous atmospheres it acts as a warning to miners of rising firedamp levels.

The outer casings of lamps are made of materials such as brass or tinned steel, which do not make a spark if they strike rock.

Further observations of the speed of flame fronts in fissures and passageways led him to design a lamp with fine tubes admitting the air.

As an experimental chemist, he was familiar with the inability of flames to pass through mesh; his experiments enabled him to determine the correct size and fineness for a miner's lamp.

The gauze in the Davy lamp rusted in the damp air of a coal pit and became unsafe, while the glass in the Stephenson lamp was easily broken, and allowed the flame to ignite firedamp in the mine; later Stephenson designs also incorporated a gauze screen as a protection against glass breakage.

For men on piece work paid for what they produced, a relighting could cost them perhaps 10% of their day's pay, encouraging them to take the risk.

Two schemes existed: either a special tool was required which was kept at the pit head, or else opening the lamp extinguished the flame.

Clanny derived lamps had a metal "bonnet" (typically of tinned iron) in the shape of a truncated cone covering the gauze above the glass cylinder.

[40] At Trimdon Grange (1882) a roof fall caused a sudden blast of air and the flame passed through the gauze with fatal results (69 killed).

[46] The poor light compared to either the Geordie or Clanny eventually led to the Davy being regarded as "not a lamp but a scientific instrument for detecting the presence of firedamp".

A strong enough current of air could travel through the tubes (later holes and gallery) and enlarge the flame, eventually leading to it becoming red-hot.

[48] The pin could only be released by applying a vacuum to a captive hollow screw; not something that a nicotine starved miner could do at the coal face [citation needed].

Clanny abandoned his pumps and candles and developed a safety lamp which combined features of both the Davy and Geordie.

Whilst the Clanny will continue to burn if laid on its side, potentially cracking the glass; the Mueseler will extinguish itself due to the stoppage of convection currents.

The top of the tube is closed by a horizontal mesh attached to the body of the lamp by small bars to conduct heat away.

Air enters through a series of small holes drilled in the lower brass ring supporting the glass.

The gauze-covered holes and passageways restrict the flow to that required for combustion, so if any part of the oxygen is replaced by firedamp, then the flame is extinguished for want of oxidant.

[24] The base also contained an interlocking mechanism to ensure that the wick was lowered and the lamp extinguished by any attempt to open it.

[24] The lamp devised and manufactured by Evan Thomas of Aberdare[53] is similar to a shielded Clanny, but there is a brass cylinder outside the gauze above the glass.

[citation needed] An early pioneer was Joseph Swan who exhibited his first lamp in Newcastle upon Tyne in 1881[44] and improved ones in subsequent years.

[63] Clearly this stimulated development and over the next few years there was a marked increase in the use of electric lamps, especially the CEAG, Gray-Sussmann, and Oldham, so by 1922 there were 294,593 in use in Britain.

[64] In 1913, Thomas Edison won the Ratheman medal for inventing a lightweight storage battery that could be carried on the back, powering a parabolic reflector that could be mounted on the miner's helmet.

A newer light source, the light-emitting diode (LED), has advantages for safety lamps, mainly higher efficiency providing much longer illumination time from the same battery.