safety lamp

Modern flame safety lamp used in mines, manufactured by Koehler

A safety lamp is any of several types of lamp, which are designed to be safe to use in coal mines. These lamps are designed to operate in air that may contain coal dust, methane, or firedamp, all of which are potentially flammable or explosive. The use of open lamps, rather than the safety lamps that were then available, was one cause of the Naomi Mine explosion and the Darr Mine Disaster in Pennsylvania in December 1907.^[1]

First safety lamps

The first safety lamp was invented by William Reid Clanny, an Irish physician, who announced his discovery^[2] on May 20, 1813 at the Royal Society of Arts in London, but it was not tried out in a colliery until 1815^[3]. Within months of this demonstration, two improved designs had been announced: one by George Stephenson, which later became the Geordie lamp, and the Davy lamp, invented by Sir Humphry Davy. Most later lamps are constructed on the principle discovered by Davy, that a flame enveloped in wire gauze of a certain fineness does not ignite firedamp

Both the Davy and Stephenson lamps were fragile. The gauze in the Davy quickly rusted in the moist air of a coal pit, and so became unsafe, while the glass in the Stephenson was easily broken, and could then allow the flame to ignite firedamp in the atmosphere. Later designs, the Gray, Mueseler, Marsaut, and other lamps, tried to overcome these problems by using multiple gauze cylinders, but the glass remained a problem until toughened glass became available.^[4]

Also, the light that all these gave was poor and this was not solved until the introduction of electric lighting in mines around 1900. But it took until 1930 for the introduction of battery-powered helmet lamps to finally solve the problem.

Early illumination

A Davy lamp, an early example of a safety lamp

Prior to the invention of these safety lamps, miners used candles with open flames or phosphorescent sources of light and later flint or steel mills designed by 'Spedding.' Later, barometers were used to tell them if atmospheric pressure was low (in which case more methane seeped out of the coal seams into the mine galleries).

The use of small mammals or birds was used much later at the end of the Victorian age to warn of the presence of the deadly carbon monoxide present after underground fires or explosions, the so-called afterdamp. The method was introduced by the noted physiologist and disaster investigator, John Scott Haldane after the Laxey lead mine disaster. Such animals are much more susceptible to the gas, and will die before a human, so giving an early warning of the problem. There were numerous deaths casued by carbon monoxide from a small fire near one of the shaft bottoms. An alternative method of removing a different gas, known as firedamp (methane) involved igniting the gas deliberately to cause explosions, thus evacuating the mines of the majority of explosive or easily flammable material present.

The lack of good lighting was a prime cause of a painful eye affliction (nystagmus).

Modern lamps

Nowadays, safety lamps are mainly electric, and traditionally mounted on miners' helmets (such as the wheat lamp) or the Oldham headlamp, sealed to prevent gas penetrating the casing and being ignited by electrical sparks.

Although its use as a light source was superseded by electric lighting, the flame safety lamp has continued to be used in mines to detect methane and blackdamp, although many modern mines now also use sophisticated electronic gas detectors for this purpose.

As a new light source, LED has many advantages for safety lamps, including longer burn time and less energy required. Combined with new battery technologies, such as the lithium battery, it gives much better performance in safety lamp applications. It is replacing conventional safety lamps.^{[citation needed]}

See also

• List of light sources
• Pellistor
• Felling mine disaster
• Mining accident

Notes

References

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