History of the Pieler Lamp

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History of the Pieler Lamp

The miner’s flame safety lamp (“Davy” lamp) was developed to give light in firedamp atmospheres without igniting explosions. But, it was soon realize that the lamp had added benefits by being able to give a visual indication of the presences of firedamp. The flame in a Davy-type lamp would give off a luminous blue cap in the presence of methane. It was soon realized that the height of the blue “cap” was directly correlated to the concentration of methane in the atmosphere.

As coal mines got larger and deeper, methane became more and more of a dangerous problem. The art of mine ventilation engineering, derived from basic fluid mechanics, became a science out of necessity. But, to perform proper dilution calculations for mine ventilation designs, the concentration of methane needed to be accurately measured in all shafts, tunnels, and working areas. While a skilled fireman could use a Davy lamp for estimating fire damp concentrations, it was not accurate in low fire damp concentrations, and useless in atmospheres containing under ¾% methane.

In 1883, Friedrich Pieler, a German mining engineer, introduced a simple and delicate firedamp indicator into the Westphalian mines. The “Pieler” lamp, as it became to be known, was a large Davy- type lamp that burned alcohol. Pieler used the principal that an alcohol flame is non-luminous and burns much hotter than an ordinary Davy oil lamp. Consequently, the gas caps produced are much larger and more visible than by oil flame. Since the alcohol flame exaggerates with minute changes in methane in the atmosphere, the height of the flame could be easily measured visually and correlated to a % concentration. The Pieler lamp proved to be highly accurate in measuring firedamp in concentrations from ¼% to 2-½%.

Although there were many varieties of Pieler lamps, the construction of the lamp is quite simple. It is a large, Davy-type lamp fitted with an Argand burner that is adjustable by a sleeve moved by a screw in the base. The burner is fitted with a 1″ conical sheet-iron shield that hides the flame in normal atmospheres. As the flame elongates in the presence of firedamp, the lamp becomes more luminous. Most Pieler lamps were fitted with a graduated scale to measure the flame, but some of the early models were made without scales. Pieler lamps were made bonneted and unbonneted; with or without locks. Some were fitted with an ignitor, and internal flame extinguisher. The most prolific manufacturer was Friemann & Wolf (German). Other noted manufacturers include Cosset-Dubrelle (French), and A. Benitschke’s Sohn (Bohemia).

While the Pieler lamp was simple and accurate, it had its problems. First, the lamp was very dangerous in firedamp above 2-½% because the elongated flame could pass through the top of the gauze and ignite the atmosphere. Therefore, it was always necessary to check the atmosphere with a regular Davy lamp prior to introducing a Pieler lamp in the area to be measured. The second objection was that the oil vessel could rapidly heat up and cause excessive alcohol evaporation. This was obviously more of a problem in the bonneted type lamps because of the lack of cooling. The excessive alcohol evaporation could make the results inaccurate, causes the window to become dim with condensed alcohol vapor, and potentially cause an explosive mixture within the lamp. Usually 20 to 30 were needed between tests to let the lamp cool down. Last, unbonneted Pieler lamps were considered unsafe in explosive mixtures of moderate velocity.

Reading the Pieler Lamp

Basically, the lengthening of the flame above the hood in the lamp corresponds to the following:

For most of the Pieler lamps made, when the methane reaches 2.5% the flame will fill the gauze completely.  This is when the flame extinguisher is used, if equipped.

From studying Pieler lamps in my collection, there is a difference in the measuring scale between bonneted and unbonneted lamps.  Apparently, the restriction of air flow in a bonneted lamp changes the height of the flame caps.

The Pieler lamp saw extensive use in Europe, especially in the Austro-Hungarian region and Poland. It didn’t see much use in Great Britain or the United States. Early examples of the lamp date from the mid-1880’s. I am speculating that the Pieler lamp was in use up to World War II, when reliable electrical or electronic devices were being introduced for methane measurement in mines. In addition, I have seen a Friemann & Wolf catalog from the 1930’s that still listed Pieler lamps. (I would appreciate hearing from anyone who has additional information on the subject)

To view Pieler lamps in my collection, click on the thumbnails to the left!

References:

The Pieler Methane Detection Lamp, Manfred Stutzer.