Author: luckacco@hotmail.com

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Ashworth-Hepplewhite-Gray Lamps

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The Ashworth-Hepplewhite-Gray lamp, also know as the A-H-G or Gray lamp, is one of the earliest safety lamps designed for firedamp testing.  The basic design of the lamp includes hollow standards running vertically for admitting air from the top or near the base, and feeding the flame in an underdraft fashion.  Through utilizing shutters, the lamp can admit air from only the top of the lamp for testing of thin layers of gas close to the roof.  While just being used as a light source,  the top shutter would be closed while the shutters towards the bottom of the lamp would be opened. This would provide excellent illumination (about .75 candlepower) and safe in sir currents up to 6,000 feet per minute.

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The A-H-G lamp saw many years of service. There were many, many variations made.  Most have 4 standards, but some were made with 3.  Most were made of brass, some were made of aluminum, and some were brass and aluminum. The “Gray-Beard” lamp incorporated a Beard-Mackie indicator with the A-H-G design.

 

“Gray-Beard” Lamp. Click to enlarge.

Most of these lamps were made England by Davis of Derby, but J. Cooke, Teale, and Akroyd and Best all made them too.  In the US, American Safety Lamp & Supply and Davis of Baltimore made them.  I have not been able to identify any makers on the Continent, though I suspect that there must of been at least one maker.  Gray lamps where used from the 1880’s till the 1920’s.

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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.

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Friemann & Wolf Pieler Lamp Model 701

This particular model of Friemann & Wolf is the rarest of the three models advertised: the 700, 701, & 702.  This lamp is essentially a model 700 with a smooth bonnet.  And, like the model 700, it only measures up to 1 1/2 % methane.  The serial number on the lamp is 783,005.  It is fitted with a model 1897 igniter, and a flame snuffer.  This lamp is about 1905 vintage, and is unfired. 

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Ostrau (Ostrava) Pieler Lamp

This all brass Pieler was made by either Joseph Jermir & Comp, Erste Ostrauer Sicherheitslammpenfabrik, or “Union” Eisenindustrie GES.M.B.H. All of these manufacturers were in the Ostrau (now called Ostrava; part of the Czech Republic) area, and made lamps of similar design. This particular lamp has a sliding bonnet with a scale that measures up to 2 1/4% methane.  The magnetic lock is marked “Broucek Patent”, which is a famous type of igniter that was used in the Ostrau area, even though the lamp is equipped only with a flame snuffer and no igniter.   Circa 1900-1910.

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John Mills, New Castle Pieler Lamp

This is one of the few Pieler lamps that was made in England.  It seems that the British mining industry preferred their Ashworth lamps over lamps invented on the Continent.  This particular lamp is a very early design.  Removable bonnet, no igniter or flame snuffer, and glass viewing window instead of mica.  Note the “standard” painted on the glass.  There is no scale, but there are references in at least one book indicating that early Pielers used glass that had a scale etched on them.  Obviously, the glass probably didn’t last too long.  The lamp is probably circa 1890.

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Friemann & Wolf Pieler

Very early Friemann & Wolf Pieler, Serial No. 46710.  Notice that the lamp is made without an igniter or wick snuffer.  Also, instead of a scale, the lamp is equipped with a simple pointing device that slides up and down one of the standards.  This is to mark the height of the flame during gas testing.  Circa 1888.

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Friemann & Wolf Pieler

Early Friemann & Wolf Pieler lamp, serial no. 80643.  This lamp shows how prolific a manufacturer F & W was.  This lamp could of been made to a custom spec. The basics of the lamp is similar to a no. 700, but modified with a removable bonnet with a hinged door, and a vertical scale attached to a standard. This style is typical of Bohemian and French Pielers.  It looks like F & W took their German style, and modified it for these different markets.  Lamp is made with a magnetic lock that is stamped “C Wolf Patent”.  No igniter, but fitted with flame snuffer. Gauze is iron instead of the typical brass.  Probably circa 1890.

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A. Benitschke’s Sohn Pieler Lamp

A. Benitschke’s Sohn was a well-know manufacturer of mining lamps in what was Bohemia (Czech Republic region).  This particular Pieler lamp is fitted with a removable bonneted that has a sliding window for observation.  Note the vertical scale on one on the standards. Magnetic lock, flame snuffer, but made without igniter.  Instead of a brass gauze that Pielers usually have, this lamp gauze appears to be made out of stainless alloy.  In addition, the gauze weave is an unusual twill pattern.  Circa 1920’s.

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History

Pieler Lamps

Early Friemann&Wolf

Early Friemann&Wolf

John Mills, New Castle

A. Benitschke’s Sohn

Ostrau Pieler

F&W Model 700

F&W Model 701

F&W Model 702

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Ashworth-Hepplewhite-Gray Lamp

A-H-G Lamp made by Davis of Derby. Early design with straight standards and no middle supporting disc.  The workmanship on this lamp is superior compared to later versions. It shows that these particular lamps were not mass produced like lamps used for regular lighting.  Circa 1895.

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