Methanometer
Encyclopedia
A methanometer is an instrument used to measure methane gas in the air of a mine. The Mine Safety Appliances Company Ltd.
manufactured the first type - W8 Methanometer around 1950.and it was approved for use by the Ventilation Regulations of 1947. The Methanometer could be powered by an Edison battery cap lamp and it could be carried on a miner's belt with other tools. Methane is the main gas present in firedamp
. It is highly explosive and had previously been detected by the blue halo effect it gave to the flame of a safety lamp
.
By 1883, several instruments for measuring methane concentration in air had been developed. These relied on such methods as the differential heating of an incandescent platinum filament, or by measuring the higher absorption of infrared radiation by gas containing methane.
A catalytic-type methanometer uses an array of four heated wire filament elements, two active filaments are coated with a catalyst, arranged in a Wheatstone bridge
with two inactive elements that have no coating. When exposed to methane-contaminated air, the coated filaments heat up due to oxidation of the methane, and the resulting imbalance in the resistance
of active and inactive elements can be displayed on a calibrated meter. Such instruments require oxygen to work and can be inaccurate if methane concentration is very high. The catalyst can be poisoned
by exposure to some chemicals, again making the instrument insensitive to methane.
Mine Safety Appliances
Mine Safety Appliances, or MSA, is a maker of sophisticated safety products that help protect workers who may be exposed to a variety of hazardous conditions...
manufactured the first type - W8 Methanometer around 1950.and it was approved for use by the Ventilation Regulations of 1947. The Methanometer could be powered by an Edison battery cap lamp and it could be carried on a miner's belt with other tools. Methane is the main gas present in firedamp
Firedamp
Firedamp is a flammable gas found in coal mines. It is the name given to a number of flammable gases, especially methane. It is particularly commonly found in areas where the coal is bituminous...
. It is highly explosive and had previously been detected by the blue halo effect it gave to the flame of a safety lamp
Safety lamp
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...
.
By 1883, several instruments for measuring methane concentration in air had been developed. These relied on such methods as the differential heating of an incandescent platinum filament, or by measuring the higher absorption of infrared radiation by gas containing methane.
A catalytic-type methanometer uses an array of four heated wire filament elements, two active filaments are coated with a catalyst, arranged in a Wheatstone bridge
Wheatstone bridge
A Wheatstone bridge is an electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component. Its operation is similar to the original potentiometer. It was invented by Samuel Hunter Christie in 1833 and...
with two inactive elements that have no coating. When exposed to methane-contaminated air, the coated filaments heat up due to oxidation of the methane, and the resulting imbalance in the resistance
Electrical resistance
The electrical resistance of an electrical element is the opposition to the passage of an electric current through that element; the inverse quantity is electrical conductance, the ease at which an electric current passes. Electrical resistance shares some conceptual parallels with the mechanical...
of active and inactive elements can be displayed on a calibrated meter. Such instruments require oxygen to work and can be inaccurate if methane concentration is very high. The catalyst can be poisoned
Catalyst poisoning
Catalyst poisoning refers to the effect that a catalyst can be 'poisoned' if it reacts with another compound that bonds chemically to its active surface sites. This effectively reduces the usefulness of the catalyst...
by exposure to some chemicals, again making the instrument insensitive to methane.