In a coal mine where Methane gas is likely to be present, it is tested with the help of a flame safety lamp in two ways.
- ACCUMULATION TEST (to determine the presence of methane)
- PERCENTAGE TEST (to determine the percentage of methane )
ACCUMULATION TEST:
The purpose of this is to ascertain if there is any accumulation of gas in places where it may be suspected or is likely to accumulate. In a mine, If the mining sardar finds accumulation of gas in any place, he has to report the matter to the overman who should take steps for determining its percentage and its removal.
To test the accumulation, Switch off the cap lamp, raise the flame safety lamp cautiously with normal size of flame, or the flame is slightly reduced, and watch its behavior,if it elongates i.e.if it spires or jumps,the percentage of gas can be taken as nearly 3% or more. No efforts should be made to raise the flame safety lamp higher than is necessary to test its accumulation because this results in keeping the flame is richer mixture of methane and air which may explode inside the lamp and extinguish the flame. Even if the mixture is not explosive the gas will burn inside the lamp and it may produce Carbon dioxide which will extinguish the flame.It is unnecessary to conduct the percentage test when the flame spires up in a safety lamp as it is clear the the gas percentage is not less than 3 %.
If by mischance, the firedamp begins to burn within the gauze, it should in no circumstances be allowed to continue to burn.The examiner should his lamp from the air current, Hold it near the floor, and retreat carefully to fresh air. If this is not possible, he should smother out the flame, e.g. by covering the air-inlet holes with a handkerchief.
PERCENTAGE TEST :-
To conduct percentage test for methane with flame safety lamp remove all bright light in the vicinity and switch off the cap lamp. Lower in flame of the safety lamp with the regulating knob till there is a continuous blue line(actually, curved line) across the top of the flame just above a speck of white (or yellow) light as shown in the plate. This should be done, not in a place where gas percentage is to be detected, but at a place nearest to it and free from gas. When firedamp is present in the air at the spot of a non-luminous flame (bluish) which varies in height depending on the percentage of the gas. The size and height of non-luminous flame produced by the burning of the gas(gas cap) also depends on the size of the wick and quality of the fuel used. Hence for determining the gas percentage, the lamp to be used, the size of the wick, and the fuel have to be standardized.
An oil flame safety lamp, an convenient, handy and inexpensive device for detection of firedamp has certain limitations.
- It can only be used by the persons trained for the purpose.
- Even in most experienced hands, it can detect fire damp percentage not below 2%.
- It can be used for detection only in the accessible process within the reach of the person resting for the gas.
If black damp or carbon dioxide is present in air , the flame of oil safety lamp will diminishes in size and will be extinguished if carbon dioxide percentage is 3 more.
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| TESTING FIREDAMP BY FLAME SAFETY LAMP |
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