41. The percentage of inflammable gas in an u/g coal mine should not exceed
42. A gas mixture contains CH4, C2H6 and H2 with respective concentration of 75%, 15% and 10% by volume. The lower explosibility limit of CH4, C2H6 and H2 are 5.0%, 3.3% and 4.2% respectively. The lower explosibility limit of the gas mixture, in percentage, is
43. The voltage range of D6 methanometer . . . . . . . .
44. Ascensionally ventilated coal mine inclines ideally should have a higher methane layering number when compared to descensionally ventilated inclines. The reason is
45. An air sample produces 8% CH4 and 3% H2. If the lower flammability of CH4 is 5% and H2 is 4%, what is the lower flammability of the mixture?
46. Which one of the following is used as an escape apparatus in u/g coal mine?
47. The fan drift pressure readings and fan quantities are measured to be 500 Pa and 65 m3/s respectively at the time when NVP aids fan pressure. On reversal, the fan delivers a quantity of 50 m3/s while acting against NVP with fan drift pressure of 600 Pa. Assuming that the NVP remains constant in both cases the total resistance of the mine in Ns2/m8 will be
48. Samples of air collected in the intake and return gate roads of an advancing long wall face show 0.25% and 0.75% CH4, respectively. The panel has a production of 400t in an 8 hour shift when an air quantity of 18 m3/s passes through it. Then the methane emission in m3/te of coal mined is
49. The type of fire extinguisher that must NOT be used in case of fire in an electric substation located in an underground metal mine is
50. The S.I unit of barometric pressure is
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