EIACP (PC-RP) on Environmental Problems of Mining

Chowrasi Colliery

This was the first occasion on which on outbreak of fire resulted in an explosion on a very large scale in which coal dust played a prominent part and accounted for destruction over a large area.

The Dishergarh seam, 2.7 m thick and dipping at I in 3.5, was worked through 6 inclines and 6 air-shafts all of which were connected. This seam was known to give off gas in the neighbouring mines and even at Chowrasi mine, minute feeders of gas had been encountered from time to time which, when lighted, burned innocuously until put out. The Rules on the use of safety lamps then were not stringent and Chowrasi was worked as an open light mine except in certain forward drivages where safety lamps were used as a precaution.

On the day of the accident, the surveyor and a sirdar came to extend the chalk centre-line of No.3 Incline main dip gallery and when the surveyor raised his candle near the roof, there was a flame which, in spite of the efforts of the two men to put it out, increased and moved about until a brattice sheet, erected longitudinally in the gallery, caught fire. They then ran away.

About 420 persons were at work in the mine and as the fire spread, many of them ran out. A large quantity of smoke was seen coming out from No.3 Incline. The Manager ordered withdrawal of men through other inclines and stopped the fan. After about 2 hours when a brattice had been put up at No.2 Incline and while attempt was being made to put a stopping at the mouth of No.1 Incline which was downcasting, a violent explosion took place causing severe damage at the tops of the inclines and the air-shafts. Five minutes afterwards another explosion occurred followed by four other explosions at short intervals. The second explosion also was a violent one; but the others decreased in intensity, the last two being slight. The first two were heard distinctly a t Raniganj, 30 km away. In a few hours, flames 20 to 25 m high were coming out of some of the inclines and shafts. Nos. 1 and 6 Inclines and their air-shafts were downcasting strongly and smoke and flame continued to pour out of No.3 Incline and air-shaft and No.4 air-shaft. Owing to the unusual steepness of the incline it acted like a flue. The work of sealing up the 6 inclines and shafts took several days. As a result of the explosions 24 persons were killed belowground and 3 on the surface.

The first explosion was probably caused by the burning brattice cloth and timbers heating up the small coal, which lay on the floor of the galleries and eventually, the solid pillars and coal to such an extent that volatile gases were liberated from the coal in much the same way as these gases are given off in a coke oven. The Dishergarh seam is very rich in volatile gases which are easily liberated from the coal when it is heated. These gases, when mixed with about 10 times their own volume of air and ignited, would explode with great violence and raise into suspension the fine coal dust lying about the sides and roof of the galleries of the mine. The coal dust in turn would explode and raise more dust which would also explode and thus carry the explosion throughout the whole of the workings.

It cannot be stated definitely that the stopping of the fan and the sealing off of No.1 and 2 Inclines had any influence on the occurrence of the explosions, but the significant fact to note is that after the explosions the fire had gained such a hold on the workings as to induce enormous quantities of air to pass down No.1 and 6 Inclines and air-shafts. The fire kept burning of 3 or 4 days without any further explosion occurring. It would probably have been better to have slowed down the fan instead of stopping it altogether.

The sealing off was eventually effected by filling in those inclines and shafts which were smoking and flaming, leaving the intakes untouched. The intakes were subsequently closed gradually with corrugated steel sheets.