Date of the Accident – 22.1.1979
Owner – North Eastern Coalfield, Coal India Ltd.
Number of persons killed – 16
Place – Dibrugarh District (Assam)
A gas explosion occurred on Monday, the 22nd January, 1979 after a rest day on Sunday. The first shift commenced at 7.00 a.m. and as per the customary practice 320 workers went belowground at 6.30 a.m. The explosion occurred at about 8.30 a.m. and resulted in the death of 16 persons: 4 due to burn injuries and 12 due to inhalation of poisonous gas produced as a result of ignition of methane.
Baragolai Colliery consists of the Baragolai underground mine and small manual quarries at Tikka and Namdang Sections. The coal deposit at Baragolai is in the form of a syncline with its north limb inclined at 30° to 33° and the south limb having a steeper dip of about 70°. There are 5 coal seams with a number of thin seams occurring in patches. The area receives 250 to 350 cm of rainfall annually and the mines are highly watery.
The underground workings are approached from the surface by a pair of cross-measure drifts (adits), each about 1.6 km in length and driven from; the foot of the hill at zero level to touch the north limb of the syncline. One of the drifts has been continued to touch the south limb and surface connections are made in the 20 foot seam. In the north limb 5 dip entries have been driven upto 8 level and levels are opened on either side, east and west.
In the 60-foot seam, development and depillaring are done in close succession and at the time of the accident two depillaring districts were working, one on the eastern side where coal was extracted between 4L and 5L and another on the western side where coal was extracted between 5L and 6L. The method of extraction, known as “Bhaska” method and practiced only in this coalfield, consists of splitting the pillars into stooks of 10m x 10m and then widening and heightening the galleries to form self supporting dome structures.
The two main adits act as intakes as well as drainage outlets for the 60-foot seam. One of these adits, being the main haulage roadway: connects these entries to the workings below. There are 5 dip galleries going down below zero-level: 3 are used for hauling coal tubs upto zero-level, one is used for traveling purpose and the fifth carries the water pipes.
Ventilation of the underground workings is effected by a main surface fan in a drift near Namdang Inclines and it ventilates the development – workings of the 20-foot and 60-foot seams as also the depillaring districts in the 60-foot seam. Three booster fans help to ventilate the different districts. In addition, there are 3 auxiliary fans.
The source of gas was a large cavity in the roof. Gas accumulated in this cavity and was pushed down by a further roof fall in the cavity. The source of ignition was an arc from the live electric cable which was cut by steel supports dislodged by the roof fall. This roof cavity had not come to anybody’s notice as it was covered by steel arches and corrugated steel sheets. The existence of the cavity had been established only by noting that the volume of debris from the roof fall was much less than the volume of the void left behind as a result of the fall.
At about 8.30 a.m. on 22.1.1979 there was a fall of roof measuring about 7 m x 3.3 m in a cavity in the cross-measure drift resulting in increase in the height of the cavity to 7 m and exposing a portion of a 1.3 m thick coal seam and another 0.2 m thick coal seam. This fall in the cavity dislodged steel channel sets, corrugated steel sheet coverings, rail and timber pieces. The steel and timber pieces which fell down damaged a live cable in the drift and caused it to emit an arc. The arc ignited the gas pushed down from the cavity by the fall of roof. The flame of the gas ignition developed rapidly and moved swiftly towards the north. 3 workers who were near the haulage engine in the drift came in direct contact with the flame and were severely burnt and died in a short time. Five other workers who were in the zero-level also sustained bum injuries. One of them died later.
Death due to asphyxiation
The products of combustion containing poisonous carbon monoxide gas travelled along zero-level west and went down all the 5 dip galleries. About 250 persons were present below zero-level at the time of the accident. They got the pulsation of the mild pressure wave due to the explosion and at some places smoke was seen coming in. They all got panicky and attempted to go up to zero-level. 50 to 60 of them chose to go up through D2 haulage roadway which was the shorter route whereas the others followed the advice of the overman and took the usual travelling roadway. The workers who took the steeper haulage roadway met with smoke some way up and were overcome by CO, 12 of them died on the spot, the rest were partly unconscious and some of them were found to have rolled down the dip. All those who took the usual travelling roadway route were not affected at all. Though the haulage roadway was also the intake, it was affected due to choking of the south limb tunnel due to roof falls. Later, the haulage roadway was found to have been cleared of poisonous gases by 9 a.m. i.e. within half-an-hour of the explosion.
Rescue operations and first-aid
The Court expressed its satisfaction with the rescue work and observed that rescue operations were conducted with a commendable sense of urgency and responsibility by the officers and men of the colliery and first-aid was rendered promptly, where necessary.
The Court concluded that neither the management nor any individual person could be held responsible for the accident.
a) Self rescuers should be issued to all underground workers.
b) Steps should be taken to manufacture self-rescuers indigenously so that the needs of the industry are met within as short a period of time as possible. With the nationalization of the coal industry, CIL should take the initiative for encouraging indigenous manufacture of the equipment.
c) Training should be given to all workers in the use of self-rescuers and those who have been issued the rescuers must be persuaded to use them.
2. Alternate source of power:
On the day of the accident, the main fan had stopped at 6.45 a.m. and again at 8.20 a.m. for short periods. Although the stoppage of the fan did not in any way contribute to the accident, the Court recommended that the management should take action to provide a stand-bye generator or a separate transmission link as soon as possible, so that alternate source of power to the main ventilator is available immediately.
3. Parties to DGMS inquiries:
A representative of the management and a Workmen’s Inspector should be associated with inquiries conducted by DGMS officers.
4. Operation of earth leakage devices:
While looking into the possible sources of ignition, it was brought to the notice of the Court that the time taken for operation of earth leakage device was 1/50 of a second whereas an ignition could take place if sparking in an inflammable mixture lasted for 1/250 of a second. In the present case it had lasted for a minimum time of 1/50 of a second and it was adequate for igniting the gas mixture. To reduce incendive sparking it seems desirable that studies and investigations are undertaken to minimize the time for operation of earth leakage devices. It would appear that this time could be reduced to as low as one millionth of a second. Appropriate authorities and agencies may take up this matter for investigation.