Burnley, Lancashire. 22nd March 1962
Hapton Valley Colliery was in the N.C.B. North West Division on the boundary of the County Borough of Burnley.
The structure of management was
- Mr. R. Lowe, Area General Manager
- Mr. J. Whittaker, Area Production Manager
- Mr. W.E. Rawstron, Group Manager
- Mr. A.L. Wier Manager, and Mr. R. O’Hara Undermanager.
On the day of the explosion, Mr. B. Kennedy, a certificated colliery manager was in charge of the colliery in the absence of Mr. Weir. The colliery, which employed three hundred and eighty six men below ground and sixty seven on the surface, had a daily output of about 700 tons of saleable coal all got from two faces Nos.2 and 5 in the Union Seam.
The colliery had three shafts. No.3 was the downcast shaft used for winding men coal and materials, No.4 was the upcast shaft used for winding men only and the No.2 shaft was used for pumping water. The No.4 shaft was equipped with an electrically driven exhausting fan producing 112,000 cubic feet of air per minute and 4.3 inches of water gauge.
Following the completion in January 1962 a surface drift, 1,260 yards long and dipping at a gradient of 1 in 4.16 was brought into use as a second intake. Before this a drift connected with the mine workings, the ventilation of the mine had been assisted by a booster fan situated in the main return airway about half a mile from the bottom of the upcast shaft. Because it no longer made a significant contribution to the ventilation of the mine, the booster fan was taken out of commission and put on a care and maintenance basis in March 1962.
The colliery had always been a safety lamp mine and in addition to the electric cap lamps in general use flame safety lamps were issued to officials and elected workmen as firedamp detectors. These lamps were of the internal relighter type.
The Union Seam was 171 yards deep at the shafts and the only one that was worked at the colliery and was from 3 feet 4 inches to 3 feet 9 inches thick with a hard fireclay floor and a roof of medium strong shale. As a result of faulting, the cover at the face of No.2 District was 242 yards. The seam was gassy and in before this explosion there had been three ignitions of firedamp at the colliery.
On the No.1 face, which was discontinued, there was an ignition during shotfiring on 23rd June 1960 and another in the undercut attributed to frictional sparking on 28th July 1960. The third ignition also ascribed to fictional sparking in the undercut occurred, in No.2 return gate stable on 4th April 1961.
To reduce the risk of ignition in the undercut, the management had installed cutting jibs with an internal water feed. The cutting machine on the main face line was also fitted with a compressed air/water ejector for ventilating the undercut, but this additional safeguard could not be applied to the machines that were undercutting in the stables.
The No.2 face was 155 yards long and was advancing southwards in the solid on a rising gradient of 1 in 6.25 with a very slight rise from the intake gate to the return gate. It was started in September 1960 and the face had advanced 765 yards at a rate of about 10 yards per week. The No.5 face was advancing in the same direction and was 400 yards behind and 33 yards to the east of the No.2 face.
At the face, the coal was cut about 1 foot above the floor level by an electrically driven machine mounted on an armoured flexible conveyor. Until the 3rd. February 1962, the depth of the cut was 6 feet 6 inches but on that day the jib was changed and the depth of the cut increased to 7 foot 6 inches.
Coal in the stables was cut at the floor level by shortwall machines. After cutting all the coal was won by explosives and compressed air picks. The same type of explosive was used in taking down the ripping gate which were kept well up to the face. The normal cycle of face operations was as follows:.-
The afternoon shift advanced the face conveyor, drilled shot holes in the face, withdrew supports from the waste, drilled and cut the stables and ripped the intake gate. The night shift ripped the return gate, cut the face line and commenced filling.
The day shift completed the filling.
The roof at the face was supported by friction type props set to corrugated steel bars 8 feet long. Additional frictional props were set as breakers at the edge of the waste which was completely caved between the six yards wide intake gate pack and the 8 yards wide return gate pack. The intake gate was 14 feet wide and 10 feet high and the return gate, 10 feet wide and 8 feet high. These were supported by arched steel girders which were tilted and backed with by fire resistant wood boards.
The coal from the conveyor face was transferred to a belt conveyor in the intake gate. This was the first stage of a trunk conveyor belt system to the bottom of the shaft.
Some supplies reached the face from the surface drift and the intake gate, using the tub pack provided in that gate. Other supplies came down No.3 shaft and along the main intake airway in the tube to the cut-back. There the tubs passed through separation doors into the return airway where they were taken by endless rope haulage to a point in the return some 300 yards outbye of the face ripping. The tubs were then hauled inbye by and electrical engine direct rope engine situated near the face ripping.
The ventilation records show that for some months before the explosion, the quantity of air, as measured at a point in the intake gate 10 yards outbye from the face, was slightly in excess of 20,000 cubic feet per minute. The records also show that during the thirteen months before the explosion, the firedamp content of these samples collected at a point in the return gate, 10 yards from the face varied between 0.4 and 0.7 per cent but occasionally it was outside these limits.
Firedamp was drained by holes 120 feet long bored from the return gate into the shale above the waste at intervals of 35 yards. The holes were connected to a pipe 6 inches in diameter which was increased to 8 inches in the main return to the bottom of No.2 shaft and to 12 inches in the shaft. The firedamp was drawn from boreholes and discharged to the atmosphere by an exhauster on the surface. The quantity of gas drained averaged over 100 cubic feet per minute which represented about 55 per cent of the make firedamp on the face.
The practice was to fire shots in the intake gate stable and also in some of the top coal on the face during the night shift to facilitate the start of filling operations, The return gate stable was fired either at the end of the night shift or at the start of the day shift according to how work had progressed. The remainder of the top coal followed by the bottom coal was fired during the day shift. The intake gate ripping was fired on the afternoon shift and the return gate ripping on the night shift.
In addition to the deputies who were not authorised to fire more than 10 shots per shift there were shotfirers available on the day and night shifts and they each carried 40 detonators. In order to ensure that all demands for shotfiring were met, some of the shotfirers shifts were 'staggered' with the main working shifts. As a result there were frequently three shotfirers available at the beginning of the day shift.
The volatile content of the coal was 32 per cent but the management had not formally declared this figure to His Majesty's Inspectors and were thus required by law to ensure that a minimum of 75 percent incombustible materials was always present on the roof, side and floor of the roadways. At the last statutory sampling before the explosion the incombustible content of most of the road dust samples was well in excess of the minimum required.
A stone dust barrier consisting of seventeen heavy shelves and eight light shelves covering about fifty yards of roadway were in the intake gate, about three hundred yards from the ripping. One hundred yards further, inbye there was a similar barrier of twelve light shelves. Automatic firedamp alarms were not used at the time of the explosion.
The general impression created by witness was that the ventilation of the district had always been good and that men working on the face were obliged to wear coats or woollen garments to keep warm. There were no reports of firedamp having been detected other than occasionally in the return gate stable.
The day before the explosion, on the afternoon shift of the 21st. March, the face conveyor was moved over, the waste drawn off, the face and stables drilled, the coal in both stables cut and the intake gate ripped. Mr. J. McKillop, the deputy in charge of the district, fired the ripping. In his report for the shift he noted that there was broken roof in the intake gate stable and his recollection was that the waste behaved quite normally in that as the supports were drawn it hung first for ten yards and then stared to cave progressively throughout it's full length.
On the following night shift, the district was in a charge of Mr. R. Jackson, a deputy, and the main operations in progress were the cutting of the coal on the main face line and the ripping of the return gate. Work proceeding normally and in spite of a late start, cutting was completed before the end of the shift.
The jib of the machine drawn out of the cut and the electric cable was detached and taken into the return gate. Jackson, who examined the district twice during the night shift observed nothing unusual but did notice a slight roof break of about 2 to 3 inches throughout most of the face.
His last visit to the return gate stable was soon after 6.30 a.m. and although the stable had been cut on the previous shift he found no firedamp there. In his opinion the ventilation was very strong. He travelled the return gate twice and on both occasions observed three empty tubs and two bogies near to the direct rope hauler and attached to the rope. There were a few small roof cavities in this gate, apparently caused by the deterioration of the backing boards, which had allowed roof dirt to fall through.