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General Description and Method of Work

This face, the development of which started in May, 1951, is situated about three miles from the shafts. As it was originally intended to be an advancing single unit face, winnings (see Plan No. 1) were driven 160 yards apart, 15 feet wide and 6 feet high, in the seam in an easterly direction for a distance of 135 yards from the North East 5 Engine Plane, and were then connected by a stenton (No. 24) which was to form the face.

By the time this stage was reached, in April, 1952, it had been decided to instal a German type coal plough at the mine and the newly developed district was considered eminently suitable. As it was desired to try the plough under retreating longwall conditions, the two winnings were therefore driven a further 420 yards, where the retreating face was formed and the plough was installed by October, 1952.

The designed action of the plough, which was rope hauled by means of two electrically driven hoists, one in each gate, was to slice off up to 12 inches of coal at a time and to turn it on to an articulated face conveyor, driven by an electric motor at each end. At the intake roadhead this conveyor delivered on to a chain type feeder conveyor, which in turn fed a troughed belt conveyor whose tub loading point was situated on the North East 5 Engine Plane. The face conveyor was advanced without dismantling by means of 32 pneumatic rams, equally spaced along its goaf side and operated by compressed air supplied through flexible hoses from a pipe range of about 3-inch bore lying directly behind the conveyor for the full length of the face. The rams, the pipes and the pipe couplings were all of German manufacture and all were of light alloy.

The movement of the plough along the face was remotely controlled from the hoist, 67 yards back from the face in the intake. Push button switches controlled both the face conveyor and the plough, the operator working to signals transmitted from 14 rappers incorporated in an intrinsically safe electrical signalling system which extended throughout the length of the face, the current being supplied from a transformer in the power unit.

The combination of plough and articulated conveyor rendered impracticable the adoption of any system of roof support which required the setting of props between the conveyor and the face. Accordingly the management applied for and were granted an exemption permitting them to work the face on what is usually termed a "prop free front" basis.

The system adopted incorporated light alloy coupled bars and friction type yielding steel props, both of German manufacture, the bars being set 3 feet apart and the props supporting them in V formation so that those set to alternate bars formed rows in which their distance apart was six feet. When the face started to produce in October 1952, eleven strip packs were built in the waste. This number was reduced to ten by dropping off No, 2 pack a week or so before the explosion occurred. Until sufficient stone became available in the wastes, old timber was used in making the packs.

As the whole installation was experimental it was only worked on the foreshift each day, being manned by 13 men under the supervision of a deputy, J. Lavery. Very soon after the start it became apparent that the coal was too hard for the plough to slice off in the way intended, and to assist the plough a system of pre-cutting was introduced in which an inclined cut was made near the bottom of the seam by a compressed air driven coal cutter running on the face conveyor and so mounted that the tip of its 3-feet long jib reached the floor at the back of the cut. Pre-cutting however did not fully solve the problem, for the plough then tended to tear off very large blocks of coal which were liable to foul and disturb the roof supports. To cure this, resort was made to shot firing of the undercut coal. This was the stage which had been reached by the experiment at the time of the explosion, the face having retreated 34 yards back from the back rib.

Ventilation

The undersea Low Main workings were ventilated by four main parallel airways, dual intakes and returns, extending inbye to the North East 5 junction from the shafts, where a quantity of 78,000 cubic feet of air per minute entered the two intakes. The Plough Face was ventilated by a separate split of air from the North East 5 Engine Plane, and in October the quantity measured 10 yards from this face in the return was 2,900 cubic feet of air per minute with a firedamp content of 0. 1 5 per cent. From this date the quantity decreased, as reference to the ventilation records given as insets on Plan No, 2 show, and was recorded as low as 1,232 cubic feet per minute with a firedamp content of 0.25 per cent, on the 19th February, 1953, when the last measurement was made prior to the explosion three weeks later.

Precautions against Coal Dust

Some 240 tons of stone dust per month were used, being a consumption of 5½ lbs. per ton of coal produced, which would appear to be an average figure.

The arrangements for the cleaning up of road dust, the spreading of incombustible dust and the sampling and analysing of the road dusts were of a reasonably high standard.

In conformity with the declared policy of the Durham Divisional Board stone dust barriers had been erected in the two roadways leading to the Plough Face. I shall deal further with these barriers later in this Report.

Inspections before the Explosion

Prior to the 23rd March the Plough Face had worked on foreshift only, from 3.15 a.m. to 11.0 a.m. On the three other shifts, which made up the working day in the mine, the Plough Face formed part of a deputy's inspection district. Although nobody was at work in it during these shifts, nevertheless two inspections were made each shift and thus the total number of inspections per day of the Plough Face was eight.

Difficulties experienced in controlling the roof led the manager and his immediate superiors to re-examine the system of support, and it was as a consequence of a visit which they paid to the face in the week prior to the explosion that it was decided to increase the support by reducing the propping distances. This work, which necessitated a re-arrangement of most of the props and bars on the face and involved the temporary use of some wood props and bars, was started on Wednesday, 18th March. At the same time it was seen that the return end of the face was lagging behind the intake end and, in order to correct this, it was arranged to have a succession of cuts along the return half of the face to bring it into line. For the rest of the week all work on the face was confined to those two aspects.

At the end of the Saturday foreshift, 21st March, the face was left ready for cutting, the coal cutting machine being opposite No, 5 pack and the conveyor and supports fully advanced. As there would not be any coal prepared for ploughing on the Monday foreshift, the men, with the exception of H. Davies and J. H. Blackburn, were instructed by Deputy Lavery to attend on the backshift. Davies and Blackburn were instructed to cut the return half of the face on the Monday foreshift in readiness for the .rest of the team, and then remain on the backshift and so work a double shift.

On the following morning, Sunday, the district was inspected in accordance with the system of weekend inspections and reported satisfactory in all respects. Before the commencement of work on the Monday foreshift a pre-shift inspection was made by P. Cockerill, night shift deputy, who at 4.5 a.m. admitted Davies and Blackburn into the district, and in accordance with their usual practice the former went in to the face by the return and the latter by the intake.

The two men met on the face at the coal cutting machine where Blackburn tested for gas, found none, and hung up the detector in the air current, suspending it from a bar. They then started cutting.

Between 5.50 a.m. and 6.35 a.m. J. Musgrove, the foreshift deputy, made an inspection, travelling in by the intake and leaving by the return. He found no gas and all matters appeared to him to be satisfactory, the two men having cut as far as No. 8 pack. After his visit the men changed the machine picks and continued cutting until they reached the return end where they cut out at 8.0 a.m.

Removing the picks from the machine, disconnecting the hoses and turning off the compressed air, they then went for their bait. A quarter of an hour later they resumed work on the face at No, 5 Pack, shovelling the kirvings and fallen coal from the conveyor which they knew from experience was too heavily loaded to run. After they had cleared 50 yards or so Davies, leaving Blackburn to continue alone, went to the control panel at the hoist in the intake and, in accordance with signals transmitted by Blackburn, attempted to start the conveyor. In each case, however, it only moved about 3 feet and then stalled, being still overloaded.

At approximately 9.0 a.m., Deputy Musgrove was making his pre-shift inspection in readiness for admitting the backshift men. Taking the same route as before he spoke to Davies at the hoist, then proceeded along the face making tests for firedamp in the wastes but found none, and noted in passing that Blackburn's detector was in the same place and still alight He came across Blackburn shovelling kirvings from the conveyor at a point about 35 yards from the return end and stayed with him a short time, during which further but unsuccessful attempts were made to get the conveyor to run. Upon Blackburn saying to him, "Tell Lavery (that is, the oncoming deputy) that everything will be right for a clear start", Musgrove passed on to the return end where he found no firedamp, and from there went outbye.