The colliery was at Gyfeillon in the Rhondda Valley about two miles from Pontypridd in the heart of the South Wales Steam Coal Field. It was one of the largest collieries in the district and was owned by the Great Western Colliery Company, Limited with Messrs. Forster Brown and Rees, mining engineers of Cardiff as the consulting engineers for the company. The managing staff consisted as Mr. Hugh Bramwell, agent, Mr. William James, certificated manager, Mr. David Rees, certificated undermanager, Mr. Evan S. Richards, holder of a First Class Certificate but acting as assistant manager. Mr. W.M. John was the surveyor and Mr. R.L. Molyneaux the mechanical engineer. There were also three overmen and seventeen firemen. Mr. Bramwell was a mining engineer and certificated manager and had succeeded Mr. H.T. Wales of the 1st. January. There were three shafts at the colliery. The Hetty was the downcast and was sunk to the Six Feet Seam and was 398 yards deep. The No.2 Pit was the upcast to the Five Feet Seam at a depth of about 472 yards and the Tymawr Pit was an upcast was also sunk to the Five Feet Seam at 472 yards. Coal was raised at all the shafts. At the Hetty the Four Feet and Six feet Seams were worked. The Four Feet Seam lay 25 yards above the Six Feet and was passed through in the shaft but for greater safety and convenience in winding, all the coal was raised from the Six Feet Seam, the lowest landing in the shaft. At the No.2 Pit only the Five Feet Seam was worked and raised from the Five Feet landing. The Tymawr Pit the Five Feet Seam was being worked and raised for, the Five Feet landing.
The ventilation of the colliery was produced by two Schiele fans each of fifteen feet three inches diameter. One was place at the top of the No.2 Pit which was elliptical in section measuring 14 feet 4 inches and 10 feet 9 inches. the other was placed near the top of the Tymawr Pit which was also an elliptical shaft 16 feet by 10 feet. The downcast shaft, the Hetty Pit, was circular and 16 feet in diameter. About 270,000 cubic feet of air per minute circulated through the workings which were recognised as amongst the fiery in the South Wales District.
The whole of the colliery was equipped with modern machinery and appliances geared to a large output of steam coal and both the Hetty and the No.2 Pits had been safely worked since 1877 when the shafts were first sunk to the steam coal measures. Before this house coal had been worked. The Tymawr Pit had only been recently acquired by the Company and sunk by them to the lower steam coals. Previous to this the east workings in the Four Feet from the Hetty Pit had been extended beyond the Tymawr Pit and since the latter was the upcast shaft, it was more convenient to connect these workings to it for the purposes of ventilation, so that the large district of the Four Feet Seam at the Hetty Pit had a direct connection with the Tymawr upcast in that seam.
The explosion affected the workings in the Four Feet Seam to the east of the Hetty Pit and their connections with the landing in the Six Feet Seam.
The total number of men working in the three pits was about 1,460 of whom 950 were at work on the day shift on the day of the accident. Of this number 212 were in the east workings of the Four Feet Seam all of which were put in danger from the resulting fire. Of the 212 persons, 78 were in the East main Dip and 134 in the East Main Level.
Those in other parts of the mine, although never in danger from the fire, were all quickly withdrawn and sent to the surface.
Haulage by machinery was largely used and in common with many of the larger collieries, compressed air was used for the transmission of power for the underground machinery from the compressing plant at the surface. There were 15 haulage engines in the whole of the seams and it was at one of these engines that the disastrous fire originated.
On the East Level in the Six Feet workings, about 120 yards from the Hetty Pit, a main road, the ‘East Hard Heading’, branched off at right angles and this road rising 1 in 6, cut the Four Feet at 156 yards. It was here where the engine in question was situated. From this point the East Main Dip continued in a straight line for 270 yards and then turned to the right where it was called Sam Cull’s Dip and continued a further 400 yards. At 176 yards down Sam Cull’s Dip a pair of headings branched off at right angles to the right and 160 yards further down two headings branched off to the left. The headings to the right extended 396 yards to the rise and those to the left 114 yards to the dip. These headings and the 29 stalls at work in them formed one ventilating district, which was termed the East Main Dip and which was ventilated from the No.2 upcast shaft.
From the top of the Easy Hard Heading just inside the engine, another road called the ‘Four Feet East Level’ branched off to the right for a distance of 463 yards to the top of ‘Thompson’s Dip’. Witt’s Level was reached from Thompson’s Dip by branching off to the right and this extended 548 yards to the working headings to the rise. Thompson’s Dip continued in a straight line for a further 363 yards. On the east side there was a level 143 yards long to the working heading and on the west side another level which reached the last of the three headings for 288 yards.
The three divisions formed one large district ventilated to the Tymawr upcast shaft. These roadways were the haulage roads and the intake airways and all had a minimum square section of 50 square feet and beyond the engine for a few yards where it was split. About 72,000 cubic feet of air per minute passed up the East Hard Heading. About 57,000 cubic feet went to the East level and 15,000 to the East Main Dip, passing the engine at about 20 feet per second.
The mine was very dry and there were provisions for damping the roadways and a system of spray jets which were fixed at intervals of about 40 yards in the principle intakes. The water came from the surface by pipes some two and some one and a quarter inches in diameter, down the shaft and along the haulage roads. There were 5 miles of piping laid for this purpose.
The engine was fixed immediately over the roadway on pitch pine beams resting on the side walls of masonry. The engine had two cylinders with a twelve inch stroke which worked two loose drums by spur gearing, geared 4 to 1. The drums were three and a half feet in diameter and each had a brake fitted consisting of an iron strap to which were bolted elm curb blocks. The brake extended for half the circumference on the drum and was four inches wide. The brake leverage on the drum working the main rope was 15 to 1 and that of that working the tail rope was 45 to 1. The engine worked the haulage on the East Hard Heading, the East Main Dip and the East Level as far as the top of Thompson’s Dip.
Six trams at a time were hauled up the East Main Dip by the main rope drum and lowered down the East Hard Heading by the tail rope drum. Twelve trams at a time were hauled along the East Main Level by the main rope and lowered down the East Hard Heading by the tail rope drum. While a journey was being hauled from the East Level, the tail rope was attached behind and drawn out, so that the next empty journey could be hauled in by this rope. The rope passed round a sheaf at the inner end of the East Level. When a journey of twelve trams weighing 19.2 tons, was being lowered by the tail rope drum down the Hard Heading there would have been a strain of 3.2 tons on the drum and the breaking would have been very severe.
The woodwork holding the engine consisted of two wooden cross beams 12 inches square and, 13 feet long, one cross beam 12 by 10 inches and 13 feet long, one cross beam 8 inches square and 10.5 feet long, two longitudinal beams 14.5 by 8 inches and 16 feet long, a platform of one and half inch deal, 10 feet by 4 feet and the blocks that formed the brakes. The engine was in the main intake and the engineman had placed a canvas brattice cloth at the ends and below the drums to give shelter from the strong air current and the dust that was blown off the passing trams. Except for a small quantity of cylinder oil, olive oil for the bearings and some cotton waste for cleaning the engine, there was no inflammable material about other than the woodwork and the canvas.
There would have been a considerable amount of oily and greasy material on the wood work below the drums. The place was lit by an electric lamp which was the last of a series from the shaft bottom.
Fire had not been anticipated here and there was no provision to deal with it. There was an upright water pipe which supplied water to spray jets which had a few feet of hose attached. The pipe had a tap so that water was readily available. One bucket was kept near the engine. The engineman who normally worked the engine had been absent for some days owing to ill health. This man appeared to have been in the habit of keeping the bucket full of water and occasionally using the water to cool the brake blocks. The engineman on duty at the time of the accident did not provide himself with any water.