1. Description of the Colliery and Method of Working
The Denaby and Cadeby Main Collieries are situate in the Don Valley, South Yorkshire, and are about 2,000 yards apart from each other, being nearly midway between the towns of Doncaster and Rotherham. The area of the mineral tract being worked byt he Colliery Co. comprises about ten thousand acres.
The two shafts of the Cadeby Main Mine, which is situate close to Conisborough Railway Station, are sunk to the Barnsley Bed the only seam worked at this mine – at a depth from the surface of 763 yards, on the dip side of a large fault, which has a throw to the south of 126 yards (see Fig. 1), the coal on the north side of the fault being won by a pair of headings driven through the fault.
The output from this mine is about 3,000 tons a day, coal being wound at both of the shafts, viz., the No. 1 shaft (downcast) and the No. 2 shaft (upcast}. Both shafts are 16 feet in diameter, and 752 and 738 yards in depth respectively. Coal is wound at the No. 1 shaft from the bottom. At the No. 2 shaft the coal wound is brought to a temporary inset on a level with the seam on the north side of the fault. An inset is, however, being made at the bottom of this shaft and is practically completed, to {which all the coal drawn at this shaft will in future be brought. A portion of the coal worked on 4 the north side is brought to the No. 1 shaft, being lowered down by means of a staple pit sunk from the north side level to the south side level,
The average section of the Barnsley bed at this mine is as follows;-
Roof
_ Bind. . Ft. ins. Ft. lns.
Seam-
Coal (day bed) 1 1
Dirt (bag dirt) 0 6
Coal (bags) (timbered to at face
and left up to form a roof)1 3
Coal (top softs) 1 11
Coal (hards) 3 4
Coal (bottom softs) 2 0
Floor
Fireclay or shale.
9 7 0 6
So that according to the section the thickness of coal worked is 7 feet 3 inches; and 2 feet 4 inches of coal, or 2 feet 10 inches of coal and dirt, is left up last and allowed to fall between the packs in the goaf or waste. The under-manager of the colliery, however, informed me that 6 feet 6 inches was the height of coal generally got, and that from 10 to 20 inches was left. But of this coal about 40 per cent appears to have been recovered from the waste and sent to the surface. In the roads the bags and day beds are ripped down and sent to the surface.
A section of the seam at the shafts and of the strata immediately above and below the Barnsley bed is given below:-
(Detailed section included showing strata of rocks from 731 yards to 753 years from the surface)
It will be seen that about 49 feet above the Barnsley bed is a seam of coal 2 feet 2 inches in thickness, a fact which has an important bearing in respect of part of my Inquiry. The top coal of the Barnsley bed is of inferior quality and mixed with’ dirt. The roof of the seam is bind, variable as to hardness, being harder in the South District area than in some of the other districts of the mine. It constitutes a moderately good roof. The Barnsley-bed is a gassy, seam, and though, at any rate at Cadeby, not subject to blowers or sudden irruptions of gas, the under-manager, Mr. Bridges, informed me, that a weight coming on in No. 2 pit, some years ago, it was found necessary/to, withdraw the whole of the men from the pit on account of gas in South Yorkshire, this seam is peculiarly liable to spontaneous combustion.
At this particular colliery there have been no less than 35 fires due to spontaneous combustion-to work it safely requires, therefore, the greatest care and vigilance on the part of the management.
The dip of the seam is at the rate of about 1 in 14°to 1 in 12 to the south-west. The workings of the mine are divided into five main districts, viz.
The first North district,
The second North district,
The East district, ·
The South district,
The West district.
The system of working practised is the longwall, the distance between the gate roads being usually 40 yards. Packs are built on either side of the roads of a width of 7 feet, 6 inches, and every seven yards a gob pack is built and made 6 feet wide. The material used for building the packs is stone obtained from the waste and from the ripping in the gates. In the main roads, a good deal of ripping has to be carried out in the bind roof, which has the effect of contributing to the formation of stone dust, a fact which as will be shown shortly, had an important bearing in limiting the extent of the explosions.
All the coal was got by hand, there being no mechanical coal-cutting, ·nor were mechanical conveyors used for transporting the broken down coal along the faces; as however the coal is fairly friable a certain amount of dust was made at the face, but not in an unusual quantity
(a). Explosives
No shots were allowed to be fired except in stone drifts, and then only at week-ends when few persons were in the pit, and, as an additional safeguard, the manager alone was permitted to fire the shots.
(b) Haulage.
The mechanical haulage of the coal was carried on in the main intakes and the system of haulage in use was the endless rope electrically driven from the bottom of the shaft. The secondary haulage was performed by horses and ponies.
(c) Ventilation;
The total volume of air circulating in the mine was, at the time of the accident, about 163,000 cubic feet per minute, under a pressure (water gauge) of about 3-} inches. This ‘is drawn through the mine by a Schiele fan, 21 feet in diameter, and making about 119 revolutions per minute. A Waddle fan, 9 feet in diameter, electrically driven, which is kept as a stand-by in case of breakdown of the Schiele fan is being replaced by a reversible Sirocco fan. Although the Cadeby mine is connected with the Denaby mine by means of an emergency outlet the ventilation system of the two mines is quite separate, and the iron doors in this outlet are kept locked.
`The last entry made in the ventilation book before the explosion was on June 28th or ten days before the explosion, and contained the following particulars:
(Ventilation Chart for all districts included)
(d) Safety Lamps
With the exception of some of the lamps carried by officials, and a number of electric lamps, used when working at fire holes, the type of safety lamp found in use at the Colliery is the Marsaut
It may be mentioned incidentally that the safety lamps found in the pit after the disaster were examined and the vital ones were found to be intact. Several on the 14 level were broken and one on 19`s Crossgate had been broken from the outside.
(e) Surface arrangements for prevention of underground deposition of dust
The surface arrangements are admirably designed towards preventing the, floating dust produced by movement of the coal at the tipplers, screens, conveying belts and hoppers, from being carried down the downcast shaft and so on to the roadways of the mine. The dust is collected where made by means of funnels attached to pipes connected to an exhaust fan which creates a partial vacuum (2 1/2 inches water gauge), the current of dust-laden air passing from the fan into a cyclone where it enters steamy atmosphere maintained by a steam jet from the boilers; this prevents any of the lighter _dust from escaping by the chimney to the outer atmosphere. Where necessary the screens and hoppers are almost entirely enclosed. This arrangement, which has been in operation for about five years, has proved very effective in clearing the air about the heapstead, of dust, and practically no dust is carried by the ventilation down the downcast shaft into the underground workings.
(f) Management.
The two mines-the Denaby and Cadeby Main Collieries-are under the general control of a Managing Director, Mr. W. H. Chambers, who is well known throughout Yorkshire and the Midlands as a Mining Engineer of high standing and large experience Mr. Chambers, who lives near the collieries, took a more active part in the management than is perhaps usual in the case of a Managing Director. There was one Agent over the _two collieries, Mr. H. S. Witty, who, before September 1911, had been Manager of the Cadeby Main Colliery. Under Mr. Witty, as Manager of the Cadeby Main Colliery alone, was Mr. C. Bury (who was seriously injured in the second explosion, and died a few days afterwards). There was one Under-Manager at the mine, Mr. Bridges, an Assistant Under-Manager, Mr. Cusworth (killed in the second explosion), and Mr. Eli Croxhall(who also lost his life in the second explosion) acting as Under-Manager in the afternoon shift.
In each district there is a senior “charge” deputy, who has as colleagues an afternoon and a night shift ” charge ” deputy, the senior (and more experienced) of the charge deputies being in the morning shift, which is the most important shift of the three. The afternoon and night shift deputies are inferior to the morning deputies only in that -they receive the instructions from the under-manager through the latter, they, have the, same duties and responsibilities as the morning deputies. Besides these there is a class of 1assistant deputies, two to a district if the district is large; one if small. These men assist the charge deputies in the performance of their duties, and examine and report as if they were full charge deputies
The examination before commencement of work in the morning shift is made by the night shift deputy and his juniors, and they each, severally, report the result of _his examination.
Both the deputies and assistant deputies were carefully and well selected, and constituted a fine body of men. Generally speaking the charge deputies were drawn from ´the assistant deputies. The mine was worked by three shifts, viz. two coal getting shifts, and one repairing shift, arranged as below:
6 a.m.to 2 p.m. Coal-getting.
2 p.m.to 10 p.m. do.
10 p.m. to 6 a.m Repairing The deputies ‘go down with the workmen, that is to say, in the first cages.
The number of persons employed underground in each shift on the 8th July were
10 p.m. (7 th July) to 6 a.m. (8th July)505
6 a.m.to 2 p.m 938
2 p.m. to 10 p.m. *.52
10 p.m._to 6 a.m. [9th July] 111
The number of persons underground forthe corresponding days of the préivitiiiis_ week were :
10 p.m. [30th June] to 6 a.m. [lst July]489
6 a.m. to 2 p.m1853
* 2 p.m. to 10 p.m. …· .*238
The number of officials on each shift was as follows
Under Managers Deputies Ass Deputies
6 a.m.to 2 p.m. 2 5 7
2 p.m.to 10 p.m. 1 5 7
10 p.m. to 6 a.m – 5 7