1056 THE COLLIERY GUARDIAN. December 1, 1916. ............. easily through when the latter is at rest on bh-e walling stage, without any chance of it striking the catches in such a way as to cause detachment; and when ascend- ing, the loose sleeve—by keeping the rope central through the cone—enhances safety in this respect. Referring to fig. 7, which shows bhe detaching hook catch plates at the top, the loose sleeve itself can pass through the holes in the plates, but in ease of an overwind the four spring steel wings would collapse, and be pulled through the holes in the catch plates. The rider is constructed of angle bars and flat bar struts, as lightly as the necessary strength to withstand wear and tear will permit, and is provided with gunmetal guide shoes. A special bridge plate, as shown in fig. 9, is ■ ■ IK K" IH - kVV'i&i '• -I ♦ I ■■ Fig. 2.—Air-Lock and Headgears. fixed on the wheel frame of the walling stage to receive the rider' on its descent, and on which it rests, while the bowk descends through the opening in the walling stage to the pit bottom. In the lower part of the pit the brick lining is dis- pensed with, and the shaft is lined with H girder rings placed 3 ft. apart, with 1 in. thick backing deals between, and which formed centring for the concrete rammed in behind. The top of the shafts during sinking were provided with balanced hinged flat doors, and, as previously men- tioned, flapdoors were provided on the walling stages, but no attempt was made to carry on sinking and wall- ing simultaneously. To be responsible for the general lay-out and mechanical equipment of a large colliery at the present day is no light undertaking, as every care has to be taken to arrange and select the plant so that it will work smoothly and with the utmost economy, both as regards consumption of power and labour costs, and, at the same time, be free from the risk of breakdown or accident as far as is humanly possible; and the efforts of the management of the Great Western Colliery Com- pany in this respect as regards the new Cwm Colliery would appear to have been singularly successful. The general lay-out of the colliery is shown in fig. 10, and, as regards power, it was from the first decided to take full advantage of a bulk supply of electricity from the Treforest station of the South Wales Power Com- pany. A sub-station was erected at Cwm pit, as shown in the diagram, to the right of the two pits, and in a line about the middle of the distance between them. From this sub-station an underground conduit has been formed to the engine house on the left of the pits, and branches are taken which lead to each shaft, as shown by the dotted lines. This conduit is large and roomy, and all cables from the sub-station to the engine house, or to the shafts t as well as all compressed air pipes or water pipes to or from the shafts or engine house, are fixed to wall brackets or floor stands on these conduits, where they may be seen and examined, or attended to, at any time. On the left of the pits is the engine house and boilers. The engine house is one long building, 276 ft. by 66 ft. 4 in. inside, of structural steel work filled in with 9 in. brickwork, and having a slate roof supported on steel principals. On each side is a steel gantry for a 25-ton electrical travelling crane, which traverses the whole length of the building. Inside this building are the two winding engines (one steam, the other electric), the fan engine, and electric- and steam-driven air compressors. Figs. 11 and 12 show the interior of this engine house. The boiler shed is also covered with a slate roof, and at present the boiler unit consists of three Lancashire dished end boilers, 30 ft. long by 9 ft. diameter, with a working pressure of 1601b. per sq. in., and provided with superheaters, Green’s economiser, and induced forced draught. The cage landing is on a level with the surface, but the screens and railway sidings are on a lower level on the other side of the retaining wall, as will be seen in fig. 1. The tubs or trams will leave the cage on the right-hand side of each shaft, pass over the weigh- bridges, and thence to the tipplers, where the coal is tipped on to screens, after which it passes on to jigging distributors, and delivered on to clean- ing or picking bands, and discharged into wagons by means of lowering jib ends on the picking bands. The empty tubs run back to the shafts, their delivery to either shaft being controlled by switches. The workshops and stores form a substantial stone building, with slate roof, divided into the various % A - . f ■ L' V-’ ' 7 , ■ ’ ■ -i| Fig. 11.—Interiorof Engine House. engineers’, joiners’, and smiths’ shops and electrical and general stores. A separate store is provided for ropes and cage attachments. The lamp room is constructed wholly of ferro-concrete, with iron doors and frames, so as to be absolutely fireproof. The output of the Cwm pit is expected to reach 3,000 tons per shift of eight hours, and the winding plant is designed for an output of 200 tons per hour from the upcast or Margaret shaft, and 360 tons per hour from the Mildred shaft. Such outputs may be obtained either by raising a light load at a high winding speed or a heavy load at a slow speed. The first method involves heavy wear and tear, and a constant risk of serious breakdown or accident to men riding in the shaft-, but probably requires less capital expenditure than the latter method of dealing with heavy loads. There can, however, be no question as to which is preferable, as raising a heavy load at a slow speed, though the initial capital coSt will be greater, the result- ing economy in bhe consumption of power, the lessened wear and tear of plant, and, most of all, the enhanced safety to life and limb, more than justifies the extra capital cost. The management of Cwm Colliery wisely decided to raise as heavy a load as possible, and at as slow a speed as is consistent with the desired output. The question of winding from both pits with elec- trical winders was considered, but the colliery is depend- ing on the power supply company for the whole of the electrical power, and should anything occur to stop the supply of current, a serious position might arise in regard to the men underground. For reasons of safety, therefore, it was decided to in-st-al at the upcast shaft a steam engine, worked from the present boilers. The engine consists of two cylinders, 28 in. diameter by 5 ft. stroke, 1601b. steam pressure, and driving a small parallel drum 12 ft. diameter. The steel barrel is grooved for the ropes, and the ropes are arranged to over-eoil on themselves to avoid excessive angling. The cages will be double-deck, with two trams on each deck, and will be fitted with a counter-balance rope. The coal load will be six tons. The shaft speed is limited to 50 ft. per second, and the full angular velocity is reached in 2| to three revolutions of the drum. The decks are changed by the engine. The shaft top is enclosed, as shown in fig. 2, air locks are provided for the entry and delivery of tubs, and large doors are fitted for changing cages. The air drift to the fan (situated in the main engine house) is below ground level, as shown by dotted lines in fig. 10. The downcast shaft is provided with an electrical winder, and is designed to raise 360 tons of coal per hour, at a maximum winding speed of 30 ft. per second. Such a slow speed naturally involves a heavy net load, and the use of large cages, and a heavy equipment generally. The net load of coal is 12 tons, carried in eight trams, each holding 30 cwt. The total load on the drum is therefore a very heavy one, made up as follows :— Tons. Cwt. Coal ................................. 12 0 Eight trams ........................... 4 10 Cage .................................. 9 10 Cage chains, etc., and rope capping... 1 9 Rope in shaft ......................... 9 0 Total ........................ 36 9 Th© electrical winder is on the Ilgner flywheel system, with Ward-Leonard control. The flywheel set consists of one 1,500 kw. 485—430 revolutions per minute motor generator set, consisting of one 1,800 brake horse-power three-phase 25 cycle 2,200 volt slip- ring induction motor, directly connected to two 750 kw. 550 volt diredt-current shunt-wound commutating pole- compensated type generators, and one 220 volt overhung exciter. The flywheel is 3-8 m. (12| ft.) in diameter, and weighs 40 tons. The oil circulation for the bear- ings is forced by a motor-driven pump to an overhead tank, which gives -the necessary pressure head. The winder consists of a special heavy cast iron drum, with cylindro-conical barrels, coupled direct to two slow- speed direct-current motors, each of 900 brake horse- power, 550 volts, and runs at a speed of 28'6 revolutions per minute. The conical part of the drum barrel is in the centre, so that each rope is confined to its own side. The small diameter is 12 ft., and the large diameter 18 ft., and in order to reduce the angularity of the rope, it is arranged to over-eoil upon itself, special spirals being provided at each side of the drum to raise the oncoming rope to the proper level over the layer of rope already on the drum. This practice of over-coiling the winding rope, to which many engineers in this country