1'240 THE COLLIERY GUARDIAN. June 5, 1914. use the exhaust steam by means of mixed pressure turbo-electric generators, the remainder of the plant being operated by electric energy. Subsequently, how- ever, terms were arranged with the power company which applied to the whole of the electric energy sup- plied for this colliery, and also for the Horden and Shotton collieries, calling for a complete change in the plans. It was therefore decided to adopt electric driving plant throughout, and to dispense with steam plant entirely. The plant installed, or to be installed, is as follows :— Two main electric winding engines, each of 700 to 1,500- brake horse power. Main high-tension and low-tension switchboards in the power house. Two Beiliss and Morcom electrically driven air compres- sors, each of 535-brake horse power. Two fan motors, of 300 and 800-brake horse power respec- tively. Two lighting motor generators, each of 60 kilowatts, which convert alternating to direct current, for lighting the surface and pit bottom. Two 2,900/440 volt transformers, each of 200 kilovolt- amperes, for surface motors under 50-brake horse power. Three electrically driven Sulzer centrifugal pumps,installed in the Low Main Seam, each of 700-brake horse power. Screens, fitting shop, and saw mill motors on the surface. Endless rope haulage motors in each seam underground, each of 100-brake horse power. The system of supply is that of three-phase alter- nating current at 40 periods, 2,900 volts, this pressure being used direct on to the winder, fan, and compressor motors, and on all motors over 50-brake horse power. Current at a pressure of 440 volts is supplied from the 200 kilovolt ampere transformers previously mentioned for all motors under this size. These are all situated on the surface, no underground motors being of less than 100-brake horse power. The neutral points of both high-tension and low-tension systems are earthed on the surface. The current is brought through duplicate feeder cables from the sub-station of the power company, which is close to the colliery, to the main high-tension switchboard installed in the colliery power house. The general lay-out of the power house is shown in figs. 8 and 9. Main Winding Engines.—These are similar, and were purchased from the British Westinghouse Electric and Manufacturing Company Limited, the mechanical parts being by Messrs. Markham and Company Limited, Chesterfield. Figs. 10,. 11, and 12 show the plan and elevations of the general arrangement; the winding engine houses are arranged at each end of the heap- stead building. On each engine the drum is of the cylindro-conical type, built up of mild-steel plates and framing, and weighs 45f tons, the small diameter being 10 ft. and the large diameter 20 ft. It is arranged to carry 500 yds. of rope, although at present winding is being carried on from a depth of 300 yds. in the South pit, and from 400 yds. in the North pit. The drum is gear-driven through single reduction machine cut double helical gear supplied by Messrs. The Citroen Gear Company Limited, the motors operating when at full speed at 230 revolutions per minute. The gear ratio is 5-45 to one. The complete equipment is designed for the service shown in the following table :— Fig. 10.—Plan. jOVERSPEECT BORE K. TRANSFORMER , _DE ■ O JJNDIC B FEET -HIGH, 70 f>OONDS PRESSURE AIR-COMPRESSOR, 7 BRAKE-HOR3EPOWEI J 280 REVOLUTIONS, I 30 CUBIC FEET FREE AIR PER MINUTE FOUR LIVE COILS THREE DEAD COILS CITROENS DOUBLE-HELICAL GEAR. 12 V* INCH FACE, 15 INCH OVERSHROUDS. ------H( f(S£pOwf R) '230 RESOLUTIONS PE^ MINUTi 2,900 VOL1 'S'lLEWOib' “TDEFffr " o ATOR. Depth of shaft .................. 450 yds. Weight of coal raised per hour .. 189 tons. Weight of coal raised per wind... 3 tons 3 cwt. Weight of each cage with chains . 7f tons. Weight of each tub............... 6 cwt. Number of tubs per deck.......... Six. Number of decks per cage ........ One. Diameter of rope................. 2 in. Weight of rope per yard ......... 19 lb. Winding time .................... 45 seconds. Decking time..................... 15 seconds. It will be noted that single-deck cages are fitted. Patent keps of the Beien type are used for the cages, in order to prevent the heavy momentary currents, which would otherwise have been taken when lifting the cage off the keps for lowering. Heavy double post brakes are fitted, operated by a Whitmore air brake engine, and Ferodo lining is used on the brake blocks. The operating levers and control switches are fitted on the driver’s platform, which is enclosed in a glazed cabin. The driver’s attention is thus not distracted by the running of the machinery, and the cabin can be easily and cheaply heated in winter by an electric radiator. The gearing, which is practically noiseless, runs in oil in an oil-tight gear case. A heavy cast iron bedplate is provided, and so arranged as to take the three drum bearings, the complete motor with its three bearings, the air brake engine, and the depth indicator. The brakes are operated by weights, and kept off by the air engine. The usual emergency devices are provided for applying the brakes and cutting off the supply of power to the motor, in the event of any of the follow- ing occurrences :—(1) Overwinding; (2) overloading; (3) overspeeding; (4) failure of voltage; (5) failure of air pressure; and (6) the brakes may be worked by hand on emergency. The overspeed tripping arrangement is interesting. A small series-wound generator is coupled by a chain drive to the motor shaft, and supplies current to a circuit containing an adjustable resistance, which regu- lates the amount of current supplied at any given speed, and consequently the voltage of the generator. As the winder increases in speed, or slows down during the accelerating and braking periods respectively, the resist- ance is increased or decreased by means of a rheostat arm, operated by the drum shaft. The effect of this is that, when the winding speed is normal at any part of the’ wind the voltage of the small generator is just not sufficient to trip a relay: but should the speed at any point exceed (by a safe margin) a pre-determined amount, the voltage rises, operates the relay, trips the main switch, and puts on the brakes. In the case of an Fig 11.-Front Elevation. Fig. 12.—End Elevation. ^nch^bqre RELAY1 THREEWl' aingleSj ! JCABLESLk nJo'tfdTOR THRE1 -efffiE casles- Figs. 10-12.—General Arrangement of Electric Winding Engine. overwind, therefore, this apparatus ensures that the speed of the drum shall not be so great, when the ordi- nary overwind trip acts, that the brakes would be unable to hold the cage before it reached the hooks. A motor-driven air compressor, with receiver, is provided for supplying compressed air for the brakes. There is also a stand-by supply of air from the main air com- pressors in the power house. The electrical equipment comprises a 700/1,500-brake horse power three-phase 2,900 volt induction motor, driving the drum through the gearing previously men- tioned. The motor is rated at 700-brake horse power at