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May, 1933

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In the March and April issues of last year we gave some account of the extensive reorganisation scheme that had been undertaken by the Hartley Main Collieries Limited. At that time the winder at Dudley Colliery was still in course of erection and received rather scanty mention, but as it is one of the few double-drum winders in the country we now place a fuller account of it before our readers.

This winder has been erected in conjunction with a new headgear and heapstead, the old wooden erections being demolished as soon as the new equipment was placed in position, the whole change over having taken place without any interruption to coal-drawing whatsoever. The planning of a substitution of this kind calls for infinite care and it says much for the arrangements made in this case that not the slightest hitch of any kind occurred.

At Dudley the depth of the shaft to the Main Coal seam is 492 ft and to the Low Main seam 720 ft. The winder was designed to raise a net weight of 48 cwt. per wind and an output of 1,450 tons and 350 tons of coal per twelve-hour day from the Main Coal and Low Main seams respectively. To meet these conditions a double-drum winder was installed, one drum being fixed to the shaft While the other is loose and fitted with a multi-tooth jaw clutch. This arrangement enables the rope to be easily adjusted for winding from one or other of the levels, so that when winding from the higher seam both cages can be used without the necessity for one cage to travel to the lower depth when the other cage goes to bank.

A general view of the equipment is given in Fig. 1. The motor has a continuous rating of 330 H.P., the estimated power developed when working from the two different levels, after making the usual assumptions for shaft friction and gearing efficiency, being shown in Figs. 3 and 4. It was estimated that the energy consumption per wind would be 2.08 kWh. from the Main Coal level and 2.78 kWh. from the Low Main, but in actual working these figures were improved upon. The maximum motor speed is 288 r.p.m. and that of the drum 294 r.p.m., giving a maximum rope speed of 18.5 ft. per sec.

The motor supplied by the English Electric Co. Ltd., who were the main contractors for the plant, is of the dual-frequency (reconnect) type, and is wound for a three-phase circuit at a pressure of 2,750 volts. The synchronous speed is 300 r.p.m., and the windings are so designed that they can be changed in a comparatively short time from the 16 poles, which give this speed on the present 40-cycle system, to the 20 poles in order to retain the same speed when the frequency change-over takes place on the North-East Coast. An actual test carried out by the English Electric Company at their Stafford works showed that the necessary change-over could be effected in 20 hours. For the purpose of this test the motor was wound for 50 cycles and tried out at this frequency; it was then reconnected for the 40-cycle supply. Even making every allowance for site conditions it should thus be possible to make the necessary change-over during a week-end when the plant is not being used, so that no dislocation of the colliery output need take place.

The motor is of the standard endshield-bearing type, the endshields being split to facilitate the withdrawal of the rotor if required. To enable easy and accurate centring the bearing bushes are fitted with adjustable pads. Double-helical machine-cut gearing is employed for the single reduction to the driving drums, a Wellman-Bibby coupling being inserted between the motor and pinion shafts.

Control equipment comprises a draw-out type pillar switch for the main stator control, together with master switch, air-break contactor-type stator reversing switch, and liquid controller for the rotor circuit, the regulator having a continuous dissipating capacity of 150 H.P. Two Lilly controllers are provided, one on each drum, for emergency braking; these protect the equipment against overwinds, prevent overspeed during the full-speed period of the run, and also initiate retardation — should the winding engine-man neglect to do so — at the proper instant as the cages approach bank. A further protection against overwinds is provided by two limit switches, fitted on the depth indicator and actuated by travelling nuts at the limits of travel. These switches give protection against overwinds when the cages are working between bank and pit bottom, between bank and the intermediate seam, and between the intermediate and the pit bottom. Backing-out switches also ensure that the driver can operate the winder in the correct direction only after an overwind, that is, to bring the cage back to bank.

The winding drums, which, together with the other mechanical parts, were supplied by John Wood & Sons Ltd., of Wigan, are each 12 ft. in diameter and 3 ft. 9 in. wide. A compressed-air engine fitted with an oil-cataract cylinder operates the clutch for the loose drum through suitable control gear on the winding engineman's platform. A hand-screw brake is provided to hold the loose drum when changing levels and is entirely separate from the air-operated manoeuvring brakes, which act on both drums. The latter brakes can also be brought into operation in case of emergency by a brake solenoid, the circuit of which is controlled by the emergency devices previously mentioned. Compressed air for the brakes and clutch is supplied by a motor-driven compressor, an air-failure switch being provided to apply the emergency brake should the pressure fall below a predetermined value.

A practically identical winder has also been installed at the Hastings pit of the Hartley Main Collieries Limited, whilst similar but rather less powerful equipment has been erected at Shankhouse Colliery. The latter is illustrated in Fig. 5 and is provided with a motor capable of developing 185 H.P. on 40 cycles and 200 H.P. on the 50-cycle supply which will ultimately be used.

Drawings and Photographs accompanying the article