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Colliery Engineering

November, 1928

Winding Engines and Decking Plant.

Both winders were supplied and erected by Robey & Co. Ltd. and are similar in every respect, the cylinders being 26 in. in diameter by 4 ft. stroke and fitted with the maker's drop-valve reversing gear and overwinding equipment. They are designed to work at 160-lb. pressure and are coupled to cylindro-conical drums rising from 10 to 114 ft. in diameter by 8 ft. wide, 2 ft. of this width being occupied by the scroll and 6 ft. by the cylindrical portion. The barrels are built up of steel plates, lagged with oak, and are fitted with post brakes on each side. The scrolls are of cast iron. The headgears, which were supplied by Plowright Bros. Ltd., are of rolled-steel joist construction and carry pulleys 14 ft. in diameter made in halves.

Locked coil winding ropes are in use, 1 5/8 in. in diameter, and support single-decked cages 14 ft. long by 7 ft. wide. These are constructed of punched plates and carry six 12-cwt. capacity tubs, two abreast, making the net load of coal per wind 3 tons 12 cwt. Each cage weighs approximately 5 tons, including the chains and shackles.

Power-operated decking plant is being installed at the East Pit, both at the top and bottom of the shaft, and comprises electro-pneumatic loading equipment, automatic gates, and tub controllers for the converging tracks and controls for the diverging points. The whole of this equipment was supplied by the Westinghouse Brake & Saxby Signal Co. Ltd. Fig. 12 shows the layout at the surface for one cage, and apart from the tub controller shown on the running-off side of the shaft, which will only be installed at the pit top and, of course, the kep gear, the plant for the pit bottom is in every way similar. The forward end of the piston of each ram carries a crosshead running on rollers on a track, and to this crosshead is attached a pair of forked arms designed to engage with the rearmost axles of the third tub waiting to be decked. There is a pair of skotch-blocks close up to the shaft on each track, the distance from these skotch blocks to the forked arms of the rams being such as to accommodate three tubs. It will be noticed in Fig. 12 that the skotch-blocks have had to be "staggered" slightly on adjacent tracks, this having been necessary owing to the close pitch of the tracks, which allowed insufficient space for the skotch blocks to be set in line.

Each shaft is protected on each side by two pairs of gates which are of the collapsible type and operate by pneumatic cylinders, the latter being situated above the gates well out of the way. The keps (supplied by Messrs. Plowright, Chesterfield) are interlocked with the decking plant and operated by means of pneumatic cylinders, a detachable handle being provided for emergency operation by hand.

Each cage is equipped with a pair of back axle-detecting stops on the running-on side and a pair of tub controllers on the running-off side. Both the back stops and the tub controllers have six star wheels, which are rotated by the axles of tubs passing over them. The star wheels of the back stops are free to rotate in the forward direction but are locked against movement in the reverse direction, whilst the star wheels of the controllers are normally locked but may be unlocked through the medium of striking mechanism on the pit bank, when they will allow three tubs (six axles) to pass over them and then relock. The back stops, through a second striking mechanism on the pit bank, give an indication when either of the star wheels is in other than the normal position, and the interlocking ensures that the keps cannot be removed from under the cage while this is the case. The supply of air to the rams and to the cylinder which unlocks the controllers and operates the keps, gates and skotch blocks, is controlled by a series of electro-pneumatic and mechanically operated valves; a pair of electric relays for each cage governs the sequence of operations, and these relays, together with terminal boards and fuses through which the various circuits are fed, are housed in a watertight case. Armoured cored cable is used to carry the electric circuits between the various contact-breakers and electro-pneumatic valves.

In addition to the decking plant proper, the run of the tubs to and from the cages is further controlled by the banksman's assistant from a central position. The empty tubs returning from the tipplers approach the pit along a single track, which divides into four, to serve the cages, some distance in front of the back of the rams. A six-star tub controller situated on this single track holds back the empty tubs and when unlocked passes them three at a time. They then run over the diverging points, which are pneumatically controlled, to the several tracks. A set of skotch blocks, similar to those in front of the shaft, is situated on each track about level with the ram head to hold back the waiting tubs until they are required for decking. On the running-off side there is a pair of six-star tub controllers, one for each cage, in advance of the converging point of the tour tracks. Thus, when the two lines of free tubs are pushed out of the cage, one set is held by the tub controller while the other set runs clear the controller is then released, allowing the second set to follow. These controllers, as well as the controller, the diverging points and the rear sets of skotch blocks on the running-on side, are operated by a series of pneumatic valves by the bankman's assistant who stands on a raised platform to obtain a good view of the running of the tubs.

Control of the decking plant is carried out by the banksman by means of a three-lever control set mounted to one side of the shaft on the running-on side of the cages. Two of the levers control the decking, the third being an "emergency" lever used to arrest the forward motion of the rams should occasion arise, and also to bold the rams locked in the "back" position whilst men are being wound. A series of illuminated indicators shows whether the keps for each cage are "under" or "out" and when the back axle detecting stops in the cages are "normal."

The decking operation is carried through as follows. Just prior to the arrival of a cage at the decking level the banksman reverses the decking lever for that cage on his control set. Immediately the cage is in line (and not till then) the operations continue automatically ; the keps are inserted under the cage, and when the latter is at rest on the keps the front sets of skotch blocks are removed from the rails and the tub controllers in the cages are unlocked by the striking mechanism on the pit bank. The rams now move forward, each ramming three empty tubs into the cage and three full ones off. The star wheels of the tub controllers each relock after the six axles of the full tubs have passed over them and hold back the incoming empty tubs, while the back axle detecting stops ensure that all these tubs are fully on to the cage on each track, and prevent any movement of the tubs in the reverse direction.

The rams automatically reverse as soon as they have reached the full forward extent of their stroke, and the skotch blocks are replaced on the rails. During the backward stroke of the rams the banksman replaces his decking lever to the normal position, when, provided the arms of the rams are clear of the cage, the skotch blocks are on the rails, and the back stops in the cage are "normal," the keps will be withdrawn from under the cage.

The plunger by which the banksman transmits his winding signals is provided with a pneumatically-operated blinder which is lowered over the plunger during the time. that decking is in progress, and is not raised to allow the cage to be signalled away until the keps are proved clear of the cage after decking has been completed. The provision of this blinder prevents a winding signal being accidentally given before decking is completed; but should the banksman wish to transmit any signals while the blinder is lowered, he can, by a deliberate movement, raise the blinder by hand and operate the plunger.

It is often desirable to be able to remove the front sets of skotch blocks from the rails without operating the rams, as, for instance, when timber is being sent down shaft. For this purpose, pneumatic valves are provided which can be operated by the banksman, but the skotch blocks cannot be so removed unless the cage is in line at the decking level, and as a further safeguard the blinder is lowered over the signalling plunger whilst the skotch blocks are removed. The operation of the rear skotch blocks is quite independent of the rest of the plant, so that a clear space may be maintained in front of the cages when winding men, and during decking the next complement of tubs may be fed into position for decking in the interval between the departure of one cage and the arrival of the other.

When men are being wound, the "emergency" lever is reversed, instead of a "decking" lever. The keps are then inserted under the cage as soon as the latter arrives in line, but none of the rest of the plant is operated.

Heapstead and Screens.

A brick and steel-frame heapstead has been constructed to embrace both shafts and is connected to the screen building by a gantry (Fig. 13), down which the full tubs gravitate to a creeper. From this creeper the tubs are raised to the screen house, where, eventually, five units will be installed. The immediate programme, however, only calls for two screening units, and these have now been erected together with the necessary tippler gear and two plate picking belts. Each of the latter is 91 ft. in length and 6 ft. wide, and is fitted with a compartment on the return side to convey the refuse back to a cross belt, which delivers it to wagons designated for the spoil heap. Each unit is arranged to operate through a Broadbent clutch so that it can be put in and out of gear quite independently of the other units.

When the plant is complete it will be capable of dealing with 300 tons per hour. It is being supplied and erected by Plowright Bros. Ltd., who have also been responsible for the screen buildings and heapstead. All the floors are concrete reinforced with expanded steel, and great care has obviously been taken with the lighting arrangements, which are in every way excellent.

Ventilating Fans.

The ventilation duty is undertaken by two Sirocco fans which communicate with the West Pit by an underground drift, 24 ft. wide and 16 ft. high. One fan is directly coupled to a Belliss steam engine and the other is rope driven from an electric motor (Fig. 16). Both ventilators are similar in every respect and are of the double-inlet type having a capacity of 400,000 cub. ft. per minute at 4-in, water-gauge pressure. The engine is capable of developing 450 H.P. at 165 r.p.m., and is fitted with a speed-varying gear capable of giving any speed from the higher limit down to 95 r.p.m. At the time of our visit the engine was working at the minimum speed and the fan was circulating 16,000 cub. ft. of air per minute against ½in. w.g. Naturally, a very considerable saving in power is effected by having a speed range of this kind as the amount of ventilating current required during the opening-out stages of the colliery bears no relation to the ultimate demands. Also, the arrangement enables the ventilation to be readily cut down to any desired minimum during week-ends and holidays, and thus reduces the steam demand at a time when it is particularly desirable that it should be as low as possible. Of course, the same advantages can be secured electrically by installing a variable speed motor, but a commutator motor is a costly machine, while the ordinary induction type has a poor efficiency and has a detrimental effect on the power factor when run on low loads. Furthermore, the use of a steam drive for one of the units ensures security against failure of the ventilating current in case of an electrical breakdown.

The motor driving the duplicate fan is an English Electric machine, developing 560 H.P. at 587 r.p.m., and is run off the 3,000-volt circuit.

Other Surface Equipment.

The shops comprise two excellently arranged blocks of buildings divided into the fitting, smiths', plumbers', electricians', joiners' shops and apartments for coal-cutter repairs, motor spares, &c., and for the enginewright's, storekeeper's and timekeeper's offices. Like the other buildings on the premises, they are well built of brick with slate roofs and have a very good appearance indeed. Both roof and wall lighting is provided. A further block contains the ambulance room, report cabin, and lamp room. Both the ambulance and lamp rooms have the interior walls finished with glazed bricks and tiles, the ambulance room having been designed with rounded angles to prevent the accumulation of dust. The usual modern practice has been adopted with the lamp cabin in that it has been designed for the lamps to be given out at one side and received at the other, so that no congestion occurs through the two opposing streams of men meeting. "Ceag" electric hand lamps are in use, and a full range of equipment is available for recharging and replenishing the batteries and for cleaning and repair work.

A particularly substantial powder magazine has been erected having heavy buttress walls of brick and a concrete floor. It is 27 ft. long by 9 ft. 6 in. wide, and has been licensed to store 1,000 lb. of explosives.

Underground Equipment.

As the colliery is still in its initial stages of development — the roadways not yet having got beyond the shaft pillar — very little equipment has been installed underground. A plan showing the layout of the roadways in the Busty seam is given in Fig. 19, and a practically identical layout has been adopted in the other seams. Exceedingly spacious shaft sidings have been constructed to carry four lines of track, the finished width between the side walls being 24 ft. The side walls are of brick, 3 to 4 ft. in thickness, and are surmounted by 16 in. cross girders to support the roof. All the main haulage roads are 14 ft. wide, the height varying according to the thickness of a stone band which separates the seam into a "Top" and "Bottom" section averaging 1 ft. 8 in. and 2 ft. 8 in. in thickness, respectively ; it is generally found convenient to take the height of the roads up to the "Top" seam which has a post roof. The stone band varies in thickness from 6 ft. 6 in. to 2 ft. 6 in. in different parts of the colliery and makes a set system of working a very difficult matter, as a change in the thickness naturally involves a change in the method of extraction to get the most economical results. Four main winnings are being driven to the south and four to the east. In these the return airways are 12 ft. wide and the travelling ways 9 ft., so that, as the roads are driven at 44-yard centres, 40-yards of solid coal intervenes between them. An 80-yard pillar is left next to the return.

Six men and a boy are employed in each winning and arrange their work through three shifts. In the first shift a cutter man and the boy make a cut in the bottom seam while a driller makes the necessary shot holes in the band and top coal, it being understood, of course, that the work in the bottom seam is kept well in advance, thus leaving the band and top coal in the form of a caunch. A trestle arrangement is provided for the driller to stand upon where the band is thick. This work is accomplished with the aid of Siskol punching machines, which make a 6 ft. jud, and Hardiax drills, Penrhyn powder being used for the shots. The stone and top coal caunches are dealt with by the middle and night shifts, who leave everything cleaned up for the cutting to be commenced in the morning again. Progress is made at an average rate of 13 yards per week.

A retreating longwall system will be adopted with 80-yard conveyor faces arranged in the double unit system. The winnings will be driven 88 yards apart and the gate conveyors will be installed as shown in the sketch plan. It is proposed to convey all the coal from four double unit faces (two on each side of the main haulage) to one central loading point on the main haulage, but as yet the winnings have not advanced far enough to try out this system.

The longwall winnings will be driven to the requisite height, taking the bottom section coal and a bottom caunch. In the mothergates, the dirt band will have to be taken out and stowed as far as possible, but the side gates will be driven as a double stall and the stone stowed on the spot as the coal is extracted. A circuit will thus be formed for the ventilation during winning out and a windway left for the next retreating face after the first face is finished. During the period of winning out the mothergate will be ventilated by air tubes.

This system of retreating the longwall and conveying to a central point has already been tried in a modified form at these pits, and gives very satisfactory results. The method of extracting the top section will depend on the thickness and nature of the "band" and will doubtless vary in different districts of the pit.

Drawings and Photographs accompanying the article