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November, 1930

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The time when machine mining was adopted as a last resource to meet difficult conditions is a phase that is rapidly passing, and a complete mechanical system is now coming to be regarded as synonymous with coal-getting efficiency. Traditional methods die hard, and it might be expected that in the Northumberland and Durham coalfield, the oldest in the country, there would be a certain lack of up-to-dateness in colliery practice.

At Backworth, however, this is certainly not the case, and 96 per cent. of the output is mechanically won, there being only two small places where hand-work is at present going. Naturally many difficulties had to be overcome in changing over from hand-work apart from a resentment to a change as such, the men often show a disinclination to do their best in order to get rates that are artificially high, and also they are under some apprehension lest the machines should displace some of their fellows. In point of fact, however, the face workers at Backworth have been enabled to earn from 2s. 6d. to 3s. per day more since the machine mining was introduced, and would certainly not wish to go back to their old hand methods. Haulage arrangements, too, have to be reorganised, and indeed the whole of the line of transit from the face to the pit mouth has to be properly co-ordinated before mechanised face operations can hope to be run with success.

At Backworth the operations have a peculiar interest in that a new kind of conveyor is being used. This, the "Huwood" (marketed by Hugh Wood & Co. Ltd., of Newcastle), is of the belt type and incorporates a patent by Mr. Guy Clephan to obviate the use of a tensioning device for the belt. The fact that the belt is able to travel successfully without undue tension makes possible the claims that it lasts longer, does not narrow with use, and runs perfectly and without spilling on undulating floors.

The diagrammatic drawing in Fig. 1 shows the construction of this conveyor. It will be seen that the belt passes over two parallel driving drums, geared together, so that the arc of contact is considerably over 360°. With such a large surface of contact the tension needs to be only very slight to obtain sufficient grip to prevent slipping. The snub pulley is introduced to increase the arc of contact on the second drum and to align the belt on the return rollers. Fig. 2 shows the inverted trough frame-work, the sections being provided with dowel pin joints, flexible in the vertical plane, which in addition to ensuring correct alignment of the belt, also permits the conveyor to accommodate itself to an uneven or undulating floor. With the absence of bolts, nuts, and other small, parts, the flitting can be accomplished with a minimum of those irksome delays caused by such accessories being mislaid, and the only detachable pieces (apart from the spill plates) are the bottom rollers, which can be lifted from their supports to permit the removal of the band itself. The inverted trough, besides carrying the roller supports, also affords protection for the bottom rollers and return belt, and it is practically impossible for small coal to drop on the belt and be carried back around the return drum. Naturally this factor is of importance in prolonging the life of the belt. The spill plates have suitable projections at either end to engage with the yokes carrying the upper rollers, and they adjust themselves automatically to the line of the trough. Being all of one pattern they can be fitted to either side of the conveyor.

The driving gear is totally enclosed and runs in an oil bath, straight gears only being employed without resource to bevels or worms. Power can be supplied either by an electric motor or a compressed air turbine. It is claimed that the turbine equipment is greatly superior to the reciprocating engines when compressed air is used, as it retains a high, efficiency throughout its life and requires practically no attention or maintenance. The electric drive consists of a squirrel cage motor housed in a flameproof, dustproof and waterproof casing, on which is mounted a starting switch, the whole forming one unit. This switch is fitted with a trailing cable plug and socket of the B.E.S.A. type, so interlocked that the plug cannot be inserted or withdrawn until the switch is in the "off" position. The whole equipment has passed the Sheffield University test and is therefore permissible for use in situations where Regulations 132 and 127 apply. A 5-H.P. motor is provided, but the actual power consumption on a 100-yard face rarely exceeds more than two-thirds of this amount when delivering up to 40 tons per hour. This low power requirement is due to the absence of tension in the belt, the perfect alignment, and also to the fact that the rollers are provided with roller bearings. These bearings are dustproof and only need to be greased after many months of continuous running. Figs. 3a and b show the power requirements for a 20-in, face belt and for a 26-in, gate belt in graphical form. These curves relate to a face belt 100 yards in length and to a trunk belt 500 yards in length.

A telescopic trough is provided at the tail end of the conveyor and enables the frame to be easily adjusted to suit the length of the belt. A view of this is given in Fig. 13, and it is perhaps worth pointing out that the trough can be fully extended without in any way impairing the protection afforded to the return belt.

For trunk work the Robin principle is adopted the belt is slightly troughed on three rollers and the side guards are eliminated. As it is necessary to lengthen the gate belts daily a set of belt-lengths is kept handy, graduated in multiples of the cut, it being a few minutes' work to extend the troughing and insert a make-up piece of the required length. A special telescopic tail trough which is provided greatly facilitates this operation it is worked through a set of gears operated by a handle.

Operation at Backworth.

At Backworth the conveyors are at work in the Main Coal, Bensham and Beaumont Seams, a typical layout in the last-named seam being given in Fig. 10. The seam has a section varying between 2 ft. 4 in. and 2 ft. 8 in., and in the district we visited, the 5th West, four faces are in operation, as will be gathered from Fig. 1l. These, have a standard length of 100 yards, but if necessary the conveyor can be lengthened to 120 yards to meet special conditions. Ten to eleven fillers are employed to load the coal, their work including the timbering and drilling of the face. The coal is undercut to a depth of 4 ft. by chain machines, Anderson-Boyes 17-in, cutters having been standardised throughout the Company's pits. Formerly the depth of cut was greater but experience has proved that with the shorter cut the whole of the face operations can be co-ordinated better and much smoother working obtained the face can be left straight, properly timbered and cleared ready for the pullers at the end of the shift.

Whereas the actual arrangement of a double-unit face is as shown by Fig. 7, an interesting modification is contemplated in the near future. Fig. 8 shows this arrangement diagrammatically it involves the construction of a separate loading gate 10 yards to the right of the haulage gate. The idea is to relieve congestion on the roadway and form an adequate standage for empty tubs, both being of importance to secure that continuity of operation on which successful machine mining so greatly depends. Three pullers are required, and although their work includes the extending of the gate conveyor (which has to be dismantled and hauled back whilst the ripping is blasted) and leaving the face in absolute readiness for the cutter men, they rarely need to stay their full time underground. The method of procedure is worth noting.

For convenience the conveyor band is made up in lengths of 25 yards, fastened by easily detachable buckles and pins. First of all the belt is run until one of the buckles is about 12 yards (6 troughs) from the gearhead, so that the bottom end of the belt section is approximately underneath the top end. The top buckle is disconnected by removing the pins, and the belt is rolled back to the gearhead. This gives access to the first six troughs, which are removed and the bottom belt uncovered. The bottom joint is then unbuckled and the belt also rolled back to the gearhead. It is now possible to pull the gearhead forward — together with the rolled-up section of belt — into the new position, this being done with the aid of a sylvester. The bottom belt is now unrolled along the face again. One man deals with the gearhead, as just described, while his companions dismantle the rest of the conveyor.

To accomplish this the buckles are disconnected and the belt is rolled up in sections of 25 yards. It is then taken to the new track, rolled out, turned over and connected to the bottom belt of the conveyor head. Each section must be turned over, since, of course, what was previously the top belt is now at the bottom and the coal-carrying side is reversed. When the tail-end section is reached it is rolled back and dealt with in much the same way as the gear end, the whole being pulled forward by a sylvester, and the bottom belt connected in the new position. Two men now move forward the troughs, starting from the gearhead, and as each pan is fixed in its place the bottom roller is inserted under the belt. While this work is proceeding the third man is occupied in disconnecting and rolling up the former bottom belt and transferring it to the new track. Before running it over the rollers, it is of course reversed so that the coal-carrying side is uppermost. As each length of top belt is connected the spill plates are fixed in position, and so on until the tail end is reached. The end troughs previously left are now placed over the bottom belt and the whole made continuous again. Slack is then taken up with a sylvester fixed at the tail end, care being taken in adjusting the tensioning screws to see that the belt is in no way over-stressed, as the conveyor runs best when the belt is comparatively slack. A trial run is then given to see that all is in proper working order for the coal-filling shift.

The cut is accomplished by a team of three men, two of whom operate the machine, with one behind to clean the holing and replace the timber.

Some idea of the rate of progress made with this system in operation may be gathered from the fact that the A and B faces (Fig. 10) advanced 410 yards in 308 working days, producing 61,497 tons. An average advance of over a yard per day implies great regularity in working, the chief desideratum in operations of this kind. The C and D faces in this district show even better results and were advanced 248 yards in 186 working days. Every endeavour is made to work to schedule, and with this object in view the fullest possible check is kept on the whole of the face operations. Reports are handed in to the management at the end of each filling, cutting and pan-shifting shift, and any deficiency that threatens continuity of operation is immediately investigated. A close check is kept on stores, idle time and any mechanical defects, and every effort is made to prevent those irritating delays which are caused by minor mishaps to the machinery or negligence. All this tends to good discipline, without which machine mining cannot hope to be a success. As a matter of interest to readers the headings of the various reports are reproduced in Fig. 9.

Within the last few years Ceag cap lamps have been made available to the workers, and practically all the face men have now adopted them. At first their advantages were not altogether appreciated, but they have gradually become more popular and 500 are now in use in the Company's Maude and Eccles pits alone. The management have given a good deal of attention to the lighting problem in general, and at all the haulage junctions where there is a considerable amount of traffic Oldham 6-volt lamps are provided.

In mechanising the faces great care was taken to ensure that the haulage arrangements were adequate to transport the coal to the shaft expeditiously. To this end the 8-cwt. capacity pit tubs which were formerly in use were scrapped and Morris steel-bodied tubs, holding 14 cwt. of coal, were introduced These tubs have 12 in. diameter wheels fitted with plain bearings, and have recessed bottoms, the tare being about 6 cwt.

Whenever possible self-acting endless haulages are installed for auxiliary work, and when not, the standard practice is to use Tinsley 25 H.P. endless units, but a number of main and tail gears are also still in use. The Tinsley equipment can readily deal with 1,000 yards of normal roadway, which well exceeds the bounds of normal auxiliary work. The endless system is used without exception on all the main hauls.

Main Coal Seam.

A somewhat different system of working the faces is adopted in the main coal seam, the faces being stepped as shown in the sketch plan in Fig. 14. This method has been adopted to overcome the difficulties with the roof, which comprises 6 ft. of Blue overlaid by 8 fms. of post. Here again, however, the 100 yards length of face is standard, and a 4-ft. holing is made, the cut in this instance being made in an underlying stratum of clay. A winning panel of 50 yards wide is maintained, this carrying three roads, a haulage way, an intake and a return. The faces are worked as single units, a 25-H.P. haulage situated at alternative gates, serving two faces, connecting cross roads being put over as shown at intervals of 300 yards. A bottom caunch is driven to give travelling height, and the conveyors load directly into the tub. On an average the fillers on each face load 10 tons, of coal in a shift of 8 hours, as against 3 tons for hand mining.

The New Baths.

The baths have been established with the aid of a grant from the Miners Welfare Fund, the total cost being £20,000. They are housed in an exceedingly handsome structure, built by Gordon Durham & Co., of East Boldon, an exterior view of which is reproduced in Fig. 18 There are 2,000 lockers for working clothes and a similar number for clean clothes, 85 bathing cubicles being provided. Provision has been made so that the number of cubicles can be increased to 100 when the need arises, and, of course, space is available for a corresponding increase in the number of lockers. A view showing a section of the lockers, in this case for clean clothes, is given in Fig. 19 ; they were supplied by the Birmingham Construction Co. and are admirably designed for the purpose which they serve. Being of steel they are absolutely hygienic, and are infinitely superior to the old-fashioned suspensory hooks so far as tidiness, cleanliness and convenience is concerned. Like the building itself, they are heated by steam at a pressure of 50 lb. per sq. in., the necessary steam being generated in two Cochran boilers, one of which is a standby. The plumbing and heating arrangements were carried out by Hopes Heating & Lighting Ltd., of Birmingham, and have been very neatly executed. The pressure supply pipes are suspended from the stanchions, branches being taken to the lockers, and the returns to the boiler feed pass along the side walls of the building inside a metal casing. All these features are discernible in Fig. 19. A view of the entrance hall is given in Fig. 16, this showing the bottle-filling nozzles and dubbin boxes in the foreground, with the revolving boot sweeps and jet drinking fountains behind. There are eight boot sweeps arranged in two sections, each of which is separately operated by a ½-H.P. motor. A series of pushbutton switches, one opposite each brush, enables the brushes to be set in motion and stopped at will. The bottle-filling nozzles are operated by simply placing the bottle neck over the nozzle and pushing. Control of the establishment is effected by a Committee of men and officials, and the way in which the baths are appreciated may be gathered from the fact that practically the whole of the workers take advantage of the facilities provided. A first-class motor ambulance has recently been added to the bath equipment for the use of the dependents of all employees.

Drawings and Photographs accompanying the article