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February, 1951

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This colliery is just over a mile to the west of Ellington. The seams working are the High Main, the Yard, the Five Quarter and the Low Main. The Yard seam is encountered at a depth of 360 ft. in the shaft and is about 200 ft. below the High Main; while the Five Quarter seam is nearly 160 ft. below the Yard and approximately 25 ft. above the Low Main.

As may be expected, the High Main and the Yard seams throughout the Linton take are very similar in respect of thickness and adjacent strata as in the Ellington property. The Five Quarter has an overall thickness of between 5 and 7 ft. and contains three dirt bands. These average 4 in., 5 in., and 8 in. in thickness respectively, but vary considerably, the bottom band sometimes achieving a thickness of 3 ft Where the dirt bands are thin the full thickness of the seam is taken and the dirt bands used for gobbing, but when the bottom band has increased to 1 ft. 6 in. or more in thickness it is left in position to form a floor. The Low Main is 2 ft. 8 in. to 3 ft. thick and has a fireclay roof and a hard post floor.

Of these four seams the High Main and the Yard are approaching exhaustion, but there are appreciable reserves in the Five Quarter and the Low Main, and in addition there remain certain virgin seams such as the Bensham and the Plessey. Until the present time the development of the workings has followed the general pattern described in connection with Ellington colliery—a fact which is not surprising as both collieries had the same owner before nationalisation. However, at Linton single-unit faces have been favoured, and these are usually 70 yards in length and in many cases alternate panels are advanced from the main winning to the arbitrary boundary so allowing a centre panel to be worked on the retreat using the same gateroads; the saving in gateroad maintenance, gate-conveyor moving and gob stowage is obvious.

The faces are undercut with B.J.-D. machines and the coal blasted and handloaded on to B.J.-D. Blackett chain conveyors, which discharge on to 26 in. Meco gate belts. On one face, however, a scraper skip is working instead of a Blackett chain conveyor. The skip is hauled by the 30 h.p. Sullivan scraper hoist shown in Fig. 1, which also depicts the skip discharging on to the gate conveyor. The skip runs on the face side of the props and we understand that a good proportion of the blasted coal is thus carried on to the gate conveyor without manhandling. The remaining coal is, of course, turned over by the colliers into the path of the skip. As the face 0 MS. on this particular pane] is almost twice that in other parts of the pit the management are eager to increase the number of installations. When once accustomed to skip working the faceworkers dislike leaving but it is extremely difficult to persuade men to transfer from the conveyor faces. No rigid time cycle is followed on the skip face, and all the faceworkers share in a composite price list.

On certain faces, supports are withdrawn by power, using portable Pikrose haulers. This system is in the trial stage as yet, but the results so far are promising. The Pikrose system has also been applied to the salvage of supports from disused gateroads and Fig. 2 gives an impression of the size and portability of the power unit and the method of anchoring used. The withdrawal of a steel arch is shown in Fig. 3. Experience with power salvage has been too short to be conclusive and the management believe that there is much to be learnt before the full potentialities are realised, but already the rate of extraction has been increased by 300 per cent. The advantages from the viewpoint of safety are obvious enough.

Formerly the gate conveyors discharged direct into pit tubs but since November, 1945, a trunk conveying system has been in operation. The individual conveyors in this syttem are Meco 30 in. wide units of various horsepowers and at present the total output of the colliery is concentrated at four main loading points. From the loading stations the tubs, which hold 11½ cwt., have 2 ft. gauge wheels, and are transported in sets of four by endless overtub rope haulage to the pit bottom. Fig. 4 gives a view along a typical haulage way and in particular shows the efficiency of the illumination which in this case is by Victor flameproof filament fittings. All coal is wound at No. 1 shaft which has the onsetting inset at the Yard seam level, and as a result loaded tubs from the Five Quarter and the Low Main seams have to be hauled up a drift with a gradient ot 1 in 6 against the load. In the shaft, tubs are raised two per wind on a single-decked cage, and coal wind.ing is performed on two shifts per day to give an output which is at present in the neighbourhood of 1,500 tons.

Shaft deepening

To eliminate the need for bringing the Five Quarter and Low Main coal up a cross-measure drift to the existing pit bottom, a new inset is to be formed 65 yards below. To obtain access to the new pit-bottom level the No. 2 (upcast) shaft has already been deepened The work was entrusted to the Cementation Co. Ltd. who commenced operations in July, 1949, and finished in June, 1950. The original diameter of the shaft (13 ft.) has been maintained throughout the extension and the new length is lined with brickwork 9 in. thick. At present a connection for ventilation is being driven in the Five Quarter seam between the deepcncd shaft and an existing roadway. Fig. 5 shows the face of this heading and it will be noted. that a track-mounted A.B. arcwaller is used to cut in the coal below the middle dirt band. After blasting the coal is hand loaded directly into tubs, and the stone is packed in the side of the gallery between the roof supports. Straight gird.ers of 6 in. by 5 in. section and 12 ft. long set upon wooden props are used to support the heading. When the pit-bottom reorganisation is completed this particular roadway will house a trunk conveyor delivering on to a main locomotive road.

Work is also in hand at present constructing a new pit bottom for No. 2 shaft at the deeper level. It is intended to use this shaft in conjunction with No. 1 shaft for coal winding and also for men and materials. As Fig. 6 shows, support will be provided by 26 ft. straight girders upon 4 ft. thick walls and the distance between the walls will be 23 ft.

In order to avoid interference with the present coal winding, the deepening of the No. 1 shaft will be done during the night shift. The operation is also planned to be carried out by the Cementation Co. Ltd., as are a number of drivages in the new pit-bottom area. Figs. 8 and 9 give details of the proposed pit-bottom layout and it will be noted that all operations are designed on labour-saving lines. Mine cars of 2¼ tons capacity will be used and their movements throughout the pit bottom will be by controlled gravity feed.

To the north-east it is planned to drive a main arterial locomotive road. This will progress cross-measure on an even gradient of approximately 1 in 300 in favour of the load and. as the plan, Fig. 10, shows, will cross three or four sizeable faults. These faults divide the Linton property into four "zones" and to transport the coal from the two most northerly "zones" branch locomotive roads will be turned from the main north-east arterial. Spiral chutes will be used to lower the output from the upper seams to the horizon. Battery locomotives will be used along this road and the track will be of 60 lb. section rails. A similar locomotive road will also be driven east.

As may be expected in such a comparatively shallow pit, the make of mine water is appreciable, and any new pitbottom arrangement must make provision for storage. It is planned to construct a water lodge capable of holding 600,000 gallons or 48 hours’ make of water at present-day rates. As Fig. 9 indicates, this water lodge will consist of two parallel roadways with inter-connections driven to the dip in the Low Main seam. Support will consist of 12 ft. steel arches encased in concrete.

The existing winding engine at No. 1 shaft was supplied by Bradley and Craven Limited when the colliery started in 1896. Cylinders are 20 in. in dia. and of 5 ft. stroke. The drum is parallel, and is 12 ft. in dia., and the winding rope used has a circumference of 3¾ in. This steam. winder has given very satisfactory service and is still operating efficiently but it is felt that it will not be capable of dealing with an expected heavier load from the greater depth. The No. 2 winder was manufactured by Davison & Co. of Chester-le-Street and has cylinders 10 in. dia. with 20 in. stroke. The drum is parallel and 4 ft. 4 in. dia. and the winding rope has a 3 in. circumference. Consequently, proposals are in hand to replace them with automatic a.c. winders.

One of the electric winders will be new, but the second is to be brought from Lynemouth colliery where shaft deepening is currently in progress. The winder to be transferred, which was manufactured by the MetropolitanVickers Electrical Co. Ltd., was first installed at Lynemouth in 1934 and the nature of its service may be judged from the fact that others of this type are now to be installed at Linton, Ellington and Lynemouth.

It is driven by an a.c. motor which has a R.M.S. h.p. of 370 and a peak of 830 h.p. The drum is of the inverted bicylindro-conical type and has diameters from 8 ft. 6 in. to 11 ft. it is built in two halves each of which is keyed to the drumshaft and provided with individual brake paths. Suspended curved post-type brakes equipped with Ferodolined blocks are fitted. The brake engine is oil operated and has a control valve of the "Iversen" type which is arranged for the Metrovick two-lever system.

When the winder is controlled manually it is operated by the driver’s levers in the usual manner. Connection to a liquid controller in the rotor circuit is through an oil servo gear so that by limiting the current only very light effort is required of the driver’s lever. Reverse current braking is available for lowering loads but for normal coal winding it is rarely required.

The changeover to automatic winding is effected by a switch which transfers the control of starting and stopping to the top of the shaft. After the banksman has pressed a push button and withdrawn the keps the drum accelerates to full speed. Drum speed is controlled by the influence of a cam profile and as the end of the wind is approached this also reduces the cage speed to creeping, after which the opening of a track limit switch by a skate on the cage brings the drum to rest. Should it be desired, the control may be arranged for starting the winder by the joint action of the onsetter and the banksman. Emergency push buttons are provided at the top and bottom of the shaft by means of which the winder can be stopped immediately.

The starting circuit of the winder is interlocked with the kep levers at bank so that the keps must be withdrawn before the winder can be started. Provision is made for automatically taking up the slack rope above the top cage before withdrawing the keps, and for lowering the cage back gently on to the keps after its arrival at bank. The safety circuit includes all the normal trip switches including an oil-pressure-failure relay and a brake over-travel switch, and the circuit is so arranged that even should the main circuit-breaker fail to open in an emergency, reversing contactors are nevertheless de-energised and the brakes applied to bring the winder to rest.

The principle of the Metrovick a.c. winder control system depends upon the comparison of two voltages, one proportional to the predetermined cyclic speed and the other proportional to the actual winding speed. These two voltages are compared in a small d.c. torque motor so that if there is any discrepancy between the two speeds a proportional torque is exerted by the torque motor. This, through the medium of the oil servo mechanism, readjusts the external resistance in the rotor circuit of the main motor until the correct speed conditions are obtained. If it is necessary to reduce the speed, the d.c. torque motor automatically reverses the supply to the winder motor so applying reverse-current braking. A schematic diagram of the system is given in Fig. 11.

On the surface

Reorganisation on the surface at Linton is confined to the preparation of the heapstead for the 2¼ ton mine cars. The layout chosen is as shown in Fig. 12 and it will be seen that the disposition of the various types of points is such that only the minimum number of personnel will be required.

After screening, coal above 4 in. is hand-sorted on platetype picking belts and that from 4 in. to 1 in. is cleaned in a battery of Spiral dry cleaners. The remainder is transported over a private railway line to Ashington colliery for washing.

There is a labour force of some 1,400 on the books and at present the OMS. is in the neighbourhood of 25 cwt., but it is hoped that the improvements outlined above will lead to a steady output of 13,500 tons per week with an O.M.S. of not less than 32 cwt. for the next 70 years. The OMS. figure stated does not, of course, take into account the possibilities of improved productivity at the face through the adoption of new methods, and it will be noted that the management have so laid out the main roads that coal-face operation may easily be modified in the light of future experience.

(To be continued.)

Drawings and Photographs accompanying the article