Pleasley Colliery.
(Information from Colliery Engineering).
Pleasley Colliery, which is situated in the Notts and Derby coalfield some four miles from Mansfield and about eight miles from Chesterfield, commenced coal raising for the Stanton Ironworks Company in 1873.
Shafts 14 ft. 6 in. in diameter were put down to work the Top Hard seam at a depth of 510 yards, and subsequently cross-measure drivages were made to work the Dunsil and Waterloo seams and the number 2 shaft was sunk to 780 yards to wind the Deep Hard seam.
Throughout their lengthy incumbency, the pre-nationalisation owners established a reputation for enterprise, and they were not slow to appreciate the possibilities of long wall power loading when machines were introduced for this purpose in the early 1940’s.
Some indication of the degree of success attained at other collieries that belonged to this firm was given in an article* but not until power loading had been proved a practical proposition elsewhere was it introduced at Pleasley.
In September 1946, the first power-loading machine, a Huwood ML/1, was put to work on a long wall face in the Deep Hard seam. Excellent psychological preparation had been made by the management before the installation, and there seems very little doubt that this precaution, coupled with the hard work performed by management, officials and men during the "teething" stages, contributed in no small measure to the ultimate success of the scheme.
The degree of success obtained may be judged from the fact that at present 90 percent of the output from the Deep Hard seem is obtained by Huwood power loaders.
Coalface Arrangement.
In the district we visited, the Deep Hard seam shows a thickness of 3 ft. 4 in., and has a blue bind roof with ironstone bands and a floor of hard stone topped with approximately eight inches of soft clunch. Double-unit advancing long wall faces are set off 220 yards in length with the centre gate housing the coal conveyor and acting as intake. An undercut is made 5 ft. deep in the clunch beneath the seam by AB 15 coal cutters. These machines are fitted with AB propeller-type gummers and have been adapted to carry a thread bar for the haulage rope of the Huwood loader. 
The thread bar, is, of course, bolted to the gear-head of the coal-cutters and lies parallel to, but 3 or 4 in. behind, the cutting jib; it has the function of trailing a wire rope into the back of the kerf ready to act as a face-side haulage rope for the power loader. The rope is in lengths of 25 ft. with a thimble-less loop spliced at each end; adjacent lengths are joined together by figure-eight shackles of such a size that their passage through the threaded bar is not impeded.
Cutting is done on the night-shift; to each double-unit face there are two machines, each worked with a team of three men. Two hours before the day-shift is due to start a drilling and shot-firing team of three men commence operations. Holes are drilled at intervals of 4 ft. 6 in. and each is charged with 10 oz. of sheathed Plastex explosive. Voortman plugs, as supplied by Safety Stemming Plug Limited, are used to give a cushion of 8 in. to 9 in., and shots are fired simultaneously in sets of six. This shot-firing procedure has been found by experiment to be the most successful and is now rigidly followed.
When the day-shift loader operators arrive the power loader has been manoeuvred into a stable hole attached to both haulage ropes ready for commencing loading proper. Incidentally, the small overall dimensions of the Huwood loader render unnecessary the preparation of large stable holes, and the operators at Pleasley have indeed become so practised that practically no blasted coal from the stable is hand loaded.
The power loader used is the Huwood ML/1 type, which is 6 ft. 4 in. high and has an overall width of 2 ft. 10 in. It is driven by a high starting torque, 10-h.p. motor which is of course, fully flameproof. This one motor drives both the loading flights and the haulage drums. The are two haulage drums, one of which hauls in the wire rope previously laid by the coal cutter at the back of the kerf and the other handles a second wire rope laid along the gob side of the broken coal. The extremities of both ropes are attached to derrick props set at the other end of the face. Each rope is composed of 25-yard lengths joined by figure-eight shackles, and as the power loader reaches each successive shackle, the rope is disconnected and the 25-yard coil of rope pulled from the drum and left lying along the face. The remaining length of haulage rope is then shackled to a short length of rope permanently attached to the drum and the loading operation commenced. It will be appreciated that any breakage in the haulage rope laid at the back of the kerf is catastrophe. During the early stages of power loading the management insisted that the face-side rope was changed every four weeks, but now the matter is left to the discretion of the operators, who ensure that any doubtful rope is relegated to the gob side before being scrapped: in this manner the average length of life has been increased to three months.
Both haulage drums are fitted with plate clutches so that the operator may adjust the position of the power loader at will, and it has been found advantageous to have the gob-side end of the machine about one foot in advance of the other end loading machine. Normally, choice of two speeds is offered -- a loading speed of 2½ ft. per min. and a flitting speed of 12½ ft. per min. -- but at this colliery a pinion on the flitting-gear train has been removed so as to prevent operators from racing the machine while on load.
The loading flights are six in number and are 4 in. deep, the four inner ones being forked and the outer ones snub nosed. Each flight is caused to rotate along a circular orbit parallel to its neighbours, and the combined action of the six flights gently pushes the prepared coal from the face on to a face conveyor. Power is transmitted to the flights from the motor through a crown wheel, twin driving discs and a connecting rod, and for disengaging the flight drive a dog clutch is provided. In their retracted position the flights protrude 5 in. beyond the body of the machine, and when fully extended reach a further 11½ in. forward.
The power loading team consists of five men. In addition to the driver there is an assistant armed with a hammer and crowbar to break up lumps too large to be handled satisfactorily by either the loader or the face conveyor.
Immediately behind the machine there is a temporary-support man who erects a steel corrugated roof bar to a chalk line and secures it with a Dowty prop. A steel H-section prop is then set under the gob end of the bar by a forth man, while a fifth man erects a face side rigid prop three feet from the other prop. The man erecting the gob-side prop also assists the temporary-support man with the benk bar, and the man responsible for the face-side leg clears up the small amount of coal and spillage left by the power loader. The men are paid as a team on a dayrate-plus-incentive-bonus basis.
To minimise face cable handling, gate-end switch-gear is installed in all three gates, and the power loader pays out a trailing cable which is then picked up and returned to the same gate by the next cut of the coal cutter. This arrangement, although rather heavy in capital cost, is safer than trailing cables passing alongside the machines during cutting and/or loading.
Face Conveyors.
The face conveyors used are of the bottom carrying-belt type and have no intermediate structure. The belt, which is 20 in. wide, runs on the floor of the seam for the lower strand, and the return strand is carried on 1½- in. dia. Mild-steel pipes suspended, by straps made of old conveyor belting, from the roof bars at intervals of approximately 12 ft. For a loading ramp, 3 in. dia. Mild-steel pipes in 9 ft. lengths are laid between the faceside props and the conveyor. These pipes are anchored to the props by U-shaped grappling irons, and are laid for the total length of the conveyor, joints between adjacent pipes being made by tapered wooden plugs permanently fastened into one end of each pipe.
It will be appreciated that a conveyor track 3 ft. wide is prepared to house a belt only 20 in. in width, but this is done to allow the belt to "flow" towards the goaf at the point of loading without fouling the props.
Bow discharge is favoured and the driving units, which are installed in the mothergate end of the conveyor, are of Mavor and Coulson manufacture and 20 h.p. rating.
To accommodate the two Bow discharge units and the gate conveyor a dint is taken 18 ft. wide and 3 ft. 3 in. deep at the mothergate. The dinting is carried out by the erectors and there are six men employed on piece rates to do this work as well as moving forward 220 yards of face conveyor.
The dint, together with the two discharge bows and the presence of at least one coal cutter, make it difficult to power load across the mothergate end, and at this point approximately eight yards of coal are hand loaded, two colliers being stationed here on the day shift. In addition, at each end of the face there are 4 yards that are hand loaded and here one man is stationed during the power loading shift. When this hand-loaded stint is completed the man moves down the face cleaning up the small percentage of coal left after the loader has passed.
After loading throughout their allotted benk the power-loader team ensure that the face is in fit condition for the coal cutter to pass, and on one face they also turn the coal cutter and past the stationary loader; on the other faces the turning round is performed by afternoon shift workmen, two of whom start one hour before the regular shift to avoid delaying the conveyor erectors.
The corrugated steel benk bars and the H-section rigid props used for normal face support are set 4 ft. apart and to give both a conveyor track and a cutter race the same width. Across the gate-ends, at the stable places, and where machines are turned, these are supplemented with "bull rails" set parallel to the face. Benk packs are erected three yards wide with seven yards wastes and in each waste two square timber chocks fitted with Meco releases are built. The management prefer the wastes to collapse, which they normally do. The men engaged on pack building are also responsible for withdrawing the wastes, and on the face we visited 10 persons per day are so employed and paid on piece rates.
Supply-gateside packs are usually 6 yards wide and are built by the rippers, who also blast the road of sufficient dimensions to take 9 ft. steel arches. Four men are engaged on this work and it is performed on the night shift.
Transport.
The main gate ripping is also done on the night shift, and here four men are employed to produce a roadway sufficient to take 14 ft. by 10 ft. steel arches and to build gateside packs 8 yards wide. As in the supply gates, arches are set 2 ft. 6 in. apart on soft wood pads. To the seam thickness stones are packed between the arches and the remainder of the perimeter is adequately lagged with sawn boards. For the most part, the arches are stelled with timber, but a number of hammer-Lock struts are undergoing trials. The lip end is supported by L-shaped benk bars and a pair of horsehead girders are provided to give cover while erecting the permanent supports.
Gate-road maintenance is not particularly easy in the Deep Hard seam because floor lift occasionally causes inconvenience, and in a number of gates as many as four dintings are necessary, followed by a final back ripping.
The gate conveyors serving the face visited are 30 in. wide and travel at 250 ft. per min. An inbye conveyor 500 yards long discharges on to a second conveyor 630 yards in length. The intermediate structures on both these conveyors are of Huwood manufacture, and in each case a 45 h.p. Mavor & Coulson driving gear is used.
The outbye conveyor of the two mentioned discharges into tubs which hold 14 cwt. Of coal. These are attached by Smallman clips to an endless-undertub haulage system which takes them, in sets of four, to the pit bottom, approximately 600 yards away. The tub track is to a gauge of 2 ft. 1½ in., 30-lb. section rails being mounted upon wooden sleepers spaced 3 ft. apart.
Upon arrival at the pit bottom the loaded tubs are lowered by the retarding creepers. One creeper discharges to the upper deck level and the other to the bottom deck, track gradients being so arranged as to minimise manhandling of tubs. In both shafts the cages have four decks each carrying two tubs, and each shaft is fitted with steel guides. The winding ropes are one and seven-eighth in. dia. Locked coil construction, and flat balance ropes are used in both shafts, that in the downcast being 5 in. by 1 in. and in the upcast 6¼ in. by 1½ in.
Some Surface Plant.
The winder at the upcast shaft was manufactured by Markham & Co. Ltd. It has two cylinders 36 in. dia. By 84 in. stroke and has a drum 21 ft. in dia. The overwind-protection gear is by Thornehill & Warham and a King’s slow banker is provided, the brake engine being of Markham manufacture and operating Burns-type brake gear. A steam pressure of 150lbs. Per sq. in. is used.
The downcast winding engine is of Lilleshall manufacture and has cylinders 40¼ (?) in. dia. And 72 in. stroke, which are fitted with Mellings drop valves. The overwind-protection device, the slow banker and the brake engines are duplicates of those installed in the other winder, but in this case Black’s spring brake gear is fitted.
The engine works on a pressure of 80 to 85 lb. per sq. in. The drum, which is of the parallel type, is 19 ft. 6 in. in diameter.
Both winding engines are housed in handsomely appointed buildings finished in an agreeable combination of green and cream paint with red tiles.
At the onsetting and banking levels.
A system of interdeck signals has been fitted. This was designed in 1927 by the colliery electrical engineering staff. there are four stations at the cage -- one at the empties side and the other at the loaded side of each deck -- and signals cannot be transmitted to the winding engineman until all four stations have signalled their readiness. This arrangement, although minimising delay during cage changing, prevents accidents. The cage, upon reaching decking level, contacts an Allen West switch, which admits power to the interdeck signals circuit.
As the tub changing is completed the men at three of the stations each close a switch, the cumulative effect of which admits power to a master circuit controlled on the surface by the bottom deck banksman, who then signals direct to the winding engineman. All signals given are visible as well as audible, a high-frequency klaxon indicates to the control the closing of subsidiary switches. The removal of the cages causes the Allen West switch to break the circuit and the other switches consequently return to the open position ready for the next wind.
Should an emergency occur, a stop signal can be transmitted to the engineman, and after the emergency is passed a cut-out key, which requires two hands to operate, is used to signal. The emergency ringing key is under the control of the bottom-deck banksman, and the operation of an emergency stop-key from any of the other three stations causes a "Toughton" klaxon to sound.
Power for the interdeck signal circuit is supplied by a 12 V 100 amp,-hr. battery, which is recharged by a trickle charger from the mains supply. During man riding, the interdeck signals are, of course cut out.
Footnote:
Col. Crompton of Crompton Parkinson Limited, installed electric lighting underground at Pleasley Colliery in 1881.
* Colliery Engineering, March 1950.
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