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The following observations may be considered as supplementary to the paper contributed to this Institute by Mr. George Fowler, at the Birmingham meeting, in 1861, and published in the Transactions, Vol. X., page 161. They aim at giving a description of the further development of the methods of working the seam of coal therein described, viz., the " Main" coal of the Moira, or western division of the Leicestershire and South Derbyshire coal-field.
This paper is intended to be more of a descriptive than an argumentative one, though any questions put will of course be replied to.
This is the principal bed of coal in the district. See Map and Sections, Plate XIV. Its thickness varies between 10 feet and 14 feet. It is, taking it as a whole, a hard coal-some bands being exceedingly hard and tenacious; others are soft, commonly called dice. The enlarged Section, Fig. 3, shows the different beds or divisions of which the coal seam is made up, their thickness, and leading characteristics. It is a valuable house coal; the inferior parts make a useful manufacturing fuel; the upper divisions, when burnt, leave a white ash, the lower ones a red ash. The specific gravity of the over coal is about 10 per cent. higher than that of the nether coal.
Although containing no parting in the southern portion of the coal, field, the seam is, in the northern district, divided into two distinct beds; a dirt-bed setting in, in the middle of the seam, about the centre of the basin, which thickens out in a northerly direction until near the outcrop; the two beds are separated by no less than 60 feet of measures. It is also somewhat remarkable that, whereas in the south the upper half of the seam is the best in quality, the reverse is the case in the northern end, so that about the centre of the coal-field both divisions, or in other words, the whole seam, is, taking it altogether, of much the same quality throughout. It is in this locality that the systems to be described have been adopted. See X on Map, Fig. 1, Plate XIV. The main coal is met with at a depth of about 350 yards where deepest, which is in the neighbourhood of Moira. Section, Fig. 2. At this point it was worked in much the same manner, as will be explained under No. 1 System, the nether coal being left. See Mr. Fowler's paper before referred to. The depth at which No. 2 System is now being carried on is about 290 yards. The coal lies almost flat, but it is much broken up by faults (about as many downthrows as upthrows), varying between a foot or so up to 14 yards, running nearly east and west. The cleat of the coal in one portion of the seam is no criterion as to the direction of it in the other; for instance, the over coal may be much subject to slips (smooth slippery joints running in several directions), when the nether coal is often entirely free from them. The coal contains a good deal of pyrites or stone, which occurs in small patches, strings, and crystals, and as thin plates in the cleat or joints.
Naturally the seam is very liable to spontaneous combustion, even small heaps of slack lying upon the gate roads, and. the slack within the brattices, shown in Plate XVIII, have been known to heat and take fire. The roof is naturally a bad one. The big Rider coal is a moderately hard seam, and burns to a white ash; it is never worked. Occasionally it is found lying immediately upon the main seam, when an aggregate thickness of something like 18 feet of solid coal is the result. Again, it is here and there altogether absent, and the roof, instead of being composed of clay, is replaced by bind and occasionally by sandstone.
No workings of any description have been carried on either above or , below the main seam in the locality to which the following remarks refer. To those who are acquainted with the working of thick seams, an inspection of the plans, sections, and tabular statement of results in working given, will at once show the great contrast which there is, and the improvement No. 2 System must obviously be over No. 1 System; but for those who are not so well up in the subject, each system will be described somewhat in detail, supplemented with a few observations in support of, or prejudicial to, the one or the other.
The remark made some time ago by Professor W. W. Smyth, in reference to the wasteful system of getting the ten-yard seam of South Staffordshire may here be quoted as certainly applicable to the Moira district. He says:-"The acknowledged requisite for the most advantageous method of working, viz., the combination of the cheapest mode, of extracting the greatest possible quantity of mineral, with the safety and comfort of the men, has in this district been greatly modified by the circumstances of position, and an adherence to long established customs. In a few rare instances only have any attempts been made to substitute a new system for the old routine."
This was, up to within the last few years, the only method of working s practised. The one object in view being to extract the hardest or so called best divisions, which are chiefly confined to the upper half of the seam, led to the adoption of this system to the almost entire exclusion of any other. Plates XVII. and XIX. show the usual manner in which the underground workings were carried on, viz., a modification of the Long-wall method on the Gob-road system, i.e., commencing to work out the coal at or near the shaft, pillar, or main-road pillar side, and extending out wards towards the boundary. The mode of operating was as follows: The face of workings, which averaged about 6 feet 3 inches in height, was generally started out of the side of an opening oft' head (the headings being driven partly in the over and partly in the nether coal, say 6 feet high by 8 feet wide, thus avoiding timber for roof). The holing was 3 feet 3 inches in depth, the bottoms (grounds and scalps) were first benched up with hammer and wedge, and stacked up on one side out of the way for loading. The next operation was to draw the sprags and to break down the remaining coal, which was done by a set of men called drivers, 12 or 14 in number. They commenced work at 4 a.m., following the holers, who began several hours sooner, placed themselves along the wall at intervals of about 6 feet, and went through the laborious work of forcing off the coals by means of hammers and wedges up to the back of the holing, though very frequently much of the holing was left on. The coals were seldom if ever brought down in a mass, but were much broken up, and of course much slack was produced. The driving was followed up by the filling; four tubs were filled simultaneously, two in each end or bank. Preceded by the fillers a man was employed called a " turner-out," who overhauled the broken down coals and placed them conveniently for loading up; two tubs were filled at a time. Scarcely any small was sent out, say one tub in every ten was slack, work slack it is termed, as distinguished from heading slack or slack produced by cutting coal in driving gate-roads. This was loaded separately and paid for at a lower price than for the coal.
The fourth set of men, called “nightsmen," appeared upon the scene towards the close of the day's work. Their work consisted in pulling up the rails, clearing out the floor by throwing all the small into the goaf, setting holing sprags, drawing the back wood, setting a front rank of props, ripping the gate-road, building brattices, wax walls, etc. Figs. 1, 2, and 3, Plate XVIII. Owing to the great length of the stalls, often 100 yards, the push made towards the end of the shift to get the work out was anything but conducive to economy, an alarming proportion of large being gobbed in order to get it out of the way, to make room for the succeeding shift.
The direction of the gate-roads depended upon that which the ends or cuttings took, and these were of course regulated by the length of face required, by faults or other boundaries, the average distance apart would be from 80 to 100 yards. They were made and maintained as follows: On leaving the shaft or other solid pillar of coal, carefully built stacks or brattices of cordwood about 3 feet in width were put up on either side of the road from floor to roof, leaving a clear width between of from 8 to 9 feet. Plan and cross Section, Figs. 1 and 2, Plate XVIII. Beyond these at a distance of about 3 feet were formed walls constructed of tough, well-tempered clay called wax, about 10 inches thick, well beaten, and carefully filled in up to the solid untracked coal. This wax wall was intended to prevent fire stinks from breaking out along the rib side, which purpose it only partially or in some instances fulfilled. Wax walls or not, a fire-stink very frequently, sooner or later, made its appearance at the opening off, often giving much trouble and lasting for many years. It was the practice to fill in the spaces between the brattices and the wax walls with slack. As the faces advanced these arrangements were carried forward, always being kept up to within a few yards of the working face. The roof was ripped about 3 feet 6 inches, and generally required barring. Fig. 3 shows the condition of a gate-road after full subsidence had taken place. No packs were built in the stalls excepting at the fast ends; these were for keeping open a short air-way along the curving from the face to the shallow pits (curry pits), which were sunk down into the nether coal, and gave access to the return air-course formed beneath the goaf. See dotted lines, Plate XVIL, and Fig. 1, Plate XVIII. These curry pits were put down at say every 20 yards, and short bolt-holes, or thirls, were driven from them into the air-way, as each new pit and thirl was made the one to rear was stopped off. The return air-ways were only about 3 feet square, and frequently extended many hundred yards before joining the main air-way, if one of large dimensions were employed, which was not at one time the rule. The quantity of ventilation capable of being passed along such windings, as the air-courses were termed, was very limited. They got out of repair, and were not too often travelled.
As the workings increased in distance from home they naturally became very close and even hot, in fact anything but comfortable to work or even to travel in. Gob fires, and the breaking in of water here and there, also helped to condemn the system. Naked lights were used; gas was seldom seen. For supporting the roof ordinary puncheons were used, with clogs, or lids, about 30 inches long placed on the top of them. Cast iron props were tried, but were abandoned being considered unsuitable. The works were carried on under the Butty system; there were about thirteen butties in each stall. Holing was paid for by the stint; each holer could get six stints per shift, or 12 yards along the face, 3 feet 3 inches under. The drivers got say five sets for a day's work, a set consisting of 11 yards on the face by 3 feet forward. Filling was done at per ton. The nightsmen were made up of one butts, two slack throwers, and one repairer. All work performed in the stalls was paid for by the butties, or contractors, at fixed prices regulated by the manager and viewer. The yield per acre was about 4,750 tons. See tabular statement, page 190. In a few instances the above method of working was practiced with this difference, that instead of working ouOmrds by gob-roads, working home in the solid was substituted, the goaf being all left behind. This plan was in some ways an improvement, and the charter or contract price for getting was about 2d. per ton less, but the extra cost incurred in driving the gate-roads had to be added, so that on the whole not very much was gained by the change, though the greater convenience obtained with respect to ventilation, less chance of spontaneous fires, comparative freedom from water, gas, etc., less timber required, more easily maintained roads, a knowledge of the size and direction of faults to be crossed, and so forth, was clearly a step in the right direction.
This was commenced about four years ago. The leading features are, to work out a much larger proportion of the seam, to do away with the costly process of wedging down the bulk of the coal, to produce the coal in large masses, thus obtaining it in a better condition for stacking or carriage, and to materially reduce the cost of extraction. This method is known as working back or working home. The gate-roads, air-courses, and opening-off headings, are first driven, thus proving any faults, old workings, etc. The stall faces are then started. All brattices, wax walling, carvings, curry pits, long windings, gob fires, ripping of gateroads, etc., incidental to No. 1 System, are thus rendered unnecessary.
The gate-roads are formed in the nether coal, leaving about 5 feet of coal for a roof, and 1 foot under-foot. They are driven about 50 yards apart. See Plate XX.
These roads are driven on an entirely new method, which enables a greater proportion of round coal to be obtained than has hitherto been produced by heading in the district. In the first place, what may be called a pioneer heading (3 feet 3 inches by 3 feet 3 inches) is driven forward on one side, or in one corner, level with the floor of the intended way, to a distance of say 5 yards. Secondly, the coal is holed for about 6 feet along the side of the little head 6 feet deep. Thirdly, the coal is cut or nicked on that side which is over the little head to a depth of about 6 feet, this is termed a shoulder-cutting. Lastly, a shot is put in, say a foot or 18 inches from the roof, and the coals fall in large blocks. The finished size of such a gate-road is 1) feet wide by 8 feet high. The pioneer or little head is always kept about 3 yards in advance of the back of the large heading, For each yard advance, about 7 tons 7 cwts. of coal and small will be produced, about 73 per cent. of which is large coal. See Table page 190. The weekly advance wail be about 17 yards =125 tons.
Four men can work at the back simultaneously, viz.:-One to drive the pioneer heading, one to hole, one to shoulder-cut and drill the shot hole, and one to load up the coal. The ventilation is maintained by brattice cloth 8 feet wide. All the over coal being left, no timber is required to carry the roof. Air-ways, if formed for ventilation only, are made about 4 feet square, when of no great length, and always in the bottom coal.
Turning to Plate XXII., it will be seen that the holing is made to a depth of not less than 6 feet, and when the sprags are taken out the coal generally falls up to about 8 feet in thickness from floor. A shot has occasionally to be put in to bring the coal away, but there is a good shed at top. When three or four webs or falls have been worked off, packs about 9 feet in width are built, having spaces or bays between them 18 feet wide, excepting that opposite the gate-road, which is only 12 feet in width. Plate XXI. These packs are carried forward in parallel lines, being added to as each web is removed. Plates XX. and XXI.
The over coal, or gob coal as it is commonly called, is systematically taken down in the wastes between the packs up to the second rank of props. Coal on the top of the packs is wrought in the following way, see Plates XXI. And XXIII. :- It is worked out backwards or away from the face, commencing at a bolt-hole or thirl, which is first cut through in the gob coal a yard or two to the rear of the front of the pack, and going in about 10 yards, generally leaving about two yards of coal against the last bolt-hole. At the back of the wastes, as soon as all available coal has been got out, the timber is drawn, and the roof allowed to fall in, and should the place show signs of heating, it is forthwith stacked out, i.e., a cross pack, one built right across a waste between two ordinary packs, is put in, and when necessary, the front of it is thickly smeared with well tempered clay. The process is called waxing; but with regular working, and a moderately good roof, this is seldom required. It is customary to put in a cross pack about every 20 yards. The packs are built chiefly of stone coal got in the waste. The only drawback to this system of working seems to be the large percentage of small produced, caused by breaking up the nether coal for loading into tubs. It will often get (fall over from the face) in immense solid blocks, from G to 10 tons in weight, but will not stand much handling and knocking about.
The mode of ventilating is very simple and efficient. Besides the main current of air coursing along the faces. a second one flows through the wastes, passing from one to another through the bolt-holes in the upper coal. Plates XXI, and XXIII. As the result of changing the system, whereby the narrow windings (air-ways under the goaves) have been done away with, the water-gauge is now -6 inches as against -95 inches under the old system. See tabular statement, page 190. Gas is seldom seen, and it is usual to meet with it only in the broken down places in the backs of wastes, and against rib-sides at the goaf edges at the rise end of a range of stall faces.
The several operations performed in getting the coal in the manner just described, are carried out thus:-The holing is done by a shift of men who work from 2 a.m. till say 10 a.m.; each man holes at least one stint, that is, 7 feet in length and G feet under = 42 square feet. Butties then draw the sprags and bring down the coal; they also get the gob-coal, and assist in building packs and setting timber, stacking out, etc. At 7 a.m. the fillers come in and work till 5 p.m.; one of the butties always accompanies the turn, loading out the coals. The work is paid for in the same way as under the old system. It is generally found that the coal gets best, produces the greatest quantity of large, when it is worked about three on face to one on end, known as horn coal.
The reason No. 2 System was adopted was chiefly on account of the very high cost of getting and the large consumption of timber attending the old method. The greater uniformity in thickness and quality of the nether as compared with the over coal also favoured the change, which, although entailing the loss of a small portion of the over coal necessarily left in the wastes, amounting to say 10 per cent. of that particular bed, is probably fully compensated for in the extra quantity of large coal obtained from the nether seam due to the new system of holing and getting. The grounds also which are now obtained whole and in blocks of almost unmanageable size, were formerly knocked to pieces by the wedging system. Thus it will be noticed that the working of the entire thickness of the nether coal is a clear gain. Compare Plates XIX. and XXII.
As regards accidents due to the change of system, so far there has been nothing serious whatever, and it is considered that the new method is quite as free from danger as the old one. Gas when seen is now much further away from the men than before. No change in the lighting has been introduced, naked lights being the rule. Shot firing is only practiced when the coals will not easily fill, and when it is required to break up blocks too large to be dealt with, with hammer and wedge. The whole length of face only being turned over or gone through once a week allows the roof to settle and weigh upon the timber to a considerable extent, and it is thought that the driving of more gate-roads, say about double the number now formed, would materially benefit the system; it would at any rate enable the output to be largely increased if required without extending the pit room; in fact were it practicable, four times the number of hands could be put into the same length of face, or the output increased in like proportion. It must not be supposed that the so-called slack sent out of the works is really quite small stuff, for about 66 per cent. of it consists of cobbles and nuts, the remainder being dust. About 10 per cent. of the gross output is slack. Were it practicable a considerable extra quantity of slack would be sent out without seriously affecting the safety of the stalls in regard to fire stinks, it is necessary, however, to have something to gob with in order to prevent them.
The advantages derived from the alteration of the systems of working may be summed up as follows:
1.-Less waste in working, or nearly double the yield for the same area worked.
2.-Less liability to accidents, particularly from fire-damp.
3.-Almost entire immunity from spontaneous combustion.
4.-Reduced cost of getting, including timbering.
5.-Less pit room required, or in other words, quadruple the output for the same length of face.
6.-Less men per stall to the extent of 41 per cent., or an increased weight of coal got per man per day.
7.-A far better roof to work under.
8.-Ability to work the lower half of the seam where the upper portion is inferior.
9.-Having the coal-field proved before commencing to work back, thereby enabling faults to be crossed and dealt with in the most advantageous way.
10.-The abolition of wedging down the coals; a very laborious, wasteful, and expensive operation.
11.-Increased facilities as regards ventilation of the working places and gate-roads.
12.-Greater comfort afforded to both men and horses whilst at work, due to a purer and cooler atmosphere, more even roads, more space to work in, and getting more work out of the men per shift.
In conclusion, the revolution in the system of working this seam of coal has resulted in two main features:
1.-Greatly increased economy in working expenses combined with much less waste of coal in the pit.
2.-A lowering of the average selling price per ton in consequence of two things:
a.-A smaller proportion of the best quality due to the working of about one-half the area for the same output. b.-Getting the lower portion of the seam, which is comparatively soft, and for which something like two shillings per ton is obtained less than for the upper part of the seam. So that although profits may be no greater than formerly, they will continue under similar circumstances to be made over double the time that they otherwise would, because the seam is only being exhausted at one-half the former rate.
The author hereby acknowledges his thanks to Mr. G. Buxton, who has assisted in preparing this paper, and under whose supervision the new system of working described has been so successfully carried out.
The PRESIDENT said, that this was a very interesting and descriptive paper, about work they were not accustomed to here. He proposed a vote of thanks to the author, which was carried by acclamation.
From: The North of England Institute of Mining and Mechanical Engineers Transactions, Vol. XXXII (1882-83), p181-190