The writer, in giving a short account of the sinking of the shafts at Claravale colliery, intends principally to describe the difficulties encountered from large feeders of water, and generally the arrangement of machinery adopted in the accomplishment of the work.

The Claravale colliery is one of a group of five collieries owned by the Stella Coal Company — viz., Emma, Addison, Stargate, Blaydon Main, and Claravale — which, combined, have a yearly Output of about 600,000 tons of coal.

Claravale colliery is situated 1 mile east of Wylam station, and stands on the south side of the Carlisle branch of the North-Eastern Railway. There are two shafts, 99 feet apart, each 14 feet in diameter, and both have been sunk to the Brockwell seam, which lies at a depth of 395 feet. The sinking of these shafts, owing to the extraordinary quantity of water, occupied a period of over three years. When it was first determined to sink these shafts, every endeavour was made to ascertain what feeders of water were likely to be met with, and the result of these enquiries showed that a quantity of 500 gallons per minute was the probable maximum. It was therefore determined to sink the pits with the pumping-arrangements applied to the winding-engine, and to erect a large Hathorn-Davey pumping-engine (as a permanent plant) to raise 2,500 gallons per minute, and thus to carry out an extensive scheme of drainage for three of the collieries. Instead, however, of a feeder of 500 gallons, there was found the quantity of 2,000 gallons per minute for some time, and of 1,100 gallons per minute permanently. If, of course, by any possible means, the actual feeder could have been foreseen there would have been very much less difficulty and delay attached to the winning, as machinery of sufficient power would have been made ready and applied in the beginning.

It being decided that the shafts should be 99 feet apart, a temporary heapstead was erected, with a sinking-engine for each shaft, as shown in Figs. 1, 2, and 3 (Plate IX.). Sinking operations were commenced at the No. 1 shaft on April 22nd, 1890. The sinking-engine at this shaft had two horizontal cylinders, each 14 inches in diameter by 16½ inches stroke, drum 5 feet in diameter, and geared at 4 to 1.

The No. 1 shaft was marked out with a diameter of 16¼ feet, but the sandy nature of the ground soon obliged this to be increased to 19¼ feet. On the following day a small quantity of water appeared in the shaft, and caused the sides to fall in. The sand was cast out, and four oaken cribs, 6 inches square, with battens 7 inches by 21 inches, were inserted. The water, becoming troublesome, was taken out at intervals by a watertub, which emptied into a cistern fixed on the heapstead.

The next operation was the driving of piles from the surface 7 inches by 2½ inches by 15 feet long, shod with iron, the shaft being thereby reduced to 17½ feet in diameter. The water at this stage was 13½ gallons, and as it gradually increased to 26 gallons per minute, sinking ceased, until a special pump, 6 inches in diameter by 2 feet stroke, and steam cylinder 12 inches in diameter, was fixed on a baulk 12 inches square, and hung in the shaft by a rope from the crab-engine.

The stone-head was reached at a depth of 31 feet, and sinking continued, with short interruptions for lowering the special pump, till a depth of 87 feet was reached. At this point a feeder of water was tapped, and, increasing from 20 to 200 gallons per minute, the special pump could not cope satisfactorily with it.

Sinking was, therefore, discontinued till a lifting-sett, 18 inches in diameter by 6 feet stroke, was attached to the winding-engine (Figs. 1 and 2, Plate IX.). The horizontal winding-engine with two cylinders, each 24 inches in diameter and 5 feet stroke, actuated the pumps by means of a crank applicable for 5 or 6 feet stroke on the second motion-shaft, on which was a spur-wheel 12¼ feet in diameter, driven by a pinion 5¾ feet in diameter on the drum-shaft. The pumping quadrant was connected to the crank by a connecting-rod in two pieces (Fig. 2, Plate IX.). The pumps were hung in the shaft by hanging-spears of pitchpine 8 inches by 6 inches, in lengths of 30 feet, attached to the ground-crab by a hemp rope, 3 inches in diameter, passing over the pulley-blocks, as shown in Figs. 4, 5, 6, and 7 (Plate X.).

While this machinery was being erected, a concrete ring 8 feet deep by 2 feet wide was formed in the shaft, and walling proceeded with, the finished diameter of the pit being 14 feet. The walling consists of fireclay lumps, 9 inches wide by 6 inches deep by 12 inches long, moulded to suit the circumference of the shaft.

On the erection of the pumping-arrangements (Fig. 8, Plate X.), sinking was resumed; but the feeders increased very rapidly, till they reached 450 gallons, and later 600 gallons, per minute. Unfortunately, at this time the bed-plate of the winding-engine was broken, and delayed the work for two or three days; but, after this damage had been repaired, all went well, the feeder remaining at 600 gallons, until the Towneley seam was reached at a depth of 191 feet 2½ inches. It may here be remarked that No. 2 pit was being sunk during the time occupied in the above operations (Fig. 9, Plate X.). Having reached the Towneley seam, a scaffold was fitted up, and a heading was driven 99 feet, and holed into the bore-holes, which had been put down in advance of the sinking in No. 2 pit. While this connexion was being made, a length of walling was completed.

On resuming sinking, the next difficulty encountered was a feeder of 200 gallons, bringing the total up to 800 gallons per minute; and it was deemed necessary to fix a special pump, with a steam-cylinder 21 inches in diameter, and a pump-barrel 14 inches in diameter and 3 feet stroke, in the Towneley seam to raise to the surface the water which was collected from both shafts above that seam. Considerable trouble was caused by the bursting of the working-barrel of this special pump, which twice occurred, and in each case immediately on starting — in fact, no water was pumped — and it was decided to substitute a different type of pump. The type of special pump which failed in two instances, immediately on starting to pump, was that in which the working-barrel and clack-seats were formed of one casting, and that which proved successful was that in which the clack-seats were made of separate pieces, known as the box-type, as in the case of the Hathorn-Davey underground pumping-engine.

During the time when this special pump was being fixed, headings were driven east and west in the Towneley seam.

Shortly after the new special pump was set to work, and sinking resumed, the pumping-crank of the winding-engine sett failed, by a fracture near to the pin-hole. No serious delay ensued, as the crank had been provided with a second pin-hole, so as to enable the pumps to be worked with a 5 as well as a 6 feet stroke.

When the sinking arrived at the white sandstone overlying the Tilley seam, a large feeder of 500 gallons (making a total of 1,800 gallons per minute) was met with, and quickly increased to 2,000 gallons, to be raised to a height of 230 feet. The winding-engine pumping sett, on which a new 6 feet stroke crank-pin had been fitted, was kept going at fifteen strokes per minute, and water-tubs were worked by the sinking-engines in each pit, but the water could not be lowered. Eventually, after struggling for some time with this feeder of 2,000 gallons per minute, sinking was abandoned until the permanent pumping-engine was erected. This engine was a Hathorn-Davey compound expansive condensing engine, fitted with steam-jackets ; the low-pressure cylinder was 68 inches and the high-pressure cylinder 88 inches in diameter by 10 feet stroke, working at a boiler-pressure of 80 lbs. per square inch. The engine worked a single lifting-sett, with a bucket 24 inches in diameter, at the No. 2 shaft. This lifting-sett arrangement was only temporarily used for sinking purposes, and was afterwards replaced by two ram-pumps 22 inches in diameter, as will hereafter be described.

After a delay of about three months, the 24 inches sett of pumps was ready for work, and sinking was resumed with one sett of pumps 18 inches in diameter in No. 1 pit, and one sett 24 inches in diameter in No. 2 pit; but as the feeder still varied from 1,700 to 2,000 gallons per minute, it was determined to tub off the sandstone lying above the Tilley seam, which was extremely porous, and notorious in this district for its feeders of water (Fig. 10, Plate X.). With this purpose in view, a bed was formed for a wedging-crib in a stratum of blue metal, which was impervious to water, and situated 6 feet below the post or sandstone. A length of 36 feet of tubbing, in segments 4 feet long by 2 feet high by inch thick, was accordingly placed in both shafts. When all was sealed off, it was found that about 950 gallons per minute had been kept back by the tubbing. Up to that time, the 18 inches sett of pumps, down to a depth of 271 feet, had been delivering to the surface; but the delivery was now turned into the Towneley seam, and so flowed along the drift between the shafts to the 24 inches sett of pumps in No. 2 pit (Fig. 11, Plate X.).

When the sinking had attained a depth of 356 feet, the feeders were 1,030, and at 864 feet 1,100 gallons per minute, which quantity was maintained until the Brockwell seam was reached at a depth of 898 feet; and, in fact, it is the constant feeder of the colliery at the present time, after three years of working.

So far, the sinking of No. 1 pit has been briefly described, and it is now desirable to consider the progress made by the No. 2 pit. There was no particular difficulty in the sinking of this shaft, as the water drained from it to No. 1 pit until a depth of 68 feet was reached (Figs. 8 and 9, Plate X.), when it was found necessary to put down a bore-hole 8 inches in diameter to the Towneley seam, in which a connexion had been made from the No. 1 shaft. Before reaching the Towneley seam, the 8 inches hole was found to be too small, and it was enlarged to 4 inches in diameter; but even then it was incapable of running off the water to No. 1 pit, and finally a second hole, 7 inches in diameter, was bored, which enabled the Towneley seam to be reached. It was at this stage that the special pump before mentioned was erected, and the accompanying difficulties of the failure of the working-barrels ensued. When the improved type of special pump had been erected, sinking progressed favourably until the sandstone overlying the Tilley seam was encountered.

As in No. 1 shaft, all operations were abandoned until the main pumping-engine, temporarily adapted to work a lifting-sett 24 inches in diameter and 10 feet stroke, was ready. When this pumping-plant had been erected, sinking was resumed, the 24 inches sett of pumps being hung by hanging-spears of pitchpine 10 inches by 8 inches, in lengths of 40 feet, and attached to a special steel galvanized rope 3 inches in circumference, passing over 4 and 3 pulley-blocks, as shown in Figs. 4, 5, 6, and 7 (Plate X.). An accident then occurred, which illustrates the extreme care necessary in dealing with heavy pumping appliances. While a short pump was being added, the Y-bolts, which connect the spears to the quadrant, being loosed, the spears slipped away and broke the crab-chain (made of 1 1/8 inch B.B.B. iron having a breaking strain of 45 tons) and also so damaged the crab-rope socket that it had to be replaced.

As soon as the sandstone above the Tilley seam was drilled into, more water appeared and quickly rose in the bottom of the shaft, and as illustrating the open nature of this rock, it was found that the water had come from No. 1 pit, leaving it quite dry. The feeders at this time were 2,000 gallons per minute, as described in the sinking of No 1 shaft. The tubbing-off of the Tilley seam sandstone was then completed.

Sinking with the 24 inches sett of pumps had now reached a depth of 245 feet, and the weight became so great, viz., 100 tons hanging over locks on a steel-rope 3 inches in circumference, that it was not thought advisable to carry it to any greater depth. To obviate this difficulty, a cistern was fixed just below the Towneley seam, and the 24 inches sett was pumps was lifted to this point (Fig. 11, Plate X.). The arrangement of delivery was now as follows :— Bore-holes having been put down to the three-quarter seam, and a connexion made in that seam from the No. 1 shaft, the water was conveyed thereby to the 18 inches sett of pumps, which delivered into a cistern, from which the 24 inches sett of pumps delivered to the surface (Fig. 11, Plate X.). After continuing the sinking favourably for some time, a serious accident occurred: a spear-joint of the 24 inches sett of pumps gave way, all the bolts 1 3/8 inches in diameter having failed, causing the pistons to move so rapidly that the cover of the low-pressure cylinder (68 inches in diameter) was split in several places. The damage was temporarily repaired by plating, and eventually a new cover was obtained.

It may be mentioned that, owing to the enormous quantity of water and to the rapidity with which it rose in the pit-bottom, it was quite impossible to change either the clacks or the buckets at the doors, and consequently, whenever a failure occurred, which was very frequent, the slow and laborious task of lifting the whole of the spears to the surface and fishing for the clack had to be resorted to.

When a depth of 827 feet had been reached, the placing of the permanent ram-pumps was commenced. There are two ram-pumps each 22 inches in diameter by 10 feet stroke, and the rising main-pipe 20 inches in diameter is common to both. The well in which the suction-pipes are placed is 14 feet by 6 feet by 15 feet deep, and the chamber in which the various working-parts are situated is 20 feet high by 14 feet square. The clacks are of double beat type, grathed with gutta-percha, and are arranged in nests of 7, each clack being 9 inches in diameter with a lift of inch. The rising main-pipe is secured to the shaft-buntons, 10 inches square, at intervals of 25 feet, by collaring-buntons 8 inches square. The whole of the pumps rest on five steel girders, 2 2/3 feet in depth (See Fig. 12, Plate X.).

The crab-engine, used for lifting the various pumps and other heavy weights, was of the following dimensions :— Cylinder, 8 inches in diameter by 16 inches stroke ; drum, 6 feet in diameter ; geared at the worm, 30 to 1; intermediate shaft geared 4½ to 1 ; and second shaft geared 7½ to 1. It can be set to run at 225 revolutions to 1 of the drum, or at 1,012 to 1 of the drum, and is capable of lifting a weight of 60 tons.

The ram-pumps are capable of raising 2,500 gallons of water per minute to a height of 327 feet at a speed of 8 double strokes, or 160 feet of piston speed per minute.

The Brockwell seam was reached at a depth of 395 feet without any further mishap.

The water below the level of the ram-pumps (which are at the three-quarter seam level) is raised to the ram-pumps by means of a tail-bucket sett of pumps attached to one of the ram-pump spears lifting 96 feet, the bucket being 18 inches in diameter, and 10 feet stroke. Provision has also been made for the addition of a second tail-pump, should the feeders below the ram-pumps require such assistance. When the two tail setts are in use they will raise 1,770 gallons per minute up 96 feet, making a total of 300 pump horse-power.

When the sinking had been completed, it was considered expedient to erect underground on a level with the main ram-pumps a duplicate pumping-engine to meet contingencies, and capable of raising 1,500 gallons per minute when running at 24 strokes per minute. This engine has two cylinders, each 28 inches in diameter by 4 feet stroke, working rams 14 inches in diameter into a rising main-pipe 12 inches in diameter. The engine is of the duplex (quadruple acting) type, working with steam, whose pressure at the engine is about 70 lbs. per square inch.

The total capacity of the two pumps, in case of emergency, reaches 4,000 gallons per minute, leaving a margin of 2,900 gallons over the average feeder, which has been found to be roughly 1,100 gallons per minute.

As the reserve engine is intended simply to be used in case of a serious breakdown of the permanent pumping-engine, economy of steam was not considered essential, and therefore the high-pressure type was adopted as being cheaper in first cost.

Figs. 13, 14, and 15 (Plate X.) illustrate the spear-catcher, as used to recover broken spears of the 24 inches sett of pumps, and Figs. 16 and 17 represent the clack-drawer.

The writer regrets that he is unable to give any satisfactory particulars as to the coal consumed per indicated horse-power per hour, it being impossible to obtain sufficient water to keep the pumps going more than half-speed for any length of time.

The whole of the sinking of these pits was successfully carried out under the superintendence of Mr. J. B. Simpson, managing partner of the Stella Coal Company, assisted by Messrs. Archbold and Pedelty, engineers, and Mr. W. Rochester, colliery manager, and it is owing to the courtesy of the Stella Coal Company that the writer has been enabled to collect the information necessary for this paper.