Volume 17 (XVII), 1898-1899, published 1900
Description of the Pumping-Plant at the Stank and Yarlside Mines in the Furness District of North Lancashire.
By Jas. Davison.
The iron-ore mines of Furness are situated within the area of the Carboniferous Limestone of the district. This limestone is thickly-bedded and traversed by numerous vertical joints, in which there is frequently more or less open space. It is also subject to weathering, and lends itself to the formation of subterranean channels and caverns by percolating waters. These channels in many instances extend long distances and penetrate to great depths, forming underground watercourses which drain the surface of the country and convey large quantities of water into the mines that come in contact with them. There is also in the western part of the district a considerable fault running in a northerly and southerly direction, by which the limestone is thrown down westward to unascertained depths, and the Permian sandstone overlying it is brought into juxtaposition with the limestone on the eastern side of the fault. This sandstone is also proved to be a very heavy water-bearing rock.
The Stank and Yarlside mines are situated in the south-western corner of the Carboniferous Limestone area, close to the great fault, and extend eastward along the course of several veins. The workings of the mines have from time to time come into contact with several large caverns and underground watercourses, as described above, and considerable quantities of sand and water have been liberated on several occasions in the course of the development of the mines. Strong dams of concrete and brickwork, with heavy doors of pitch-pine plated with steel to close on such emergencies, have been built. In one instance the volume of water that came away after blasting in one of the bottom-levels was so great that the men had barely time to climb the ladders to the upper working. The door, put in to protect the pumps, being open for the purpose of approach to the workings where the men were engaged, and there being no time to close it, the water rose so rapidly that in 15 minutes there was over 90 feet of water in the shaft. The pumps were worked for a month under water, without lowering it, and finally a a diver was employed to go down and close the door.
The large quantity of water that has now to be dealt with being unforeseen in the earlier development of the mine, engines and pumping plant of comparatively small size only were provided; but, as necessity has arisen, one pumping-engine and plant after another has been erected until, at the present time, there are 6 and sometimes 7 engines delivering water to the surface. About two thirds of the water is pumped from the 720 feet level and one-third from the 420 feet level. The quantity of water pumped varies from a maximum of 6,860 gallons per minute in winter to a minimum of 4,940 gallons in summer. The average quantity per minute pumped during 1898 was 5,662 gallons, which is equal to over 8,000,000 gallons in 24 hours ; and the maximum quantity in winter is 9,878,400 gallons in 24 hours.
Adit-levels are brought to the pumping-pits from the lowest points of the adjoining valleys, to shorten as much as possible the vertical distance of pumping.
The following table describes the types of engines and pumps with which the mines are now furnished and their dimensions :—
No. 11 Pit. — In addition to the above pumping-plants, there is also an auxiliary horizontal engine (with a cylinder 25 inches in diameter) formerly used as a winding-engine. This has been compounded and geared 5 to 1 to work two 24 inches rams, each 5½ feet stroke, pumping from the 720 feet level to the 558 feet level to supply the two 20 inches rams at the No. 10 Pit.
The No. 5 Cornish and the No. 11 Hathorn-Davey are the two pumping-engines (each one of its type) which do the largest amount of work. No. 5 pumping-engine averages throughout the year 5 strokes per minute, and delivers 238 gallons each stroke, equal to 1,190 gallons per minute to an average vertical height of 882 feet. No. 11 engine averages 6.27 strokes per minute, and delivers 267 gallons each stroke, equal to 1,674 gallons per minute, to a vertical height of 550 feet. The average duty of these two engines is about equal.
The following remarks on the different types of engines now at work at these mines are offered for the consideration of the members :—
(1) Engines with geared wheels, pumping-shafts, cranks, etc., where heavy pumping is concerned have been found very unsatisfactory and expensive in working and repairs ; the various and severe strains set up in the several working-parts are almost sure to lead to occasional if not frequent breakdowns, and the transmission of power from part to part must occasion loss. The experience gained at these mines is in condemnation of the use of the geared engine for heavy pumping.
(2) The Cornish engine is well adapted to its work, but being only single-acting it cannot do as much work as a similarly sized double-acting engine will do. Its action during the stroke is more irregular and violent than the Hathorn-Davey engine, causing greater shock in the pump, and making it nesessary to divide the pump into shorter lifts.
The ponderous beam and strong building necessary to carry it occasion greater outlay in erecting this class of plant, and in case of loss of the load in the pit the result is often a very serious breakdown. With these exceptions, and as regards repairs in an ordinary way and the matter of duty, the engine does not appear to be inferior to any other type of engine
(3) The Hathorn-Davey engine is double-acting, and therefore a much smaller engine of this type will do the same amount of work as that done by the larger single-acting Cornish engine. In addition to this, it allows of two rams being used, which discharge into the same delivery-pipe ; there is also less shock in the pumps, owing to the more uniform speed during the stroke : consequently longer lifts can be used, which means fewer clack-boxes, rams, stuffing-boxes and glands, and these lessen the first outlay and also the cost in working, and a much cheaper building can also be used to house the engine. There is further the fact that loss of load in the pump does no damage to the engine, and this has been proved at the No. 10 pit Hathorn-Davey engine on several occasions. This engine has been at work nearly 19 years, and the piston has never been known to strike the cylinder-end. The valve-arrangements on the No. 11 pit Hathorn-Davey engine, which are of the double-beat Cornish type, do not govern the engine as perfectly as the ordinary slide-valves on the No. 10 pit Hathorn-Davey engine. In putting down this type of engine, it has been found that it is very important that the connecting-rods, bell-cranks, gudgeons and bearings be made of the very best materials and of ample size, otherwise a great deal of trouble and expense will be incurred in renewing and strengthening them.
Referring now to the class of pump — ordinary plunger or rampumps attached to heavy spear-rods connected to the bell-cranks of the horizontal engine or beam of the Cornish engine, as the case may be, are almost exclusively used, In the smaller pumps, the clack-boxes are placed immediately under the delivery-pipe, and they are furnished with side-doors and hinged flap-clacks, leather "geared" or "grathed." For the larger pumps, chambers are opened in the sides of the shaft for the clack-boxes, which are furnished with heavy top-covers and double-beat valves geared with strips of guttapercha, set on edge in dovetailed grooves cut in the face of the beat of both seating and crown of valve. The drawings supplied show the arrangement of pumps as fixed in the pit (Figs. 1 and 2, Plate VIII.), and also the details of the valves used in connexion with the 20 inches ram-pumps (Fig. 8, Plate VIII.).
For the Cornish engines, the lengths of lift vary from 240 to 860 feet, but it is found that the shorter lifts are much better in working and are not so troublesome as regards keeping the joints tight and maintaining the glands in good order. With the Hathorn-Davey engine, there is no trouble with blown-out joints in the pumps, although the lifts are over 878 feet in vertical height they work without shock, and the glands will last for 2 years without repacking.
It has been found that it is desirable that all foundations for heavy permanent pumps should be built on solid rock or cement concrete, and where girders are used that they should be made of wrought iron or steel and never of timber, as with timber it is almost impossible to avoid springing, and thereby causing broken joints and sometimes pipes.
The cost of pumping at these mines averages 1¼d. per 1,000 gallons pumped. This is not considered high, having regard to the price paid for fuel owing to the distance of the mines from the coal-fields. The duty of the engines is not set forth, as this depends so largely on the kind of fuel used, the temperature of the feed-water, the efficiency of the feed-water heaters, and other conditions which in this brief paper it is difficult to mention in detail. What is more especially aimed at is to set before the members of the Institute, on their visit to this district, the extraordinary quantity of water that has to be dealt with and the means employed to cope with it, and to invite discussion thereon.
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