While the circular form of magnet is that generally favoured, variations are made to comply with different requirements. Some articles, such as steel rails, pipes and iron rods, from their distinctive shape, only present an extremely limited surface upon which the magnetic pull can be exerted. As a rule, to enable such articles to be handled with efficiency and speed, two magnets, rectangular in form, and spaced a short distance apart, are used. The magnets are coupled together, but maintained a specific distance apart by spacing bars, while they work in unison. While the area available for contact upon each magnet is somewhat reduced, as compared with the circular type, this deficiency is counterbalanced by the ability to apply the magnetic lifting effort at two points.
It is doubtful whether the true money-saving possibilities of the lifting-magnet are really appreciated. The initial outlay may appear heavy—in the case of the British magnet to which I have referred it ranges from £150 to £600—$750 to $3,000—according to dimensions, face-form and lifting capacity—but this expense is readily recouped. The lifting-magnet is not only a time-saver but it enables given work to be accomplished with fewer men. In some instances this displacement of labour has attained striking proportions. At one steel-works a lifting-magnet of 52-in. diameter was installed at a cost of £400—$2,000. It is employed for handling pig-iron, and in this work has dispensed with fifty men. The saving in wages, which its introduction has rendered possible, sufficed to defray the capital cost of the apparatus during the first three months of its use.
The results recorded at another establishment are equally impressive. A 36-in. magnet was acquired, and for one specific duty—loading trucks—was employed for a total of twenty hours during the month. Previous to its acquisition this work was carried out by manual labour, and it used to demand the combined efforts of ten men for ten hours to load the vehicle, the cost being £4—$20. With the magnet the truck is now loaded in two hours and at a cost of 8s.—$2—this figure being inclusive of all charges—electric current, depreciation, interest, labour, etc. In the course of the year the magnet puts in 240 hours truck-loading, the number of trucks dealt with during this time being 120. The saving effected by the utilization of the magnet is thus £3 12s.—$18—per truck or £437—$2,185—per year. Seeing that the magnet at the time of its installation cost £150—$750—it will be seen that it pays for itself approximately three times over in the course of each twelve months, and that upon one single range of duty for an insignificant period of time.
Under manual conditions of handling scrap and at the current contract trade union rate the cost is 1s. 4d.—33 cents—per ton. With the lifting-magnet, including labour and depreciation, the cost is only one penny—2 cents—per ton for this work—a reduction of 1s. 3d.—31 cents—per ton! At the works of the Stobie Steel Company, Dunston-on-Tyne, the initial cost of the lifting-magnet was recovered during the first four months it was used. This company declares that the annual saving which its employment effects is £800—$4,000.
But the applications of the magnet are not confined to lifting and carrying operations. As an instrument for breaking up masses of steel too large to be handled conveniently, or to be passed into the cupola of the furnace, it cannot be excelled, either in point of efficiency, safety, or economy. Breaking-up is carried out by what is known as the “skull-cracker,” which comprises a roughly-cast ball of steel which may weigh as much as 22,400, 27,000 or even 36,000 lb. This is picked up by the magnet and lifted to the desired height. The current is then switched off, releasing the ball to fall and to strike the scrap-boiler or some other cumbrous piece of junk a terrific blow.
While the “skull-cracker” has been in vogue for many years with mechanically operated devices, and so is not peculiar to the magnet, yet this latest development represents the highest achievement yet attained in this particular direction. Under mechanical conditions from four to six men are required to carry out the work successfully. With the magnet and ball the task can be fulfilled by two men—if exigencies so demand it can be completed single-handed by the crane-magnet operator—while the time occupied in such essential destruction is very much less, more efficiently accomplished and with complete safety, because under mechanical conditions breaking-up is generally regarded as highly dangerous work. A further advantage is offered by this system. The “skull-cracker” can be lifted and dropped alternately until the scrap has been reduced to suitably sized pieces, and then the magnet, disdaining the ball, can pick up the pieces of junk to bear them away to the furnaces without any delay.
Despite the forward strides which have been made in regard to the adoption of the magnet in the British iron and steel trades during the past four years, this system of handling ferrous metals is still in its infancy. It has been neglected far too long. Yet it is a force which in the future must play an increasing important role, because it is generally admitted that, to offset the higher wages incidental to production, it is imperative for manufacturers to exploit fully every possible time, labour, and money-saving device. The magnet is one of the most attractive contributory factors to this end, especially in connection with the handling of iron and steel waste, that has yet been contrived.
CHAPTER XVI
RECLAIMING 321,000,000 GALLONS OF LIQUID FUEL FROM COAL
It has been said, doubtless with a good deal of truth, that Britain owes her manufacturing prosperity to her abundant domestic resources of fuel. But, in the exploitation of our coal reserves, we emulate the rat in the corn-bin. We waste quite as much, if not more, than we ever use. The country around our collieries is disfigured with huge dumps, among which are thousands of tons of what is really low-grade fuel. Occasionally a tip-heap will catch fire, to burn sullenly for weeks and months. One such large dump in the United States burned uninterruptedly for years. This would not be possible if there were not present a large volume of combustible matter—coal—associated with the so-called useless material.
The colliery tip-heaps, while formidable in the aggregate, and representing a crushing indictment against our so-called advanced scientific attainments, merely constitute one, and a minor, tangible illustration of the great coal-waste issue. No matter in what direction we may turn in this colossal industry, we find evidences of improvidence and stupendous losses in varying degree.