The Mechanical Handling and Storing of Material

414 THE MECHANICAL HANDLING OF MATERIAL The following figures have been obtained, during the test of a 50-in. magnet of this type, at the plant of the Youngstown Sheet and Tube Co.:— Total weight of pig iron unloaded from steel gondola - 109,350 lb. Weight of average lift (including small lifts when cleaning up the car) 785 „ Trips required to empty gondola - - - - 139 CurrenLon magnet - - - - - 1 hr. 15 min. Current off magnet - - - - - 50 „ Time consumed in unloading gondola - - - 2 hrs. 5 „ Current required to energise magnet - - - 30 amperes at 220 volts. From the foregoing figures the cost of operation is easily calculated, assuming cost of current to be l|d. per kilowatt hour; 30 amperes at 220 volts correspond to a power Inner Pole Shoe. Fig. 586. Cutler-Hammer Lifting Magnet. the capacity on different materials, for the four sizes Cutler-Hammer Co. :— consumption of 6,600 watts which was required for one hour and fifteen minutes; this gives a total power consump- tion of 8’25 kw. hrs., which at l^d. per kilowatt hour gives a total of a little more than one shilling for the cost of current for energising magnet required during the period to unload the pig iron. The following table gives of lifting magnets made by the Material Lifted. Diameter of Magnet. 36 In. 42 In. 52 Tn. 60 In. Pig iron for casting machines Pig iron cast in sand - Boiler plate scrap Scrap wire - Rail cuttings and crops - Skull cracker - Lb. 800 720 630 450 720 10,800 Lb. 1,170 1,100 1,080 540 l,20'> 18,000 Lb. 1,9'0 1,800 1,440 72<> 1,620 18,000 Lb. 2,340 2,160 900 22,500 Weight of magnet 1,630 3,000 4,700 6,800 The magnet of the Witton-Kramer Electric Tool and Hoist Co., of Witton, Birmingham, which is shown in Fig. 587, differs from those previously described particularly in that the windings are treated similarly to the type S. A. magnet with the exception that it is immersed in a boiling asphalt compound, and the coils are kept under great pressure in this liquid at a temperature of approximately 200° Fahr. The shield which protects the coil is either of non-magnetic manganese steel or of an extra hard phosphor bronze, and the pole shoes are generally bolted to the casing, but in some instances they are soldered. The controllers for these magnets are of the drum type, and in some cases oil-