CRUSHING AND PULVERIZING MACHINERY. 



449 



BALL MILL. 



A polygon. Plates, angles, bars, bolts, 

 .and rivets machine-fitted and having 

 only the strength of an angular construc- 

 tion, held together with bolts and rivets. 



Perforations in the grinding-plates ex- 

 tend from inlet end to the opposite end, 

 and the material escapes through these 

 throughout the whole length of the 

 grinding surface. The peening grad- 

 ually closes these perforations, thus con- 

 stantly reducing the capacity. 



Injudicious feeding will pack the ma- 

 terial between the perforated exits and 

 the screens, and stop the sieving action. 

 It is frequently necessary to remove the 

 screens to again put the mill into service. 

 Choking damages the screens. 



Best obtainable information shows 

 about 40 H.P., operating under normal 

 conditions. 



Maximum charge 4400 to 4500 Ibs. 

 Take the ball mill at 100 per cent per 

 ton of balls. 



The grinding-plates form in part the 

 support for the screens. 



The life of the lining is governed by 

 the nature of the material ground. 

 Eighteen months seems to be a safe 

 average. 



As, however, the grinding-plates form 

 a principal part of the ball mill, the re- 

 lining of the mill involves the discon- 

 necting of many of the main parts ar.id 

 takes a gang of men several days. The 

 cost of relining is further increased by 

 the fact that the plates must be partially 

 finished, it being only possible therefore 

 to use in them material which can be 

 readily machined. 



Since the grinding-plates form also the 

 supporting plates, care must be exer- 

 cised not to let them wear down too far 

 or the balls will fall through the screens 

 and dust casing. 



KOMINUTER. 



A drum like a section of a steam- 

 boiler. 



The material travels from the inlet 

 end to the opposite end across SOLID 

 grinding-plates and escapes through 

 large openings amply protected from 

 the action of the balls. 



The kominuter can be intentionally 

 overfed until the screens are completely 

 choked. Running the kominuter with- 

 out feed for 20 min. will clear the screens. 

 The inside screen is usually coarse and 

 strong. It serves to limit the amount of 

 material passing to the outside final 

 screen, and at the same time protects 

 the final screen from excessive wear. 



Operating under normal conditions, 

 between 40 and 45 H.P. With maxi- 

 mum charge of balls and materials about 

 45. 



Maximum charge 6600 Ibs. 



The kominuter has given 125 per cent 

 per ton of balls, as compared with 100 

 per cent from the ball mill, showing a 

 capacity of about 85 per cent more than 

 that of the ball mill. 



The screen device derives its support 

 wholly from the drum itself, and is in no 

 way connected with the grinding plates 

 or with any part subject to heavy wear. 



The life of the lining is at least equal 

 to that of the ball mill, but as the komi- 

 nuter will grind at least 50 per cent 

 more than a ball mill of equal size the 

 wear per ton of finished product is ob- 

 viously very much smaller. 



The relining of the mill is done with 

 much greater ease and at much less cost, 

 as all plates can be handled by one man 

 and merely passed through the manhole, 

 no disconnecting of the principal parts 

 of the mill being necessary. 



The grinding-plates are not machined, 

 which reduces the cost and permits the 

 use in the plates of the material best 

 suited for the purpose, irrespective of its 

 suitability for machining. 



Since the drum itself forms the sup- 

 porting plate, the grinding plates can be 

 worn out completely Consequently very- 

 little metal is thrown away in the re- 

 placement of a lining. 



