452 



CEMENTS, LIMES, AND PLASTERS. 



A test run on clinker of a kominuter recently installed gave a 

 product of 60 barrels per hour. The kominuter was fitted with 14- 

 mesh screen and the product gave a residue of 55 per cent on a 50-mesh 

 sieve. 



Another plant using fresh clinker got a product of 35.3 bbls. per 

 hour from one kominuter. This product gave the following results on 

 a sieve test: 



At a third plant clinker averaging ^-inch size was handled by the 

 kominuter at the rate of 15,114 Ibs. per hour. The product gave the 

 following sieve results: 



Ball mills. Ball mills are now made by a number of manufacturers, 

 the types most commonly found at the Portland-cement industry being 

 the Smidth, Gates, and Krupp, and in wet-process plants, the Bonnot. 

 Of these the Smidth ball mill is being gradually replaced by the Lind- 

 hard kominuter, and is now recommended by its manufacturers only 

 for coal-grinding. It will therefore be omitted here and described on 

 pages 516-519. 



The wear of steel balls in ball mills working on clinker will vary 

 usually between the limits of T V and ^ Ib. per barrel cement. As the 

 balls at eastern points cost about $120 per ton, the cost per barrel 

 will therefore range between \ and % cent. 



Gates ball mill. This mill is described by its makers as follows: 



"The Gates ball mill consists of two circular side plates provided 



with inwardly projecting and eccentrically located shelves. The side 



plates have rigidly attached to them at their centers hubs which are 



mounted on a heavy shaft which revolves in dust-proof bearings. One 



