LIMESTONE-CRUSHING TEST.

New Zealand Journal of Agriculture, Volume XV, Issue 4, 20 October 1917, Page 190

LIMESTONE-CRUSHING TEST.

A report supplied by the Public Works Department on a trial at Otira of the patent “Lightning” crusher with samples of Nelson Marble Company’s stone states that each of two 10 cwt. samples went through , the machine in seven minutes, equal to 86 cwt. per hour, or 34’4 tons per day of eight hours. The cost of crushing worked out at i - 265. per ton, the following charges being included : one man feeding, one engineman, coal, oil, maintenance, interest on capital cost of engine and crusher (£500), and depreciation. The crushed samples were passed through sieves with the following result : Retained on 16-mesh sieve, 0-5 per cent, (due-to damaged bar) ; retained on 400-mesh sieve, 35-1 per cent. ; retained on 900-mesh sieve, 6-6 per cent. ; retained on 5,776mesh sieve, n-2 per cent. ; retained on 32,400-mesh sieve, n-6 per cent.; passed 32,400-mesh sieve, 35-5 per cent.

The rate of crushing given is very high when the degree of fineness is taken into consideration, the maker's rating of the machine being only 2|. tons per hour. It will be seen that practically the whole of the product passed through a 16-mesh sieve, but 35-1 per cent, was retained on a 400-mesh sieve. If finer crushing is required this can be arranged by placing the screen-bars of the machine closer together. The agents for the crusher (Messrs. Richardson, McCabe, and Co., Wellington) consider that the distance apart should then be about in., as against | in. in the Otira trial. There would, of course, be a slight corresponding reduction of output, but even so the output claimed by the makers would be maintained.-— B. C. Aston.