A pebble lining for a 5 by 22-ft. tube mill
A pebble lining for a 5 by 22-ft. tube mill will cost about $200 and may last 7 to 8 months. It is the cheapest form of lining used, in first cost. To increase the life of this class of liner chilled iron bars may be cemented in with the pebbles, the bars being laid longitudinally with the mill and spaced 1 ft. apart. The iron now takes most of the wear and we have a lining retaining the advantages of lifting bars but with less weight and expense than the all-metal linings.
For those who desire to experiment with concrete pebble linings I have devised a method which I believe will overcome, at least in part, the objections put forward. The pebbles are laid in cement in cast-iron frames open at back and front. These frames are put in the mill like so many bricks or sections of El Oro lining and while laid in cement for greater safety the mill may be used at once as the frames are interlocked and form a complete circle inside the shell. The pebbles can be cemented in the frames any time before use. Fig. 33 illustrates the idea. A liner of this type was used by Barry in West Australia but was found to be of a temporary nature and was discarded in favor of metal liners.
"A new system of tube mill lining has been devised and put into use at the mill of the Liberty Bell Gold Mining Co., at Telluride, Colo. Hard cast-iron ribs are laid with the regular courses of silex blocks, greatly increasing the life of the lining as a whole. A lining in a 5 by 22-ft. mill, containing seven rows of ribs, or one rib for every four rows of blocks, gives a life of 2 years and 7 months of continuous operation. In all our 5 by 22-ft. mills, we have placed 10 rows of ribs, or one rib for every three rows of silex blocks, and to all appearances our expectance of a life of 3 years will be reached.
"The material used in lining a 5 by 22 -ft. mill includes 900 silex blocks averaging 4% by 5 by 8^2 m- and weighing approximately 13 lb.; also, 19 cu. ft. of Portland cement, 19 cu. ft. of clean sand and 10 rows, or 50 pieces, of hard cast-iron ribs. These ribs are given a taper, measure 1% by 2 by 4J in., and are 47^ in. long. They weigh approximately 110 lb. each. They are cast in Telluride, since the local foundry provides the best hard iron that we have been able to obtain.
