Pebble crushing is very topical: as we dig deeper into mines, the ore is getting harder and ore grades are declining, causing the build-up of pebbles in mills to become a greater concern. If pebbles are not dealt with appropriately, they start to occupy a large part of the mill and reduce its processing capacity.

Installing a pebble crusher on site significantly reduces the effects of pebbles build-up and can increase throughput by as much as 25 per cent*.

“We now offer pebble crushing solutions as part of the overall mill optimisation,” says Amit Zadoo, Mining Comminution Sales Manager at Weir Minerals.

So what are the key features to look for in a crusher? Mr Zadoo lists his top 5 below.

1. Tight closed side setting (CSS). CSS is a very important crusher parameter, as it defines the maximum product size and has a significant effect on crusher capacity and crusher liner wear.

2. Very high clamp pressure. “We often see crushers that cannot sustain a consistent, tight CSS over a period of time, for example, over one or two shifts,” says Mr Zadoo. “The crushing force of the pebble crusher has to be very high to hold the setting continuously for a long period of time to deliver a fine crushed product.”

3. Robustness of the crusher, which applies equally to the weight of the machine and its fatigue life. “Pebble crushing is the toughest of crushing applications, so the crusher has to be robust,” explains Mr Zadoo. “Our Trio TC crushers are typically 40-50% heavier than similarly sized machines in the market and provide a new level of robustness from the fatigue perspective.”

4. Ability to handle variable feed. When a crusher has the capacity to handle variable feed such as that produced in most mill circuits, a surge bin is not required. According to Mr Zadoo, the benefits are significant: “As a result of having a crusher able to handle variable feed, our customers save money that would otherwise go towards a surge bin and feeder arrangement. Being able to dispense without a bin and feeder arrangement also saves space, which is a big plus for sites where space is at a premium.”

5. High power. “To crush big rocks, you need large motors. I will conclude my list with the logical requirement of high power for pebble crushing applications.”

To sum up, the most important factors in selecting a pebble crusher are its ability to operate at tight settings and to withstand regular and significant tramp events. The smaller the crush size, the more rapidly the pebble load will be reduced; Mr Zadoo recommends using a heavy, robust crusher, such as the Trio® TC series, to achieve higher throughput rates in the milling circuit.

* McIvor, R. & Greenwood, B. (1996). Pebble Use and Treatment at Cleveland-Cliffs’ Autogenous Mill Operations. Proceedings of the International Autogenous and Semiautogenous Grinding Technology, SAG 96

*Article published in the July-September 2019 issue of The Asia Miner