
For primary crushing with a reduction ratio of 6 to 1. When a relatively coarse product is desired, top size usually larger than 38 mm (1 1/2) Closed Circuit Crushing System To control top size from a single crusher operating in an open circuit, material must remain in the crushing chamber until the material is reduced to top size. Nov 11, 2020 The crusher was born out of a need for a high capacity underground primary crusher that did not require a primary feeder, scalper, and the associated infrastructure therein. Minimizing the need for high cost stationary grids to control topsize underground was a requisite, and the large topsize acceptance was met with the UG design.