Abstract: In open-pit mining, it is a common practice to use a blasting method to blast off the ore from the rockmass, which is then transported to a crusher plant for a primary crushing after the classification by a grate grizzly. Due to the blast-related causes, the large fragments of ore   sometimes can not pass the grizzly, leading to the interruption of the crushing process. In underground mining, large fragments of ore can also be produced, which may block the ore-pass opening, sluice screens or various grate grizzlies, thus seriously affecting the normal production. It is right for solving such problems that the fixed type hydraulic crusher is developed, which can also be used in underground mines as an new efficient secondary crushing machine.

Key words: Hydraulic crusher, Secondary crushing, Solution for grate grizzly blockage.