A Grizzly Screen is a heavy-duty, robust screening device consisting of a series of parallel steel bars, rails, or beams arranged in a grid pattern with fixed or variable openings, used primarily in mining and quarrying operations to scalp or separate oversized rocks, boulders, and coarse material from finer material before it enters crushers, conveyors, or other processing equipment. Named for its resemblance to the bars of a prison cell or the claws of a grizzly bear, this type of screen is designed to withstand the high impact forces associated with the dumping of run-of-mine (ROM) ore directly from haul trucks or loaders.
In bauxite, gold, iron ore, and diamond mining operations, grizzly screens are installed at the primary crusher feed hopper or ROM pad to prevent oversized rocks from damaging crusher components and to control the feed rate of material. They may be static (fixed) or vibrating, with vibrating grizzlies providing more efficient screening and self-cleaning action to prevent blinding or blockage by sticky clays, a common problem in tropical bauxite operations.
The aperture size of a grizzly screen determines the maximum particle size that passes through, with oversize material either rejected as waste, sent to a separate crushing circuit, or broken by hydraulic rock breakers mounted near the screen. In diamond mining, grizzly screens must be carefully designed to avoid diamond breakage, using wider bar spacings and reduced drop heights where possible. Regular maintenance and replacement of worn or broken bars is essential to operational safety and efficiency.