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Spider Assembly: Upper Shaft Support for Gyratory Crushers

The spider assembly is the structural framework that supports the upper end of the main shaft in gyratory crushers, maintaining shaft alignment while transmitting radial and axial loads into the top shell structure. The assembly consists of the spider cap casting, which houses the spider bushing, typically two to four spider arms that bridge from the cap to the top shell rim, and various wear components that protect these critical structural elements from material damage. The spider cap is manufactured from high-strength alloy steel casting at 200-250 HB, precision-machined to accept the spider bushing with correct interference fit for heat transfer and prevention of bushing rotation. The spider must absorb both continuous radial loads from the gyratory oscillating motion and intermittent impact loads from oversized feed material falling through the feed opening.

Spider components operate in one of the harshest environments in the crushing plant, continuously exposed to falling run-of-mine material, airborne dust, moisture, and extreme temperature variations in outdoor installations. Spider arm liners manufactured from Mn14-Mn18 manganese steel per ASTM A128 protect the structural arm castings from impact and abrasion as feed material deflects off the arms entering the crushing chamber. Rim liners shield the spider rim from material circulation at the top of the chamber. The spider bushing, typically cast from C93200 leaded tin bronze (SAE 660), provides the bearing surface for shaft oscillation and requires consistent lubrication with NLGI #2 EP grease delivered by automatic lubrication systems. Regular inspection and timely replacement of spider wear components prevents expensive damage to the major structural castings, which can cost ten times or more than the protective liner components.