Inspection Detail

Inspection: 311668651 - Robertsons Ready Mix Inc

Inspection Information - Office: San Bernardino Mining &Tunneling District Office

Investigation Summary

On May 8, 2009, the crew at a sand and gravel plant discovered that a 400-HP, electric motor powering a cone crusher had lost its cooling fan cover. The plant was run dry, and the seemingly undamaged cover was replaced. On May 11, 2009, plant operations were started and ran for five hours, until the fan cover again fell off. The crew repaired some welding cracks in the motor support, replaced the cover after visually inspecting it, and restarted plant operations. Employee #1, a plant operator in training, went to the crusher deck to inspect motor function. As he walked past the motor, the fan disintegrated, and the aluminum cover shattered. A piece struck Employee #1, causing an open fracture of the tibia and fibula of his right leg, just above his ankle. Employee #1 was hospitalized. The investigation concluded that possible causes of the fan disintegration were damage to the fan caused by the cover falling off or preexisting fatigue cracks. Either condition would have been aggravated by excessive vibration from the cracked welds in the motor support.

Keywords: FRACTURE, DISINTEGRATED, TIBIA, STRUCK BY, FLYING OBJECT, LEG