Employees were manually removing a motor control center unit from a control room. The unit was set on four tripod dollies, with one in each corner of the unit. One co-worker was pushing the unit while the injured employee was on the right side of the unit guiding it as it was being moved. While pushing the unit, one of the wheels on the tripod dolly got hung on the edge of the uneven concrete surface. The dolly then slid inward and tipped to the right side. The unit fell on the injured employee, resulting in a dislocated right shoulder and a fractured pelvis.