An employee was lowering the boom of the manlift. The manlift basket became entangled with a rope attached to a pulley used to hoist screens and tools to the top of the plant. As the manlift descended it put tension on the rope which broke the gantry frame. A section of the frame struck the employee's head/shoulder area. The employee lost consciousness and sustained multiple fractures to his skull, face, shoulder and ribs. The employee was wearing personal protective equipment at the time.