During a mechanical inspection of the crown block on top of a drilling derrick, one of the turnbuckles on the side brake was found to be fractured. A decision was made to repair weld the turnbuckle as a replacement part was not available at the drilling site. The welder raised concerns that the turnbuckle was made from cast metal and could not be welded without special welding rods. He was advised by the mechanic on duty and the rig manager that, despite this, he should proceed with the repair. The repaired turnbuckle was then put back into service.
The repaired turnbuckle subsequently failed during drilling operations and the console handle for the side brake suddenly became non-responsive, causing the travelling block and drill-string to fall to the floor of the drilling rig. Fortunately, no injuries were sustained.