The Case of the Aluminum Dump Trailer's Failed Repair Welds
Structural repairs fractured on aluminum dump trailer caused an immediate loss of revenue to the owner/operator. After travelling less than 100 miles, the weld repairs, by a repair shop contractor, failed and the dump trailer collapsed unexpectedly, while loaded with sand. The weld failures resulted in significant expenses and the owner was not able to receive reimbursement from weld repair shop.
Metallurgical effects of welding aluminum plates and observations of material samples removed from the dump trailer contained defective repair weld regions. Practical considerations about the repair weld failures addressed weld joint design, defective and non-fused welds with the Gas Metal Arc Welding (GMAW) process, cleanliness, heat input, welding variables and undocumented welder proficiency.
The weld repair contractor designed the repair joint and weld. He strengthened the damaged and broken welds on the fractured aluminum dump trailer frame. Prior to the repairs the trailer had only original welds and no other repair welds. The contractor’s repair weld joint design and shop welding practices were visually assessed and inadequate. The repair welds were unsuitable for the intended service and structural trailer applications. The 90o corner configurations at weld intersections deviated from common structural welding practices in AWS D1.2 Structural Welding Code - Aluminum. The base metal oxides and slag were not removed before weld repairs which resulted in non-fused and porous welds.
Hydrogen embrittlement was observed in the repair weld regions as a result of improper surface metal preparations and lack of surface cleanliness.
The weld joint fit-up had square corners, not rounded, and the weld quality was poor. The weld joint configurations did not comply with Federal DOT and CFR requirements. The variation in base material thicknesses, unclean weld surfaces and defective welding were the primary factors in the weld failures.
The Lessons Learned:
Repair facility management provided a low-bid budget to the insurance company and a fast-track schedule. The price and quality were more important than proper aluminum weld joint preparations, sound welding techniques, code compliance and highway safety.