Failure of forklift forks

A large plywood manufacturing plant has a fleet of 20 forklifts in service. Recently, the failure of a hydraulic hose of one forklift truck caused a sudden drop of the load being lifted. As a result of the impact with the floor, one of the forks broke in two pieces inside the heel. The fracture surface suggested the prior existence of fatigue cracks before failure. No cracks were detected on the forks during routine inspections carried out by liquid penetrants few months before the accident. This drove the plant management to carry out a detailed study of the service conditions and structural integrity of all forks in service. The study shows that abusive service conditions were the reason for the initiation of fatigue cracks inside the heels of forklift forks. Changes in the loading and transportation practices were recommended in order to avoid future fatigue cracking. Routine periodic non-destructive testing by using magnetic particle inspection was advised.