Front End Loader Hoist Lift Hose Failure

A hoist lift hose on a loader failed catastrophically. The hoses were a 100R13 type (as classified in AS3791-1991) with 50.8 mm nominal internal diameter. They consisted of six alternating spirals of heavy wire around a synthetic rubber inner tube with a synthetic rubber outer sheath. Failure of the lift hose was approximately 50 to 100 mm away from the "upper" end of the hose, with the straight coupling that attaches to the hydraulic system. The return hose was in much better condition, with no apparent deformation and only small areas of mechanical damage to the outer sheath. There were two modes of failure of the wire: tensile and corrosion related. The predominant corrosion mechanism appeared to be crevice corrosion related, with the corrosion being driven by the retention of water by the cover material around the wire strands. In this case study (and in most wire-reinforced hydraulic hoses), the wire reinforcing strands were a medium-carbon steel in the cold drawn condition. Radiographic nondestructive testing (NDT) was recommended to determine when a hydraulic hose should be replaced.