Failure Caused by Malposition Defects and Failure Simulation of Electric Transmission Line Compression Fittings

Through the investigation on failure cases caused by malposition defects of transmission line compression fittings, it was found that large quantity of cases were caused by the defect that the tail of aluminum pipe wasn′t pressed against the steel anchor, which led to corrosion of steel cores in the aluminum pipe. The effects of malposition defects and related corrosion on stress worsening and core fracture were studied in dealing with two clamp failure cases, combined with experimental analyses and simulation analysis. The experimental analyses mentioned above included visual inspection and the check of dezincification and corrosion pits. The analyses indicated that when the tail of aluminum pipe was not forced against the steel anchor, the stress in steel cores on steel pipe orifice was 3.1 times as high as normal, and did not reach the breaking strength. However, bad seal resulted in the crevice corrosion of steel cores, leading to appearance of pits and cracks. When the depth of corrosion pits reached 0.5 mm, the maximum stress in the pits was 8.3 times as high as normal, reaching the tensile strength of steel cores. The appearance and expansion of pits worsened the stress state of steel cores till the cores broke. The research has great value in the precaution and diagnosis of similar failures.