Analysis of failed lubricating oil pipeline used on AMAGB of an aircraft

The SS tube of the lubricating pipeline has failed by fatigue. The fatigue was of high cycle-low stress type. Analysis shows that the failure was due to presence of assembly stresses. It appears that anchoring of the pipeline has resulted in the assembly stresses. No metallurgical and/or mechanical abnormalities were found responsible for the failure. Anchoring of the pipeline of the type in question is not a general engineering practice and hence should be avoided. Also, care must be taken to avoid any assembly stresses during fixing of the pipeline