42 Inch Vac transfer line developed leak at 6 clock position at the 20 inch branch connecting location which was connected at 12 clock position of the pipeline. Total 2 no of branch in which one no of branch location leak observed in 42 in header due to internal erosion. In other branch location at 42 inch header the thickness was found to be 4mm over a length of 500mm at 6 clock position straight bottom to the 20 inch branch. The line is of P5 metallurgy with SS 316 clad. original thickness 12.7mm. The line was in service for 19 years. Remaining locations thickness was found to be above MAT. Only in 2 branch locations at localized location severe erosion observed.
In this instance, the leak was found to be due to turbulence and velocity which caused erosion but are there any other factors which cause this kind of failure?