Failure Analysis of Pharmaceutical Clamp Ferrules

Abstract

The purpose of this case study is to determine the cause of failure of DIN 1.4435 BN2 (AISI 316L with very low ferrite contents) clamp ferrules applied in pharmaceutical systems. Leakage was observed during operation in the clamp pipe connections of the ultra-pure fluid delivery systems. The surface of clamp ferrules showed remarkable discoloration and cracking. It was identified that the failure was caused by defects related to the autogenous laser conduction welding procedures. The intragranular cellular welded structures, which solidified with austenite as the primary product of solidification, showed a complete absence of hot cracks, minor delta ferrite, and minimum microsegregation. The welded components failed eventually owing to unstable welding profiles and significant porosity. Recommendations were given to prevent the recurrence of similar failures.