Failure analysis of stainless steel bellows

Two bellow sealed valves used to control the flow of sodium in pipelines of the Component Testing Facility (CTF) at the Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam, failed prematurely. The failure of both these valves occurred by intergranular stress corrosion cracking (IGSCC) of the stainless steel bellows. This premature failure occurred in the sensitised stainless steel of the bellows due to the conjoint action of high tensile stresses, caused by superimposition of operating stresses over residual stresses, and sodium hydroxide environment which was formed by reaction between sodium and moisture in the cover gas.