The present paper describes a series of detailed integrity assessments of a set of hydro station load bearing intake gate chains. They examined the likelihood of (a) sub-critical crack growth by stress corrosion cracking (SCC), and (b) fast unstable fracture occurring during further service. The likelihood of failure occurring in the bearing pins was relatively remote whilst sub-critical extension by SCC and fast fracture were considered likely in the link plates. Notwithstanding these findings, (a) a cracked plate discovered in the previous set of chains had already resulted in link plates with a reduced susceptibility to SCC in the new chains, (b) the old plates had provided 6 years service before cracking was observed, and (c) in contrast to their observed successful performance in situ, had high interference fit stresses been prevalent some plates would have failed during the past 3 years of service. Consequently, the chains were retained in service for a further 3 years.