Radical studies by TWI into the issues surrounding chloride stress corrosion cracking of duplex stainless steel, used offshore, are helping the Health and Safety Executive to pursue its aim of reducing hydrocarbon releases in the UK.
Presently the number of failures in the North Sea's UK sector is unacceptably high according to the HSE, and it wants to reduce it to half of the 1999/2000 level.
HSE contracted TWI to use its contacts and experience to perform an operational review in the SCC field and catalogue the experiences of North Sea operators which had experienced cracking problems.
TWI revealed that there was inconsistency in the UK offshore sector over temperature limits and coating practices to guard against external chloride stress corrosion cracking. It also addressed the subject of internal chloride stress corrosion cracking and highlighted that the absence of oxygen in process fluids cannot be relied upon as the sole factor in preventing SCC.
TWI advised that agreed working limits should be established and design guidance developed to combat SCC. It also recommended that it is necessary to understand the mechanism of internal chloride SCC in anaerobic conditions.