Stress corrosion cracking of 316L oxygen reactor pressure vessels

Two 316L stainless steel oxygen delignification (OD) pressure vessel reacto rs were found to have through-wall stress corrosion cracking (SCC) after ni ne years of service. The SCC was typical under-insulation corrosion (UIC) o n the outside of the vessels. The most severely cracked sections of both ve ssels ic ere replaced with duplex stainless steel. Acoustic emission testin g (AET) was used to determine the fitness-for-service of these cracked pres sure vessels and the effectiveness of UIC-SCC prevention measures. Experien ces are described with other nondestructive testing methods and coatings fo r preventing UIC-SCC, to which all 316L oxygen reactors located close to bl each plants are susceptible.