Analysis of Level Control Valve Seat from the Recycle Condensate Separator an the Ft. Lewis, Washington, SRC Pilot Plant

摘要

A seat from the level control valve for the recycle condensate separator at the Ft. Lewis Solvent Refined Coal pilot plant was removed from service when cracks were noticed during routine maintenance. One crack extended completely through the 17-4 PH stainless steel trim set. Metallographic examination and hardness measurements revealed that the aging temperature used in heat-treating the martensitic precipitation-hardenable steel was too low, resulting in a material with an improper balance of tensile and impact properties. Residual stresses due to fabrication probably combined with the corrosive environment to produce stress corrosion cracking. The offensive species could not be positively identified, but hydrogen is thought to be a contributory factor. (ERA citation 04:028805)