Release from a desulphurisation unit of a refinery

A leak occurred on a line connecting the hot separator to the cold separator of a refinery diesel desulphurization.
The alert was given by the activation of the fixed H2S detector.
The 30 bar pressure line contained essentially hydrogen with a high concentration of H2S. The operators stopped the unit and isolated the leak in about ten minutes. The line was pierced at a bend at 135 ° C following a bend at 90 ° C. The accident investigation showed that the presence of the elbows resulted in turbulence which created a localized depression: this configuration favoured the formation of deposits (in particular during the stops of the water wash pump). Deposition corrosion developed until the line was punctured. A 90 ° elbow inspection was performed by the site inspection department but not at 135 ° C.

Localised corrosion in pipe elbows, until the line was punctured.

process gas pipe

The operators stopped the unit and isolated the leak in about ten minutes.