While steaming out equipment during a maintenance shut down, we recently discovered a leak in our crude unit vacuum section transfer line. The line, which runs from the vacuum heater to the vacuum tower, is a 36” clad pipe. Materials for the base material is 1/2” thick ASTM A515 Grade 55 carbon steel, and the cladding is 1/8” thick ASTM A240 TP405 stainless steel.
The leak occurred at a mitred elbows, slightly downstream of the mitre weld. Upon thorough inspection it was found that there was only one leak in the line, at the location of the mitre weld, but there was also severe corrosion/erosion of the cladding at the transition where the pipe connects to the tower (this transition consists of an enlargement which goes from 36” to 48” prior to connecting to the 48” tower nozzle). There was also some minor thinning of the cladding at other points downstream of welds in straight runs of pipe.
Has anyone had similar experiences, if so, has the cause been confirmed and what are the inspection techniques being used to find this type of localized corrosion/erosion? Any thoughts or discussion would be appreciated.
The leak occurred at a mitred elbows, slightly downstream of the mitre weld. Upon thorough inspection it was found that there was only one leak in the line, at the location of the mitre weld, but there was also severe corrosion/erosion of the cladding at the transition where the pipe connects to the tower (this transition consists of an enlargement which goes from 36” to 48” prior to connecting to the 48” tower nozzle). There was also some minor thinning of the cladding at other points downstream of welds in straight runs of pipe.
Has anyone had similar experiences, if so, has the cause been confirmed and what are the inspection techniques being used to find this type of localized corrosion/erosion? Any thoughts or discussion would be appreciated.
