Breakage of the heat exchange tube and tube sheet
Thread Content
A heat exchanger that has been in use for one year experienced leakage of the fluid in the tube side to the shell side. Shell side material: Q345R, heat exchange tubes: S30408, tube sheet: 16MnⅢ+S30408. The heat exchange tubes and tube sheet are joined using strength welding plus expansion bonding. The parameters are as follows: the piping schematic shows fractures in the baffle; several heat exchange tubes at the connection points with the tube sheet are fractured, while the weld joints between the heat exchange tubes and the tube sheet remain intact; the nozzles in the shell side have suffered severe corrosion. Friends, please analyze the reasons. Thank you.
If it’s just the tube that’s broken, judging from the location of the break, it is likely a manufacturing defect. Reasons for shell-side corrosion: Is MDEA sulfur-containing (lean stream, not rich)? The breakage of the baffle may be caused by high-pressure airflow erosion following pipe rupture.
Is the connection location at the medium inlet? Without an anti-scour plate, the medium can flow in and scour the heat exchange tubes, leading to fractures. Also, how is the expansion joint formed? Is it possible that the location of this expansion joint is too close to the inner tube sheet?
Does the location of the fracture correspond to the shell side inlet, and is any anti-erosion protection in place? Check whether the shell-side heat exchange tubes on the other tube sheet are broken; look at the location of the breaks in the tubes to see if they were caused by excessive vibration of the tube bundle during operation Is the piping medium liquid-filled?
Shell-side corrosion causes crevice corrosion in the portion of the heat exchange tubes that extend into the tube sheet (the section that is not sealed by expansion joints). When the tubes crack, high-pressure steam from the tube side enters the shell side, resulting in intense boiling in that area; the tubes and baffle plates in that region suffer further damage due to vibration. Personal suggestion: swap the media in the tube side or upgrade the shell side material
It could be caused by the vibration of the tube induced by the shell-side medium
Check what the maximum temperature difference is; the temperature difference stress may have a certain impact； Also, corrosion on the shell side may have a certain impact as well ； The location of the fracture should be in the heat-affected zone resulting from welding; the stress conditions in that area are indeed not very good.