Seeking advice on cracks in heat exchange tubes
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The newly manufactured gasket changer uses 30408 material for both the heat exchange tubes and the tube sheet. Two days after it was put into use, more than 10 tubes in the heat-affected zone of the tube ends cracked. What could be the reason? Weld first and then expand; welded using a tube sheet welder.
Wubi input? Was it used for 2 days? What is a medium? Operating conditions? Weld first and handle the accounting later; this can easily cause cracks in the weld during expansion jointing. What is the distance between the pipe end and the tube sheet before welding? Is it edge trimming after inflation? During expansion bonding, it is not allowed to perform this process within a range of 15 mm from the tube sheet surface, as this can easily lead to cracks. Some cracks are very small, while others are delayed cracks. It’s normal not to be detected during inspection. Personally, I think it happens when there is swelling due to the operator’s improper handling – at least they didn’t follow the procedural documents and worked too close to the tube sheet. Personally, let’s continue downstairs and discuss more other possibilities.
Heavy oil in the shell side at 120 degrees, water in the tube side at 60 degrees; the distance between the tube ends and the tube sheet is 4 mm, with no trimming. The crack did not reach the expanded section of the tubes. After welding, pressure testing was carried out twice with no leaks detected; however, leakage occurred after 2 days of operation.
Are the material and specifications of the heat exchange tubes in compliance with the standards?
There should be no problem with the heat exchange tubes; all the cracks are in this area. It might be related to running
Cracks in the heat-affected zone are very likely due to improper use of welding materials
It is very likely related to the working conditions; if there are issues with the welding materials or the base material, problems will arise during welding
Expansion joints are installed on the shell side cylinder; isn’t thermal expansion increased as a result?