Cracks at the tube ends of heat exchange tubes
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There are cracks at the ends of the heat exchange tubes – what causes this? Material 316L
Please provide the operating conditions; the more detailed, the better it will be to make a judgment
Lengthening the cut ends of the heat exchange tubes should be able to avoid this issue.
Media-related causes can be ruled out; the medium is non-corrosive to 316L and is in gaseous form.
Could you please provide more details? There are a total of 16,000 pipe ends of various types, and 300 of them were found to have cracks – all due to the fact that the ends were not properly cut
Because there are detection blind spots at the tube ends during tube manufacturing, factories, in order to maximize profits, cut only a very short portion of these ends; as a result, some of the detection blind spots remain unremoved. Welding and other processes during manufacturing can cause these defects to grow larger. To avoid this issue, it is required that the heat exchanger tube manufacturers remove the blind areas at the ends of the tubes, or conduct random PT tests on those tube ends.
That is indeed one reason, but according to consultations with the original supervision engineer, cutting off the ends was a requirement of the project. But it still cracked; I don’t know why.
The cut should be made a bit longer to remove the blind area for non-destructive testing; if the defect is within the detectable area, ultrasonic and eddy current tests will trigger an alarm.
This is the end part of the tube at the time of removal; generally, we cut off about 200 millimeters from it. Some manufacturers cut less in order to save material
What you call \"cutting the ends\" is what we in the manufacturing factory refer to as \"making them flat-ended\" – that is, after the pipes are installed, a hydraulic machine is used to ensure that all pipe ends have the same length of 4–5 units. I think this is done by the manufacturing factory when removing pipes, in order to save material, by cutting less material at the clamping part of the pipe removal machine