The heat exchange tube is broken
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What I said last time was wrong. After observation, it is not the weld that is leaking. Our factory has an air preheater that is a fixed tube sheet heat exchanger. The tube takes away steam and the shell takes away air. The fixed tube sheet and tube materials are all made of white steel (304), and there are fins on the tubes. After the tube sheet and tube were welded, after several months of use, the superheated area of the tube broke and steam leaked. Did thermal expansion and contraction cause the tube to break? Please give some guidance from experts! !
I still don’t quite understand what you’re saying. It’s best to introduce the working conditions of the heat exchanger you mentioned in more detail, so that people who want to help you can make an accurate judgment and come up with practical analysis and solutions.
Could it be that the material of the tube and shell side is different, the temperature difference is large, and the expansion joint problem is not considered?
What are the medium temperatures on the shell side and tube side? Is there a big difference?
The reasons for this are as follows:: 1. It is related to the large temperature difference between the tube and the shell ； 2. The fins are related to the vibration of the tube, and the steam produces vibration ； 3. Regarding the installation method. Solution: 1. Reduce steam pressure and temperature ； 2. Install shock absorbing device ； 3. When starting to use, add steam and heat up slowly.
What was said above is good, but the quality of some domestic stainless steel pipes is too poor. You can analyze the material.
The heat exchanger our company improved for a petrochemical enterprise also encountered the above situation. The heat exchange tube was a horizontal groove tube. The main reason is that the steam speed is too fast, causing the heat exchange tube to vibrate violently near the tube plate, causing the heat exchange tube to break. solution: Install anti-collision plate and adopt baffle rod structure.
I agree with the point above. At the same time, is it corrosion or pressure reduction? This post was last edited by wxjh65 on 2008-1-10 14:37 ]
The short-term solution is to seal the broken pipe from both ends of the tube sheet； The long-term solution is to calculate and analyze the stress of the heat exchange tube. If it fails, modify the heat exchanger, such as adding an expansion joint to the shell, or simply remanufacturing the heat exchanger.
The steam temperature on the tube side is about 120 degrees. Since the factory is in the north, the air temperature on the shell side is below minus 10 degrees in winter, and the hottest in summer will not exceed 34 degrees. Since the material is relatively good, the corrosion may also be stress corrosion. The heat exchanger is rectangular, and baffles cannot be added due to its structure. The broken heat exchange tube may (I guess it is possible) be caused by thermal expansion and contraction. Consider adding an expansion joint or redesigning the heat exchanger.
No expansion joints? This should be the key to the problem
I strongly support the point above. Material is the most important. No matter how good your design is, if the material is not good, everything will be wasted.
How many processes does the heat exchanger tube process in the poster's question have? The temperature difference stress of the tube sheet is also a reason that cannot be ignored.