Issues with replacing heat exchanger tube bundles

If there is a leak in the heat exchange tubes, the usual approach is to plug the tube; this is because the heat exchange area is designed to be 15% to 20% larger, so replacing the tubes is not common – it’s quite troublesome to do so, as one has to cut and grind the tube first before inserting a new one.

Our approach: We drill out the welds at both ends of the tube end, create a tube sleeve, place the sleeve at one end, tap the heat exchange tube outward, and once enough of it is exposed on the other side, pull the tube out. Generally, the tube is not replaced, as it might be impossible to pull it out after part of it has been pulled.

It’s generally difficult to replace a single heat exchange tube; usually, the solution is to block it off. However, I have a question: in heat exchangers with very small diameters, the number of heat exchange tubes is likely to be quite low. In such cases, if one of these tubes fails, it will have a significant impact on the total heat exchange area of the heat exchanger. What should be done in this case? Just replace the heat exchanger! I hope those with experience in this area can share their insights.

It is easier to replace the tubes in heat exchangers with smaller diameters than those with larger diameters.

We have a precedent for replacing pipes, but it wasn’t done using a drill, as the drill bit is sharp and makes it difficult to remove the welds that connect the pipe to the tube sheet. After much effort, the pipe still remained stuck to the tube sheet. Instead, we used a boring machine to remove the weld material, then used a sleeve to expand the end of the pipe so it could pass through the hole in the tube sheet, after which the pipe was pulled out from the other end. If the shell side is severely corroded, it is difficult to pull out the tubes ； If the heat exchanger diameter is small (DN≤500), it is easier to extract tubes.

When designing a heat exchanger, the actual heat exchange area of the heat exchange tubes is usually slightly higher than what was planned; typically, the tube ends are sealed, and the tubes are only replaced individually when it is absolutely necessary.

In the case of a U-tube heat exchanger, the tube bundle can be removed, but only the outer tubes can be replaced

Let me explain the solution adopted by our factory, and at the same time address the question from the fourth floor. What we do is to use a reamer to remove the ends of the tubes, then use a sleeve or specialized tool to push something from one end to the other. After that, a new tube is installed, and the ends of the tube are connected to the tube sheet either using a tube joining tool or by expansion welding, depending on the required strength. Relevant pressure tests are then carried out on the tube ends; if they pass these tests, it’s fine. In cases where it’s really not possible to remove the damaged tube, the damaged part at the tube sheet end is trimmed flat, and a tube of a smaller diameter is inserted into the damaged tube, which is then connected using expansion welding. This method can also be used for U-tubes, although damage to the U-tube section cannot be repaired in this way

The tubes can be blocked first; when the heat exchange efficiency declines, the tube bundle can be replaced. Different heat exchangers require different approaches – you can consult the engineering department or the heat exchanger manufacturer

Replacing the tube bundle is too troublesome, and it involves high costs. The best solution is what the others mentioned: replace the heat exchange tubes; either straight tubes or U-shaped tubes will work! The methods have been described in detail by the previous speakers, so there is no need to repeat them here!