Heat exchanger tubes and tube sheets are two of the most important components of a heat exchanger. They are responsible for transferring heat between two fluids, and a good connection between them is essential for the efficient operation of the heat exchanger.
There are two main methods for connecting heat exchanger tubes to tube sheets: welding and expansion. Welding is the more traditional method, but it can be time-consuming and expensive. Expansion is a newer method that is faster and more economical, but it is not suitable for all applications.
Welding
Welding is a permanent connection method that creates a strong bond between the heat exchanger tube and tube sheet. There are two main types of welding used for this purpose: arc welding and TIG welding.
Arc welding is the most common type of welding used for heat exchanger tube to tube sheet connections. It is a fast and efficient process, but it can be difficult to get a consistent weld quality.
TIG welding is a slower process, but it produces a higher quality weld.
Expansion
Expansion is a fast and economical mechanical method for connecting heat exchanger tubes to tube sheets that uses a tool to expand the end of the heat exchanger tube so that it fits tightly into the hole in the tube sheet. This creates a seal between the tube and tube sheet that is both leak-tight and pressure-resistant. However, it is not suitable for all applications. For example, expansion is not recommended for heat exchangers that are operating under high pressure or temperature.
Strength expansion joints are designed to withstand high pulling forces by relying on the plastic deformation of the tube end. They are suitable for applications with low design pressure (≤ 4 MPa) and design temperature (≤ 300℃), and where there is no severe vibration, large temperature difference, or obvious stress corrosion.
Strength welding joints are the most widely used type of tube-to-tubesheet connection. They offer high strength and can be repaired if necessary, but are not suitable for applications with large vibration or gap corrosion.
Combination
Combination expansion-welding joints are used when a high level of sealing performance is required, or when the joint must withstand severe vibration or other challenging conditions. The two main types of combination joints are expansion-before-welding and expansion-after-welding.
Explosive expansion is a type of strength expansion that uses a high-pressure gas shock wave to expand the tube end into the tube hole. It is particularly well-suited for thin-walled tubes, small-diameter tubes, and thick tube plates.
Explosive expansion is a specialized type of strength expansion that is particularly well-suited for thin-walled tubes, small-diameter tubes, and thick tube plates
Factors to consider when choosing a tube-to-tubesheet connection method include:
Design pressure and temperature
Operating conditions (vibration, temperature swings, corrosion)
Required level of sealing performance
Ease of maintenance and repair
Best Practices
Regardless of which connection method you choose, there are a few best practices that you should follow to ensure a good connection between the heat exchanger tube and tube sheet:
Prepare the surfaces properly. The surfaces of the heat exchanger tube and tube sheet should be clean and free of any debris before the connection is made. This will help to ensure a good bond between the two surfaces.
Use the right tools and equipment. Make sure to use the right tools and equipment for the job. This includes using the correct size expander tool or welding machine.
Follow the manufacturer's instructions. Be sure to follow the manufacturer's instructions for the connection method you are using. This will help to ensure that the connection is made correctly.
Inspection
Once the connection has been made, it is important to inspect it to ensure that it is sound. This can be done visually or using a non-destructive testing (NDT) method such as ultrasonic testing.
By following these best practices, you can ensure that the heat exchanger tubes and tube sheets in your heat exchanger are properly connected. This will help to ensure the efficient and reliable operation of your heat exchanger for many years to come
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