What is typically the most common cause of out of roundness in existing exchanger shells?

The most common cause of out of roundness in existing exchanger shells is often linked to welding repairs to the shell. When repairs are made, especially if they involve significant welding, heat can be introduced to the material, leading to thermal expansion and contraction. This can alter the shape of the shell as the metal behaves differently after being heated and cooled, potentially leading to distortion or out of roundness.

Additionally, welding processes can introduce residual stresses into the material, contributing to changes in its shape. Over time, these stresses may lead to permanent deformation, so the cumulative effects of welding on an exchanger shell can significantly impact its overall geometry.

Understanding the relationship between welding and the physical integrity of pressure vessels is crucial in maintenance and inspection practices to ensure these components retain their intended performance characteristics.