What should be done if residual water remains in the exchanger after hydrotesting?

When residual water remains in an exchanger after hydrotesting, adding corrosion inhibitors is a prudent action to take. Hydrotesting typically involves filling the exchanger with water to test for leaks and assess the vessel's integrity. If water is left in the exchanger, it can become a medium for corrosion, especially if the environment is conducive to microbial growth.

Microbiologically influenced corrosion (MIC) is a well-known issue that occurs when certain microorganisms thrive in stagnant water and create localized corrosion on the metal surfaces. By introducing corrosion inhibitors, you can significantly reduce the risk of corrosion by creating a protective film on the metal surface, which inhibits the electrochemical reactions that lead to corrosion. This preventive measure is vital in maintaining the integrity and longevity of the pressure vessel.

Generally, leaving residual water and resuming operation without addressing the potential for corrosion is imprudent and poses significant risks. Performing a vacuum suction could help eliminate the water, but if not immediately feasible, adding inhibitors is an effective method of managing the immediate corrosion risk until more definitive actions can be taken.

Replacing the exchanger is an extreme and costly measure that should be avoided unless there is significant damage or failure detected.