During a wet layup, what should the residual level of oxygen scavenger be maintained at?

During a wet layup procedure, maintaining proper chemical levels is crucial to protect equipment, particularly from corrosion. The recommended residual level of oxygen scavenger, commonly measured in parts per million (ppm), helps to effectively reduce the amount of dissolved oxygen in the water. Dissolved oxygen can lead to corrosion and rust formation in systems when they are out of service.

The correct level of 250 ppm ensures that there is a sufficient amount of oxygen scavenger present to neutralize oxygen and prevent any potential corrosion damage. This concentration strikes a balance where there is enough scavenger to provide protection without being overly excessive, which could lead to other issues, such as high levels of byproducts or excessive treatment chemicals that can complicate future operations.

Choosing levels like 50 ppm might not provide adequate protection against corrosion, particularly in long-term wet layups, while levels of 400 ppm or 600 ppm could indicate an over-saturation which might also introduce unwanted complications. Maintaining the proper level at 250 ppm is considered optimal, thus ensuring system safety and longevity during the layup period.