What must be done to hydrostatically tested cylinders and apparatuses after testing?

After hydrostatic testing, it is crucial for cylinders and apparatuses to be thoroughly dried. This step is vital to prevent corrosion and ensure the integrity of the unit. Water or moisture left inside the cylinder can lead to rust and degradation of the internal components, which could compromise the cylinder's performance and safety during its next use.

Thorough drying is essential because it removes any residual water that could accelerate corrosion. The techniques for drying may include using air drying, heat drying, or blowing out the moisture with compressed air, depending on the type of cylinder and the materials used in its construction.

Once drying is completed, other actions such as painting, refilling, or inspecting may follow, but ensuring that the apparatus is completely dry is the primary step necessary to maintain the longevity and functionality of the equipment.