Why is flushing before hydro testing and drying after hydro testing important?
Microbiologically induced corrosion (MIC) is a potential damage mechanism that can occur during the hydrostatic testing process.
Solids such as sand, which may be present in the piping system before it is filled or carried along with unfiltered hydrotest water, can provide nourishment for bacteria and promote bacterial growth.
Water treated with chemicals often cannot penetrate sand deposits. Proper flushing prior to hydrostatic testing can remove the sediments and thus the places where bacteria can settle and grow. Thus, flushing prior to a hydrostatic test is essential to minimize the risk of MIC.
If the hydrotest water remains in the system for an extended period of time after hydrotesting (i.e., prior to commissioning), MIC may begin to occur in the stagnant water. Therefore, it is recommended to drain the water completely after the hydrotest and dry the system to prevent bacterial growth and MIC.