For steel sprinkler piping, corrosion that results in pipe leakage or obstruction is the most significant issue for owners of water-based fire protection systems (FPS), in terms of both cost and system reliability. Repair of corrosion damage due to mechanical failure or water damage significantly adds to the lifecycle cost of sprinkler protection systems in buildings. Hence, to properly maintain functionality of FPS, corrosion mitigation of sprinkler piping is needed.
For dry pipe systems (dry and preaction), residual water and dissolved oxygen in water are the main factors contributing to corrosion and leakage of sprinkler piping.1 Corrosion mitigation of steel sprinkler piping in these systems has been successfully achieved through nitrogen supervision to reduce the oxygen concentration by using an on-site nitrogen generator.
For wet pipe systems, causes of pipe corrosion and leakage are more complicated than those of dry pipe systems. Common causes may include trapped air, corrosive water chemistry, periodically supplying oxygenated water into the FPS (fresh sprinkler water recharged during regular maintenance), and microbiologically influenced corrosion (MIC).
A previous study has demonstrated that corrosion mitigation of wet pipe systems filled with non-corrosive tap water can be achieved through nitrogen purging.3 The current study used untreated pond water containing corrosive anions and MIC-causing bacteria as an accelerated testing environment to explore the feasibility of using nitrogen as a deoxygenation gas to mitigate corrosion of sprinkler pipes in a modified wet type FPS.
Keywords: Sprinkler Pipe Corrosion, Nitrogen Purging, Corrosion Mitigation, Dry, Preaction and Wet Fire Protection System,MIC