Abstract
For steel sprinkler piping systems, corrosion that results in pipe leakage or obstruction is the most significant issue for owners of water-based fire protection sprinkler systems (FPS), in terms of both cost and system reliability. Corrosion damage leading to mechanical failure or water damage significantly adds to the lifecycle cost of sprinkler protection systems in buildings. A nitrogen generator inerting system was used to study the effectiveness of using nitrogen as a supervisory gas to mitigate sprinkler pipe corrosion for both dry and wet type FPS.
In this study, a compressed nitrogen corrosion test apparatus was designed and constructed which supplied a blanket of pressurized nitrogen within a test pipe array including galvanized steel pipe (dry system) partially filled with tap water, and black steel pipe (wet system) filled (95%) with tap water. For comparison/control purposes, the test apparatus also included a (compressed) air test pipe array. Corrosion test coupon assemblies consisted of galvanized steel and carbon steel coupons, which were fully immersed in the tap water and removed periodically for corrosion rate calculation based on weight changes over exposure time.
The 12 months testing results show that corrosion rates of carbon steel and galvanized steel coupons in simulated dry pipe systems containing trapped water can be reduced with compressed nitrogen. The data show that corrosion rates of carbon steel coupons in simulated wet pipe systems with tap water can also be reduced with compressed nitrogen.
