NITROGEN GAS MITIGATION TO INHIBIT CORROSION
Dry and pre-action systems are the world’s second most common type of fire suppression system. With increasingly widespread use of these systems, the issue of corrosion has become very common. Internal corrosion of dry and pre-action fire suppression systems is a growing concern for the fire sprinkler industry. Corrosion in these systems causes failures resulting in property damage, production downtime, and increased maintenance costs. Additionally, corrosion impacts system hydraulics and reduces the efficiency of fire sprinkler system designs. Historically, dry and pre-action fire suppression systems have used compressed system air as the primary supervisory source. Compressed air, however, contains both oxygen and moisture promoting a corrosive system environment.
Approval agencies, design engineering firms, and component manufacturers have teamed up to investigate the main cause of corrosion in fire sprinkler systems. Recent testing shows the removal of Oxygen in both wet and dry pipe fire sprinkler systems can extend the life cycle of the systems by as much as 3-6 times.
Based on the test results, venting wet fire sprinkler systems and using Nitrogen in dry and pre-action systems will give you the maximum life cycle for your system components. The recent NFPA 13 code change for 2016 requires the venting of wet pipe fire sprinkler systems. This can be accomplished by manually or automatically venting of oxygen. The approval agency FM is now aware of the benefits of reduced oxygen in both wet and dry fire sprinkler systems to the point of restricting the use of air compressors and requiring wet systems to be vented.
Because of the strong need for corrosion protection sprinkler systems, Potter Electric Signal Company conducted a test comparing the effects of using 98% pure nitrogen gas compared to compressed air systems. The systems were half filled with water and then allowed to sit for 12 months. After 12 months the systems were tested and it was found that:
- The use of 98% nitrogen in lieu of compressed air as a supervisory gas reduces corrosion in both galvanized and black steel systems regardless of whether or not trapped water is present. The corrosion reduction potential ranges from 48% to 91% when compared to compressed air.
- Using 98% nitrogen gas in lieu of compressed air increases the life expectancy of a dry or pre-action system on an average of 5.3 times.
- The use of galvanized steel instead of black steel results in higher metal loss rates when compared in equivalent environments.
- The use of 98% nitrogen gas in a relatively dry, black steel environment has the lowest corrosion rate overall.
Based on these results, using nitrogen gas for fire protection systems will help increase the life of the system by causing less corrosion.
For more information on nitrogen gas use for fire protection systems, please contact VFS today!