Compressed air is out and Nitrogen is in. This is both an observation of evolving standard practices in fire protection, and a summary of the solution to corrosion issues in dry and pre-action sprinkler systems.
The use of high purity Nitrogen as a supervisory gas is not new to fire protection. Use of high pressure cylinders can be traced back to the 1970s, and Nitrogen generators have been utilized in the industry for over a decade. Engineers and installing contractors alike are now seeing the impact of replacing compressed air with high purity Nitrogen, and here's why:
A Trip to Fire Protection Science Class
The science behind why Nitrogen is superior to compressed air for use in dry and pre-action fire protection systems is simple. Just like the "fire triangle," the fire protection industry refers to a similar "corrosion triangle." Electrochemical corrosion takes place any time unprotected metal interacts with moisure and Oxygen. As a result, the most effective way to inhibit the corrosion process is to replace the compressed air (or Oxygen) with high purity Nitrogen. To put things more simply, corrosion experts have found that adding Nitrogen to black steel or galvanized pipe can increase the life of the system by as much as 3 to 10 times that of a system with compressed air (Oxygen). In some cases, high purity nitrogen can mitigate corrosion issues and extend the life of the piping beyond the life expectancy of even the building itself.
How Nitrogen Generators Help Extend the Life of Fire Protection Piping
Regardless of the size of the Nitrogen generator, the startup process remains the same. An air compressor brings the sprinkler system up to pressure within thirty minutes (per NFPA code). After the fill process is complete, the Nitrogen generator takes over supervisory pressure. An air maintenance device with a regulator, not a pressure switch, is required for each individual dry or pre-action system valve. A purge device is also placed at a remote point on each dry or pre-action system. In general, this arrangement is very similar to that of a traditional air compressor, except corrosive oxygen is replaced by high-purity Nitrogen within the fire protection piping itself.
Advancements in technology have made Nitrogen generators more dependable and cost effective than than ever before. Companies that specialize in Nitrogen generation have increased the industry standard for purity from 95% to 98%, which has increased the effectiveness of Nitrogen generators when it comes to stopping corrosion. Additionally, the separation process of Nitrogen from atmophere has improved, thus increasing the production and purity levels of Nitrogen overall, making it easier to obtain and install.
While many new fire protection system specifications are now including Nitrogen, more than half of generator installations occur in pre-existing systems (according to South-Tek Systems). In the past, ongoing corrosion issues were typically resolved with large-scale replacement of fire protection pipe and fittings. Today, Nitrogen allows fire protection maintenance and installing contractors to extend the life of existing systems and avoid future headaches for facility managers and building engineers.
Stephen G. Churchill
Fire Protection Service Sales Engineer
J.C. Cannistraro, LLC
Curated Content Source: Clint Williamson, South-Tek Systems, Inc.