Why Use Nitrogen

Why Use Nitrogen?

Actual corrosion found during an NFPA 25 internal pipe inspection.
The interior of preaction and dry sprinkler piping is subject to corrosion, which can lead to clogged sprinkler heads, leaks, and pipe failure. This corrosion can be of two distinct types. Oxidation corrosion takes place in the presence of oxygen and is accelerated by the presence of water. Microbiologically influenced corrosion (MIC) takes place in the presence of certain microbes that attack metal, again in the presence of water and in many cases oxygen. Reducing the damaging effects of this corrosion is best accomplished by greatly reducing or eliminating the amount of water and oxygen left in the pipe.


Section of pipe removed from a preaction sprinkler, showing overall internal corrosion with accelerated corrosion at the bottom from standing water. This also shows edge corrosion from improper coupling groove placement. Not shown: pinhole leak in the area of accelerated corrosion.
Ordinary air compressors that are used to provide supervisory pressure keep the oxygen concentration inside the pipe the same as normal air—ideal for oxidation corrosion to take place. Ordinary compressors also do not dry the air—residual water system testing remains in low points, and moist air can actually increase standing water within pipes from condensation. The introduction of high-purity dry nitrogen with a low dew point reduces or eliminates these two problems. The interior of the pipe remains dry, with very little oxygen remaining to attack the metal.
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Did You Know?
  • Your dry-pipe or preaction system piping may look brand new on the outside, but what about inside? Residual water and oxygen in the pressurized air could be rusting the interior of that pipe right now. This rust can weaken the pipe, cause pinholes to form, and even clog up the sprinkler heads in the event of a fire. NFPA 25 – Standard for the Inspection, Testing and Maintenance of Water-Based Fire Protection Systems mandates internal inspection of sprinkler pipes at least every 5 years. Are your pipes rusty? Have them internally inspected by a qualified fire protection contractor before it’s too late.