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Utilizing Nitrogen in Dry Pipe Sprinkler Systems

Friday, March 22, 2019

Corrosion has become the bane of the fire sprinkler market. It can lead to numerous problems that include leaks and faulty valves and heads. This, in turn, can lead to loss of property, money, and even life if the problem goes unnoticed. Corrosion in sprinkler systems can happen in as little as a few months and can have a serious impact on the lifespan of the system. An increasing trend in the industry is to use nitrogen as the prominent gas in dry pipe sprinkler systems. The use of nitrogen gas considerably decreases the effects of corrosion in steel pipe.

There are three components needed for corrosion to happen. They are water, iron, and oxygen. If just one of the three components are eliminated from the equation, corrosion can be mitigated. Oxygen dissolves into the water which allows the iron to oxidize and form iron oxide, more commonly known as rust. Since the most common gas currently used in dry pipe systems is air, which is made up of roughly 21% oxygen, there is a great opportunity for corrosion to occur. One may also think that if the system is dry, there should be no water in the pipes at all, so no corrosion. This is a misunderstanding because water will be always trapped in the system no matter how many precautions are taken. There will always be water trapped from hydrostatic testing as well as the humidity in the air supplied to the system; the piping will never be 100% dry.

Nitrogen has become a more prevalent option in the recent years to use as a replacement gas in dry systems. Nitrogen is an inert gas that does not react with metals, so corrosion cannot occur. The goal of a nitrogen system is to displace the percentage of oxygen in the sprinkler system and replace it with the nitrogen. A nitrogen generator does this by forcing air through a filter that separates the nitrogen from the other gasses and adds it to the system until the oxygen levels are reduced to 1-3%. A system with 97-99% nitrogen will be essentially non-corrosive.

Many advantages besides the mitigation of corrosion come with the use of utilizing nitrogen in lieu of air as the gas in dry pipe sprinkler systems. Per NFPA, the use of 98% nitrogen, on average, increased the life expectancy of a dry fire sprinkler system up to 5.3 times. Which can save the customer time and money by not having the expense of repeat service calls. Nitrogen systems also allow the systems to be used with black steel pipe instead of galvanized which can save around 30% on piping cost.

Corrosion is a persistent problem in fire sprinkler systems that has the ability to be greatly reduced with the addition of a nitrogen system. Dry pipe systems are no longer an advantageous option when used with air that has an abundance of oxygen. Instead, the trend should shift towards the utilization of nitrogen which significantly reduces the effects of corrosion as well as saves the customer time and money.

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