Potter: Sprinkler systems last longer with nitrogen

ST. LOUIS—A new Potter Electric Signal Co. study shows that replacing air with nitrogen as the supervisory gas in dry and pre-action sprinkler systems dramatically reduces rust and makes the systems last more than five times longer.

Potter, based here, makes a line of nitrogen generators specifically designed for fire sprinkler systems, said Josh Tihen, the company's corrosion product manager. He told Security Systems News that using nitrogen instead of air in the system “allows someone to install a sprinkler system and have the ability to know that it's going to last significantly longer.”

That's a selling point for dealers, he said. He said most dry or pre-action systems “are experiencing failures or [needing] repairs … anywhere from five to 15 years after they've been installed.”

That's of concern to end users, Tihen said. “A sprinkler system is an asset to the building but if you're having to repair it consistently, we're seeing a lot of building owners becoming frustrated with these dry or pre-action systems because of the amount of money they're going to have to continuously invest in maintenance,” he said.

But the study, recently released by Potter Corrosion Solutions, showed that replacing air with nitrogen can make a system last on average 5.3 times longer. That means that if a system using an air compressor would last 15 years, that same system could last for more than 70 years using a nitrogen generator.

Tihen is the author of a paper titled “Corrosion Inhibition of Dry and Pre-Action Fire Suppression Systems using Nitrogen Gas.” He and his team conducted “a yearlong experiment that proves the beneficial effects of displacing the oxygen in a fire sprinkler system with 98 percent nitrogen,” according to Potter.

Dry and pre-action sprinkler systems are the second most common type of fire suppression system, according to the research paper.

In dry systems, the piping array itself is not filled with water. The systems are used in situations where the pipes may be exposed to freezing conditions, such as the outdoor garden centers of big home improvement stores or in grocery store freezer units, Tihen said.

Data centers also typically don't use wet systems because they don't want pipes filled with water above their electronic equipment, he said. Such high-value applications tend to prefer pre-action systems that have a secondary source, such as a smoke or heat sensor, which must also go off before the sprinkler system activates.

Although water is not held in the pipes of a dry system, it is in the system itself below a valve riser, and will release when the pressure in the pipes changes and the valve pops open, activating the sprinkler system, explained Eric Lauver, Potter's communications manager.

Tihen said that an air compressor is used to maintain a certain level of pressure in the pipes so that the valve doesn't open and send water through the system.

But that air injected into the pipes has water vapor in it that can condense in the pipes, Tihen said. Also, water is run through the pipes when the system is tested and even though it is drained out, a small amount remains, he said.

NFPA codes say all sprinkler pipes must be made of galvanized or black steel, Tihen said. But the combination of iron in the steel, the oxygen in the air and the residual water in the pipes are the three ingredients necessary for rust to occur, which decreases the life of the system, he said.

Replacing the air with nitrogen prevents the rust reaction from occurring, Tihen said. “You're getting rid of the oxygen leg of the triangle,” he explained.

Tihen will present his findings at an American Fire Sprinkler Association (AFSA) webinar scheduled for April 9. According to the AFSA, “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.”

A nitrogen generator is more expensive than a normal air compressor, Tihen said. However, he said, “the additional cost is easily outweighed by the life expectancy increase that you're going to get on a fire sprinkler system.”

In addition to its corrosion solutions, Potter's other products include fire sprinkler monitoring solutions, such as a self-testing flow switch for wet sprinkler systems that requires no discharge of water. Potter billed that product, released last year, as an industry first.

Tihen said that Potter constantly does research for product improvement. “We've been working on corrosion prevention in fire sprinkler systems since 2001 and we have a wide a variety of different products available,” Tihen said.

For more information and to download the research paper, go to: www.PotterNitrogen.com.