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When dry and pre-action fire protection systems experience internal corrosion in their piping network, several problems can ensue for building owners and operators. The build-up of corrosion product deposits can reduce the efficiency of the sprinkler system and water leaks from pinholes can cause property damage. According to NACE International member Ockert J. Van Der Schijff, senior manager with engineering and scientific consulting firm Exponent, Inc. (Natick, Massachusetts), the cost to repair a single pinhole leak in a sprinkler pipe is usually in excess of $1,200 per event. Even more alarming is that often times before the pinhole leak has occurred, tuberculation, scaling, and other corrosion products have accumulated within the sprinkler piping, which cause obstructions that will slow down the water flow in the event of a fire, or potentially plug a sprinkler head and render it completely inoperable.
Dry and pre-action sprinkler systems are not charged with water, but use compressed supervisory gas instead, says Scott Bodemann, senior vice president of sales & marketing for South-Tek Systems, LLC (Wilmington, North Carolina). The pressure of the supervisory gas in dry systems balances a valve in the sprinkler system with water line pressure until a pressure drop occurs when a sprinkler head is activated. Water is then introduced into the piping to suppress the fire. Pre-action systems essentially utilize the same principal, but require activation of an additional signal such as a temperature sensor or smoke alarm before the valve opens and water is introduced into the piping. Typically, dry and pre-action fire protection systems use compressed air as the supervisory gas to keep the piping system pressurized. However, compressed air from the atmosphere contains both moisture and oxygen, which can cause corrosion of the steel piping.
A proven solution to mitigate corrosion in sprinkler systems is the use of compressed nitrogen instead of compressed air as the supervisory gas. The nitrogen displaces the oxygen within the sprinkler piping and effectively removes a significant contributor to corrosion. To meet the need for this continuous supply of compressed nitrogen gas, South-Tek has developed a corrosion inhibiting nitrogen generating system, the N2-Blast, that provides inert nitrogen specifically for fire protection systems.
Many new dry and pre-action fire protection systems are constructed of hotdip galvanized steel, although the...