Corrosion Prevention within Fire Protection Systems

FPS Corrosion

Corrosion in Fire Protection Systems (FPS) has been an ongoing issue for many building management teams throughout the world. Typically more common in dry and pre-action Systems, the internal corrosion of piping poses a serious threat to the quality and integrity of the FPS. As corrosion becomes more extreme, pinhole leaks develop within the piping causing excessive wear on the air compressor and other components within the FPS. As the leaks develop further, the air compressor becomes unable to maintain the proper supervisory pressure and thus the piping must be replaced. These costly repairs will become a routine necessity over time if nothing is done to inhibit the corrosion.

Corrosion occurs when three conditions are met. First, there must be an unprotected metal such as worn away or small scratches in the inner coating in the piping. Second, there must be an electrochemical potential. This is defined as a thermodynamic measure that combines the concepts of energy stored in the form of chemical potential and electrostatics. The final condition that is required is the presence of an electrolyte such as moisture.

Initially, dry and pre-action FPS undergo two tests. The first is a hydrostatic test where water is introduced into the system. This is done to ensure that leaks are not present and also to time how long the water takes to reach the inspectors test valve. The second test fills the FPS with compressed air which is another method of checking for leaks. Per NPFA guidelines, pressure within the largest zone much be achieved within 30 minutes and there must not be more than a 1 PSI drop in pressure for 24 hours. Although the water from the first test is drained, it is inevitable that residual moisture is left behind. Since the two initial tests introduce an electrolyte (i.e. oxygen, water, moisture) into the FPS, this immediately sets into motion the development of corrosion within the piping.

As corrosion occurs, the pinhole leaks that develop will cause the air compressor to cycle excessively and as those leaks become more exaggerated, the air compressor will eventually not be able to maintain the required supervisory pressure. This could lead to devastating outcomes such as destroyed office equipment, damaged office furnishings and even the weakening of structural components within the building. Other effects of pinhole leaks in the FPS include disruption to normal operations, loss of revenue due to shutdowns, and the high expense of ongoing repairs. Corrosion has also been known to cause complete failure in emergency situations since the fragments left behind from the corroded piping can clog sprinkler heads, tragically rendering them ineffective in the event of a fire.

Failure of a FPS is certainly a dangerous and potentially tragic scenario. Rather than continuously replace sprinkler pipe, the best solution is to prevent the root issue of corrosion from occurring. This solution is as simple as eliminating the source of corrosion, the electrolyte, by introducing Nitrogen as the supervisory gas. Nitrogen is a non explosive, inert, dry gas that offers as low as a -70 degree dew point. If moved effectively throughout the entire FPS, Nitrogen can absorb any residual moisture left behind from the hydrostatic test and also continuously keep the system moisture free. In addition, Nitrogen is less detrimental to the soft parts within the FPS, such as seals and gaskets, whereas compressed air can cause oxidation of these polymeric parts over time.

In conclusion, Nitrogen is the ideal choice as a supervisory gas for dry and pre-action Fire Protection Systems. It facilitates the complete dehydration of the FPS and in doing so virtually eliminates the potentially harmful electrolyte. As a result, the Nitrogen inhibits the development of corrosion within the black or galvanized steel.


Resource:

The N2-Blast FPS Corrosion Prevention Systemfrom South-Tek Systems provides a cost effective, continuous supply of nitrogen for FPS that eliminates the need for gas cylinders and chemical corrosion inhibitors as well as protects against FPS Corrosion.