Use Nitrogen Generators to Mitigate Risk in Cold Storage

Posted by Tim Adams on Apr 16, 2021 3:46:00 PM

In recent years nitrogen has become widely accepted by the fire protection industry for dry and pre-action sprinkler systems. 

We talked about the oxygen corrosion and ice plug issue found within freezers in cold storage in a previous post.

Now, we'll talk about why an FM Approved membrane-type nitrogen generator offers superior moisture removal of the pressure maintenance gas while also protecting from oxygen corrosion. 

Nitrogen Generators and Corrosion Protection       

For corrosion to occur in steel piping, three (3) elements must be present: 

  1. Metal
  2. Liquid Water 
  3. Oxygen 

These three (3) components form the "corrosion triangle." 

The easiest and most cost-effective way to prevent corrosion from occurring in a fire sprinkler system is to remove the corrosive oxygen within the pipping. Using an FM Approved membrane type nitrogen to reduce the pressure maintenance gas's oxygen content to less than 2% will prevent oxygen corrosion from occurring. 

In a cold storage facility, there are areas where temperatures are above 32°F, such as riser rooms, loading docks, and coolers that become prone to internal oxygen corrosion. 

During annual testing, these systems are trip tested, introducing water into the system. Though the systems are drained after testing, trapped water will always remain. With trapped water now in the system, all three (3) essential components for oxygen corrosion are present.

If a regenerative desiccant dryer is to be used, experts and professionals must know that a regenerative desiccant will offer no corrosion protection as this equipment does not remove any considerable amount of liquid water present in system piping. A desiccant dryer still introduces 21% oxygen into the sprinkler system promoting oxygen corrosion. 

Nitrogen Generators and Ice Plug Management

Much like controlling corrosion, an FM Approved membrane-type nitrogen generator offers superior protection against frost buildup and ice plugs.

A membrane-type nitrogen generator can protect against ice plugs due to nitrogen being a "dry" gas. At 98% purity, the nitrogen gas has a consistent dewpoint of -70°F to -90°F. A desiccant dryer can only produce a dewpoint of about -40°F, if maintenance is performed diligently per manufacturer requirements; it is not a consistent dewpoint even at that.

Unlike a membrane-type nitrogen generator, the desiccant in an air dryer begins to break down, resulting in a dewpoint fluctuation. This leads to ice plugs leaving a facility without fire protection without any warning to the owner or AHJ. 

Get the Right Equipment for the Job

Nitrogen generators like the PGEN models offered by Engineered Corrosion Solutions have a proven track record in cold storage applications. Read more about how a large warehouse facility used a nitrogen generator to eliminate ice buildup.

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Tim Adams

Written by Tim Adams

Project Engineer