As a fire sprinkler contractor, we know that your goal is to build and maintain sprinkler systems that are effective, reliable, and headache-free. Corrosion and ice plugs are some of the main concerns affecting these goals.
However, with these items, you’re relying on science and technology to alleviate these concerns, and you’re only as good as the information you have available to you.
That’s why we wanted to provide you with the information you need to understand the difference between regenerative air dryers and nitrogen generators and the effectiveness of each in eliminating ice plugs and corrosion.
Regenerative air dryers were once recognized by governing standards such as FM Global as the default option for ice plug prevention in freezer applications. As technology has evolved and the practical application has been proven effective, it’s become clear that nitrogen generators are the superior solution to both corrosion mitigation and ice plug prevention.
Why Were Compressed Air Dryers the Solution of Choice at One Point?
The intent behind using a regenerative air dryer is to achieve a supervisory gas dew point that is at least 20⁰F below the lowest freezer temperature served by the supervisory gas source. By attaining this target dew point, science would suggest that ice plugs would not form within the fire sprinkler system piping. Years of empirical data prove the opposite. It has been proven that maintenance of these units is not often performed correctly over time. Air dryers are very maintenance-intensive, and as a result, the low dew point of the supervisory gas is lost, and ice plugs form. This activity can render a cold storage facility completely without fire protection unbeknownst to any facility owner/manager or AHJ.
What Makes Nitrogen Generators the Right Choice?
While oxygen corrosion will not occur in freezing environments (oxygen molecules can only dissolve in liquid water), the -80⁰F dew point of 98% nitrogen gas effectively prevents frost buildup and ice plugs in fire sprinkler systems serving freezers. This extremely low dew point is not lost over time, even if annual maintenance procedures are not followed.
Nitrogen generators also offer the following benefits over compressed air dryers:
- Many more systems can be served by a single nitrogen generator than a single regenerative air dryer
- Actual operational effectiveness (no ice plugs)
- Corrosion mitigation in areas maintained above freezing temperatures (loading docks, coolers)
- Significantly less maintenance cost and labor
- Reduced energy usage
Common Myths v. the Facts
You may encounter some of these common myths when solving your corrosion problems.
1. Nitrogen Generators Can’t Keep Up with System Leak Rates.
Fact: Nitrogen generators are designed to maintain system pressure in a dry/preaction system in compliance with NFPA 25 standards (1.5 psi loss per hour)
2. Buildings with Shorter Lifespans Don’t Need Nitrogen Generators.
Fact: Corrosion prevention should be the goal regardless of the building’s lifespan as there is an inherent risk to life and property due to rust buildup, even over a short period. It is irresponsible to think in this manner.
3. Nitrogen Generators Are Costly.
Fact: Nitrogen generators have been proven to be less expensive than air dryers in many applications. Even in those cases where there is a slight cost increase, the risk of using an inferior technology simply isn’t worth it.
4. Nitrogen Generator Maintenance is Challenging.
Fact: Nitrogen generators require annual filter replacements; replacement procedures take less than 10 minutes to complete, and replacement kits are easily acquired.
5. Compressed Air Dryers Are Equally Effective at Corrosion Prevention.
Fact: Science tells us the primary cause of corrosion in fire sprinkler systems is the reaction of oxygen, gas, water, and steel, which form rust. There is always water present in a dry or preaction system; air dryers do not remove moisture. The most direct way to control corrosion is to remove the drying reactant, oxygen. Compressed air dryers not only fail to remove oxygen but they maintain oxygen levels, providing no additional level of corrosion control vs. a standard air compressor.
What Fire Sprinkler Contractors Should Do
Fire sprinkler contractors should continue to educate themselves and understand the science, even if the science contradicts long-standing assumptions.
Nitrogen generators are a proven technology that will cause system piping to outlast the life of a building in most cases and prevent risk associated with ice plug formation.
Science has proven the effectiveness of nitrogen generator technology. Now, we have to continue to ensure that we move forward with facts based on science. Fire sprinkler contractors can use this technology to protect the investment of a sprinkler system long-term.
And, more importantly, ensure the sprinkler system can effectively protect lives and property.