It's important for fire sprinkler experts to understand the unique risks, and the best solutions, for corrosion when you are working in a warehouse or logistics facility. In this article, we'll look at the risks and solutions so you can feel confident that you understand the "what" and the "why" of using nitrogen to mitigate and control corrosion in these large facilities. 

Risks in Warehouse and Logistics Facilities

RISK #1: OBSTRUCTIONS

From Day 1 after installation, the corrosion process begins in trapped air locations of the wet system. Scaling and debris begin to accumulate inside the system.

Frequent system flushing and fire pump testing move these deposits all over the sprinkler system causing it to collect behind sprinkler heads and delay water delivery inside the pipe.

Since you are not pulling sprinklers every year to check for obstructions, you’ll never know your head(s) is blocked until you have a fire in the building with no water coming out of the activated sprinkler. 

These obstructions along with the lack of visibility create big risk.

RISK #2 PIPE FAILURE & PROPERTY DAMAGE

Free oxygen pulled into the closed system from draining will always trap in the same place if systems are un-vented.

Corrosion activity will happen in your system peaks or high points. Unfortunately, in these large facilities, those points are commonly located above equipment and processing areas or above large racks for high-piled storage.

The pipe will eventually leak over the equipment and stored products resulting in property damage & loss. Additionally, the leak will usually occur in an area that is hard to get to without shutting areas of the building down and moving that equipment in order to get to the pipe with a lift for repair.  

Repairing the problem will also involve the tedious process of draining the system down, filling it with more fresh oxygen, and making the metal fail around the area you just repaired.

This leads to a domino effect that will continue to get worse once leaks develop inside the system, which will require the system to be drained for repair more and more frequently.

Nitrogen Solutions for Wet Pipe Systems

Understanding Gas Composition inside an empty sprinkler system

Sprinkler systems are completely closed. This gives us the ability to:

• Completely dilute gas content during system filling (venting)
• Fully remove oxygen using pressure and concentrated gas prior to filling

When the sprinkler system is drained down, the atmospheric gas content that has filled the pipe network is 78% nitrogen, 21% oxygen, 1% other. Keep in mind that gasses are not subjected to gravity inside a closed system like water is; the 78%/21% gas content can be completely altered or removed.

Creating a non-corrosive environment

The best way to control corrosion activity on these big wet systems is the address the oxygen prior to putting water back inside the system. If we make a non-corrosive environment before we leave non-flowing water sitting inside a closed black iron system, you will not have corrosion problems.

You can create a non-corrosive environment in 2 ways:

1. Pressure: Pressure enables different gasses to mix together inside a closed system or a tank. Pressure is also how mixed gasses are exhausted from the closed system, like letting air out of a balloon.
2. Concentrated 98% Nitrogen Gas: A nitrogen generator is provided in the facility that rapidly makes its own high purity nitrogen and stores it in a receiver tank.

How Nitrogen helps create a non-corrosive environment

The WPNI process (wet pipe nitrogen inerting) utilizes an air compressor that forces compressed air through a gas separation membrane (filter) and separates the 21% oxygen.

Our 78% nitrogen is now 98% pure nitrogen which can be used for dilution inside a sprinkler system.  

The high purity nitrogen gas is pressurized into the empty wet system fed from the receiver tank into the wet system to 30 PSI. Now, you add the 98% mix with the 78%/21% already inside the system.

Each time that 30 PSI of pressurized gasses is released, we take a reading with a gas analyzer to determine not the nitrogen purity, but how much oxygen is left inside the pipe network.

We can tell that the system is oxygen-free when the 78% nitrogen content increases to 98%-99% as it’s released from the system.

When this is achieved, all of the gas pressure can be released without needing to leave nitrogen inside the system. All we’ve done is made an oxygen-free non-corrosive environment, and now the sprinkler system can be filled and will be non-corrosive.

If this procedure is done following any drain down activity prior to putting water back inside it, this will preserve the black iron internally and the nitrogen generator always will provide a constant source of concentrated gas inside the facility to use when you do this process.  

Make an oxygen-free sprinkler system and do it properly; you’re going to get the same result every time.  

Ready to create a non-corrosive environment in your warehouse sprinkler system? Talk to the experts!