Fire sprinkler professionals recognize that corrosion is one of the most challenging issues facing the industry today. Dry pipe systems tend to have the spotlight when it comes to corrosion, but wet systems have their fair share of corrosion-related issues as well.
Wet sprinkler systems experience corrosion along the air-water interface in the high points of the branch lines. The least expensive, most effective way of reducing the amount of corrosion taking place is to remove the air from these high points. Hence the need for a vent.
Placing a vent on existing systems does two things to extend the life of the existing piping.
- It reduces the amount of oxygen available to react with the pipe wall.
- The vent will move the air-water interface up the branch lines where corrosion will now occur on “new” piping material, buying extended system life.
The 2016 version of NFPA 13 requires venting air on all wet pipe fire sprinkler systems. There are several options for venting, but not all of them are equal.
Venting Options: Pros and Cons
option 1: Ball Valve
The simplest and least expensive option is to simply install a ball valve at the high point of the system. However, it is doubtful this valve will be opened and used to vent any air from the system once installed. If a different contractor services the system than initially installed it, they might not know this ball valve exists. The use of a ball valve as a vent is just to meet the bare minimum code requirements and will most likely not be used effectively to reduce the amount of corrosion taking place.
Option 2: Single Float Air Vent
The next option for vents available to remove corrosive oxygen is a single float air vent. The problem with these vents is that they should be plumbed to a drain or include a catch pan to ensure water does not discharge over the protected space. Piping to a drain or having catch pans to collect water is recommended because these products are highly prone to failing and leaking water over protected areas and finished goods. Plumbing to a drain also often results in a higher cost installation than using a vent with a redundant failsafe.
Single float vents are commonly used on fire pumps, and there is almost always a puddle of water found beneath them. If these vents do not plumb to a drain, the drain is by machinery, or the catch pan is not large enough to contain the spill, the cost of damaged property and goods could come back on the contractor if it is within the system warranty period. There is a lot of risk associated with single float vents that fire sprinkler professionals could avoid by selecting a higher quality product in the first place.
Option 3: Automatic Air Vent
By far, the best way of removing the trapped air pockets in a sprinkler system is to use an automatic air vent with redundancies and fail-safes built-in.
There are a few vents on the market that offer these, but they, too, are not created equal. Some have electric components that need annual battery replacement. It is unlikely this will occur given the remoteness of these vents.
Others offer single float vents with a catch pan and water shutoff valve that will close to prevent the overfilling of the catch pan. This single-use shutoff valve has no way of determining whether it has been activated without physically going to the vent and checking. Once this valve closes, there is no way for the oxygen to escape, and the vent is rendered useless.
The Best Automatic Air Vent on the Market
The highest quality and best automatic air vent on the market has two float valves that provide dual redundancy, so the vent doesn’t need to pipe to a drain. This vent - the Ejector Automatic Air Vent (PAV-W) - is built by Engineered Corrosion Solutions (ECS).
There have been thousands of these vents installed without failure. This vent does not require an annual battery or single-use components replacement, unlike other automatic air vents.
It has a pressure gauge included that fire sprinkler professionals can see from the floor beneath to ensure the first float has not stuck open, and water is putting pressure on the second float. Should this be the case, the vent only needs to be shaken or washed out until the first float moves freely. It also has the lowest clearance height available, does not require a hanger, and is both FM-approved and UL listed. Along with these advantages, it is also the only vent that fire sprinkler professionals can retrofit to a nitrogen inerting or supervised air vent.
These advantages, coupled with the fact that only contractors deal direct with ECS engineers who are experts in fire sprinkler corrosion mitigation, make ECS the best provider of automatic air vents and “The De Facto Standard in Fire Sprinkler Corrosion Control.”
