Better Late Than Never
“I chose Jason Webb to write an article for the Member Takeover edition of the Inspection, Testing, and Maintenance column of National Fire Sprinkler Magazine because of his vast knowledge of, and passion for, the fire protection industry. Jason has had various roles in the fire protection industry and now works for Potter Electric Signal. Potter continues to stay on the cutting edge of fire sprinkler technology and produces exceptional products. There is no doubt that his article will be very informative.” –Vince Powers
If you ask facility managers about their biggest maintenance concern regarding their fire sprinkler system, many will tell you it’s corrosion. Thankfully, as an industry, we have made tremendous strides towards designing in corrosion mitigation methods from the start. Many specifications today call out nitrogen generators as the source of supervisory air for dry and preaction systems. But what do we do about existing systems that have no preventative strategies in place?
Over the past decade or so, there has been a significant amount of research into corrosion in sprinkler systems and, more importantly, what we can do to mitigate its effects. Countless articles have been published and presentations made on the subject. Corrosion continues to plague our industry, causing maintenance headaches, turning facility managers attitudes about fire sprinklers negative, and sometimes even resulting in system failures. All this despite proven methods for successfully managing it.
Common sense tells us that corrosion doesn’t happen overnight, but in reality, it does. While the results of corrosion may not be apparent for a while, the process begins almost immediately. Any time you bring together steel, water, and oxygen, corrosion will occur. Some factors, like heat and cold cycles or certain water supply characteristics even accelerate the process. But regardless, over time, corrosion will take place unless you completely remove one of those three components.
Corrosion is especially common in dry pipe systems since removing 100 percent of the water that comes from testing and condensation is all but impossible. That coupled with the fact that air compressors needed to replace escaping supervisory air bring in a fresh supply of oxygen as the operate. Often that oxygen brings with it added moisture from the atmosphere where the compressor is located.
All these are reasons why taking steps to reduce corrosion early on, at the design and installation phase, is so critical. Just because the initial installation didn’t take corrosion prevention measures into account doesn’t mean that it’s too late. There are things you can do now to extend a system’s life and reduce ongoing maintenance concerns. Like anything, the first step is establishing a baseline from which to start the corrosion prevention measures. A good place for that to begin is with an internal inspection.
The first reference to opening the system and looking inside on a regular basis went into NFPA 25 in the 2002 edition. This critical task helps ensure that corrosion or other obstructive material is identified so that steps can be taken to mitigate it. But with the changes to NFPA 25 beginning with the 2014 edition that took the prescriptive requirements out of the standard for opening up the system, it’s more important than ever to adequately assess the actual conditions inside the system. This still often means looking inside the pipe.
Another option for trying to quantify the severity of corrosion is the use of corrosion monitoring stations. These devices are placed on the sprinkler system and are exposed to the same environment as the systems itself, thereby simulating the conditions inside. Corrosion stations come in a variety of configurations and usually have multiple means of detecting and measuring corrosion.
For existing systems, whether an internal assessment reveals corrosion, corrosion monitoring devices alert you to a problem, or something more ominous like pinhole leaks beginning to appear, the priority becomes taking action to slow the corrosion process. Just as with new systems, replacing the supervisory air with nitrogen can dramatically and quickly change the conditions inside the sprinkler system. Since nitrogen generators just replace the air supply, retrofitting a nitrogen generator onto an existing system is not a difficult task.
It’s important to understand that adding a nitrogen generator to an existing system will not repair damage already done. If pinhole leaks or other serious corrosion is present in some areas of the system, those sections of pipe need to be replaced. But once that’s done, and a nitrogen generator has been added to the system, the ongoing corrosion process begins to slow immediately due to the lack of oxygen. The added benefit of the extremely low dew point of the nitrogen being introduced is a reduction of the moisture available to support the process as well.
It’s never too late to take steps to reduce the damaging effects of corrosion in sprinkler systems. The key is to take those steps as early in the system’s life as possible. The earlier nitrogen is added to an existing dry or preaction system, the less corrosion will impact it.•