Dec 2002

Microbiologically Influenced Corrosion (MIC) – Part 2

In our April 2000 article, we detailed what microbiologically influenced corrosion (MIC) is and what it can do to fire protection system (FPS) piping. This is a continuation of our previous article.

The concerns from a fire protection standpoint include the following:

– Formation of tuberculation nodules in FPS which could obstruct pipes and sprinkler heads and cause a reduction in the inner diameter of the piping leading to additional friction loss under flow conditions

– Localized wall thinning which results in pin hole leaks and premature failure

– The end effect is property damage resulting when leaks occur in cleanrooms, over production or energized equipment, or on to high valued storage. Secondly and even potentially more damaging, an impaired or obstructed fire protection system fails to function properly during an emergency.

Since the early 1990’s, the fire protection industry began to discover pipe leaks and obstructions that were MIC related. Some experts now estimate that MIC is responsible for more than 30% of the corrosion in FPS. In 1996, the National Fire Sprinkler Association formed an “MIC Task Group” to address the issues associated with MIC. The work of this task force continues and they are also compiling suspected MIC cases on the designated reporting page of their Internet-accessible Web site. Other associations and organizations have created task groups to address this issue. NFPA has also recently formed a new Microbiologically Influenced Corrosion (MIC) Research Project with the aim to understand internal degradation and leakage of sprinkler system components due to MIC and to evaluate the performance of systems affected by MIC. The project will document the current state of knowledge of MIC, the magnitude and parameters of the problem in sprinkler systems, and will also include testing to document MIC dynamics, prevention, and mitigation.

If you suspect your FPS is infected, the first step is to have all possible water supply sources and the interior of the system analyzed for bacterial levels and activity. If MIC is confirmed in an existing system, actions should be taken immediately to treat the water source(s) and clean or replace the affected pipe sections as needed. Pipe cleaning may not be an option if the corrosion is excessive. The need to replace large sections of piping is a real possibility and should be determined by qualified professionals, taking into account many factors (future longevity, required system performance (hydraulics), exposures, etc.).

What was once an obscure topic affecting only certain regions is now becoming a widespread issue and concern in the fire protection industry in several countries.