August 14, 2009
Microbiologically Influenced Corrosion (MIC) is a condition created in fire sprinkler systems by the introduction of steel eating microbes into the sprinkler system piping. These microbes are borne by the incoming water service, whether treated or not, and have been known to cause major damage on piping systems. Five elements must be present for MIC to thrive. These elements are: water, steel (black pipe or galvanized), oxygen, microbes and nutrients (nutrients are borne in the same waters that distribute the microbes). Other nutrients that support the MIC colonies are thread-cutting oil, pipe manufacture and construction debris and nutrients injected by frequent testing of the piping systems. Eliminating any one of these five contributors will greatly reduce the possibility of damage to your piping system.
Recommendation for Existing Facilities
MIC can occur in any piping system. Dry and Pre-Action systems frequently flooded for testing or filled with moist compressed air are more susceptible to MIC damage than wet systems. Regardless of your location or your water source, we suggest immediately testing your fire sprinkler water per NFPA 13, 15.1.5* and taking the following steps:
• Test a sample of water to determine which types of microbes are present and determine the proper treatment for remediation.
• Conduct a visual inspection of a representative sampling of mains to determine if MIC “tubercles” are present.
• Clean pipes with an approved cleaning agent and treat with a MIC retardant chemical.
• Implement maintenance procedures in compliance with NFPA 25, 13.2* through 13.2.4* (2004).
The best way to address MIC is through proper specifications. The following steps are a good best practice for new projects.
• Use schedule 40 piping in a Fire Sprinkler System and treat with a MIC retardant coating as provided by Allied Tube and Conduit, Inc.
• Install all piping so that it is 100% drainable.
• Flush newly installed systems and treat with MIC retardant chemicals.
• Install Dry and Pre-Action systems with a Nitrogen Gas (or similar inert gas induction system instead of compressed air system).
Holder Construction Company provides you with a MIC consulting resource which can perform or provide chemicals for testing of your water as well as instructions and chemicals for MIC mitigation.
For further information or assistance, please contact Holder through the Contact Us page.