Corrosion in Fire Sprinkler Systems Instructor • JOSH TIHEN, is the Corrosion Solutions Product Manager at Potter Electric Signal Company. He is a chemical engineer who is a member of the American Institute of Chemical Engineers, the American Chemical Society, and the National Association of Corrosion Engineers. He currently serves as the Vice Chair of TEG 159X Building Fire Protection Systems: Corrosion and Deposit Control committee for National Association of Corrosion Engineers. 2 Overview • Objectives – Discuss the problems corrosion causes in fire sprinkler systems – Identify the causes of corrosion – Take an in-depth look at the current state of corrosion technology – Evaluate the economic impact that corrosion has on fire sprinkler systems Safety The biggest concern is that corrosion will cause a sprinkler system to fail. 50% Blockage (California, 5 year old system ) Failed Sprinkler Head (Illinois, 12 year old system ) Issues Corrosion is known to produce many problems in the fire sprinkler market – Pinhole leaks – Temporary shutdowns – Loss of property – Loss of production – Total system replacements – Reduces effectiveness of fire sprinkler design – Personal injury Issues What is the life expectancy of a fire sprinkler system? VdS 20-year long survey of corrosion in sprinkler systems: Class I - Little damage is found the pipe array should just be flushed. Class II - Medium damage is found, so that some but not all pipes show increased damage, those pipes must be replaced. Class III - Considerable corrosion and deposits the complete pipe array or parts of it must be replaced. Fontana Wet system Class I 8 Indianapolis Wet system Class II 9 Hartford Wet system Class III 10 Wisconsin Wet system 3” main Class III 11 VdS Survey Evaluated wet pipe systems after 25 years: 65% - Class I 32% - Class II 3% - Class III Over 1/3 of systems have significant corrosion issues Cincinnati Dry system Class I 13 Minneapolis Dry system Class II 14 Illinois Dry system branch line Class III 15 VdS Survey Evaluated dry systems at 12½ years: 27% - Class I 51% - Class II 22% - Class III 73% of dry systems have significant corrosion issues Types of Corrosion There are 2 main types of corrosion in FSS 1) Generalized Corrosion (Rust) 2) Microbiologically Influenced Corrosion (MIC) Generalized MIC Generalized Corrosion Generalized Corrosion, also known as rust, requires 3 things: 1) Water 2) Iron 3) Oxygen Generalized Corrosion Cell (Rust reaction) MIC The term Microbiologically influenced corrosion (MIC) is used to designate corrosion due to the presence and activities of bacteria. The three main type of bacteria are • Acid Producing Bacteria (APB) • Sulfur Reducing Bacteria (SRB) • Iron related bacteria (IRB) MIC MIC corrosion can cause quick failures. Galvanized Schedule 40 after only 3 1/2 years Galvanized Schedule 10 after only 18 months MIC in FSS FM Global study found 40% of corrosion was influenced by MIC and 60% of corrosion was generalized corrosion. NFPA Code NFPA 13 126.96.36.199 Water supplies and environmental conditions shall be evaluated for the existence of microbes and conditions that contribute to microbiologically influenced corrosion (MIC). Where conditions are found that contribute to MIC, the owner(s) shall notify the sprinkler system installer and a plan shall be developed to treat the system…. NFPA Code NFPA 25 188.8.131.52 Tubercules or slime, if found, shall be tested for indications of microbiologically influenced corrosion (MIC). Dry and Pre-action Corrosion flourishes in Dry and Pre-action systems because they are NEVER 100% DRY. Trapped water from hydrostatic testing, combined with humid air supplied constantly by the air compressor creates a perfect storm. Typical “Dry” System Generalized Corrosion Corrosion requires 3 things: 1) Water 2) Iron 3) Oxygen If eliminate one, you stop corrosion. Generalized Corrosion Cell (Rust reaction) Nitrogen Replace the Oxygen with Nitrogen. Nitrogen is an INERT gas. It does not react with metals. Thus, no oxidation or rust occurs! Nitrogen Tests Nitrogen Tests After 4 months Nitrogen Tests After 4 months 30 Compressed Air After 20 months 31 Compressed Air After 20 months 32 98% Nitrogen After 20 months 33 98% Nitrogen After 20 months Nitrogen Tests Corrosion Coupon Testing Manifold After 12 Months Steel Coupon Compressed Air Steel Coupon 98% Nitrogen Galvanized Coupon Compressed Air Galvanized Coupon 98% Nitrogen After 12 Months Compressed Air Black Steel Galvanized 98% Nitrogen Black Steel Galvanized Nitrogen Tests Nitrogen Tests Water Metal 98% Nitrogen Inhibition Effectiveness (% Protection) Trace Steel 45.40% 1.83 Trace Galvanized 91.80% 12.20 Half Full Steel 78.60% 4.67 Half Full Galvanized 61.60% 2.60 69.35% 5.33 Average Life Expectancy Multiplier Nitrogen Tests Galvanized Pipe 40 41 How do you supply nitrogen to a fire sprinkler system? 42 “Reliable Source” The trick to this is removing that 21% oxygen from the fire sprinkler piping and replacing it with pure nitrogen. The earth’s atmosphere is 78% nitrogen and 21% oxygen Nitrogen Generator Nitrogen generators provide on-site reliable nitrogen production. Nitrogen Generator Nitrogen Cabinet Dryer Air Compressor AMD Nitrogen Storage Tank (98%+ N2) Nitrogen Generator The nitrogen membrane is the “heart” of the nitrogen generator. Nitrogen Generators Nitrogen Purging Process Nitrogen Generators Sizing a Nitrogen Generator • Largest riser size • Supervisory pressure • Total system capacity Nitrogen Generators Design with Nitrogen in mind • Use black steel over galvanized – save 30% on average of sprinkler piping • Use a lower supervisory pressure – smaller compressor needed • Feed more than one system – “Plant Nitrogen” Parking garage installation Recommendations Dry Systems • Use nitrogen over compressed air • Use black steel over galvanized • Implement a corrosion monitoring program Questions?