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
23.1.5.1 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
14.2.1.3 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?