CASE STUDY:
Data Center in the Atlanta, GA Region

DPNI: Dry Pipe Nitrogen Inerting

Project Background

A data center in the Atlanta area was originally built in 2009. The fire sprinkler system was comprised of ten (10) preaction system, each consisting of schedule 10 mains and schedule 40 branch lines.

During the initial construction, the specifying engineer suggested the use of nitrogen as a pressure maintenance gas, but the building owner declined. By 2013, the systems had experienced numerous leaks on the main piping of the preaction systems.

ECS nitrogen generatorThat same year, ECS was contacted to determine what next steps were required to mitigate the risk of future leaks in the mission critical facility. A nitrogen generator was installed within several months to limit the reintroduction of oxygen into the system piping, and a permanent gas analyzer was installed to ensure oxygen levels were kept to a minimum.

Subsequently, a series of internal investigations were performed to identify areas of the original galvanized piping that needed replacement and to continue to monitor the internal condition of the sprinkle piping.

Project Timeline



June 2014

First corrosion assessment performed, identified severe corrosion in feed main piping of the preaction systems.

  • Large amounts of trapped water present in this piping, combined with the compressed air pressure maintenance gas, resulted in localized corrosion of the galvanized pipe, eventually resulting in leaks.
  • Pipe samples taken from the systems identified localized corrosion of up to 69.2%.
  • Only metal loss consistent with oxygen corrosion was observed.
  • Partial replacement of feed main piping on five (5) of the systems was performed
June2014_Zone 2

Zone 2 – feed main (2014)



February 2016

Second corrosion assessment performed, additional feed mains were scoped for three more systems (not previously inspected). Significant damage was found in the original galvanized mains, with metal loss of up to 90.6%. The feed mains for these three additional zones were also replaced with black steel pipe.Feb2016_Zone 4

Zone 4 – feed main (The pitch of the pipe traps a significant amount of water and iron oxide debris.)



August 2017

Third corrosion assessment performed, piping over the data halls and electrical rooms (original galvanized piping, not previously replaced) was reinspected to look for increased levels of corrosion. The piping was still in good condition.

Zone 4 main_2016

Zone 4 – feed main (2016)

Zone 4 main_2017

Zone 4 – feed main (2017)



November 2018

Zone 4 main_2018

Zone 4: 4” Main – Original Galvanized Pipe. The original galvanized piping of zone 4 did not contain any trapped water or evidence of significant corrosion.

Fourth corrosion assessment performed, original galvanized piping over data halls was reinspected to look for evidence of increased corrosion.

  • Still dry and in good condition.
  • No liquid water/oxygen, no corrosion. Replaced black steel mains were inspected for signs of corrosion since install. Almost completely dry, no corrosion. Where water was present, no corrosion due to limited availability of oxygen.
  • Two additional areas of original piping were inspected that were not previously scoped. Some localized corrosion of the original galvanized mains was observed.


November 2019

Fifth corrosion assessment performed, prior to this video scoping, the first leak since the installation of the nitrogen generator was reported, having occurred on some of the original galvanized piping not previously replaced/ inspected.

  • Additional areas of the original galvanized system piping were inspected that were not previously accessible (over critical areas). Some localized corrosion was found, where trapped water was present.
  • The majority of this damage occurred prior to the implementation of the nitrogen generator, but a leak eventually formed at the location of localized metal loss at the weld seam of the pipe.
  • Replacement of the remaining accessible galvanized pipe is planned for the future.

Zone 10: 3” Main – Original Galvanized Pipe over Chiller Room B

Nov2019_Zone 10

(Scoping north from the south end of the main over Chiller Room B, trapped water was present the entire run. Some tubercles were observed over the run, so a pipe sample was identified to quantify the severity of the corrosion. )



Video Scoping Comparisons
4 year old replaced Black Steel Pipe, No Corrosion at Pool of Tapped Water under Nitrogen


4 year old replaced Black Steel Pipe. No corrosion at pool of trapped water under nitrogen.

5 year old Galvanized pipe, corrosion and tubercles under compressed air


5 year old Galvanized pipe. Corrosion and tubercles under compressed air.

 

2014 pipe sample from corrosion assessment Internal corrosion as received, pipe sample from 2014 assessment

Final Takeaways

Galvanized piping is acutely susceptible to leaks developing resulting from oxygen corrosion. Implementation of a nitrogen inerting corrosion control strategy has significantly limited the internal corrosion rates in the system.

The ideal way to mitigate risk in mission critical applications is to perform a corrosion assessment, surgically replace damaged piping, and implement a nitrogen-based corrosion control strategy.

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