corroded-galvanized-2
Corroded Galvanized Main with Trapped Water
zinc-oxide
Zinc Oxide and Iron Oxide Deposits on Bottom of Main
under-deposit
Under Deposit Accelerated Oxygen Corrosion

CASE STUDY:
Mission Critical Data Center

WPNI: Wet Pipe Nitrogen Inerting

Project Background:

The 100,000 square foot data center was originally built and opened in 2002 with double interlock preacon fire sprinkler systems to protect the data halls. Galvanized steel piping was used for all of the preacon fire sprinkler systems. AŌer 8 years of service leaks began to develop in the 3” galvanized schedule 10 main piping. All of the leaks occurred within the main line piping under accumulaons of trapped water. The metal loss was characterized by highly localized aƩack with many deep singular round boƩomed pits beneath the trapped pools of water.

Based on the history of leaks occurring in the facility, Engineered Corrosion Solutions was contracted to identify the root cause of the corrosion and develop a corrosion control strategy to prevent future leaks.


Water supply
– municipal water supply with fire pump

Fire sprinkler system design configuration
  • Five (5) preaction risers protecting the data center
  • “Tree” type fire sprinkler design configuration
Fire sprinkler piping materials
  • Rolled groove schedule 10 galvanized main piping
  • Threaded Schedule 40 galvanized branch lines

Preliminary Assessment Work

A corrosion assessment survey was performed in July 2010 to determine the extent of damage within the fire sprinkler piping. The video scoping results indicated that there was extensive damage due to oxygen corrosion within the schedule 10 mains at any locaon that acted to trap water, which was present throughout much of the mains. The schedule 40 galvanized branch lines exhibited minor corrosion and contained only minor amounts of trapped water. Analysis of pipe samples extracted from the system mains revealed oxygen corrosion ping resulng in wall penetraons of up to 62.5%.

The oxidaon reacon of galvanized steel pipe and oxygen produces zinc oxide and iron oxide deposits. Once the protecve zinc layer has been breached, oxygen corrosion is liberang iron atoms from the underlying black steel substrate resulng in highly localized corrosion and resultant failures.

Implementaon of ECS Dry Pipe Nitrogen Inerng (DPNI)

In early 2011 the client elected to install the ECS nitrogen generator and employ the patented “fill and purge” breathing technology to remove oxygen from the fire sprinkler piping and provide nitrogen gas for pressure maintenance. The ECS PGEN‐20 Nitrogen Generator was installed and commissioned to supply nitrogen to the 5 preacƟon sprinkler systems within the facility.

ECS-Protector
ECS Protector Dry SMART Vent ‐ PSV‐D
  • No pipe replacement was performed
  • Installaon of ECS Nitrogen Generator (PGEN‐20)
  • Performed DPNI on all 5 preacon fire sprinkler systems using ECS nitrogen inerng protocol for dry pipe fire sprinkler systems
Recommendations:
  • Perform limited pipe replacement of the 2” branch lines on either side of the roof apex, approximately 60 feet of pipe on each branch line
  • Install ECS Protector Nitrogen Inerting Vents on each of the wet pipe zones
  • Install ECS Protector Nitrogen Injection Ports on each of the wet pipe risers
  • Perform nitrogen inerting of the fire sprinkler systems using the ECS nitrogen inerting protocol for wet pipe fire sprinkler systems
  • Use nitrogen cylinders to supply the necessary nitrogen gas for the inerting procedure on the fire sprinkler systems
nitrogen-vent ECS Nitrogen Inerting Vent

Financial Analysis of Repair Options

The most common response to escalating leak frequency and increasing fire sprinkler system repair costs is to completely remove and replace the fire sprinkler system piping. Esmated replacement cost of the fire sprinkler piping for this facility was $2 per square foot for a total of approximately $900,000.

Results and Conclusions

Despite the significant damage found during the assessment, no fire sprinkler system piping was replaced within the facility prior to the installaon of the ECS nitrogen generaon system. Under a nitrogen atmosphere the corrosion in the fire sprinkler system piping would be stopped, even in locaons with trapped pools of water. Since repair of inial leaks and installaon of the ECS PGEN‐20 nitrogen generator there have been no recorded addional leaks within the preacon fire sprinkler systems in the facility.

nitrogen-generator
ECS Nitrogen Generator (PGEN‐20)
pressurized-cylinders Pressurized Cylinders providing nitrogen gas

Fire Sprinkler Contractor Feedback

Fire sprinkler contractors who have performed the wet pipe nitrogen inerting (WPNI) procedures report that the entire process is very manageable and significantly easier than applying chemical corrosion control agents. The entire wet pipe nitrogen inerting procedure can easily be performed on a typical 1,000 gallon sprinkler system within 2‐3 hours. It is also possible to perform the procedure on several zones at the same me. Once the fire sprinkler contractor has been certified by the ECS Nitrogen Inerting Team, the contractor does not require on‐site support or supervision.

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