Project profile: Installing a large clean agent system in a complex environment

A government data center opted for a clean agent suppression system to protect its mission critical facility.

Corey Wallace

08/07/2014

Figure 1: This shows the primary and secondary clean agent tank installation in the data center. Courtesy: Southland Industries

Southland Industries recently designed and installed one of the largest clean agent fire suppression systems in the nation. The stakes were high as the goal of the project was to protect sensitive data stored on hundreds of servers within a large government facility. The project was particularly complex not only due to its large size and stringent standards for security, but also because it needed to seamlessly integrate with a double interlock pre-action system and an energy-efficient containment method of air cooling.

The immediate challenge facing the design team centered on accommodating the agency’s requirement that the building have continuity of operations. The agency needed to be able to perform system maintenance and upgrades without losing power to the system or any of its functionality. Any kind of system disruption—even one consisting of only a few minutes—was simply not acceptable.

Designing and installing this clean agent system required not only meticulous planning, but also creative thinking that led to a set of innovative and smart solutions for the building owner. It served as a reminder that regardless of any apparent incompatibilities among systems performing different functions, there are ways to design and structure them so they operate as a cohesive whole.

To ensure continuity of operations, project engineers designed a double interlock pre-action system to reduce the chance of accidental water discharge in the event of a fire. This would assure that water would only be discharged as a last resort in the 66,000-sq-ft data center space. As a first line of defense, a clean agent system using 3M NOVEC gas would be used.

Figure 2: Installation, accessibility, and serviceability are key considerations in the storage tank arrangement. Courtesy: Southland Industries

Installing a clean agent system in such a massive area required a creative approach by the team. Regulations required that clean agent “storage containers shall be located as close as possible to or within the hazards they protect” (NFPA 2001, Section 4.1.3.2). But the configuration of the building was not conducive to situating the clean agent system close to these protected areas. The server room and mechanical gallery are located in the center of the second floor over a 3-ft raised floor. The ceiling height of the server room is approximately 12 ft, and the space above the ceiling to the deck is approximately 4 ft. The electrical power supply via switchgear equipment is located directly below the server room space. All of this made it impractical to place the clean agent tanks on the same floor as the servers.

Given these constraints, the team determined that the best solution would be to locate the clean agent primary and secondary supply tanks on the ground floor, even though the protected hazard—the servers and mechanical gallery—are located on the second floor, 20 ft above and several hundred pipe lengths away.

This complicated matters even further, requiring the team to ensure the clean agent system’s fire-extinguishing gases could just as efficiently reach the protected areas as they would if they were located closer to them. This meant making sure that the system was equipped with the appropriate amount of gas and was forceful enough to pump that gas into the areas.

None of the clean agent systems certified at that time were right for the job. The project required a newer system that had a higher discharge pressure. After thorough evaluation and analysis of needs, the team eventually settled on the 500 psi NOVEC 1230. The system was so new that it was still going through its final approval process by UL, a third-party listing agency, as it was being installed. A few months before the project was turned over to the owner, the system gained official UL approval.

In addition to the many challenges already identified, the team needed to address the issue of arranging the various fire life safety systems and MEP trades and equipment in a limited amount of space. The fire suppression piping, along with the other trades, required detailed coordination to prevent interference and a lack of constructability. To prevent potential conflicts, the piping was designed, planned, and coordinated in 3D to reduce field changes. This allowed for the inclusion of bracing in the clean agent piping (similar to seismic bracing) to hold the pipes in place against the force of pressure that is exerted when the clean agent gas is discharged. By strategically locating the pipe, any potential interference with the other trades was prevented.

Another focus of concern was the need to prevent pipe corrosion. It was important to make space for a nitrogen system to prevent corrosion of the pipes of the double interlocked pre-action system, which employs schedule 40 black steel pipe. Concern about future corrosion prompted the pre-action system to be supervised by an inert gas such as nitrogen in lieu of standard air. However, space was not made available on the second floor to accommodate the infrastructure needs of the nitrogen system. As a result, the nitrogen generator and storage tank had to be located on the first floor in the clean agent storage tank room. From there, the supervisory nitrogen is piped up from the first floor to the pre-action valves on the second floor. The pre-action valve is required to automatically revert to a non-interlock configuration in the event of a power loss. Upon the return of power, the pre-action valve returns to its standard release method.

Finally, the project also needed to meet the requirements of and be certified to U.S. Green Building Council LEED Gold, version 3.0. It would be registered through the Green Building Certification Institute, with performance goals based on a “high-performance green building” as defined by the Energy Independence and Security Act of 2007.

To reach LEED certification in a building with many servers, the agency employed the containment method using barriers to trap and direct airflow to control cooling. The challenge with this method, however, is that the structure created obstructions that would make it difficult for the clean agent gas to reach it. The hot aisle containment areas are large enough to walk in and therefore require sprinkler protection as well as clean agent protection. The aisle utilized ceiling grids down the center for lights and fire protection devices but had 2-ft-wide open areas along the length of the enclosure. To address this, the project team altered the clean agent nozzle locations so that they entered into each of the containment areas.

Corey Wallace is an associate principal engineer with Southland Industries. He holds a bachelor’s in mechanical engineering from the University of Mississippi and a master’s of engineering management from Christian Brothers University.

Tuesday, August 19, 2014

Largest Novec System in the country

Project profile: Installing a large clean agent system in a complex environment

A government data center opted for a clean agent suppression system to protect its mission critical facility.

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