Designing efficient data centers: Fire, life safety
Doug Bristol, PE, Electrical Engineer, Spencer Bristol, Peachtree Corners, Ga.,
Terry Cleis, PE, LEED AP, Principal, Peter Basso Associates Inc., Troy, Mich.
Scott Gatewood, PE, Project Manager/Electrical Engineer/Senior Associate, DLR Group, Omaha, Neb.
Darren Keyser, Principal, kW Mission Critical Engineering, Troy, N.Y.
Bill Kosik, PE, CEM, LEED AP, BEMP, Senior Engineer – Mission Critical, exp, Chicago
Keith Lane, PE, RCDD, NTS, LC, LEED AP BD&C, President, Lane Coburn & Associates LLC, Seattle
John Peterson, PE, PMP, CEM, LEED AP BD+C, Program Manager, AECOM, Washington, D.C.
Brandon Sedgwick, PE, Vice President, Commissioning Engineer, Hood Patterson & Dewar Inc., Atlanta
Daniel S. Voss, Mission Critical Technical Specialist, M.A. Mortenson Co., Chicago
CSE: What are some of the unique challenges regarding fire/life safety system design that you’ve encountered for data centers? How have you overcome these challenges?
Voss: Certain municipalities limit a fire zone’s coverage area from approximately one-third to one-half of what the NFPA 101: Life Safety Code allows. This, of course, requires more fire protection detection and extinguishing zones. If after meeting with the AHJ, they are not flexible in their local code amendments, then the design must meet the municipalities’ stricter requirements.
CSE: What fire/smoke and security features might you incorporate in data centers have that you wouldn’t see on other projects?
Keyser: The most common fire-suppression approach is double-interlocked preaction suppression systems. This is a dry-type, water-based system, prone to corrosion that results from trapped water and/or moisture-laden supervisory air. Mitigating corrosion is a key feature. Beyond the cost associated with replacing sprinkler piping, actually replacing it in a live data center exposes the client to significant risk. As a standard, we implement a nitrogen generator system to provide the supervisory air required for preaction sprinkler systems. This is an inherently dry medium, eliminating the moisture that’s introduced by traditional compressed-air systems. Additionally, the science behind it also shows that the nitrogen inerts the chemical reaction that causes corrosion at the air/water interface. This provides additional protection when a system has been charged for annual testing.
Peterson: The data center’s security has increased as exposures, thefts, and other embarrassing leaks have surfaced. Because of this, our secure-workplace specialists analyze how the data center operates to prevent corporate or other sensitive information from being captured.
Cleis: Fire alarm systems in data centers are often stand-alone and are connected to the overall building fire alarm. These systems typically consist of densely positioned smoke detectors or a pipe system that draws air and samples that air over the entire area. A data center’s stand-alone fire alarm system can be used as a releasing panel as part of a gaseous-agent fire suppression system. There are various types of gases that are currently available. Systems are designed to avoid any costly accidental release of these gases. Traditional water-based fire suppression systems can be wet- or dry-type. Dry-pipe systems are more common in data centers. These systems are designed to only flood when a “double interlock” occurs, with a loss of air pressure in the dry pipes indicating a melted fusible link and detection of smoke from a detector in the data center. These systems are designed to avoid accidentally introducing water to the data center.
Voss: Most commonly, the fire system uses a cross-zoned detection system with a dry-pipe distribution system connected to a deluge valve. Most data centers have a very early smoke-detection annunciation (VESDA) system that reacts much faster than standard fire alarm smoke detectors commonly found in other projects.
CSE: What types of systems have you put in place to guard against natural disasters, such as hurricanes, wildfires, floods, earthquakes, etc.?
Voss: Water-detection systems under raised-access flooring of the data center along with water detection in sump pump pits and recessed truck docks. To guard against earthquakes, seismic sway and additional structural supports for mechanical and fire protection piping systems and electrical feeder conduits. Lighting fixtures also receive cable supports anchored to the building structure above to guard against earthquake damage.
Gatewood: Uptime threats from nature come in many forms. Fire/life safety response can be integrated with modern sensors and a bit of analytics; life safety system responses can notify and manage staff and the data center’s systems. An example of an innovative solution we deployed was an autonomous automated warning and control system that can detect severe weather and response accordingly. We combined wind-speed sensors and lightning-strike distance/rate sensors to detect and react to violent weather. Should wind speeds exceed a preset level, the system alarms and prepares the plant to abandon exterior dry coolers in favor of interior, safely bunkered fluid coolers. Coupling this wind-speed sensor is a lightning-flash-rate/distance detector used for alarming outdoor athletic venues. It has been shown that lightning-flash rates are proportional to a storm’s severity (except the drastic immediate flash-rate drop preceding a storm dropping a tornado or microburst). Together, the data from these commonly manufactured devices have been integrated to alert and automate people and equipment responses to weather threats.
Keyser: Due to the critical nature of these types of facilities, we have been asked to provide vertical and horizontal piping support for data centers, regardless of their seismic zone classification.
Peterson: Redundancy of data centers has been a key strategy for many providers; however, most still prefer to have each site capable of operating as an island should disaster strike. Our risk assessments have been clear to point out and classify the greatest risks so that clients can either invest to harden the data center as they deem appropriate or examine relocating.
CSE: Describe unique security and access-control systems you have specified in data centers.
Peterson: Security is becoming another top issue for many data centers, just after reliability and efficiency. Spending will increase to train everyone in data center security, from cyber to physical, and also workplace security. Our secure-workplace specialists have realized that data breaches go beyond the keyboard and into how the spaces operate and flow together to ensure sensitive information is not exposed for thieves to easily steal. Along these lines, security specialists and consultants will see growth to match the security needs that some providers are already providing as a base service.
Voss: Crash-rated fences, boulders, dry moats, and crash-rated access gates. Each of these was designed to prevent a 15-ton vehicle moving at 30 mph from illegally entering the site.
CSE: Do you see any future changes/requests to the structural design of a data center building with regard to fire/life safety systems?
Keyser: We are seeing more multistory facilities. This influences the type of construction, compartmentalization with fire walls, the method of fireproofing steel members, etc. This also impacts nonstructural elements, such as fire pumps, regardless of the available water supply,
Voss: Currently, I don’t see any fire/life safety issues that would affect the data center’s structural design. We are always watchful of new and revised codes.
CSE: How have the cost and complexity of fire protection systems involved with such structures changed over the years?
Bristol: We’re starting to see most data centers going with VESDA and preaction as opposed to clean agent systems, due to long-term cost of ownership with clean agent systems as compared with VESDA plus preaction.
Keyser: Higher electrical densities have resulted in more deployments of either hot- or cold-aisle containment to efficiently address the generated heat. The type of containment chosen will dictate the layout of the fire suppression. The elimination ceiling removes the preferred method of capturing heat required for a sprinkler head to operate in an actual fire event, resulting in additional coverage above the ceiling plane. Additionally, in colocation facilities, the tenants’ requirements may not be known during the initial construction. Flexibility is a necessity, as the rack layout and quantity may not be known or can change. Beyond the redesign and constructions cost of modifying the sprinkler system, if there are already other tenants in the colocation space, shutting down the sprinkler system and the risk of doing intrusive rework is not an option. To address this, we reduce the maximum square footage sprinkler heads are capable of, therefore more heads are installed, and we install them on flexible dry pendent-style heads. This allows the client to adjust head locations to an adjacent tile without compromising the spacing, and it does not require a system shutdown or pipping rework.
Voss: We have not seen significant change, except that many customers are no longer willing to pay the premium for the high-dollar fire suppression systems. This is especially true as data centers continue to grow in size.
CSE: What unique clean agent (or other) suppression systems have you specified for data centers? Please describe.
Keyser: High-pressure mist-type systems with double-interlocked preaction configuration, which are commonly used in European and Asian markets, have gained popularity here in the states.
Voss: Turning the clock back a bit, several smaller to midsized data centers had various types of Halon fire suppression systems, which are now outdated. On a data center in Wisconsin, canisters of argon gas were installed for the data hall suppression system.