Data Center Fire Suppression Systems: What Facility Managers Should Consider

By Jeffrey Tubbs, Garr DiSalvo, Andrew Neviackas  
OTHER PARTS OF THIS ARTICLEPt. 1: A Comprehensive Approach To Data Center Fire SafetyPt. 2: Evaluating Fire Detection Options For Data CentersPt. 3: This PagePt. 4: Data Center Fire Protection: Containment and Commissioning Pt. 5: Showcase Products: Fire Safety

Facility managers have a range of factors to consider when it comes to data center fire suppression systems. The primary fire protection systems used within data centers typically include: wet pipe sprinklers, pre-action sprinklers, and special suppression (i.e., clean agent, inert gas, or mist). Suppression systems need to consider higher challenge areas such as automated information storage systems units and tape libraries.

A wet pipe sprinkler system is the most basic sprinkler system option. This system, however, is always water-filled and is therefore usually not a preferred approach in data centers. These pipes have the potential for false discharge and water leaks or pipe failure, which could damage equipment and disrupt service. Welded pipe systems are preferred, although mechanical pipe connections are still found in many older facilities.

Two water-based fire suppression methods are typically preferred for data centers: single and double interlock systems. Single interlock systems rely on a separate event such as a smoke detector to activate before water is released into the system. In this case, if an individual sprinkler were to fail or break due to mechanical damage without a detector in alarm, the system will not release water into the pipes. After water fills the pipes, the system acts as a traditional wet pipe system and will not discharge water until temperatures in the room are high enough to activate a sprinkler.

A double-interlock pre-action system provides additional redundancy before water is released into pipes. Both a detector actuation, typically a smoke detector, and a sprinkler actuation must occur simultaneously before water will enter pipes. Usually the most critical applications warrant such a system.

Alternative suppression systems, clean-agent or inert gases, are the most common non-water based protection systems in data centers. These gaseous agents actuate early in a fire scenario to protect the data and IT equipment. Clean agents were developed as a replacement for Halon 1301. Because these systems do not use water, they are considered less likely to damage electrical equipment.

Clean agents are classified as either halocarbon agents or inert gases. Both types require a minimum design concentration based on agent classification and potential fire scenario to extinguish a fire. Factors such as pre-discharge warning signals, manual discharge stations, space considerations for agent supply, reserve agent supply, total flooding, or local flooding applications need to be considered when designing clean agent systems. NFPA 2001, Standard on Clean Agent Fire Extinguishing Systems, provides guidance on the design of clean-agent fire extinguishing systems.

Water mist provides another alternative. These suppression systems use high pressure water to produce very fine water droplets, with most droplet diameters less than 1000 microns. Mist systems have benefits similar to clean-agent systems. See NFPA 750, Standard on Water Mist Fire Protection Systems.

Many authorities having jurisdiction (AHJs) will not allow an alternative automatic extinguishing system to be the only means of fire protection in a data center. Typically, a pre-action sprinkler system is required in addition to an alternative system. Alternative suppression systems are typically used for property protection and business continuity, extinguishing a fire in its earliest stages. Sprinkler systems provide complete sprinkler coverage required by code, in the event the alternative system fails.

In all instances, the fire alarm and suppression systems are required to be interfaced in a data center fire protection application. A control panel, often referred to as a "releasing panel," relies on input from the fire alarm detection system to then subsequently open pre-action valves, initiate alternative suppression, sound pre-discharge alarms, shut down ventilation, or other actions. It is important in any design that all required interfaces be thoroughly examined and considered.

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  posted on 12/9/2013   Article Use Policy

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