Uncommon Sensors

It has been a long time coming. For nearly a century and a half, the familiar sprinkler in one form or another has been one of the soundest loss prevention investments available. The 19th century saw interest grow in developing such a device. One sprinkler-like invention was even developed by Hiram Stevens Maxim—who later earned fame as the inventor of the modern machine gun. But his invention lacked a crucial innovation supplied by one Henry S. Parmalee who tested the first automatic fire sprinkler system in 1874, relying on a solder alloy that would melt at a relatively low temperature, to control the release of the stream of water. Since then, many manufacturers have created products using a similar principle.

The most prominent impetus for revisiting sprinklers comes from the world of modern distribution, where ever-larger warehouse structures combine high vertical storage and enormous enclosed volumes for the sake of efficiency. Lifting and retrieval technologies make it possible to store products higher than ever before. To minimize fire risks, some businesses have installed sprinkler systems within the rack configurations often used to store products and pallets. Moreover, in some industries, such as paper, where on-end storage of roll paper coupled with overhead cranes are in widespread use, "stacks" up to 80 feet (24 meters) in height are not uncommon.

In those storage environments in particular, traditional sprinklers encounter tremendous challenges. If a fire begins at or near the base of a paper stack, the temperature at the ceiling level may not reach a sufficient temperature to activate until the fire has grown substantially and perhaps extended far beyond its original location. The combination of high storage and potential fire spread, dubbed "highly challenging fires" (HCFs), demands a response that goes beyond the protection recommendations involving traditional sprinklers, notes Christopher Wieczorek, assistant vice president, research group manager for fire and explosion protection at FM Global.

FM Global researchers decided to explore the notion that the essential "problem" with sprinklers is exactly the same as their greatest strength: the detection and actuation mechanisms are shared. This has yielded remarkably reliable and predictable responses to fire, but it is insufficient when fires are potentially at a great distance from the sprinkler. Moreover, the distance involved increases the possibility that sprinkler activation might still be insufficient to substantially reduce a conflagration.

Given the technologies now available, the option of activating sprinklers on the basis of sensors located at a distance, such as in a deluge system, but where large groups of sprinklers are activated simultaneously, could be expanded to an intelligent protection system with limited and controlled sprinkler operation. A catchy name was developed to convey the combination of detection at an early stage (by being as close as possible to what is being protected) and response, namely, Simultaneous Monitoring, Assessment and Response Technology (SMART). As it turns out, SMART technology really is "smart" in the sense that it uses small, inexpensive computer chips to assess sensor inputs and determine the best response across a system of discharge devices.

Although SMART may have begun as merely a concept, it soon took physical form in an effort to make a practical determination of how to best identify a hazard and respond effectively.

Experiments at laboratory scale were conducted in the Small Burn Lab at the FM Global Research Campus. A range of various fire sizes and fire locations were used to test detection capabilities, followed by efforts to distinguish optimal sprinkler spacing and activation scenarios.

For both detection accuracy and speed of response, the experiments showed the value of using more than one detector technology, specifically, the rise of temperature and the presence of smoke. Having two different sensor types reduces the likelihood of a false trigger and can help "triangulate" the exact location of a fire more successfully than a single sensor.

Yibing Xin, senior lead research scientist at FM Global, cautions that SMART is not a product—FM Global does not manufacture detection or protection equipment; rather it is "a proof of concept for a new protection system to deal with the limits of traditional sprinklers," he says.

Speed of actuation was a goal and, according to Xin, in a test of a 42-foot (13- meter) tall roll paper storage, a traditional sprinkler would not activate until flames were approximately 50 feet (15 meters) above the floor. "Our SMART system activated when the flames were only 14 feet (4 meters) tall," he says, a two-thirds reduction.

"By separating the sprinkler from the detection process and activating the sprinklers in an intelligent manner, more timely and efficient protection is provided for extremely challenging scenarios. We have also opened up the possibility of using different kinds of sensors or a network of sensors, perhaps one day including infrared and video image-based detection," he adds. Because SMART is a proof of concept, Wieczorek notes that development efforts focused on applying commercial-off-the-shelf (COTS) technology to minimize time and resources, utilizing smoke and heat detector products, software logic, and a solenoid-operated sprinkler or group of sprinklers. The prototype was used with a "wet" sprinkler system, but the technology could also be adapted to a dry-pipe system.

Wieczorek says FM Global plans to continue to share details of its work to date and is open to working with industry. "The key is to ensure that the best possible technology is available to clients," he says.

"We believe in many applications a ceiling-only approach using traditional sprinklers is not adequate," Xin notes. "With SMART sprinkler technology we aimed to connect rapid detection, intelligent fire location and suppression to create more cost-effective solutions for FM Global clients."

Although the SMART sprinkler research completed thus far is only for proof of concept, it is a significant step to put FM Global at the forefront of developing loss prevention technology—maintaining a position it has held in the industry for more than a century.

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