NFPA Journal - March/April 2013 - (Page 48)

PROTECTING IKEA where sprinklers farther from a fire activate prior to the closer and more effective sprinklers—led the technical panel to specify a maximum deflector distance below the ceiling of 14 inches (35 centimeters). The overall test plan was guided by new requirements in the 2013 edition of NFPA 13 on developing alternative sprinkler system designs for storage. A new chapter identifies important parameters to address in a test program, such as high and low clearance location presents a different challenge to the sprinkler system. Running the tests In the summer and fall of 2012, six full-scale tests were conducted at UL that investigated a range of parameters identified in Chapter 21 of NFPA 13 (see “Testing at a Glance,” page 45). The goal of the tests was to control the fire spread—this was the key challenge across all of the tests—and to limit ceiling temperatures to protect A primAry concern resulting from the test program was the potential for fire to ignite commodities across the eight-foot aisle. caption from the top of the commodity to the sprinkler, sprinkler location in relation to the ignition location, and safety factors to be included when applying the design criteria. The distance from the top of the stored commodity to the ceiling or roof deck has for many years been recognized as an important factor to address in developing sprinkler protection criteria. A high clearance between the top of the commodity and the ceiling can delay sprinkler activation and allow the fire to spread horizontally along the racks prior to the activation of the sprinkler system. It may also impact the flow of the hot gases along the ceiling and result in undesirable sprinkler activation patterns. As a result, the new guidance provided in Chapter 21 of NFPA 13 includes requirements at both a high clearance from the top of the commodity to the ceiling and a low clearance from the top of the commodity to the ceiling. Both conditions were addressed as part of the test program. In addition, the ignition source location was varied in the tests to consider ignition locations centered between two ceiling sprinklers as well as an ignition location directly under a sprinkler. Each ignition 48 NFPA JOURNAL MARCH/APRIL 2013 the roof structure. The tests primarily used standard exposed expanded plastic commodity consisting of stacked polystyrene meat trays stored on pallets. In total, more than 1,000 pallet loads were used in the tests, which were witnessed by technical panel members and project sponsors live at UL and worldwide via live webcast. The results showed that the vertical barriers in combination with an overhead sprinkler system were effective in slowing the horizontal spread of the fire down the racks. In each test, flames reached the ceiling of the test lab, 35 to 45 feet (10.6 to 13.7 meters) above the floor, in approximately 45 seconds. The initial sprinkler activation occurred between 39 and 52 seconds after ignition in all tests, despite varying configurations of commodity storage height and ceiling height. Ceiling temperatures remained low in all of the tests. When used in conjunction with vertical barriers, the sprinkler design criteria was generally effective at limiting fire spread along the racks. In most of the tests, the fire was able to spread around the ends of the vertical barriers in the aisles, but the vertical barriers typically controlled the fire exposure to the adjacent pallet loads, which allowed the sprinkler system to be effective at limiting further fire spread. A primary concern resulting from the test program was the potential for the fire condition to ignite commodities across the eight-foot (2.4-meter) aisle. Polystyrene foam, such as the meat trays used in the tests, emits a high level of thermal radiation when it burns, meaning that the fire exposure to adjacent racks is relatively high compared with other types of commodities. During the tests, flames from the racks extended into the aisles, and in most cases the water spray from the sprinklers protected commodities across the aisles. In the sixth test, however, the activation pattern from the sprinklers did not adequately protect the commodities across the aisle, which ignited. Additional testing may need to be conducted to further investigate the required aisle width, or to possibly limit the stored commodities. While the current classifications in NFPA 13 do not differentiate between Group A plastics, such as polystyrene, polyurethane, polypropylene, and polycarbonate, differences in the fire performance of plastics can significantly impact the needed sprinkler protection. The results also suggest that additional testing using actual IKEA commodities might help further improve the efficiency of IKEA’s sprinkler systems. For IKEA, the testing provides support for protection of its commodities using more efficient sprinkler protection criteria. The Technical Committee on Sprinkler System Discharge Criteria will likely consider the research at its July meeting. Considering the absence of criteria for exposed expanded plastics in NFPA 13, it is IKEA’s hope that the Committee will acknowledge the efforts made by the Foundation and the project’s sponsors to close a gap in the standard. Steve Wolin, P.e., is a principal of Code Consultants, Inc. in St. Louis, Missouri.

Table of Contents for the Digital Edition of NFPA Journal - March/April 2013

NFPA Journal - March/April 2013
Contents
First Word
In a Flash
Perspectives
Firewatch
Research
Heads Up
Structural Ops
In Compliance
Buzzwords
Outreach
Electrical Safety
Wildfire Watch
Cover Story: Storage Occupancies
Fifty Years of Smoke Detection
Industrial Occupancies
Chicago 2013
Fire Analysis + Research
Section Spotlight
What’s Hot
Looking Back

NFPA Journal - March/April 2013