FM Global updated their Data Sheet 8-9 with new high-piled rack storage protection schemes. These new protection options can reduce installation costs by as much as 50%. Large-scale fire tests were used to validate these alternative designs. They demonstrated that large orifice sprinklers and higher flow rates can be successfully applied to not only simplify the sprinkler system but also reduce the total sprinkler water demand. These new protections apply to all commodities including high hazard (plastics) commodities.

Previously, UL fire tests successfully demonstrated the feasibility of new protection schemes based on large orifice in-rack sprinklers in favor of using traditional in-rack sprinkler for high-piled storage applications. It was shown that for the tested scenarios (with 35 ft to 43 ft of rack storage, Group A Plastics) face sprinklers could be eliminated and in-rack sprinklers needed only be mounted at one or two vertical levels and only applied in the longitudinal flue spaces.

FM Global’s New Protection Schemes

Traditional in-rack sprinkler systems are used to protect rack storage for high hazard commodities and large storage heights. Per NFPA 13 Standard², Installation of Sprinkler Systems, in-rack sprinklers at various vertical levels (usually every 5-10 ft) may be required depending on the commodity hazard, shelf condition, and storage height.

However, the use of in-rack sprinklers based on NFPA 13 requirements are often met with concerns by building owners for increased installation costs and by warehouse operators for the additional risks of damage to the sprinkler heads during loading and unloading of the racks. FM’s alternative in-rack sprinkler designs improve on conditions on both fronts.

FM Global further expanded and generalized the application of large orifice in-rack sprinklers in high-piled storage applications. Recently these new protection schemes were added to FM Global Property Loss Prevention Data Sheet 8-9, Storage of Class 1, 2, 3, 4, and Plastic Commodities¹.

The new provisions in FM’s Data Sheet 8-9:

• Allow in-rack sprinklers to be installed every 30 to 40 feet vertically (!) depending on the commodity hazard being protected.
• Allow for storage above the top in-rack sprinkler level to be as high as 35 to 40 feet (!) depending on the commodity hazard being protected³.
• Size the water supply accounting for both, the ceiling and in-rack sprinkler systems, based on the larger of the two system requirements only (i.e., worst case of the two demands).

The results of these new provisions are:

• Reduced Cost: (1) Reduced number of in-rack sprinklers based on increased vertical spacing and increased storage height above the top row of in-rack sprinklers. (2) Reduced water demand, potentially eliminating the need for a fire pump and/or water tank.
• Reduced Risk of Water Damage: (1) Typically only one or two levels of in-rack sprinklers are applied reducing the risk for accidental damage to the sprinkler heads during loading and unloading of the racks. (2) While face sprinklers are still required in the new alternative in-rack system designs, their number is reduced. In addition, the face sprinklers only need to be mounted at in-rack level(s).

For more information see FM Data Sheet 8-9, Sections 2.3.4, In-Rack Sprinklers, and Sections in 2.3.6.6 (2.3.6.6.3.4, 2.3.6.6.3.5 and 2.3.6.6.3.6), Alternative In-Rack Sprinkler Designs. These sections detail alternatives in-rack sprinklers designs, which can be used to protect all commodities addressed in the data sheet.

It should be noted, that FM’s new alternative in-rack sprinkler designs must not be used to protect open-top containers, unless they are located on the bottom tier level. Furthermore, the alternative in-rack sprinkler designs are for wet-pipe systems and open-frame rack storage only.

References

[1] Property Loss Prevention Data Sheet 8-9, Storage of Class 1, 2, 3, 4, and Plastic Commodities, FM Global, Norwood, MA

[2] NFPA 13, Standard for the Installation of Sprinkler Systems, 2013 Edition, NFPA, One Batterymarch Park, Quincy, MA

[3] Rack Rate, NFPA Journal March/April 2016, NFPA, One Batterymarch Park, Quincy, MA