Large K-factor sprinklers help designers meet the challenge of safeguarding these environments with ceiling-only protection.




In-rack sprinklers can be a burden in warehouse operations, even with trained personnel that are aware of the risks and damage by impact. Mix in seasonal items, constant movement of rack levels of storage, the untrained public and you have a pretty good idea of the need the Big Box Retailers have to eliminate in-rack sprinklers in their retail environment.

In late 1999, retailers worked together with two manufacturers to develop a protection method that would provide ceiling-only protection, allow the use of slatted and some solid shelving, use low operating pressures and provide wider spacing (extended coverage). Aware of customer concerns and after many full-scale fire tests, the fire sprinkler industry has developed and introduced extended coverage sprinklers for extra hazard and storage occupancies. These large K-factor sprinklers provide the complete package for the retail and high-ceiling storage needs of the fire sprinkler industry. Without being specific to model and type, a few of the immediate benefits of this technology are as follows:
  • Better Fire Protection - Shown in full-scale fire tests.

  • Fewer Branch Lines - Spacing up to 15 ft. vs. 12 ft. (12.5 ft. in a 25 ft. bay).

  • Fewer Sprinklers - Area of coverage up to 196 sq. ft. vs. 100 sq. ft.

  • Lower Operating Pressures - Minimum 7 psi, calculated by S x L rules, not (square) EC coverages.

  • Fusible Solder Link Technology - Less susceptible to damage.

  • UL-Listed and FM-Approved for Most Applications.

  • Specific Application Protection - Retail applications.

  • Retrofit of Existing 130 sq. ft. Installations - Systems that were installed using 130 sq. ft. may now be upgraded to storage protection above 0.25-gpm/sq.-ft. density.

    These sprinklers are Control-Mode Extended Coverage Sprinklers (EC) for extra hazard and high-piled storage occupancies in accordance with NFPA 13. They are especially valuable when protecting occupancies that require an area/density application of water while providing better fire protection than standard spray sprinklers.


  • Table 1 - Test Series SP 18

    Comparative Testing

    New technologies are tested against baseline performance. The base testing for virtually all of the density/area curves for high-piled storage were done with K5.6 (80) sprinklers in the early 1970s. Current laboratory protocol includes more stringent pass/fail criteria than existed in these baseline tests. The early 1970s testing was used to develop the current density/area curves used in NFPA 13. New technologies such as the K25.2 EC and K16.8 EC pendent sprinklers (see photos) must duplicate the same testing with equal or better results. Tables 1 and 2 and Figures 1 and 2 are examples of the improved fire protection provided by both of these larger K sprinklers.

    A K16.8 extended coverage pendent sprinkler.

    Retail Stores

    In late 1999, the retail industry approached the fire sprinkler industry with a challenge to develop a ceiling-only sprinkler design for storage and display of Class I through Class IV commodities, cartoned Nonexpanded Group A plastics, and Nonexpanded Exposed Group A Plastics in retail stores without the use of in-rack sprinklers. Adding to that challenge, retail environments have unique shelving arrangements and variable heights of storage and buildings. Serious debate was occurring over shelving types used by the retail industry that challenged the solid-shelf gondolas and slatted-wood rack shelving that would require in-rack sprinklers at every level. After extensive product development and fire testing (data shown above), the fire sprinkler industry was successful in developing a K25.2 EC sprinkler meeting the needs of the retail industry.

    Table 2 - Test Series #65

    For Home Depot, Sam's and Like Stores

    A wet pipe system designed to meet two separate design points - 0.6 gpm/ft2 density over 2,000 ft2 and 0.7 gpm/ft2 density for the four hydraulically most demanding sprinklers with 500-gpm hose stream allowance for a 2-hour duration - is permitted to protect single- and double-row slatted shelf racks when the following conditions are met: 
    (1) An extended coverage sprinkler with a nominal K-factor of K-25.2 (363) listed for storage occupancies shall be provided.

    (2) Shelves shall be slatted using a 2-in. thick by maximum 6-in.-wide slat held in place by spacers that maintain a minimum 2-in. opening between each slat.

    (3) There shall be no slatted shelf levels in the rack above nominal 12-ft. level. Wire mesh (greater than 50% opening) shall be permitted for shelf levels above 12 ft.

    (4) Solid plywood shelving (3-1/2 ft. × 8 ft. 3 in.) shall be permissible over the wood slats at the 5-ft. level.

    (5) Perforated metal (open area of 40% or more) shall be permitted over the slatted shelves up to the 60-in. level.

    (6) Other than what is allowed in this section, solid plywood or similar materials shall not be placed on the slatted shelves.

    (7) Solid veneered particleboard displays shall be permissible, provided that all flues are maintained and only one display is installed per bay.

    (8) Max. roof height shall be 30 ft. in the protected area.

    (9) Maximum storage height shall be 22 ft.

    (10) Aisle widths shall be a minimum of 8 ft.

    (11) Minimum transverse flue spaces of 3 in. every 10 ft. horizontally shall be provided.

    (12) Minimum longitudinal flue spaces of 6 in. shall be provided for double-row racks.

    (13) Storage in the aisle shall be permissible, provided the aisle storage is no more than 4 ft. high and a minimum clear aisle of 4 ft. is maintained.

    For Wal-Mart and Like Stores

    A wet pipe system designed to meet two separate design points - 0.425 gpm/ft2 density over 2,000 ft2 and 0.50 gpm/ft2 density for the four hydraulically most demanding sprinklers with 500-gpm hose stream allowance for a 2-hour duration - is permitted in solid-steel cantilever-style retail shelving racks (gondola racks) when the following conditions are met:
    (1) An extended coverage sprinkler with a nominal K-factor of K-25.2 (363) listed for storage occupancies shall be provided.

    (2) The storage height shall not exceed 12 ft.

    (3) The ceiling height shall not exceed 22 ft. in the protected area.

    (4) Gondola rack structure shall not exceed 48 in. in aggregate depth or 78 in. in height.

    (5) A minimum aisle of 5 ft. between storage shall be maintained.

    (6) Rack lengths shall be no more than 70 ft.

    Figure 1 - Temperature Control

    For Best Buy and Like Stores

    A wet system designed to meet two separate design points - 0.425 gpm/ft2 density over 2,000  ft2 and 0.50 gpm/ft2 density for the four hydraulically most demanding sprinklers with 500-gpm hose stream allowance for a 2-hour duration - shall be permitted in solid-steel cantilever-style retail shelving racks (gondola racks) when the following conditions are met:
    (1) An extended coverage sprinkler with a nominal K-factor of K-25.2 (363) listed for storage occupancies shall be provided.

    (2) Storage height shall not exceed 15 ft.

    (3) Ceiling height shall not exceed 25 ft. in the protected area.

    (4) Gondola rack structure shall not exceed 60 in. in aggregate depth or 8 ft. in height.

    (5) A perforated metal deck at the 8 ft. level shall be permissible with storage placed on top with or without flue spaces to a maximum height from floor of 15 ft.

    (6) Rack lengths shall not exceed 70 ft.

    (7) A minimum aisle space of 6 ft. shall be provided.

    A K25.2 extended coverage pendent sprinkler.

    For Target and Like Stores

    (NOTE: Target has done additional testing since this criteria was published.)

    A wet pipe system designed to meet two separate design points - 0.45 gpm/ft2 density over 2,000 ft2 and 0.55 gpm/ft2 density for the four hydraulically most demanding sprinklers with 500-gpm hose stream allowance for a 2-hour duration - is permitted without the use of in-rack sprinklers when the following are met:
    (1) An extended coverage sprinkler with a nominal K-factor of K-25.2 (363) listed for storage occupancies shall be provided.

    (2) Storage height shall not exceed 15 ft.

    (3) Ceiling height shall not exceed 20 ft. 6 in.

    (4) Shelving structure shall not exceed 48 in. aggregate depth or 12 ft. in height.

    (5) Shelving shall be permitted to be made of solid particleboard.

    (6) A minimum aisle space of 3 ft. shall be maintained.

    (7) Shelving length shall be a maximum of 70 ft.

    For Office Depot and Like Stores

    A wet pipe system designed to meet two separate design points - 0.38 gpm/ft2 density over 2,000 ft2 and 0.45 gpm/ft2 density for the four hydraulically most demanding sprinklers with 500-gpm hose stream allowance for a 2-hour duration - is permitted without the use of in-rack sprinklers in steel retail sales floor shelving racks where the following conditions are met:
    (1) An extended coverage sprinkler with a nominal K-factor of K-25.2 (363) listed for storage occupancies shall be provided.

    (2) Storage height shall not exceed 14 ft.

    (3) Ceiling height shall not exceed 20 ft.

    (4) Solid metal shelving shall be permissible up to the 72 in. level and wire shelving shall be permissible up to the 10 ft. level.

    (5) The solid metal shelving shall not exceed 66 in. in aggregate depth with a 6-in. longitudinal flue between two 30-in.-deep shelves.

    (6) A minimum aisle space of 5 ft. shall be maintained.

    (7) A minimum longitudinal flue of 6 in. shall be maintained.

    (8) Rack length shall be a maximum of 70 ft.

    Figure 2 - Commodity Damage and Number of Sprinklers Activated in Test

    For Bed Bath and Beyond and Like Stores

    A wet pipe system designed to meet two separate design points - 0.49 gpm/ft2 density over 2,000 ft2 and 0.55 gpm/ft2 density for the four hydraulically most demanding sprinklers with 500-gpm hose stream allowance for a 2-hour duration - is permitted without the use of in-rack sprinklers in retail solid-shelved steel rack structure when the following conditions are met:
    (1) An extended coverage sprinkler with a nominal K-factor of K-25.2 (363) listed for storage occupancies shall be provided.

    (2) Storage height shall not exceed 16.5 ft.

    (3) Ceiling height shall not exceed 22 ft.

    (4) Shelving structure shall not exceed 51 in. aggregate depth or 148 in. in height.

    (5) The intersection of perpendicular steel racks shall be permissible as long as no storage is placed within the void space at the junction of the racks.

    (6) The top shelf shall be wire mesh.

    (7) A minimum aisle width of 4 ft. shall be maintained between shelf units and other displays.

    Summary

    The above requirements, using the K25.2 technology for many of the ‘big box’ retailers, were based on fire testing that stretched over a long period of time. The K16.8 is a relatively new technology, and the initial testing has shown the sprinkler performance as an area/density device to be extremely effective. 

    The extended coverage storage sprinklers are simply the most powerful control-mode sprinklers ever developed. In addition to better fire protection, they provide an economic advantage to the user.

    References

    Kung, Hsiang-Cheng, Vincent, Bennie G., and Troup, Joan M. A., “Performance Evaluation of Tyco Model EC-25 Control-Mode Extended-Coverage Sprinklers for Storage Occupancies,” FMRC Report J.I. 3007168/3007169, May 2001.

    Pabich, Martin J., and Sheppard, David T., “Report of Large-Scale Fire Tests of Retail Shelf Display and Rack Storage of Cartoned Group A Plastics Utilizing Extended Coverage Sprinklers Having a Nominal F-factor of 25.2,” UL Report 00NK22528, NC4119, November 2000.

    Troup, Joan M. A., “Full-Scale Fire Test Performance Evaluation of Central’s Model K17-231TM Sprinklers,” FMRC Report J.I. 0D1R8.PR (2), January 1998.

    Troup, Joan M. A., and Chicarello, Peter J., “Large-Scale Fire Tests of Stored Commodities Protected by Central Model D.64 Sprinklers,” FMRC Report J.I. 0W0R4.RR, September 1992.

    National Fire Protection Association. Installation of Sprinkler Systems – NFPA 13, 1999 to 2007 Edition.