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Alternative Sprinkler System Designs for Storage Protection

Fire Sprinkler International 2014. Alternative Sprinkler System Designs for Storage Protection. Kerry M. Bell Principal Engineer Fire Sprinkler and Pump Equipment UL LLC 20 May 2014. Overview .

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Alternative Sprinkler System Designs for Storage Protection

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  1. Fire Sprinkler International 2014 Alternative Sprinkler System Designs for Storage Protection Kerry M. Bell Principal Engineer Fire Sprinkler and Pump Equipment UL LLC 20 May 2014

  2. Overview • Historical development of new sprinkler technology for use in accordance with the NFPA 13, Standard for the Installation of Sprinkler Systems • Discussion on the new Chapter 21 in the 2013 Edition of NFPA 13 that provides the opportunity for more cost efficient storage sprinkler system designs to be developed. • Information and data from large scale fire testing that highlights the importance of having appropriate large scale fire test data to evaluate/validate the ability of the sprinkler to provide the desired level of protection for a storage facility.

  3. NFPA 13 and New Sprinkler Technology • For decades, NFPA 13 has encouraged the development of new sprinkler technology. • 1973 Edition of NFPA 13 • 4-1.1.3Special Sprinklers may be installed with larger protection areas or distances between sprinklers than are specified in Sections 4-2 and 4-5 when such installations are made in accordance with approvals or listings of a nationally recognized testing laboratory.

  4. NFPA 13 and New Sprinkler Technology • Over the years, this text has been revised to provide additional guidance and clarity related to the development of new sprinkler technology as illustrated in the 2013 Edition of NFPA 13 as follows: 8.4.8 Special Sprinklers. 8.4.8.1* Special sprinklers that are intended for the protection of specific hazards or construction features shall be permitted where such devices have been evaluated and listed for performance under the following conditions: (1) Fire tests related to the intended hazard (2) Distribution of the spray pattern with respect to wetting of floors and walls (3) Distribution of the spray pattern with respect to obstructions (4) Evaluation of the thermal sensitivity of the sprinkler (5) Performance under horizontal or sloped ceilings (6) Area of design (7) Allowable clearance to ceilings Text Source: NFPA 13 2013

  5. NFPA 13 and New Sprinkler Technology Non-Storage Sprinkler Technology • Extended coverage light hazard sprinklers • Extended coverage ordinary hazard sprinklers • Attic sprinklers • Combustible concealed space sprinklers

  6. Ceiling Sprinkler Types Currently Referenced in NFPA 13 for Use in Storage Applications at Discharge Densities of Greater than 13.9 mm/min (0.34 gpm/sq. ft.)

  7. Ceiling Sprinkler Types Currently Referenced in NFPA 13 for Use in Storage Applications at Discharge Densities of Greater than 13.9 mm/min (0.34 gpm/sq. ft.)

  8. New Chapter 21 of NFPA 13 - 2013 General 21.1.1 Sprinklers intended to protect storage fire risks shall be permitted to be installed using water supply design criteria that are different from the design criteria specified for the sprinklers described in Chapters 12 through 19 when specifically listed for such use within the limitations described in this chapter. Text Source: NFPA 13 – 2013

  9. New Chapter 21 of NFPA 13 - 2013 21.1.6 A series of large-scale fire tests involving challenging test scenarios that address the range of variables associated with the intended application of the sprinkler shall be conducted to evaluate the ability of the sprinkler to protect storage fire risks that are representative of those described in the manufacturer’s installation and design parameter instructions and referenced in the listing. Text Source: NFPA 13 – 2013

  10. New Chapter 21 of NFPA 13 - 2013 • For a sprinkler system design to be covered under Chapter 21, it must be validated through large-scale fire testing--typically 3 or 4 large scale fire tests. • Test parameters that are to be considered during the test series include: • Ignition location • Maximum storage height • Sprinkler spacing • Sprinkler temperature rating • Ceiling height • Clearance from storage to ceiling • Sprinkler distance below ceiling • Minimum operating pressure of sprinkler • Highest commodity hazard • Storage arrangement type • Aisle width

  11. New Chapter 21 of NFPA 13 - 2013 • Sprinkler System Design Based Upon Test Results • If all four tests yield acceptable results then the design is based on: • Worst-case test result during test series increased by 50% (safety factor), and • Minimum of 12 sprinklers for standard coverage type sprinklers [Nominal area = ~111 m2 (~1200 ft2)] • Minimum of 8 sprinklers for EC sprinklers on 3.7 m x 3.7 m (12 ft x 12 ft) spacing [Nominal area = ~111 m2 (~1200 ft2)] • Minimum of 6 sprinklers for EC sprinklers on 4.3 m x 4.3 m (14 ft x 14 ft) spacing [Nominal area = ~111 m2 (~1200 ft2)] • The resulting demand area shall not be less than 71 m2 (768 ft²). Text source: NFPA 13 – 2013

  12. New Chapter 21 of NFPA 13 - 2013 Additional Installation and Design Criteria Text Source: NFPA 13 – 2013

  13. New Chapter 21 of NFPA 13 - 2013 Additional Installation and Design Criteria • Minimum obstruction criteria is based upon based upon the number of sprinklers included in the sprinkler design and correlates to existing criteria in NFPA 13 for CMDA, CMSA, Extended Coverage and ESFR sprinklers. • A smaller number of sprinklers in the design results in more stringent obstruction criteria to reduce the potential for excessive sprinkler operations during a fire. • As an option to the prescribed obstruction criteria described in Chapter 21, large scale fire testing with obstructions can be conducted to validate alternative obstruction criteria for a specific sprinkler. Text Source: NFPA 13 – 2013

  14. New Chapter 21 of NFPA 13 - 2013 21.1.7 The manufacturer’s installation and design parameter instructions for these sprinklers shall specify in a standardized manner the end-use limitations and sprinkler system design criteria including at least the following: (1) Commodity or commodities to be protected (2) Storage arrangements allowed (3) Installation guidelines including obstruction and ceiling construction limitations (4) Maximum ceiling and storage heights with associated minimum operating pressures and number of sprinklers required to be included in the hydraulic calculation (5) Hose stream allowance and duration Text Source: NFPA 13 – 2013

  15. Comparison of Sprinkler Design Requirements in Chapters 12- 19 vs. Chapter 21 of NFPA 13 -2013 Chapters 12 – 19 *Ceiling-only sprinkler options Lowest Demand Permitted in Chapter 21

  16. Sprinklers Currently Referenced in Chapter 21 of NFPA 13 -2013 Note: NFPA 13 provides detailed information on the allowed coverage areas, number of design sprinklers, minimum design pressures, hose stream allowances and water supply duration for both the pendent and upright EC-CMSA sprinklers referenced in Chapter 21. • Sprinklers are permitted to be listed (certified) in accordance with Chapter 21 without the design criteria specifically referenced in this chapter.

  17. Example of Fire Test Series for Sprinkler Protecting 10.7 m (35 ft) Rack Storage Under a 12.2 m (40 ft) Ceiling Test 1 – Investigates ability of sprinkler to effectively attack a fire originating in a location beneath a sprinkler.

  18. Example of Fire Test Series for Sprinkler Protecting 10.7 m (35 ft) Rack Storage Under a 12.2 m (40 ft) Ceiling Test 2 – Investigates ability of sprinkler to effectively attack a fire originating between four sprinklers with the highest storage height and smallest sprinkler clearance to top of commodity clearance which generally creates the greatest HRR from the fire prior to sprinkler operation.

  19. Example of Fire Test Series for Sprinkler Protecting 10.7 m (35 ft) Rack Storage Under a 12.2 m (40 ft) Ceiling Test 3 – Investigates ability of the sprinkler to attack a fire originating in an an area between two sprinklers where the sprinkler discharge is impacted by the sprinkler frame arms and obstructed by the supply pipe if it is an upright style sprinkler.

  20. Example of Fire Test Series for Sprinkler Protecting 10.7 m (35 ft) Rack Storage Under a 12.2 m (40 ft) Ceiling Test 4 – Investigates ability of the sprinkler to attack a fire with a large clearance between the sprinkler deflector and top of storage.

  21. Why is it Important to Conduct Large Scale Fire Testing Using Multiple Ignition Locations? • Due to the unique discharge characteristics of each sprinkler design, the weakest level of protection with respect to location of fire origin relative to the sprinkler can vary depending on the sprinkler’s construction characteristics: • The water discharge characteristics throughout a sprinkler’s coverage area are not uniform. • The overlap of water spray from adjacent sprinklers varies within the sprinkler coverage area. • Water discharged from a sprinkler is obstructed by the sprinkler frame as well as the piping for upright style sprinklers. • Response time of the sprinkler can vary depending upon ignition location.

  22. Actual Delivered Density (ADD) Testing -- A Dynamic Water Distribution Test for Storage Type Sprinklers ADD testing is a useful tool to investigate a sprinkler’s discharge characteristics; however, this testing is conducted with open sprinklers which does not investigate the potential for sprinkler skipping to occur.

  23. NFPA 13-2013 Revisions Based Upon Large Scale Fire Test Data • For nominal K=200 (14.0) Pendent ESFR sprinklers, 2013 Edition of NFPA 13 was revised to limit the use of these sprinklers in new installations to a maximum ceiling height of 10.7m (35 ft) rather than the previously referenced 12.2 m (40 ft) ceilings. • Larger K-factor ESFR sprinklers can still be used for ceiling heights of 12.2 m (40 ft.) and 13.7 m (45 ft).

  24. Fire Test Results of Nominal K=200 (14) ESFR Pendent Sprinkler 6.1 m (20 ft) Clearance Comparison of UL and FM Storage vs. Non-Storage Sprinklers

  25. Illustration of Sprinkler Skipping – Nominal K=200(14.0) ESFR Sprinkler with Cartoned, Unexpanded Group A Plastic Commodity and a 12.2 m(40 ft) Ceiling Height

  26. Illustration of Sprinkler Skipping – Test 3 from FPRF Exposed Expanded Group A Plastics Project Using ESFR Sprinklers

  27. Summary • Since the 1970’s, NFPA 13 has included text that encourages the development of new sprinkler technology. • The new Chapter 21 of NFPA 13-2013 provides another opportunity to develop more cost efficient sprinkler protection for storage facilities. • It is important for the Chapter 21 sprinkler system design criteria to be properly validated with large scale fire testing that takes into account multiple ignition locations and the potential for sprinkler skipping to occur. • For sprinkler system designs not referenced in NFPA 13, users, designers and approval authorities can request to review the large scale fire test data that supports a sprinkler system design covered by Chapter 21 of NFPA 13.

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