Comparative fire performance tests using water and antifreeze solutions discharged from standard spray sprinklers
RESEARCH AND DEVELOPMENT TECHNICAL REPORT ABSTRACT
A series of fire tests were conducted in UL’s fire test facilities located in Northbrook, IL to determine the effectiveness of sprinklers discharging water compared to certain antifreeze solutions currently referenced in the NFPA 25 standard for Inspection, Testing and Maintenance of Water-Based Fire Protection Systems, [1]. The primary focus of this research initiative was to develop comparative test data related to fires that may originate in a light hazard occupancy; however, comparative data was also developed using an existing fire test protocol utilized for sprinklers intended for use in the NFPA 13 standard for the Installation on Sprinkler Systems, [2] that relates to an ordinary hazard occupancy. Lastly, additional exposure to fire tests beyond those described in previous antifreeze research initiatives was conducted on antifreeze solutions currently referenced in NFPA 25 and are included in this report.
In order to compare fire test performance related to a light hazard occupancy, a fuel package was developed that (1) had fire size characteristics similar to an office work station type fire and (2) could be controlled with sprinklers discharging water at a density of 0.10 gpm/ft2, which is the density that is referenced in NFPA 13 for light hazard occupancy protection.
The sprinkler system consisted of a total of 36 upright standard spray sprinklers having a nominal discharge coefficient of 5.6 gpm/psi½ installed on a 14 ft x 14 ft spacing with the deflectors located approximately 3 in. below the ceiling. The sprinkler piping was arranged in a “tree” branch line configuration with sufficient supply and branch line piping to accommodate a total volume of approximately 500 gallons of antifreeze solution. A total of six tests were conducted using the light hazard fuel package located between two sprinklers on separate branch lines.
Three tests were conducted using a nominal sprinkler discharge density of 0.10 gpm/ft2 for the duration of the test, which correlated to a discharge pressure of 12.3 psig for water. One test was conducted using water as a wet system, one test was conducted using water as a simulated dry system, and one test was conducted with 500 gallons of a 50 percent (by volume) glycerin antifreeze solution followed by water. During the test using water in a wet system, a total of four sprinklers operated compared to 12 sprinklers that operated during the test using the glycerin solution followed by water. During the simulated dry system testing with water, a total of 10 sprinklers operated.
Three tests were conducted using a higher sprinkler discharge pressure, based on a nominal 24 psig discharge pressure for water, to simulate a higher starting pressure for a sprinkler system that was hydraulically designed for a 0.10 gpm/ft2 discharge density. One test was conducted with water, one test was conducted with approximately 500 gallons of a 50 percent glycerin antifreeze solution followed by water, and one test was conducted with 500 gallons of a 38 percent glycerin antifreeze solution followed by water. During the test using water, a total of two sprinklers operated compared to seven sprinklers that operated during the test using the 50 percent glycerin and five sprinklers that operated during the test using the 38 percent glycerin solution.
For sprinkler systems protecting an ordinary hazard occupancy using an antifreeze solution volume greater than 40 gallons, UL 2901, the Standard for Antifreeze Solutions for use in Fire Sprinkler Systems[3], requires fire testing using a fuel package described in UL 199, the Standard for Automatic Sprinklers, [4]. This fire test is used by UL to certify most standard spray sprinklers.
For this testing, four open sprinklers were arranged to discharge either water only or antifreeze solutions followed by water onto the fire. The nominal sprinkler discharge density used for this UL 199 fire test is 0.15 gpm/ft2 and the sprinklers are required to control the fire such that the ceiling temperature above the fire is generally maintained below a nominal 600 °F after 5 minutes of water discharge.
Three tests were conducted; one using water, one using 38 percent glycerin antifreeze solution followed by water and one test using a 30 percent propylene glycol antifreeze solution followed by water. During the three tests, the ceiling temperature was reduced to below 600 °F after 5 minutes of water discharge compared to approximately 1450°F for the glycerin solution and 1350°F for the propylene glycol solution prior to being followed with water.
At the time of publication of this report, there were no antifreeze solutions that are UL Listed for ordinary hazard occupancy applications with system volumes greater than 40 gallons.
For all tests with the antifreeze solutions, the test pressure was adjusted due to the difference in density between antifreeze and water to maintain the required flow rate and discharge density.
A description of the test parameters and results for the light hazard type tests is provided in Table 1. A graphical presentation of the ceiling temperatures for the ordinary hazard type fire tests are described in Figure 1.
Currently, UL 2901 describes three types of fire tests as follows:
- Exposure to fire (evaluates the antifreeze solution for resistance to ignition and substantial contribution to the fire)
- Fire fighting effectiveness — Residential dwelling units
- Fire fighting effectiveness — Ordinary hazard occupancies, UL 199 – 350 lb Wood Crib Fire Test for sprinkler systems with volumes greater than 40 gallons.
Tables 2-4 provide information on the results of the fire testing that has been conducted on the legacy NFPA 13 glycerin and propylene glycol antifreeze solutions using the three UL 2901 fire tests and the light hazard fire test described herein as compared the acceptance criteria that is required for UL Listing. For ordinary hazard occupancy applications using an antifreeze solution volume greater than 40 gallons, UL 2901 requires fire testing using a fuel package described in UL 199.
Summary
The series of tests demonstrated differences in performance between concentrations and types of antifreeze solutions as
compared to water at the same discharge densities. In general, the following observations were made based on the data contained in this report:
The ceiling temperatures during the light hazard fire testing with antifreeze solutions were higher and the number of
operating sprinklers was greater as compared to water.
The ceiling temperatures during the ordinary hazard fire testing with antifreeze solutions did not significantly decrease until
the transition from antifreeze to water occurred during the test.
The results from the tests imply that the antifreeze solution concentration and fire size impact the performance as compared to water. As the concentration of the antifreeze solution increases or as the fire size increases, the difference in performance is greater.
References
- National Fire Protection Association. (2020). NFPA 25, Standard for the Inspection, Testing, and Maintenance of Water-Base Fire Protection Systems
- National Fire Protection Association. (2019). NFPA 13, Standard for the Installation of Sprinkler Systems.
- Underwriters Laboratories Inc. (2020). Standard for Safety for Antifreeze Solutions for Use in Fire Protection Systems, UL 2901.
- Underwriters Laboratories Inc. (2020). Standard for Safety for Automatic Sprinklers for Fire-Protection Service, UL 199.
- Antifreeze Systems in Home Fire Sprinkler Systems — Literature Review and Research Plan, Fire Protection Research Foundation, June 2010.
- Antifreeze Systems in Home Fire Sprinkler Systems — Phase II Final Report, Fire Protection Research Foundation, December 2010.
- Antifreeze Solutions Supplied through Spray Sprinklers — Final Report, Fire Protection Research Foundation, November 2012.
For more information visit https://www.ul.com/insights/comparative-fire-performance-tests-using-water-and-antifreeze
Author(s) Email
Kerry Bell – Kerry.M.Bell@ul.com
Jeff Hebenstreit – Jeffrey.R.Hebenstreit@ul.com
Pravinray Gandhi – Pravinray.D.Gandhi@ul.com
Kelly Opert – Kelly.Opert@ul.com
Ben Gaudet – Benjamin.Gaudet@ul.com
