UL Overview

Jan. 7, 2004
Understanding the Operational Testing of Fire Sprinklers
With the increased awareness and concern for building safety, there is a growing need for facilities to be fitted with effective security and safety systems. While it is critical that these systems be properly designed and installed, it is equally important for these systems to be periodically inspected, tested, and properly maintained.For decades, fire sprinklers have proven to be an extraordinarily effective tool for protecting life and property from fire. The National Fire Protection Association (NFPA) Standard for the Inspection, Testing and Maintenance of Water-Based Fire Protection Systems – NFPA 25 – contains detailed inspection, testing, and maintenance requirements for fire sprinkler systems. This comprehensive standard includes requirements for all components of a fire sprinkler system. As indicated in NFPA 25, the responsibility for properly maintaining a sprinkler system resides with the property owner.Periodic inspection of field-installed sprinklers is an important element of a comprehensive maintenance program for sprinkler systems. As specified in NFPA 25, sprinklers showing signs of leakage, field painting, corrosion, damage, or loading are to be replaced. All of these conditions can lead to the degradation of sprinkler performance during a fire condition.NFPA 25 also requires replacement or representative sample testing of sprinklers based upon length of service. The frequency of sample testing depends upon the sprinkler type and installation environment. For example, while many sprinklers do not require testing until they have been in service 50 years, quick response sprinklers are to be tested after 20 years in service and 10-year intervals thereafter. Due to the anticipated aggressive installation environments for many dry type sprinklers, these are to be tested after 10 years of service and 10-year intervals thereafter. NFPA 25 also indicates that sprinklers installed in harsh environmental conditions are to be replaced or representative samples tested on a five-year basis.Underwriters Laboratories Inc.’s (UL’s) program for conducting operational tests on sprinkler samples removed from field installations is intended to assist property owners in assessing the operating characteristics of sprinklers in service. Per NFPA 25, no less than four samples, or one percent of the number of sprinklers per individual sample, whichever is greater, are to be tested. As a part of UL’s field sprinkler testing service, identification tags are available for use by property owners and others at no charge.UL’s testing of field sprinklers includes both a qualitative and quantitative evaluation. Each sample is examined before testing to ascertain the sprinkler manufacturer, model or sprinkler identification number, style, type of heat responsive element, temperature rating, and year of manufacture. The condition of the sprinkler is also noted, such as corrosion, damage, or painting.The testing includes an assessment of the ability of the sprinkler to operate as intended. To conduct this assessment, sprinkler samples are subjected to the Sensitivity-oven Heat Test as described in the Standard for Automatic Sprinklers for Fire Protection Service, ANSI/UL 199. During this test, the inlet of the sample is pressurized to approximately five psig and quickly plunged into an oven that circulates air at a constant temperature and velocity. The actual temperature and air velocity used for the test is selected based upon the temperature rating of the sprinkler. Each sprinkler sample is observed for proper operating characteristics including the release of operating components and time of operation. The UL report of the testing describes the condition of each sprinkler and results of the operation test as either normal or abnormal.Kerry M. Bell is a primary designated engineer with the Fire Protection Division of Underwriters Laboratories Inc., based in Northbrook, IL.

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