ESFR Sprinkler Protection of Class II Commodity in Cold Storage Warehouses using Propylene Glycol Antifreeze Agent
Currently, the NFPA standard for the installation of sprinkler systems (NFPA 13) requires that early suppression fast response (ESFR) sprinklers be specifically listed for use with antifreeze mixtures due to the concern that antifreeze will contribute to the combustion energy of the fire. The effectiveness of an ESFR sprinkler system in suppressing a fire depends on the antifreeze concentration, sprinkler discharge characteristics, rate of discharge, duration of antifreeze mixture flow before water flow without antifreeze, storage arrangement, and protected commodity. A series of three large-scale rack-storage fire tests has been conducted to evaluate the effectiveness of two different ESFR sprinklers using certain discharge rates and pre-charged agent volumes consisting of a 50/50 volume fraction propylene glycol—water mixture in providing protection for 12.2-m high cold storage warehouses. The Standard Class II commodity was used as a fuel to simulate the fire challenge in some of these warehouses. Two fire test scenarios were used: 9.1 m high rack storage with ignition centered below a sprinkler; and 10.7 m high rack storage with ignition between two sprinklers. The test results for an ESFR pendent sprinkler having a nominal discharge coefficient of 36 L/(min kPa 1/2) discharging a 50/50 volume fraction of propylene glycol—water antifreeze mixture, at a rate of 606 L/min with 4160 L of pre-charged agent volume demonstrated the ability to provide a level of fire suppression for Class II commodity up to 10.7 m in 12.2 m high buildings. This method of sprinkler protection provides an alternative to dry-pipe or pre-action sprinkler protection for cold storage warehouses where the stored commodity is no more challenging than the Standard Class II commodity.