Fire Safety Science Digital Archive

A series of seven large-scale rack storage fire tests was conducted, using four ESFR sprinkler models, to determine the required sprinkler spray characteristics for achieving effective protection of rack storages of the FM standard plastic commodity up to 10.8 m high in a 12.2 m high warehouse. All four models have a nominal K factor of 0.34 l/s/(kPa)1/2, and the sprinkler discharge pressure was maintained at 517 kPa. The sprinkler spacing was 3.05 m x 3.05 m. The test variables include storage height/ceiling clearance, ignition location and sprinkler models. The sprays of the sprinkler models used in the fire tests were characterized by their drop size distribution, center-core thrust force, and water distribution under no-fire condition. For ESFR sprinkler protection, the effect of drop size distribution was demonstrated to be unimportant through the fire tests. For the case with ignition directly over a sprinkler, the spray center-core thrust force and the water flux under no-fire condition over the top surface of a two pallet-load by two pallet-load fuel array directly underneath the sprinkler have been shown to be critical for achieving fire suppression. A minimum center-core thrust force of 101.3N/m² measured at 1.77 beneath the sprinkler deflector, and a minimum water flux of 0.614 l/s/m² measured over a 2.15 m x 2.15 m area 4.42 m beneath the ceiling directly under the sprinkler have been found to be necessary for achieving fire suppression. For the case with ignition centered below two sprinklers and with 10.8 m storage height / 1.77m ceiling clearance, only the water flux under no-fire condition over the fuel array top was shown to be critical. A measured water flux of 0.667 l/s/m² over a 2.15 m x 2.15 m area, centered below the two sprinklers, 1.77 beneath the ceiling, was found to be sufficient for achieving fire suppression.