A Scientific Analysis of Stored Plastic Fire Tests

Abstract

An analysis is made of freeburn and sprinklered Plastic Storage Tests conducted at Factory Mutual Research Corporation (FMRC) from 1970 to 1979. The analysis includes: 1) the freeburn fire growth rates dependent on plastic commodity and storage arrangement; 2) the temperature histories in the freeburn fires; 3) the response time of the first sprinkler operation in the sprinklers operation in the sprinklered tests; and 4) the number of sprinklers (and, therefore, indirectly the fire severity) activated as a function of the growth rate and the maximum burning rate measured in freeburn tests. Fire growth rates depend on the overall geometry of the array, on the arrangement and the volume occupied by the plastic commodities inside the carboard boxes. Temperature histories near the ceiling are correlated using relations applicable for unsteady fires. The sprinkler response time can be predicted by a simple expression of the heating history of a sprinkler fusing element in a growing fire. Based on the experimental results, it is suggested that the number of sprinklers activated in the sprinklered tests depends on a characteristic growth time of the freeburn fire growth and on the heat release rate at the moment of first sprinkler activation. Freeburn tests are not sufficient in general to classify the hazard which a commodity and storage arrangement will present to a specific sprinkler protection. An additional parameter required for classification is the time characteristic for fire extinction or control, which depends on the sprinklers and the geometry and contents of the stored plastic configuration.