Variability of sprinkler response time index and conduction factor using the plunge test

Abstract

In order to predict sprinkler activation time, the response time index (RTI) and the conduction factor (C factor) may be required. This paper describes the use of a wind tunnel to determine both quantities for different types of sprinklers and to identify appropriate distributions for RTI values that could be used as part of an activation modelling sensitivity analysis. Sprinklers were tested with their yoke arms perpendicular and the parallel to the airflow, which gave the lowest and highest RTI, respectively. The results were analysed using the ANOVA method and the two-sided t-test. Analysis suggests that a normal distribution can be used to describe the RTI and that mean and standard deviation values for sprinkler activation design calculations are 95 ± 5 and 164 ± 10 (m.s)1/2 for a standard response sprinkler in the perpendicular and parallel orientations, respectively and 45 ± 6 (m.s)1/2 and 103 ± 19 (m.s)1/2 for a fast response sprinkler in the perpendicular and parallel orientations, respectively. Practical application: Sprinkler systems are the primary means of providing fire suppression in buildings. The likely time of operation of a sprinkler to a developing fire is of interest to designers and to calculate this time it is necessary to know the activation characteristics of the sprinkler. These characteristics depend on the type of sprinkler, its installation and the variability of individual sprinklers. This paper presents wind tunnel test results and suggested statistically derived values for the response time index and conduction factor for several types of sprinkler.