An Investigation of the Causative Mechanism of Sprinkler Skipping

The purpose of this work is to identify the cause of sprinkler skipping, a phenomenon whereby sprinklers operate out of the expected sequence. From a list of several mechanisms, three feasible ones are selected for investigation i.e., impingement of water droplets from previously activated sprinklers onto fusible elements, condensation of water vapor onto fusible elements, and entrainment of hot gases into the spray of operating sprinklers. New instrumentation is developed in order to make psychrometric and spray cooling measurements in the ceiling flow of a large-scale fire. A series of large-scale fire tests using these instruments and a controlled heptane spray fire source are conducted. The results indicate that droplet impingement is the causative mechanism of sprinkler skipping.