Determination of activation temperature of glass bulb sprinklers using a thermal liquid bath

摘要

A thermal liquid bath was used to determine the activation temperature of a wide range of temperature rated (57-182℃) glass bulb (3 and 5 mm diameters) sprinklers using water and glycerine. An optical switch and a thermocouple were installed adjacent to each sprinkler (within 10 mm) to record the activation of each glass bulb in the liquid bath having a uniform temperature distribution ( ± 0.5℃). All the tests for determining the activation temperatures of glass bulb sprinklers were conducted in the liquid bath using a 0.277℃/min rate of temperature rise. Based on a heat transfer analysis, this rate is within the maximum allowable rate of rise of water and glycerine temperatures, which allows the glass bulb temperature to closely follow the liquid temperature. The sprinkler activation temperature was evaluated in terms of percentage rating, which is expressed as the percent variation of the average activation temperature, as measured in the liquid bath, from the nominal rated temperature. Sprinklers (93℃ rated or lower) activation temperatures in water were consistently within ±3.5% of rating. In glycerine, the activation temperatures of sprinklers rated between 93 and 182℃ performed within 3.5% of their rating.