Maximum temperature to withstand water film for tempered glass exposed to fire

• The maximum temperature to withstand water film for tempered glass was figured out.
• Significant parameters of glass breakage under fire were analyzed and compared.
• Parameters of the water film were calculated and analyzed.
• A tentative solution was proved to be feasible and effective at high temperature.

Improper activation of the sprinkler or the cold water sprayed from the fire-fighting lance may accelerate the crack even fallout of the heated glass when encounter a fire. The objective of this work is to investigate the maximum temperature to withstand water film for tempered glass exposed to fire, and to find a way to keep the glass integration when the temperature exceeds the maximum endurance. Twenty-six tests were conducted in this study. The water film was not opened throughout in the control group. In other tests, the water film was opened when the maximum glass temperature reached different values. The only difference is the water film sprayed on the exposed glass surface in protection-cooling-type water film tests, but formed 20 mm apart from the hot surface in fire-separating-water-film tests. The results illustrate that the critical temperature, or a temperature scope, for 6 mm tempered glass to withstand water film is a value or range of value approaching 250 °C. It is also found that crazing of tempered glass generally occurs in the rapid cooling process, rather than the rapid heating process. The thermal shock caused by the sudden cooling can account for this phenomenon. The fire-separating-type water film was proved to be effective to protect glazing when its temperature outnumbered the critical value.