An experimental study to assess the feasibility of a three stage thermal conductivity model for intumescent coatings in large space fires

Abstract

This paper presents an experimental study to investigate the performance of intumescent coatings exposed to large space fires, focusing on the feasibility of a three stage constant effective thermal conductivity model. A total of 54 steel plate specimens protected with intumescent coatings of different thicknesses were tested under ISO 834 fire and three large space fire temperature-time curves. It was found that the performance of intumescent coatings could be divided into three different stages: melting, expanding and full expansion, corresponding to the steel temperature ranges of 100°C–300 °C, 300°C–400 °C and above 400 °C respectively. The feasibility of representing the temperature dependent thermal conductivity of intumescent coatings in large space fires by three stage constant effective thermal conductivities was validated with the tests. The relations between constant effective thermal conductivities of three stages and that under ISO 834 fire were investigated. The applicability of the proposed model for large space fires has been checked by comparison between the calculated steel temperatures using the proposed model and the test results. The proposed model allows the fire test results under ISO 834 fire to be adapted to large space fires, and simplifies the temperatures calculation procedure of intumescent coating protected steel in large space fires.