PERFORMANCE PREDICTION MODELLING AND THERMAL ANALYSIS OF HEAT RESISTANT CLOTHING

Abstract

Heat resistant clothing is the primary component for the effective and safe performance of firefighting operations. Firemen who actually go into the fire to rescue people are themselves prone to fire burns. Hence, heat resistant clothing is essential for safety of fire fighters and effective rescue operations. Heat resistant clothing prevents heat from the fire reaching the human body and saves the fireman from being exposed directly to the fire. This is achieved by preventing heat conduction and by reflecting most of the heat flux incident on the clothing. However, if the heat resistant clothing fails when the fireman is going through the flames or near it for rescue operations, then it will pose a serious threat to the life of the fireman. The human body can tolerate temperature roughly around 50-550C whereas the temperature of the fire is 20 times this limit. So if a fire suit fails in actual fire conditions, then it will definitely cause heavy personal injury to the fireman using the clothing and will further hamper the rescue operations. Hence it is extremely crucial to stringently test the heat resistant clothing before rendering it safe within the prescribed limits for real life fire scenarios. Fire fighters’ heat resistant suit is designed to offer the wearer with a limited amount of safety from burn injury if suddenly exposed to an intense short duration flash fire or short time exposure to a flashover condition. This level of protection has been made possible through the development of new heat resistant fabrics and insulating materials. Though there has been a rapid development in the fire protective materials, but the test and evaluation procedures for complete fire protective ensembles still lack behind. So far humans have been used to test the clothing. A person actually wears the clothing and walks into a manmade fire. If he feels heat then he makes some signal and the fire is immediately extinguished by firemen. This is a very crude and inaccurate method for testing the clothing as the actual heat conduction of the clothing cannot be accurately deduced. Moreover, the heat tolerance varies from person to person and also if the heat resistant clothing is not suitable, it will immediately cause personal injury to the person testing the clothing. iv This necessitates alternative methods for testing heat resistant clothing which will not only eliminate humans from actually going into the fire for testing the clothing but also gives more accurate and reproducible test results. This can be achieved by design and development of Fire Suit Evaluation Facility in which a human dummy is used for testing. The instrumented manikin, fitted with sensors, is exposed to a known heat flux. The data from the instrumented manikin is used for analysing the performance of the suit. The data is further utilized for burn injury prediction. This is a completely automated state of the art facility and one of its kinds in the country. This alternative method envisaged for the testing of heat resistant clothing is as per internationally accepted ASTM F1930 standard. In addition, Modelling & Simulation is undertaken to model different types of heat resistant Ensembles and to predict their performance for different fire environments. The simulated model is validated against the experimental results. The development of modelling and simulation capability enabled more accurate performance prediction of futuristic materials & fire protective ensembles. This method further aid in reduction of design & development time required for the same.