Fire calorimetry tests

The versatility and accuracy of the oxygen consumption method in heat release measurement was demonstrated. The critical measurements include flow rates and species concentrations. Some assumptions need to be invoked about (a) heat release per unit oxygen consumed and (b) chemical expansion factor, when flow rate into the system is not known. Errors in these assumptions are acceptable. As shown, the oxygen consumption method can be applied successfully in a fire endurance test to obtain heat release rates. Heat release rates can be useful for evaluating the performance of assemblies and can provide measures of heat contribution by the assemblies. The implementation of the heat release rate measurement in fire endurance testing depends on the design of the furnace. If the furnace has a stack or duct system in which gas flow and species concentrations can be measured, the calorimetry method is feasible. The information obtained can be useful in understanding the fire environment in which assemblies are tested. 

Hirschler, M.M., Smoke in fires Obscuration and toxicity, Plenary Fecture, Business Communications Company Conference on Recent Advances in Flame Retardancy of Polymeric Materials, May 15-17, Stamford, CT, Eds. G.S. Kirshenbaum and M. Lewin, pp. 70-82, Norwalk, CT, 1990 Hirschler, M.M., How to measure smoke obscuration in a manner relevant to fire hazard assessment Use of heat release calorimetry test equipment, J. Fire Sci., 9, 183-222 (1991). 

Cone calorimetry (CC) is one of the most effective medium-sized polymer fire behavior tests. The principle of cone calorimeter experiments is based on the measurement of the decreasing oxygen concentration in the combustion gases of a sample subjected to a given heat flux, in general from 10 to 100 kW/m [83]. Figure 4 illustrates the experimental set-up of a cone calorimeter. Standardized in the United States (ASTM E 1354), the cone calorimeter test is also the subject of an international standard (ISO 5660). 

Fire calorimetry (4,11,20,25) (see under Testing to Obtain Engineering Data) is used to obtain HRP as the slope of heat release rate versus external heat flux or as the ratio x c°/Dg = HOC/Lg, from individual measurements. Table 7 contains HOC and x (=HOC//ic°) for common polymers while HRP are listed in Table 8. The heat of combustion of the fuel gases, hc, was measured separately in a pyrolysis-combustion flow calorimeter (26) (see section on The Pyrolysis-Combustion Flow Calorimetry). 

A.L. Bridgman and G.L. Nelson, Heat Release Calorimetry and Radiant Panel Testing A Comparative Study, Proceedings of the International Conference on Fire Safety (Jan. 13-17, 1986), 11, 128-139 (1986). 

Materials that in themselves are normally stable, even under fire conditions Materials that exhibit an exotherm at temperatures greater than 500°C when tested by differential scanning calorimetry (DSC) Materials that do not react with water heat of mixing less than 30 cal/g Less than 0.01 W/mL... 

Scudamore MJ, Briggs PJ, Prager FH. Cone calorimetry—a review of tests carried out on plastics for the Association of Plastic Manufacturers in Europe. Fire Mater. 1991 15 65-84. 

This would not be problematic if standardized, reliable, reproducible, and inexpensive laboratory tests were available to estimate each of the required properties. Although several specialized laboratory tests are available to measure some properties (e.g., specific heat capacity can be determined by differential scanning calorimetry [DSC]), many of these tests are still research tools and standard procedures to develop material properties for fire modeling have not yet been developed. Even if standard procedures were available, it would likely be so expensive to conduct 5+ different specialized laboratory tests for each material so that practicing engineers would be unable to apply this approach to real-world projects in an economically viable way. Furthermore, there is no guarantee that properties measured independently from multiple laboratory tests will provide accurate predictions of pyrolysis behavior in a slab pyrolysis/combustion experiment such as the Cone Calorimeter or Fire Propagation Apparatus. 

FIGURE 26.4 Probability for flame spread versus heat release capacity of compounds. (Cogen, J.M. et al., Correlations between pyrolysis combustion flow calorimetry and conventional flammability tests with halogen free flame retardant polyolefin compounds, Fire Mater., 2009, 33, 33-50.)... 

As discussed in Section 2.4, there are four basic methods for assessing the fire hazard of commodities for warehouse storage. This includes small-scale fire tests, subjective physical comparison, intermediate or full-scale fire tests, and fire tests based upon calorimetry. The most accurate assessment of the fire hazard of a commodity will be obtained with intermediate or full-scale fire tests and with some commodities, fire tests based upon calorimetry. 

As a consequence of a very serious fire under the steel roofs in a large car plant in USA the Underwriters Laboratories Inc., developed a new UL test method, which uses oxygen consumption cone calorimetry to quantify roof covering materials. This test was used to quantify the contribution of roof covering materials to the fire under the roof by capturing effluent from beneath the roof assembly and recording the rate of heat production in kW/min. 

The new UL test method utilises a collection hood and duct system prescribed under various nationally recognised fire test procedures including the UL 1715 Standard [54]. The test structure is a masonry room measuring 2.4 m wide by 3.7 m long by 2.4 m high, with one 2.4 m wide open end. Heptane fuel burners are used to provide the internal fire source. The test method utilises oxygen consumption calorimetry to quantify the roof covering materials. 

The trials undertaken to calculate the HRR have shown that this parameter can be used to obtain an adequate correlation of the course of burning of the belt in the full-scale gallery fire test. This makes it possible to develop a fast method of testing the flammability of conveyor belts by oxygen consumption calorimetry. 

In further work Wachowicz [26] compared large-scale gallery testing with cone calorimetry in the evaluation of the flammability of conveyor belts. A good correlation is shown between results of conveyor belt flammability during combustion in a fire testing gallery and predicted HRR based on bench scale cone calorimetry. 

EG leads to formation of a char layer characterised by the presence of worms resulting from its expansion. It was found that the higher the filler content the lower the compression strength. The presence of APP or MC results in worsening of thermal conductivity while the presence of EG leads to an increase in thermal conductivity. Cone calorimetry and the LOI test were used to study the fire behaviour. The best... 

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