Cone calorimeter, development

Fire-test method development has followed two separate but complementary paths. One path, theoretically oriented, is characterized by the measuring of scientifically-meaningful fire properties, such as mass loss and rate-of-heat release. This approach also includes the development of mathematical models incorporating these properties to predict propagation and flame spread. A new lab-scale apparatus, the "cone calorimeter" developed at NIST is an example of the hardware now available to measure these fire properties. 

V. Babrauskas, Development of the Cone Calorimeter. A Bench-Scale EHR Apparatus Based on Occggen Consumption, NSBIR 82-2611, U.S. Dept, of Commerce, Gaithersburg, Md., 1982. 

A discussion of test methodology is beyond the scope of the present paper. However, the fact that established tests do not accurately reflect the behavior of materials in fires has been widely recognized (9), and the search for more meaningful techniques for the evaluation of engineering materials has continued to be a valid research objective. The development of the cone calorimeter, a bench-scale tool for the evaluation of fire properties of materials (10a) at NBS, is of particular significance in this context. 

Babrauskas, Vytenis. Development of the Cone Calorimeter—A Bench-scale Heat Release Rate Apparatus Based on Oxygen Consumption. U.S. Department of Commerce NBSIR 82-2611, 1982. 

Mass Loss Rate as a Function of External Heat Flux. The technique for the measurement of mass loss rate as a function of heat flux was developed in 1976 at FMRC using the Small-Scale Flammability Apparatus (8 ). Several other flammability apparatuses are now available for such measurements, such as OSU Heat Release Rate Apparatus (13) and NIST Cone Calorimeter (1 4). 

Babrauskas, V., "Development of the Cone Calorimeter - A Bench-Scale Heat Release Rate Apparatus Based on Oxygen Consumption," 1984, Fire and Materials, 8, 81. 

The cone calorimeter was developed at the National Bureau of Standards (NBS), currently the National Institute of Standards and Technology or NIST by Dr. Vytenis Babrauskas in the early 1980s 47 It is presently the most commonly used bench-scale calorimeter. A bibliography compiled... 

Babrauskas, V., Development of the cone calorimeter—A bench-scale heat release rate apparatus based on 02 consumption. Fire and Materials 1984, 8, 81-95. 

Leonard, J., Bowditch, P, and Dowling, V., Development of a controlled-atmosphere cone calorimeter. Fire and Materials 2000, 24, 143-150. 

Higher irradiation levels give better reproducibility, more clearly defined ignition, and shorter measurement times, but correspond to more developed fires. Thus particularly for flame-retarded polymers, a smaller irradiation level often corresponds better to the fire protection goals addressed. Cone calorimeter results for the HRR at small irradiances correspond to flammability tests such as LOI and UL 94, if a reasonable set of materials are compared and the behavior is not dominated by dripping effects. Thus different considerations govern the choice of external heat flux.76 77... 

Figures 15.8 and 15.9 illustrate examples of how cone calorimeter data can be used in the development of flame-retarded materials. PA 66-GF without Pred showed typical fire behavior for noncharring polymers containing inorganic glass fiber as inert filler,69 when high external heat flux is applied. The shape of the HRR curve is divided in two different parts. In the beginning, the surface layer pyrolysis shows a sharp peak, followed by a reduced pyrolysis rate when the pyrolysis zone is covered by the glass fiber network residue layer. When Pred was added, the PA 66-GF samples were transformed into carbonaceous char-forming materials, which led to a...

Schartel B, Hull TR. Development of fire retarded materials—interpretation of cone calorimeter data. Fire Mater. 2007 31 327-354. 

B. Schartel and T.R. Hull, Development of fire-retarded materials Interpretation of cone calorimeter... 

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. 

In the early 1980s, Vytenis Babrauskas, at the NIST (then NBS), developed a more advanced test method to measure RHR the cone calorimeter (ASTM E 1354).71164 This fire test instrument can also be used to assess other fire properties, the most important of which are the ignitability (as discussed earlier), mass loss, and smoke released. Moreover, results from this instrument correlate with those from full-scale fires.165-170 To obtain the best overall understanding of the fire performance of the materials, it is important to test the materials under a variety of conditions. Therefore, tests are often conducted at a variety of incident heat fluxes. The peak rates of heat release (and total heat released) of the same materials shown in Table 21.15 at each incident flux, are shown in Table 21.16.147... 

Within ASTM, technical committees associated with plastics, electrical materials, textiles, protective clothing, thermal insulation, consumer products, detention and correctional facilities, and ships have developed tests that are often application tests that are of specific interest to the products involved. One fire test has spawned more application standards than any other, primarily because of its vast use in the United States ASTM E 84 (Steiner tunnel). Thus, NFPA 262, UL 1820, UL 1887, ASTM E 2231, ASTM E 2404, ASTM E 2573, ASTM E 2579, and ASTM E 2599 are all test methods and practices based on the Steiner tunnel test. In some cases, the base apparatus is being modified (although usually it is permissible to conduct the ASTM E 84 test in the apparatus of the other test, but it is often not permissible to conduct the other test in any apparatus complying with the ASTM E 84 apparatus). The other test method that has resulted in many application standards is the cone calorimeter the standards are ASTM D 5485, ASTM D 6113, ASTM E 1474, ASTM E 1740, and ASTM F 1550. 

The laminate construction in FRP parts can have an effect on flame spread and smoke test results. A study was conducted by Stevens15 and published in the proceedings of Composites 2007 conference. This study looked at how glass fiber content and panel thickness affected the ASTM E-84 flame spread index (FSI) and smoke developed index (SDI). The effects of fiber content and thickness on cone calorimeter results were also evaluated. Another study was conducted by Dempsey16 looking at the effect of glass content in several fire tests, and in this paper, he also found a correlation between the FR performance and glass content. 

Cone calorimetry according to the ASTM E1354138 or ISO 5660139 standards are commonly used in the laboratory to screen flammability of materials by measuring heat release characteristics of the compound.116140 This device is similar to FPA but does not have the versatility of FPA. The cone calorimeter can determine the ignitability, heat release rates, effective heat of combustion, visible smoke, and C02 and CO development of cable materials. This test has been used extensively for wire and cable material evaluation. The microscale combustion calorimeter (MCC), also known as pyrolysis combustion flow calorimeter (PCFC), was recently introduced to the industry for screening heat release characteristics of FR materials.141142 This device only requires milligram quantities of test specimen to measure the heat release capacity (maximum heat release potential). Cone calorimetry and MCC have been used in product development for flammability screening of wire and cable compounds.118... 

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