Intermediate Scale Calorimeter Research Articles

Ignition, Heat Release Rate and Suppression of Elastomeric Materials

The focus of this paper is to determine flammability characteristics of rubber materials that are common to vehicle tires, conveyor belts, and electrical power cable insulation and to compare the thermal magnitude of cargo quantities of these materials to other fuels that are publicly transported. Although a literature review was performed, very little data was fo und on this topic. Standard flammability test procedures were used to measure the critical flux for ignition, critical ignition temperature, and heat release rates (HRR) of rubber compounds common to tire tread materials and conveyor belt covers. Both the intermediate scale calorimeter: ISO 14696, ASTM E-1623 (ICAL) and the cone calorimeter: ISO E-5660, ASTM 1354 (Cone) provided the bulk of the data. Critical ignition flux and vertical flame spread data for rubber based electrical insulations were determined using a radiant panel from a modified ASTM flame spread apparatus: ASTM E-162. thermogravimetric analysis was also used to evaluate thermal decomposition progression of selected test materials. Further, suppression tests were conducted on tire piles to evaluate agents to extinguish and control tire fires. Also, the HRR of the tire piles were measured and compared to work performed by others. Results confirm that the area heat release rate of rubber materials is directly proportional to exposure flux intensity. The critical exposure flux for ignition of a variety of rubber-based materials is approximately 20 kW/m2 to 30 kW/m2 and the critical temperature for piloted and non-piloted ignition were independent of exposure intensity at ~400°C and ~600°C respectively. In large quantities, rubber tire loads have total HRR comparable to the heat released from similar areas of liquid hydrocarbon spills.

Validating Thermal Response Models Using Bench-Scale and Intermediate-Scale Fire Experiment Data

The thermal response of a fiber reinforced polymer composite was measured by the bench-scale Cone Calorimeter and Intermediate-scale Calorimeter (ICAL) fire experiments. Finite-rate and infinite-rate pyrolysis models were used to predict the response of the composite panels under the same thermal boundary conditions as in the fire tests. It was shown that both models can give acceptable temperature, mass loss, and effective char thickness predictions. The effect of internal gas convection on thermal response predictions was determined insignificant at low heat flux levels. The thermal insulation at the back surface of the composite panel significantly increased both temperature and mass loss predictions.

A simplified model for predicting the ignition of FRP composites with validation using intermediate‐scale fire experiment data

ABSTRACTThis study presents a simplified theoretical model to predict the ignition of FRP composites of general thermal thickness (GTT) subjected to one‐sided heating. A simplified GTT heat transfer model to predict the surface temperature of GTT composite panels was developed, and the exposed surface temperature was used as ignition criterion. To validate the GTT model, intermediate scale calorimeter fire tests of E‐glass fiber reinforced polyester composite panels at three heat flux levels were performed to obtain intermediate‐scale fire testing data in a controlled condition with well‐defined thermal boundary conditions. The GTT model was also verified by using results from finite element modeling predictions. This model can be used to estimate the surface temperature increase, time‐to‐ignition, and mass loss of FRP composites for fire safety design and analysis. Copyright © 2013 John Wiley & Sons, Ltd.

Precision of the Cone Calorimeter and ICAL Test Methods

Repeatability and reproducibility are typically determined for standard fire test methods on the basis of an interlaboratory test program (round-robin) to define their precision. Significant differences in precision were found in the past between the repeatability and reproducibility of small-scale and intermediate- and large-scale fire test methods that all utilize oxygen calorimetry to measure heat release rate. Repeatability of heat release rate related measurements with small-scale apparatus has been found to be significantly better than the repeatability of the intermediate and large-scale apparatuses. In this paper, the results of two round-robins are compared on the basis of relative repeatability standard deviations and relative reproducibility standard deviations calculated for individual materials for individual test parameters. The first one was a cone calorimeter round-robin and the second was an intermediate-scale calorimeter (ICAL) round-robin. The objective and subjective factors that might have contributed to the differences between the two test methods in both repeatability and reproducibility were analyzed. The most important factors that caused the differences in the ICAL round-robin were higher theoretical uncertainty of the ICAL, inadequate pre-round-robin calibrations, the small numbers of participating laboratories and samples tested, prevalence of fire-retardant-treated materials, and possible failure of some of the laboratories to fully comply with the standard. These factors, especially the fact that the testing procedures and apparatuses in the participating laboratories may not have been in complete accordance with the standards, indicate that the results of the round-robins did not reflect the real precision of the test methods. However, the terminology using the two components of precision, repeatability and reproducibility, is maintained in this paper except where a specific distinction is noted. Recommendations are made on how to improve the results of future fire test round-robins.

Use of the cone calorimeter to detect seasonal differences in selected combustion characteristics of ornamental vegetation

The flammability of living vegetation is influenced by a variety of factors, including moisture content, physical structure and chemical composition. The relative flammability of ornamental vegetation is of interest to homeowners seeking to make their homes ‘fire safe’. The relative importance of the factors influencing fire behaviour characteristics, such as flammability, is unknown. In the present study, oxygen consumption calorimetry was used to obtain selected combustion characteristics of ornamental vegetation. Peak heat release rate, mass loss rate, time to ignition and effective heat of combustion of 100 × 100-mm samples of foliage and small branches were measured using a bench-scale cone calorimeter. Green and oven-dry samples of 10 species were collected and tested seasonally for a period of 1 year. Similar measurements were made on whole shrubs in an intermediate-scale calorimeter. The range of cone calorimeter peak heat release rates for green and oven-dry samples was 1–176 and 49–331 kW m−2, respectively. Moisture content significantly reduced heat release rates and increased time to ignition. Peak heat release rates for Olea europea and Adenostoma fasciculatum were consistently highest over the year of testing; Aloe sp. consistently had the lowest heat release rate. The correlation of peak heat release rates measured by the cone calorimeter and an intermediate-scale calorimeter was statistically significant yet low (0.51). The use of the cone calorimeter as a tool to establish the relative flammability rating for landscape vegetation requires additional investigation.

Surface temperature measurements on burning materials using an infrared pyrometer: accounting for emissivity and reflection of external radiation

AbstractThis paper demonstrates the successful use of an infrared pyrometer, operating in the 8–10 µm wavelength band, to measure the surface temperature of combustible specimens in a heat release calorimeter. The temperature histories of ten different materials were measured in the ICAL (intermediate scale calorimeter). The set of materials comprised four wood products, gypsum board, polyisocyanurate foam, PVC floor tile, PMMA and two non‐combustible boards. A small‐diameter bare thermocouple was installed on each specimen in order to determine an accurate temperature for comparison.The spectral emissivity and the spectral flux reflected from the surface were measured simultaneously and used to correct the apparent temperature measured by the pyrometer. The spectral emissivity and reflected spectral flux were both constant prior to ignition for all the combustible materials. During the burning phase all the combustible materials had a spectral emissivity very close to unity. The agreement between the temperatures measured with the pyrometer and thermocouple was not affected by the flame. The wood products, the polyisocyanurate foam and the calcium silicate board required no correction for reflected spectral flux over the whole temperature range. Copyright © 2004 John Wiley & Sons, Ltd.

Intermediate scale heat release calorimetry (ICAL): precision information and latest developments

A fire test instrument is required for use with composites and non-homogeneous products, as well as for specimens with discontinuities and surface irregularities, which is small enough not to require a complete full-scale product. The intermediate scale calorimeter, ASTM E1623 (ICAL) addresses that need. It is a gas-fired radiant panel (consisting of a series of small panels) which exposes, vertically, a 1 × 1 m sample, up to 150 mm thick, to a heat flux of up to 50 kW m−2. Two wire igniters are located near the top and bottom of the radiant panel. The entire specimen holder assembly is on wheels, so it can be brought closer or further away from the radiant panel. The radiant panel and specimen holder are mounted on a load cell, under a hood, so that all major fire properties can be assessed, including heat, smoke and combustion product release, mass loss, ignitability and flame spread. The ICAL has the following six major applications: (a) source of engineering data for performance-based codes; (b) basis for a classification system for degrees of combustibility; (c) screening tool for full-scale room-corner tests; (d) tool for limited fire reconstructions, where it allows for studies of flame spread, and also heat and smoke release; (e) alternative means of assessing ignitability of exterior claddings, instead of the presently-used test with very limited usefulness; (f) as a screening tool for fire resistance tests (theoretically), because it allows estimation of fundamental fire properties such as the thermal inertia (kρc, where k is the thermal conductivity (kW (m−1K−1), ρ is the density (kg m−3), and c is the thermal conductivity, (kJ kg−1K−1)). Recently, a precision interlaboratory round robin was conducted with three laboratories and six specimens (together with one added specimen each for two laboratories). Data analysis shows that the repeatability and reproducibility of the method is typical of modern fire tests. Moreover, it is suitable beyond the limited initial application to wood products. In fact, ICAL is a useful test method for research and development, with good potential as a regulatory tool. © 2000 Society of Chemical Industry

Impact of air velocity on ignition in the Intermediate Scale Calorimeter (ICAL)

Higher surface temperatures were required for ignition in the Intermediate Scale Calorimeter than in the Cone Calorimeter. Air velocity measurements were made in front of calcium silicate and particleboard specimens in the Intermediate Scale Calorimeter and temperature measurements were carried out on their exposed surfaces. The higher ignition temperature in the Intermediate Scale Calorimeter was the result of the high induced upward air velocity due to the large specimen size (1.0 m by 1.0 m). This caused the flame to blow off. A higher surface temperature was needed to produce a downward flame spread rate sufficient to overcome the upward air velocity. To counteract this effect, a horizontal projection plate extending 100 mm out from the bottom edge of the specimen was installed. This created an eddy, causing a downward air velocity near the surface at the bottom of the specimen The igniter was a hot wire across the width of the specimen at a height of 100 mm. The flame quickly spread down from the igniter to the bottom edge and attached there. Under these conditions the temperature required for ignition of particleboard in the Intermediate Scale Calorimeter was less than it was in the Cone Calorimeter.

Impact of air velocity on ignition in the Intermediate Scale Calorimeter (ICAL)

Higher surface temperatures were required for ignition in the Intermediate Scale Calorimeter than in the Cone Calorimeter. Air velocity measurements were made in front of calcium silicate and particleboard specimens in the Intermediate Scale Calorimeter and temperature measurements were carried out on their exposed surfaces. The higher ignition temperature in the Intermediate Scale Calorimeter was the result of the high induced upward air velocity due to the large specimen size (1.0 m by 1.0 m). This caused the flame to blow off. A higher surface temperature was needed to produce a downward flame spread rate sufficient to overcome the upward air velocity. To counteract this effect, a horizontal projection plate extending 100 mm out from the bottom edge of the specimen was installed. This created an eddy, causing a downward air velocity near the surface at the bottom of the specimen. The igniter was a hot wire across the width of the specimen at a height of 100 mm. The flame quickly spread down from the igniter to the bottom edge and attached there. Under these conditions the temperature required for ignition of particleboard in the Intermediate Scale Calorimeter was less than it was in the Cone Calorimeter. © 1997 John Wiley & Sons, Ltd.

The intermediate scale calorimeter development

The subject of this paper is an intermediate scale calorimeter (ICAL) which was developed at the Weyerhaeuser fire technology laboratory. The initial purpose of the apparatus was to measure heat release rate from wall assemblies, since these cannot be tested in the cone calorimeter

Testing wall assemblies on an intermediate-scale calorimeter

A new intermediate-scale calorimeter for measuring the rate of heat release based on oxygen-consumption methodology has been developed at Weyerhaeuser Fire Technology Laboratory. A 1 m2 sample, vertically oriented, can be exposed to a uniform radiant flux of up to 50 kW/m2 provided by the gas-fired radiant panel. The test method was primarily developed to test wall assemblies, since features such as the joints of assembly panels, sheets of noncombustible protective materials, cracking, material collapse, and melting and spilling of thermoplastic materials cannot be represented in a bench-scale sample. Large-scale tests are expensive and time-consuming. A series of tests was run to determine whether features known to exist in real structures during a fire could be adequately represented and reproduced in this test method. The results show that the behavior characteristics during tests are consistent with heat release data.