A laboratory-scale gallery fire test on rubber conveyor belts with fabric skeletons

The authors have conducted a laboratory-scale gallery fire test on nine different rubber conveyor belts with fabric skeletons. The interior of the gallery used in this test was 2.5 m long, 0.35 m wide and 0.35 m high. The fire test on each sample was conducted in the upward airflow of the inclined gallery as well as in the horizontal one, and both 60 mm and 90 mm wide specimens, whose length was about 1.5 m, were provided for each test. The test results were compared with those from some other small-scale flammability tests; i.e. the small-scale flame, the oxygen index and the hot plate ignition tests. In addition, some problems in the laboratory-scale gallery fire test were also discussed. As a result, it has been found empirically that determination of both the time to ignition and the flame-propagation speed could be significant in case the flame propagated over the whole length of the belt specimen in the gallery, so that the fire resistance of the belt samples could be classified in detail.     

Correlation between the hot plate ignition test and other laboratory-scale flammability tests on rubber conveyor belts with fabric skeletons

The hot plate ignition test was conducted on ten different conveyor rubber belts with fabric skeletons. In this test, a 25 × 25 mm² belt sample was placed on a stainless steel plate in an electric furnace and heated. The ‘ignition temperature’ was determined on each sample in almost the same way as proposed in Canada. The test results were compared with those from other laboratory-scale flammability tests (i.e. the small-scale flame tests, the Oxygen Index test and the laboratory-scale gallery test). The calculated results of both sample and rank correlation coefficients imply that the ‘10 signition temperature’ in this hot plate ignition test has a correlation with the results from both the Oxygen Index test and the laboratory-scale gallery test, but that it has very little or no correlation with those from the small-scale flame tests. On the other hand, it is found that the ‘60 s ignition temperature’ in this test has a far better correlation both with the results from the small-scale flame tests and with the time to ignition in the laboratory-scale gallery test than the ‘10 s ignition temperature’.     

Problems in a drum friction test for fire-resistance evaluation of rubber conveyor belts with fabric skeletons

A drum friction test was conducted on four different ‘flame-resistant’ and one ‘non-flame-resistant’ rubber conveyor belts with a fabric skeleton manufactured in Japan. These test results were compared with those obtained from the other flammability tests, i.e. a small-scale flame test, an oxygen index test and a laboratory-scale gallery test, and both sample and rank correlation coefficients were calculated. As a result, the authors have concluded that fire resistance of belting materials themselves could not be adequately assessed by the results from the drum friction test, which could have some significance only when other combustible materials exist near the drive pulleys or idlers of belt conveyors.     

Evaluation of laboratory gallery fire tests of conveyor belting

Two mid-scale laboratory gallery fire tests, the propane gallery and the BELT test, were constructed and evaluated. In both cases the fundamental parameter that can be used for ranking flammability of a belting is the total quantity of heat input into the sample, rather than length burned or flame-out time. The temperature and velocity of the ventilating air used were found, experimentally and theoretically, to be critical factors in determining the results of the tests. The two tests correlated qualitatively on a pass|fail basis; however, the BELT test was affected more by the thickness of the sample: the thicker, the more probable to pass the test. The BELT test has the advantages of easier control and producing fewer pollutants. The results of BELT, propane gallery and critical oxygen index tests on some beltings are compared.     

Investigations of conveyor belts flammability. Comparison of flammability assessment using the large-scale gallery test and cone calorimeter

The paper describes results of investigations of conveyor belt flammability in full scale, using the large-scale gallery method and using cone calorimeter. On the basis of oxygen consumption calorimetry, the amounts of heat release during burning of conveyor belts were calculated. A correlation was found between results of conveyor belt flammability obtained using both methods. Criteria for conveyor belt flammability assessment were established for the cone calorimeter method, which define a level that would be equivalent to that for the large-scale gallery test. © 1998 John Wiley & Sons, Ltd.     

Heat release rate in evaluation of conveyor belts in full-scale fire tests

The theoretical bases for calculation of heat release rate during burning of conveyor belts in the fire-testing gallery has been presented. Taking as an example the results of measurements of oxygen, carbon dioxide and monoxide content in the products of combustion of conveyor belts during the testing of their flammability in the full-scale fire gallery, the possibility has been demonstrated for using the calculations of heat release rate in an assessment of conveyor belt flammability. The total quantity of heat released during the belt fire in the experimental gallery can provide the basis to develop a new method of testing as well as the criteria for assessment of fire resistance of the conveyor belts using oxygen consumption calorimetry. © 1997 John Wiley & Sons, Ltd.     

Fire hazards of organic materials—small scale assessment of flammability and smoke generation

The flammability and smoke generation properties of a number of organic materials used in ships, including laminated materials, rigid and flexible cellular polymers, cable insulting materials and adhesives, have been evaluated. The relative flammabilities were determined by the limiting oxygen index method that gives convenient, reproducible, numerical ratings of materials. Smoke generation was assessed photometrically by measuring light attenuation under standard conditions and is reported in terms of the total amount of smoke generated, as well as the times for the smoke density to reach an arbitrary ‘critical’ level and the maximum value. Materials with low flammability and low smoke generation characteristics have been identified, as well as those that would be hazardous in the event of a fire.     

Survey of small‐scale flame spread test results of modern fabrics

The flammability of apparel worn on a person has one of the highest ratios of fire fatalities per fire, and there are few statutory requirements. A series of evaluations was conducted on the flammability of 50 fabrics (both cellulosic and thermoplastic) using the (now withdrawn) NFPA 701 small‐scale test. The fabrics covered a broad range of areal densities (weights) and many were not intended for apparel. A series of conclusions were reached. In particular, it is apparent that the following primary correlation exists between fabric weight and flammability: the heavier the fabric the better it behaves in a fire. Secondarily, however, the type of fabric also strongly affects this conclusion. This paper presents the results of the testing and offers an analysis. Copyright © 2006 John Wiley & Sons, Ltd.     

The effect of fibre content on the thermal and fire performance of polypropylene–glass composites

Thermoplastic composites demand constant improvements in fire retardant and mechanical properties to fulfil their full market potential, especially in demanding sectors such as rail, aerospace and infrastructure, where fire performance is critical. The aim of this work is to understand the effect of reinforcing fibres on the flammability of polypropylene–glass (P‐G) composites and the means of improving their fire performance in a cost‐effective manner. A number of P‐G composites with 0%, 10% and 20% (w/w) glass fibres were prepared using short length glass fibres. The effect of fibre content on the thermal stability, flammability and mechanical performance of the P‐G composites without and in the presence of conventional fire retardants was studied. It was observed that while the presence of glass fibre lowered down the limiting oxygen index value of the composite, the rate of flame spread in a UL‐94 equivalent test was also lowered. The reduction in limiting oxygen index is due to the fact that glass fibre reduces the melt dripping behaviour of polypropylene and does not let the polymer (polypropylene) move away from flame, which then burns. Cone calorimetric study indicated that the presence of glass fibre reduces the overall flammability of the composite laminate. Copyright © 2011 John Wiley & Sons, Ltd.     

Mathematical modelling of fire development in cable installations

In 1996 DG XII of the European Commission (Research and Development) approved a 3 year project on the fire performance of electrical cables. Within this FIPEC project, a major part of the work involved correlation and mathematical modelling of flame spread and heat release rate in cable installations. The FIPEC project has developed different levels of testing ranging from a small‐scale, cone calorimeter test procedures developed for cables and materials, a full‐scale‐test procedure based on the IEC 60332‐3, but utilizing HRR and SPR measurements, and a real scale test conducted on model cable installations. Links through statistical correlations and mathematical fire modelling between these levels were investigated and the findings are presented in this paper. These links could form the scientific foundations for standards upon which fire performance measurements can be based and for new fire engineering techniques within fire performance based codes. Between each testing level correlation, numerical and mathematical models were performed. All of the models were based on the cone calorimeter test method. The complexity of the models varied from correlation models to advanced physical pyrolysis models which can be used in CFD codes. The results will allow advanced prediction of cable fires in the future. Also a bench mark was established for the prediction of cable performance by means of data obtained from the constituent materials. Copyright © 2002 John Wiley & Sons, Ltd.     

The dynamic flammability and toxicity of magnesium hydroxide filled intumescent fire retardant polypropylene

The flammability properties of an intumescent fire retardant polypropylene added with magnesium hydroxide was discussed in this study. To evaluate the flammability of the material, limit oxygen index, smoke emission, tensile strength, and our exploitation dynamic flammability evaluation system, tests were assessed in experiments. The results showed that the intumescent flame retardant ammonium polyphosphate-filled polypropylene has superior flammability properties but higher carbon oxide (CO) concentration and smoke density. By adding some magnesium hydroxide additives in intumescent fire retarded polypropylene, the smoke density and CO concentration decrease; and the compound also has superior fire properties. It is concluded that intumescent system and magnesium hydroxide additives are effective on improving combustion properties for polypropylene. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:989–995, 1998     

Study of the electrical properties of flame retardant poly(vinylchloride) using positron annihilation lifetime spectroscopy

Since the large fire at the Brown Ferry cable plant which occurred at noon on March 22, 1975 in Alabama, attention has been given to the use of flame retardant cable in buildings to meet fire safety requirements. Flame retardants are used in wire and cable applications to prevent the conversion of an electric spark into fire and subsequently to prevent the spread of fire throughout a structure along the wiring. There are many substances used as flame retardants in wires and cables. In Egypt, Multi‐Purpose Reactor insulation and jacket cables have been constructed from a flame retardant substance, poly(vinylchloride) (PVC). In the present work, elemental and X‐ray fluorescence analyses have been performed to determine the composition of PVC in the jacket cable samples. In addition, the conductivity (σ), permittivity (?′), and dielectric loss (?″) as well as positron annihilation lifetime (PAL) are measured in the temperature range 30 to 140 °C. It is found that the amount of chlorine in the flame‐retardant PVC (FRPVC) jacket cable is significantly higher (5%) than the conventional PVC jacket cable. Inverse relationships between σ and free volume size and fractions (V, f) through the temperature range are obtained. However, a distinct positive relationship between σ and I₂ above 100°C is found. The results of PAL and electrical measurements indicate that FRPVC has good electrical insulation properties below 100°C. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 638–644, 2005     

A comparative evaluation of a novel flame retardant, 3-(tetrabromopentadecyl)-2,4,6-tribromophenol (TBPTP) with decabromodiphenyloxide (DBDPO) for applications in LDPE- and EVA-based cable materials

Flame retardation of polymeric materials for cables is becoming a statutory requirement due to governmental regulations to protect life and property from damages caused by fire. This and other factors such as the ever-increasing cost of existing flame retardants (FRs) have given rise to the search for better FRs. In this article, the suitability of an FR, 3-(pentadecyltetrabromo)-2,4,6-tribromophenol (TBPTP) developed from cardanol was evaluated for use in cable insulating and jacketing materials based on low-density polyethylene (LDPE) and ethylene vinyl acetate (EVA). The processability, mechanical properties, compatibility and miscibility, thermal behavior, flammability behavior, smoke generation, acid emission, aging characteristics etc., of the blends of the FR with LDPE and EVA were studied in comparison to those of decabromodiphenyl oxide (DBDPO), which is a standard FR used by the cable industry. Although TBPTP is found to be less thermally stable than is DBDPO, it exhibited better flame retardancy and has comparable thermal stability when blended with LDPE and EVA. Both LDPE—TBPTP and EVA—TBPTP blends produced less smoke than did the corresponding blends of DBDPO. In the case of the EVA—TBPTP blend, the percentage emission of smoke was almost negligible, placing EVA—TBPTP under the low smoke grade. Formulations containing a synergistic agent, promoter, and filler with the corresponding FR and polymer polymer along with an antioxidant were extruded out into wire and tested for cable properties. At 20% loading, the LOI values of the blends were 34.6 and 32.5, respectively, for the TBPTP—EVA and DBDPO—EVA blends. Vertical burning tests carried out with EVA—TBPTP cable showed that it is self-extinguishable. The processability of the compositions containing TBPTP were better than those of DBDPO. The improved processability was found to be due to the plasticising effect of TBPTP. SEM pictures of the blend showed excellent distribution of TBPTP in the polymer, indicating good compatibility and miscibility. Comparatively, DBDPO did not exhibit uniform distribution. The mechanical properties of the blends were within specifications of standard cable materials except that the % elongation of the DBDPO—LDPE blend was far too low. Aging studies also gave better properties for the TBPTP system than for those of the DBDPO system. The overall results show that the properties of EVA—TBPTP cable fall within specifications for the FARLS grade, whereas the EVA—DBDPO cable did not. In the case of LDPE, both TBPTP and DBDPO did not satisfy specifications for the FRLS grade, but the data indicate that they can be used as FRs. The superiority in properties of the TBPTP system over DBDPO is explained in terms of the structure of TBPTP characterized by the distribution of the flame-retardant element, bromine, almost evenly between the aliphatic and aromatic moieties of the molecule, which can, in contrast to the fully aromatic DBDPO, provide halogen over a wide range of temperatures to the combustion zone of the decomposing polymer. Moreover, the presence of the aliphatic segment assures improved processability and compatibility. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 3057–3073, 1997     

Some aspects of flame retardancy in high density polyethylene

The influence of the flame retardant agents, antimony trioxide and a chlorinated hydrocarbon, on the mechanical and flammability properties of high density polyethylene has been studied. Flammability was assessed by means of the limiting oxygen index test, whilst mechanical properties were measured in the tensile mode on compression moulded samples. An optimum in terms of flame resistance was found at a Sb:Cl mole ratio of 1:3 which tends to confirm that the actual flame retardant is the volatile antimony trichloride. The modulus, yield and drawing behaviour, and ultimate properties of the unoriented samples did not show significant change (< 10%) until the combined level of additive exceeded 25% by wt. Above this level it was found that the samples could not be oriented and that the elongation to break decreased markedly. Alumina trihydrate was studied as an alternative flame retardant but was found to be unsuitable for use in HDPE, since to obtain an adequate level of fire retardancy a high concentration (40%) of additive was required, which resulted in a significant deterioration in the mechanical properties.     

Validation of the lumped parameter code COCOSYS against large‐scale OECD PRISME 2 fire experiments

Fire safety analysis is a major issue for nuclear power plants (NPPs) in the context of deterministic safety assessments as well as of probabilistic safety analyses. Oil reservoirs and cables represent major fire loads. Therefore, simulations of oil and cable fires are of interest for quantifying the risk of such internal hazards in NPPs. To investigate the applicability of lumped parameter (LP) modelling, validations against fire experiments are required. In this way, results obtained with the LP code COCOSYS for simulations of oil and cable fire experiments conducted in the OECD PRISME 2 Project are presented. The PRISME 2 VSP (vertical smoke propagation) tests involving oil fires in a confined and mechanically ventilated facility were used to assess the ability of the LP code to simulate smoke propagation through a horizontal opening from the fire compartment to a compartment on top of it. As it was already identified in the “International Collaborative Fire Modelling Project (ICFMP),” this type of opening might cause problems in fire simulations, particularly for zone or LP fire models. In these simulations, attention has been paid to the coupling between the fire and the surrounding environment due to the decrease of oxygen concentration. Furthermore, different cable materials have been tested in the PRISME 2 CORE (completing and repeating) test campaign. By simulating the CFS‐3 (cable fire spreading) test with confined underventilated conditions, the applicability of the COCOSYS cable fire model with input parameters deduced from open atmosphere fire tests (CORE‐2) was analysed. Results show that the applicability of a LP fire model to predict the pyrolysis rate is partly limited for both oil and cable fires, in confined environment. However, simulations with prescribed pyrolysis rates show encouraging results in good agreement with the experimental data and underline the capability of the LP code COCOSYS to simulate the interaction between the thermal hydraulics inside compartments and the fire source.     

Current Japanese standards for flammability tests on electric cables

This paper outlines the flammability test methods and requirements for electric cables specified in some Japanese standards. Only two different methods of a small-scale flame test as specified in Clause 28 of JIS C 3005 are applied to electric cables for general use, and whether or not the flammability test should be conducted and which method should be adopted depends on the type of cables, both of which are specified in each separate standard. Cables for electrical equipment of ships have to pass another small-scale flame test as prescribed in Section 6.7 of JIS C 3410. A flame test method for flame-retardant telecommunication cables has been introduced in JIS C 3521. This specifies a vertical open tray flame test on grouped cables, almost in accordance with IEEE Standard 383. In addition to the method for a vertical open tray flame test, one for a vertical closed duct flame test on grouped cables is also specified in a Japanese Cable Makers' Association Standard, i.e. JCS 366. Some flame-retardance requirements for electric cables in Japan are listed and discussed.     

Evaluation of the smoke and flammability characteristics of polymer systems

Using Oxygen Index and the XP-2 test to measure flammability and smoke characteristics, a broad spectrum of thermoplastic and thermoset polymers, both commercial and experimental, were investigated to elucidate the effect of structure on fire properties. In general, polymers with aliphatic backbones are very flammable, but their tendency to generate smoke is minimal. The addition of flame retardants, especially halogen compounds, while reducing their tendency to burn, increases the evolution of smoke. Halogen-containing polymers are usually non-flammable, with high Oxygen Indices, but display high smoke generation. Polymers containing an aromatic group in the side chain, such as polystyrene, are both highly flammable and high smoke producing. However, polymers with the aromatic group in the main chain, such as polysulfone, polycarbonate and polyphenylene oxide, are intermediate in both Oxygen Index and smoke generation. After investigation of the various test methods available, it is concluded that no one test will be satisfactory to measure the flammability characteristics of polymers and that a combination of methods must be used.     

Cable tray fire tests in a confined and mechanically ventilated facility

Cable fires are one of the main fire hazards in nuclear power plants. As part of the cable fire spreading (CFS) campaign of the OECD PRISME‐2 programme, 3 real‐scale cable tray fire tests were performed in open atmosphere (1 CFS support test, named CFSS‐2) and in a confined and mechanically ventilated facility (2 CFS tests, named CFS‐3 and CFS‐4). This study aims at investigating the effects of confined and ventilated conditions on cable tray fires that used a halogen‐free flame retardant cable‐type. The CFS‐3 and CFS‐4 tests involved 2 ventilation renewal rates of 4 and 15 h^?1, respectively. The confined conditions lead to decrease the fire growth rate and the peaks of mass loss rate and heat release rate, compared with open atmosphere. The reductions are larger for the lower ventilation renewal rate. Furthermore, it is shown that the CFS‐4 test may be classified as a well‐ventilated fire and the CFS‐3 test as an under‐ventilated fire. For this last one, its fire characteristics and its consequences in the fire room highlight an oscillatory behaviour, with the same low frequency, for about 30 minutes. These oscillations arise from successive combustions of unburnt gases.     

Cone calorimeter testing of foam core sandwich panels treated with intumescent paper underneath the veneer (FRV)

Surfaces of novel foam core sandwich panels were adhered with intumescent fire‐retardant paper underneath the veneers (FRV) to improve their flammability properties. The panels were evaluated by means of cone calorimeter test (ASTM E 1354). Variables tested were different surface layer treatments, adhesives used for veneering, surface layer thicknesses, and processing conditions, having the objective of obtaining similar or better flammability as that of solid particle boards. Previous research showed that sandwich panels without FRV compared to panels with FRV generally had much higher heat release rates, somewhat higher heat of combustion and much higher smoke production due to the polymeric foam component of tested panels. The present study shows that using FRV adhered to the surface layer of sandwich panels dramatically improved flammability properties; the best FRV performance resulted from panels produced with thicker face layer (5 mm) and lower press temperature (130°C) and adhered with an acrylic thixotropic adhesive. Such protected foam core particleboard has heat release rate profiles as low as that is typical of commercially available fire‐retardant–treated plywood, thus implying a low flammability rating when tested in accordance with both single burn item (Euro Class B anticipated) and steiner tunnel (North America Class A anticipated) tests.     

The effect of accelerated ageing of building wires

The fire performance of two electric cables (building wires) designed for indoor use has been tested, both as new products and after accelerated thermooxidative ageing. The cables were aged for a maximum time of 16.5 weeks at 80°C. The cables are commercially available, and were constructed using a PVC material in one case and a non‐halogenated polyolefin‐based material, called Casico, in the other. The effects of ageing on the fire performance of the cables, and the chemical changes that have caused the observed fire behaviour, have been investigated and are discussed. Special attention is paid to the behaviour of the plasticizers that are used in the PVC cable, and how the fire behaviour is affected by the loss of plasticizers from the cable and by the migration of plasticizers between the parts of the cable (insulation, bedding and sheathing). Copyright © 2007 John Wiley & Sons, Ltd.