Flame spread characteristics

Flame spread characteristics of product first ignited... 

The test method described in ASTM E 162 also evaluates opposed-flow flame spread characteristics of a product, and is referred to in regulations that pertain to various modes of transportation. 

Part 5 is relevant to floor coverings since these are required to have a surface with low flame spread characteristics and are tested in accordance with Resolution A.653(16). This defines a method of determining surface heat spread in a vertical orientation under a heat flux of 49.5 kWm" at the initial part of the sample length reducing to 1.5kWm- after 740 mm. Thus carpet fabrics must have higher flame resistance than normally expected for such a horizontally orientated textile. Consequently, flame retarded wool (e.g. Zirpro -treated wool see Chapter 8) will feature as an important fibre in appropriate woven or tufted stractures which combine both the necessary aesthetic and technical requirements. 

It is seen from Table 6.7 that, without exception, in a wide range of commercially available fire retardant polymers the incorporation of fire retardant additives into the formulation produces distinct improvements in LOI values and flammability and flame spread characteristics of the polymers listed. 

The properties derived from ASTM E1321 provide information about the flame spread characteristics of materials and can serve as an indication of their hazardous characteristics [38]. The test results provide material fire parameters that correspond to property data required by theories of surface flame spread [38]. The analysis may be used to rank materials performance by some set of criteria applied to the correlation or the analysis may be employed in fire risk growth models to develop a more rational and complete risk assessment for wall materials [38]. 

This is a more elaborate and more severe flame test, and it is a type-approval test. It submits the specimen to a continuous fierce flame and tests its flame spreading characteristics. 

Quintiere has studied the ignition and lateral flame spread characteristics of solid surface under the influences of external radiations, and found that the rate of flame spread rises and the ignition time decreases with increasing the external imposed radiation. Moreover, Quintiere showed that the rate of flame spread could be expressed as Vya q - — where q is the niinimum flux for piloted ignition and q is the external applied radiation flux. Brehob and Kulkami performed... 

Corrosion Resistant Fiber-Reinforced Plastic (FRP). Fiber glass reinforcement bonded with furfuryl alcohol thermosetting resias provides plastics with unique properties. Excellent resistance to corrosion and heat distortion coupled with low flame spread and low smoke emission are characteristics that make them valuable as laminating resins with fiber glass (75,76). Another valuable property of furan FRP is its strength at elevated temperature. Hand-layup, spray-up, and filament-win ding techniques are employed to produce an array of corrosion-resistant equipment, pipes, tanks, vats, ducts, scmbbers, stacks, and reaction vessels for industrial appHcations throughout the world. 

The surface burning characteristics (flame spread index and smoke developed index) for wood and wood products as measured by American Society for Testing and Materials (44) can be reduced with fire retardant treatments, either chemical impregnation or coatings (48). Fire retardant treatments also reduce the heat release rate of a burning piece of wood (49,50). The heat release rates (51) of the burning materials are an important factor in fire growth. 

A knowledge of the ignition characteristics of the propellant and the heat-transfer characteristics of the igniter permits the igniter designer to determine the propellant ignition-delay for a particular system. The next question is How fast does the flame spread across the propellant surface The answer to this question determines the burning area on the propellant surface as a function of time this is the function AB(t) required to solve Eq. (6) for the chamber pressure as a function of time. 

It is useful to consider the transient aspect of the flame spread problem. The ratio of characteristic times for the solid and the gas phase, based on d as a characteristic length scale, is... 

Theoretical studies are primarily concentrated on the treatment of flame blow-off phenomenon and the prediction of flame spreading rates. Dunskii [12] is apparently the first to put forward the phenomenological theory of flame stabilization. The theory is based on the characteristic residence and combustion times in adjoining elementary volumes of fresh mixture and combustion products in the recirculation zone. It was shown in [13] that the criteria of [1, 2, 5] reduce to Dunskii s criterion. Longwell et al. [14] suggested the theory of bluff-body stabilized flames assuming that the recirculation zone in the wake of the baffle is so intensely mixed that it becomes homogeneous. The combustion is described by a second-order rate equation for the reaction of fuel and air. 

Flame Spread The speed at which a flame will cross the surface of a material, influenced by the physical form of the fuel, air supply, the moisture content of the fuel, specific gravity, size and form, the rate and period of heating, and die characteristics/nature of the heat source. A higher flame-spread critically affects the severity of the fire in a given period of time. 

The purpose of bench-scale reaction-to-fire tests is to measure the flammability characteristics of materials, i.e., ease of ignition, flame spread propensity, heat release, and production of smoke and toxic combustion products. Some tests are designed to measure only one of these characteristics. Other tests are more sophisticated and can be used to measure several characteristics at the same time. 

The performance of a material in a growing pre-flashover fire is affected by its ignition characteristics in primarily two ways. First, flame spread over the surface of the material can be viewed as a series of subsequent ignitions of incremental areas. Second, the flame spread process is typically initiated in an area that is heated by an impinging flame from a burning object. In both cases, a flame is present in the vicinity of the material that is heated to ignition. The focus of this section is therefore on piloted ignition. 

The majority of the materials with low flame spread (or low heat release) also exhibit low smoke release. However, it has been shown in several series of room-corner test projects (with the tested material lining either the walls or the walls and the ceiling), that -10% of the materials tested (8 out of 84) exhibited adequate heat-release (or fire growth) characteristics, but have very high smoke release (Table 21.17 and Figure 21.16).189190 These materials would cause severe obscuration problems if used in buildings. A combination of this work, and the concept that a visibility of 4 m is reasonable for people familiar with their environment,191 has led all the U.S. codes to include smoke pass/fail criteria when room-corner tests are used as alternatives to the ASTM E 84 Steiner tunnel test. 

In small-scale laboratory tests (characteristic sample dimensions of less than 0.2-0.3 m), conduction or convection are the dominant heat transfer routes. It has been shown horizontally or vertically, that 90% of the heat generated in a laminar flame spreading along a thermally thick PMMA sample is transferred by conduction across the condensed phase, and only about 10% by convection through the gas phase. In the case of thermally thin samples, on the other hand, the heat is predominantly transferred through the gas phase, independent of the flame propagation direction... 

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