Fire endurance

ASTM E119-88 building materials fire endurance... 

Building code requirements for fire performance are mainly concerned with noncombustibiUty (41), fire endurance (42,43), and surface burning characteristics (44). Wood, even in its treated form, does not meet the building code requirements for a noncombustible material. However, for some specific apphcations where noncombustible materials are required, the codes permit the substitution of fire retardant treated wood. 

Available analytical methods for determining the fire resistance (or fire endurance) of wood members have been reviewed by White (8). A finite-element heat transfer model for wood-frame walls was developed by the University of California-Berkeley (9) with funding from the FPL. 

Brenden and Chamberlain (6) measured heat release rate from wall assemblies having fire-retardant-treated studs and gypsum board as interior finish in the FPL fire endurance furnace using three methods (a) the substitution method, by which the amount of fuel required to maintain the ASTM E-119 time-temperature curve for a... 

The FPL vertical wall furnace used in our study was described in some detail by Brenden and Chamberlain (6). This furnace is normally used to evaluate the fire endurance of wall assemblies. The basic guidelines for the furnace test method are given in the ASTM E-119 standard (5). The method was designed to evaluate the ability of a structure to withstand a standard fire exposure that simulates a fully developed fire. The furnace is gas fired, and its temperature is controlled to follow a standard time-temperature curve. A load may be applied to the assembly. The failure criterion can be taken as time at burnthrough, structural failure, or a specified temperature rise on the unexposed side of the wall—whichever comes first. The construction of the furnace is not specified in the ASTM E-119 standard. 

Heat release rates from the calibration run and the walls were made using Equations 1 to 13. The fire endurance results will be discussed in another paper. The tests were terminated shortly after structural failure or burnthrough of the wall assembly. The test termination times are given in Table II. 

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. 

Some of the other properties of interest for fire hazard assessment cannot be measured with RHR calorimeters. They include flame spread, limiting oxygen index (LOI, or simply oxygen index, 01 both names have been used, but the author s preferred nomenclature is the one used here) and fire endurance. 

Fire endurance properties are always measured directly on finished products, and are specific for a particular application. 

Refrigerated vessels handling flammables should also be provided with fixed fire protection in a manner similar to that of other storage tanks and vessels. Water spray protection or fireproofing of vessel surfaces that could be fire exposed should be considered. Where fireproofing is used, it should be specified for a fire endurance rating of 1 hr. 

Fireproofing may also be used as passive protection for pressure vessels. Fireproofing reduces the fire exposure heat input to the protected vessel and the rate of increase of the vessel wall temperature. Outside surfaces of vessels that may be exposed to fire should be covered with a fireproofing material having a fire endurance rating of 2 hours. Refer to Chapter 7 for additional information on fireproofing. 

The structural fire endurance of a structural system is a measure of its ability to resist collapse during exposure to a fire. The thermal/structural response models evaluate the time-temperature history within a solid exposed to a fire environment. The time-temperature history, or design fire exposure, can be a... 

The property of a wood material or assembly to resist the penetration of fire or to continue to perform a given structural function, or both, is commonly termed fire resistance. The measure of elapsed time that a material or assembly will exhibit fire resistance under the specified conditions of test and performance is called fire endurance. Large furnaces are used to measure fire endurance of walls, floors, roofs, doors, columns, and beams under the standard ASTM E119 (30) time-temperature exposure conditions. 

Commercial fire-retardant treatments generally do not add significantly to the fire endurance of assemblies. It is often more advantageous from the cost standpoint, either to use thicker wood members or to select species with lower charring rates, than to add the cost of the fire-retardant treatment. In some assemblies, however, it has been found worthwhile to use some fire-retardant-treated components in order to gain the extra time which will bring the fire endurance time up to the goal desired. For example, treated wood studs in walls and treated rails, stiles, and cross bands in solid wood doors have been used. 

NFPA 251 Standard Methods of Tests of Fire Endurance of Building Construction and Materials... 

Other types of isocyanate-based polymer foams, such as polyiso-cyanurate foams modified by oxazolidone, carbodiimide or imide linkages, have outstanding properties in flame retardance and fire endurance without the addition of any flame retardants... 

The second factor important in obtaining highly flame-retardant isocyanurate foams is the NCO/OH equivalent ratio. Fire endurance, i.e., flame retardance) and temperature resistance, can be increased with increase of the NCO/OH equivalent ratio when polymeric isocyanate is used as the polyisocyanate component. 

Inflammable materials like a wood can be use for the fire door by the Ministry of Constniction Notice No.ll25 in 1990. Wood has good fire endurance when it was made with a large thickness dimension. A door, however, cannot be made with such a large thickness dimension for building purpose, especially in thin panel-stile constructed doors flames the thin panels on fire. 

Wood is essentially a good fire endurance material because it forms a carbonized layer on the surface during combustion which prevent flame development. The fire endurance is proportional to the cross section dimension of it A glued laminated wood for structural members called gluelam for building purposes make good use of this characteristics. It is difficult to make a door, especially a panel- stile constructed one which has a large thickness dimension. Such a door is usually made thin with a nice profile. Therefore fire retardant wood has been tried for such style wooden fire door. 

It s well known that materials made of wood like a veneer, a chip board, a fiber board etc. are treated with phosphorus and nitrogen such as ammonium phosphate, urea-phosphoric acid mixture, dicyandiamide-phosphoric acid mixture and other phosphoric amines or amides to improve their fire resistance. They form a carbonized layer acceleratively on cellulose materials which gives them superior fire endurance. Ishihara and Kobayashi improved the fire endurance of wood by coating . ... 

Here an insoluble chemicals layer has been tried to make on a surface of wood to improve the fire endurance and the treat wood has been applied to the development of a wooden fire door. 

Furthermore in order to increase the chemicals content and density still a compressing treatment was tried. Like Tab.l the fire endurance of treated wood was improved by compressing treatment, even the untreated wood. Regarding to the fire endurance, compressed wood with 20% of chemicals loading performed better than uncompressed wood with 30% of it. It is concluded that the above-mentioned... 

Tab.l Fire Endurance Of 15mm Thick DFP Treated Wood... 

To improve the fire endurance of wood it should be more effective and important to enhance the ability of fire retardance at the surface of wood. 

By the fire test it was recognized that the ability of fire endurance of a wooden door depended on the thickness of materials and the flame came out from panel inserted portion which was thinnest. The thickness of the carbonized layer was about 20mm after testing. From this point it was judged it was unnecessary to use fire retardant wood for thick door parts like a stile. Meanwhile it was necessary to improve the panel inserted portion to prevent flame penetration, because panels as door parts are constructed independently and the gaps of the panel inserted portions are extend more by shrinkage with wood combustion. 

Furthermore wood compressed by high pressure in heat-pressed treatment showed better fire endurance, even for untreated wood. As a result the functional gradient in wood would be more pronounced. The method is, however, not practical because compressed wood swelled in water. It is easy for an entrance fire door to be affected by moisture and water... 

Laminated board with raised fire retardance of the surface layer showed high fire endurance as well as compressed wood. 

It was recognized that it was more effective to raise the fire endurance at the surface of wood. 

Flexural modulus, effect on, 129 Flexural strength, effect on, 129 Tensilt modulus, effect on, 130 Tensile strength, effect on, 130 Fine particles, 126 Fire codes, 461 Fire endurance, 461 Fire, 48, 80, 461-491 performance, 485-491 rating, 461, 464 resistance, 48, 80 Firebrake ZB, 470 Firemaster CP-44HF, 471 Firemaster PBS-64HW, 471 Fish-skin, 617... 

Kodur, V. K. and L. A. Bisby (2005). Evaluation of fire endurance of concrete slabs reinforced with FRP bars. Journal of Structural Engineering 131(1) pp. 34 3. 

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