Penetrating flux, fires

Design practices stem from standard fire test procedures in which the temperature history of the test furnace is regarded as an index of the destructive potential of a fire. Thus, the practice of describing the expected effects and damage mechanism is based on temperature histories. This standard design practice is convenient but lacks accuracy in terms of structural performance. The severity of a fire should address the expected intensity of the heat flux that will impact the structure and the duration of heat penetration. A simple analysis of the expect nature of an unwanted fire can be based on the heats of combustion and pyrolysis of the principal contents in the facility. The heat of combustion will identify the destructive nature of the fire, while the heat of pyrolysis will identify the severity of the fire within the compartment itself and will also identify the destructive potential of the fire in adjacent spaces. 

Premix radiant wall burners are mounted horizontally through the wall of a furnace. The burner tip, which penetrates only a few inches inside the hot face of the furnace wall, fires radially along the wall. These burners are almost exclusively used in ethylene cracking furnaces, either alone or in conjunction with floor-mounted, wall-fired burners to provide a uniform heat distribution to the process tubes. In some cases several hundred radiant wall burners are installed in a furnace to fine-tune the radiant heat flux to the process tubes. Figure 18.11 is a rendering of a radiant wall burner. 

Since oxygen vacancy defects also tend to decrease the Q-factor, the firing atmosphere and post-firing anneahng must be carefully considered. This is reminiscent of the severe processing problems of high-temperature superconductors (see Section 9.7). In fact, the dielectric loss in ceramics is analogous to the resistance experienced by flux penetration in type 11 superconductors. 

A procedure for safety verification in the event of a postulated fire is to determine the maximum heat flux arriving at the buildings important to safety and to determine whether the barrier resistance provided by the exterior skin of the building (concrete, steel, doors and penetrations) is sufficient. 

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