High-fire period

Then, burner manufacturer North American Mfg. Company of Ohio produced a burner that controlled the temperature to 10°F (5.6°C) by a lot of spin or no spin (on/off control). The result was that the high-fire period was lengthened and the cutback period was reduced. A hot heat was ready in about 5 hr instead of 8 hr. Temperature measurements were taken with five thermocouples along the length of the pit bottom. When the pit temperature was thought to be uniform and the ingots ready to be rolled, the front-to-back temperature difference was 175°F (97°C). 

Most burners are efficient at high fire but less so at intermediate rates and particularly at low fire. An on/off burner is therefore apparently efficient from an energy-utilization viewpoint. However, when the burner is called on to fire, in the case of forced-draft burners a purge is usually necessary which will both cool down the process and cause a delay in response, and in the case of natural draft there will be heat losses due to ventilation in the off period. 

During charging and melting, the EZ-Fire burners were fired 25% from the air/fuel burners and 75% from the oxy/fuel burners. During extended waiting periods, the oxy/fuel burners were shut off, but otherwise the burners were kept at high fire... 

Installation improvements consisted of creating 2 large cells to confine fire resulting from a sodium leak during a fire period of 30 minutes at a temperature of 1100°C, until the fire stops. The cell dimensions are 24 m high, 15 m wide and 10 m deep (Fig. 1). 

Conventional Sintering Equipment. Like drying furnaces, sintering furnaces (29,76,85) can be periodic or continuous in nature. Periodic kilns offer greater flexibiHty continuous tunnel kilns are more economical. Advanced ceramics are typically siatered in high purity, controUed atmosphere furnaces by electric resistance heating. Ceramic furnaces used to fire traditional ceramic ware are generally heated with inexpensive natural gas, oil, wood, or coal. 

Combustible Dusts Dusts are particularly hazardous they have a very high surface area-to-volume ratio. When finely divided as powders or (dusts, solids burn quite differently from the original material in the bulk. Dust and fiber deposits can spread fire across a room or along a ledge or roof beam very quickly. On the other hand, accumulations of dust can smolder slowly for long periods, giving little indication that combustion has started until the fire suddenly flares up, possibly when no one suspects a problem. 

Polyimide It is a high-cost heat and fire resistant plastic, capable of withstanding 500°F (260° C) for long periods and up to 900°F (482° C) for limited periods without oxidation. It is highly creep resistant with good low friction properties. It has a low coefficient of expansion and is difficult to process by conventional means. It is used for critical engineering parts in aerospace, automotive and electronics components subject to high heat, and in corrosive environments. 

Silica bricks are manufactured from crushed ganister rock containing about 97 to 98 percent silica. A bond consisting of 2 percent lime is used, and the bricks are fired in periodic kilns at temperatures of 1,500 to 1,540°C (2,700 to 2,800°F) for several days until a stable volume is obtained. They are especially valuable when good strength is required at high temperatures. Superduty silica bricks are finding some use in the steel industry. They have a lowered alumina content and often a lowered porosity. 

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