Furnaces ovens

The concentration of fuel in air in a process should be maintained at or below 25 percent of the LFL, with automatic instrumentation and safety interlocks however, up to 60 percent of LFL is permitted by the NFPA—except for ovens or furnaces. (Ovens and furnaces are covered in NFPA 86.)... 

Ofen-trocknung, /. kiln (or oven or stove) drying. -tlir, -tiire, /. door (esp., the fire door) of a furnace, oven, kiln or stove (Ceram.) wicket, -verkokung, /. coking in ovens, -ziegcl, m. fire brick stove tile, -zug, m. furnace (or oven or kiln) draft, offen, a. open (of sound) hollow clear, clever, frank. — offener Dampf, direct steam, live steam. 

Some door gaskets in furnaces, ovens, and wood and coal stoves may contain asbestos. The asbestos-containing door gaskets on wood and coal-buming stoves are subject to wear and can release asbestos fibers under normal use conditions. Handle the asbestos-containing material as little as possible. 

Practically all p3n ometric installations are designed as an aid in furnace or oven operation. Some of the factors which work difficulty in the regulation of furnaces, ovens, kilns, tanks, etc., are (1) Inconstancy of heat supply. (2) Variation of internal absorption or generation of heat. (3) Variation of heat lost by radiation, convection, etc. (4) Unsteady supply or composition of material to be heat treated. 

For medium or low temperature furnaces/ovens/dryers operating below about 1400 F (760 C), a forced recirculation furnace or recirculating oven delivers better temperature uniformity and better fuel economy. The recirculation can be by a fan and duct arrangement, by ceiling plug fans, or by the jet momentum of burners (especially type H high-velocity burners—fig. 6.2). 

If the flames are developed in the heating chamber proper, as in figure 1.1, or if the products of combustion (poc) are circulated over the surface of the workload as in figure 3.17, the furnace is said to be direct-fired. In most of the furnaces, ovens, and dryers shown earlier in this chapter, the loads were not harmed by contact with the products of combustion. 

Warning Do not count on any continuous furnace always running at a continuous rate. Every furnace, oven, dryer, heater, boiler, and incinerator has to start up from cold or cool down from hot occasionally therefore, designers and operators should build in flexibilities that will avoid damage to equipment and product during noncontinuous situations. 

In summary, the authors wish to quote some wise points from Mr. Ralph Ruark s article in the July 2001 Ceramic Industry (pp. 27-30) on What to Avoid when Buying a Kiln (reference 76), much of which also applies to buying a furnace, oven, dryer, melter, incinerator, boiler, heater. 

Sankey diagram = a visual aid to understanding the disposal of heat released in a furnace, oven, boiler, or kiln— by use of arrows of widths proportional to the magnitude of the heat flow. 

The capability to use substitute energy sources means that the combustors (e.g., boilers, furnaces, ovens, and blast furnaces) of a facility had the machinery or equipment either in place or available for installation so that substitutions could actually have been introduced within a specific time period without extensive modifications. 

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