Tunnel furnace

Surface Flammability of Building Materials Using a 8 Ft. Tunnel Furnace, 1984. Critical Radiant Flux of Floor Covering Systems Using a Radiant Heat Energy Source [NIST(NBS) Flooring Radiant Panel], 1993. 

In the ASTM E84 25-foot tunnel furnace test (34) for measuring flame spread of building materials, an igniting pilot flame is applied to the underside of a horizontally mounted specimen. The flame heats the combustible material to pyrolysis, and the flammable gases given off are ignited by the pilot flame. 

Eickner and Schaffer (10) found that monoammonium phosphate (Figure 2) was the most effective of different fire-retardant chemicals in reducing the flame-spread index of Douglas-fir plywood. They used the 8-foot tunnel furnace of ASTM E286 (37). 

Figure 2. Relationship of flame spread to level of chemical retention in 3/8-in. Douglas fir plywood evaluated by the 8-ft tunnel furnace method...

Figure 7. Importance of fuel nitrogen content. All data taken in AR/O2/CCL, tunnel furnace, ultrasonic nozzle, 5% excess 02 (Reproduced with permission from Ref. 16. Copyright 1979, The Combustion Institute.)...

ASTM E 286-85 Standard Test Method for Surface Flammability of Materials Using an 8-ft (2.44-m) Tunnel Furnace, 9 pp (Comm E-5)... 

Chamber and muffle furnace Tunnel furnace Fluid bed... 

Fire tests in a 25-foot tunnel furnace were carried out according to standard ASTM E84 by the Underwriters Laboratory and the Hardwood Plywood and Veneer Association. Results are given for the flame spread index (FSI) and smoke developed index (SDI). The values obtained from burning the test materials represent a comparison with that of Va inch inorganic reinforced cement board expressed as zero and red oak flooring expressed as 100. 

Test samples were fir boards 244 cm in length using three sections measuring 51 x 1.3-cm wide by 244-cm long for a total specimen length of 732 cm, coated with fire-protective composition S ASB for indoor application. Maximal temperature in the tunnel furnace was approximately 370°C. 

True specimen volume, 402 TT Electronics (AEI), 172 Tunnel furnace, 461 25-ft tunnel test, 461... 

Cameras monitor and record material flow processes in reheat furnaces, vacuum degassers, continuous casters, blastfurnaces, electric arc furnaces, continuous annealers, galvannealers, tunnel furnaces, and other operations. 

Chamber furnaces are the most common furnace construction. Their actual design has been adapted in many sub-forms in order to meet the needs of the differing thermal treatments of various types of casting and production. Some examples of chamber furnaces are bogie hearth furnaces, top hat furnaces, hub open-hearth furnaces, etc. Chamber furnaces with continually running conveyance means are called tunnel furnaces. Heating is provided either electrically, or with gas or fuel oil. 

Other forms of straight-line continuous furnaces are woven alloy wire belt conveyor furnaces used for heat treating metals or glass lehrs (fig. 1.5), plus alloy or ceramic roller hearth furnaces (fig. 1.6) and tunnel furnace s/tunnel kilns (fig. 1.7). 

Conveyorized tunnel furnaces or kilns may be stretched versions of their batch equivalents, divided into several zones. Many types of conveyors are used. Figure 4.6 shows... 

Example 6.1 This is a case study of a 45 ft (13.7 m) diameter donut (see glossary) rotary hearth furnace, similar to figure 1.8, that was having problems with low production capacity. The inside cross-section dimensions of the donut-shaped, circular gas and load passageway (a circular tunnel furnace) are 4.5 ft (1.37 m) high x 12 ft (2.66 m) wide. Most of the furnace gas flow is counter to the load movement. 

This material usually contains only small amounts of residual carbon or boron carbide but no metals, and is thus the favored process for the technical synthesis of less contaminated borides. The process is carried out in tunnel furnaces under hydrogen or in a vacuum at 1600-2000°C, i.e., below the melting point of the boride. It is thus a reaction sintering procedure yielding a high-porosity product which can easily be crushed and milled. Additional refinement is obtained by multiple vacuum treatments with metallic or B4C additives to compensate nonstoichiometries. The final product is then called vacuum quality . 

Manufacture of refractory bricks by baking in small batches was not economical. Lot of fuel was wasted, and time was required to heat and then cool the batches. Hence, the baking operations were then carried out in a long tunnel furnace with heat recovery (air preheating using heat of hot bricks from exit end). 

In the procedure of ASTM E 286-1969 (reapproved 1975), a horizontal light beam is measured in the vertical vent pipe of the 2.44-m tunnel furnace (cf. Section 3.2.1, Fig. 3.94). The smoke density index (4) is determined in a similar way as in the method of ASTM E 84-198la. 

Thorium tetrafluoride is produced fairly readily by reacting the pure oxide with anhydrous hydrogen fluoride by a typical dryway technique. A simple tunnel furnace made of inconel may be used, with inconel trays. A 98 per cent yield can be obtained in about 10 hr at 5S0°C, using an excess of the fluorinating agent. 

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