Skid pipes

Rotary Hearth Furnaces Rotary hearth furnaces have no water-cooled skid pipes, so the soak zone can be less than one-fifth of the total furnace length. Very rapid heating results in a short heating zone, but requires a long soak zone for thick material. Rotary hearth furnaces have problems, such as ... 

See figure 8.13 for cooling-water heat losses for the previous components of a typical skid pipe system—all in Btu/sq ft of bare pipe surface, even for cases where the bare pipe is covered with insulation. 

Fig. S.13. Cooling-water heat losses to skid pipe systems. All but the 3" insulation curves are courtesy of Bloom Engineering Co., Inc.

Modern full insulation reduces heat loss from pipes by more than 85%. The volume of cooling water required is less. Figure 9.3 shows a typical arrangement of skid pipes and supports for a pusher reheat furnace. 

Fig. 9.3. Insulated water-cooled skid pipe and support arrangement for a pusher type furnace.

Fig. 9.4. Some types of skid pipe and support pipe insulators. Courtesy of Plibrico Company.

Fig. 9.10. Double-high skid pipes admit more radiation from the bottom zone to the loads than do single-high skid pipes, which must be wider for the same load bearing capacity. Equally spaced skid rails (top view) average more heat transfer to the load s undersides than do unevenly spaced rails lower view)—by a ratio of 0.61 0.57 for one speoific set of dimensions.

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