As kiln design and technology have evolved, we have seen a shift in both kiln equipment specification and drying schedules. Nearly all the changes have their root in the economics of either building a kiln or operating a kiln. A good example is the main fan design, where the first kilns had one electric motor placed outside the kiln chamber with large steel shafts running down the length of the kiln. As electric motors have become less expensive relative to a large shaft running down the length of the kiln we have seen a shift toward the more logical design of: "one motor per fan". During this evolution we have seen a steady increase in the main fan capacity to dry lumber at lower temperatures in order to improve drying quality.
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Older kilns |
Newer kilns |
Comments: |
| Control systems |
Vapor tension temperature controls |
Computerized and networkable |
The benefits of computerized kiln controllers with networking and information collection can help improve your kiln performance significantly and reduce energy costs. |
| Air circulation |
Less |
More |
The larger fan capacity can be controlled using frequency controls or interval fan operation. |
| Heating |
More heat surface |
Less heat surface |
Older kilns needed more heat surface to transfer the heat to the air at higher drying temperatures. Steam was commonly used on older kilns, whereas today you have more options. |
| Venting |
Less venting, no power. |
More venting andpower exhaust |
Drying with lower temperature requires more venting, since each cubic meter or foot of air carries fewer moisture grains. |
The above comparison is only a general guide and should help you understand the need for different kiln schedules between new and older kilns. It is also important to understand this evolution when trying to convert older kiln schedules to a modern kiln.
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