PDF Publication Title:
Text from PDF Page: 045
lumber to a higher humidity than the humidity to which it was exposed just before going into the dryer. (The exception is in equalizing and conditioning, when there is no risk of degrade.) Therefore, with very wet lumber (Stage I), begin the schedule at the indicated first step of the schedule. However, do not inject moisture into the dryer's atmosphere during heat-up of the dryer and warming of the lumber. If moisture is added, it is likely that it will condense on the cool lumber, thereby increase the lumber's MC. With partially dry lumber (Stage II or III), it is even more critical to avoid adding moisture back to the lumber. Doing so will greatly increase the extent of surface checking, honeycomb, and warp. Therefore, the best way to start-up the kiln is to measure the MC of the surface of the lumber (a moisture meter is the most reasonable way to get this MC - just touch the needles to the surface; don't drive them into the wood) and then set the initial kiln EMC to be 0%, 1%, or 2% below the surface MC. After 12 to 24 hours, these conditions are then gradually changed to the conditions required in the schedule. In any case, however, never let the start-up conditions be drier than the level recommended in the schedule. The choice of 0%, 1%, or 2% is based on the risk of checking and the quality of the lumber up to this point. If the species has little risk and is in good shape, then use 2% below. In most cases, especially with oak, 1% is the recommended value. With lumber with checks or other degrade, then 0% would be best (but even then, damage can occur). In all cases, the dry-bulb can be the setting recommended in the schedule, or lower. With predried lumber entering the kiln directly from the warehouse predryer (and not stored outside), the EMC in the kiln should be 1% or 2% lower than the EMC in the predryer. Equalizing and Conditioning Procedures Equalization is accomplished by setting an EMC in the kiln that is 2% or 3% below the average final MC desired. For example, if the average final MC is 7% (i.e., 6 to 8% MC), then the equalization MC is (7 - 2 =) 5% or (7 - 3 =) 4%. The lower EMC does not provide as good of machining and gluing quality. The required equalization settings are presented in Table 9. Equalization begins when the driest sample reaches 2% (or 3%) below the average target final MC. The higher the temperature, the faster drying will continue. Usually, the temperature used is the same as the final step in the schedule. Equalization continues until the wettest sample reaches the target final MC. For 7% target, equalization begins when the driest sample reaches 5% and continues until the wettest reaches 7%. At this point all lumber in the kiln, if samples are properly taken, will be between 5 and 7% MC. 45PDF Image | Principles and Practices of Drying Lumber
PDF Search Title:
Principles and Practices of Drying LumberOriginal File Name Searched:
DryingLumber.pdfDIY PDF Search: Google It | Yahoo | Bing
5,000 BF Shipping Container Lumber Dry Kiln For Quality Lumber The 5,000 BF container kiln consists of one 40 foot high-cube aluminum shipping container... More Info
Shipping Container Lumber Dry Kilns by Global Energy Global Energy designed and developed the container kiln back in 1991. The purpose is to give access to portable sawmill owners, furniture makers, and small business the value added profit of dry kiln lumber and quality hardwoods... More Info
Vacuum Kiln Conversion Kit for Lumber and Wood Dry Kilns Convert your existing conventional dry kiln into a fast drying vacuum kiln. Similar to vacuum bagging in the boat building and aircraft industry, we have come up with a proprietary process which allows you to build a very simple vacuum kiln at a fraction of the price, and without the intensive conventional metal chamber structure... More Info
Vacuum Pump Cart System for Bagging Clamping Wood Drying and more Vacuum Cart with 2HP Pump and Dual Pistons with multiple multiplex vacuum ports and liquid reservoir... More Info
Vacuum Bagging Basics Vacuum bagging is a method of clamping, which has traditionally been used in the composites industry, but can also be used for vacuum drying materials, including wood products... More Info
| CONTACT TEL: 608-238-6001 Email: greg@globalmicroturbine.com | RSS | AMP |