In some species and species groups, many pieces with high post-drying
moisture content (wet pieces) are present after kiln-drying of lumber.
Often, they cannot be economically eliminated by equalization, especi
ally for dimension lumber for which a 15 percent average final moistur
e content is desirable. A mill study was conducted in which lumber (2-
by 8-in. hem-fir) was sorted after being dried; any wet pieces were r
edried in a separate kiln. The results indicate that 14 percent less t
otal kiln time is required at a given production rate if 20 percent of
the pieces are redried. Kiln-operation expenses are reduced by $4.56
per thousand board feet (MBF). Average lumber value is increased by $9
.40/MBF because of reduced overdrying. Additional material-handling co
sts were $1.95/MBF. Gross profit margin increased by $12.01/MBF. The p
ayback period for the additional equipment installed to sort and resta
ck wet pieces was 6 months.