Sterilization to limit pretreatment decay: Internal temperature during kiln drying of Douglas-fir poles

IRG/WP 01-40206

J J Morrell, P G Forsyth, K L Levien

Sterilization to limit pretreatment decay: Internal temperature during kiln drying of Douglas-fir poles. Fungal colonization of poles following peeling has been the subject of considerable concern among electric utilities. While the presence of fungi does not, in itself constitute a risk, the survival of these fungi through the conventional treating processes could allow them to continue to degrade the pole once it is placed in service. Previous research has shown that pressure treatments in heated, oil-based solutions expose the poles to sufficient heat to eliminate established decay fungi. Many treaters in North America are shifting towards kiln drying to reduce treatment times, but there is little data on the internal temperatures in poles during conventional kiln treatments. In this report, we describe field tests to monitor internal temperatures in Douglas-fir poles during treatment. In general, temperatures did not reach the generally accepted lethal target temperature for eliminating fungi from wood (67°C for 75 minutes), but the times when temperatures were between 60 and 65°C approached 40 hours in some charges. Prolonged exposure to these elevated temperatures should also eliminate established decay fungi. The results suggest that internal temperatures during kiln drying reach levels that should eliminate the risk of pre-treatment decay fungi surviving the treatment process.


Keywords: BASIDIOMYCETES; DOUGLAS-FIR; POLES; KILN DRYING; STERILIZATION

Conference: 01-05-20/25 Nara, Japan


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