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Pressure Treatment of Eucalyptus Camaldulensis Poles with Oil-borne Preservative.

M. Younus-uzzaman
Research Officer
Wood Preservation Division, Bangladesh Forest Research Institute, P.O. Box 273, Chittagong-4000, Bangladesh.

Khurshid Akhter
Research Officer
Wood Preservation Division, Bangladesh Forest Research Institute, P.O. Box 273, Chittagong-4000, Bangladesh.

Abstract/ Executive Summary:

Eucalyptus camaldulensis poles were treated with 50:50 creosote-light diesel oil mixture. The poles contained an average of 53.85% sapwood which was readily perishable by wood destroying organisms if untreated. The poles were treated by the Bethel Full-Cell process using varying pressure and duration to evaluate the effect on penetration and retention of the preservative mixture. It was found that with the simultaneous increase of both treating pressure and time, no significant increase in pent ration was achieved. On the other hand, with the increase of treating pressure only, the retention of preservative in the sapwood was increased significantly. A penetration of 3.5 cm with retention of 318.45 kg/m³ in the treated sapwood could be obtained by using 10.57 kg/cm² pressure for 3 hours. This amount of penetration is considered adequate to protect the sapwood region of the pole.

Keywords: Heartwood, Oil-borne preservative, Penetration, Retention, Sapwood, Eucalyptus

Location: Wood Preservation Division, Bangladesh Forest Research Institute, Chittagong.

Start Date: 01-07-1994

End Date: 30-06-1995

Program Area: Postharvest and Agro-processing

Commodity: Eucalyptas

Objectives:

To determine the optimum treating schedule of Eucalyphes camaddulernsis by pressure with 150 to 218 kg of 50:50 creosote-light diesel oil mixture per cubic meter.

Methodology:

Seventeen E. camaldulensis poles of about 7.62 to 8.3 m long were collected from 12 years old plantation of Silviculture Research Station, Charaljani, Dinajpur. Both the outer and the inner barks of the poles were removed. It was necessary to scrape the poles with a metal scraper to remove the inner bark (Hunt and Garratt 1967). The poles were then stacked for air drying in open shed for reducing the moisture content of the poles up to 20-25 percent. Before treatment all the poles were sized into requisite length (3 m long), and the average thickness of sapwood, heart wood, diameter, percentage of sapwood and heart wood zone were given below.

Average diameter of pole : 17.70 cm

Average thickness of heart wood zone : 11.60 cm

Average thickness of sapwood zone : 2.70 cm

Maximum thickness of sapwood zone : 3.26 cm

Minimum thickness of sapwood zone : 2.16 cm

Average length : 3.00 m

Average percentage of sapwood zone : 53.85%

Average percentage of heart wood zone : 46.15 %

A mixture of creosote and light diesel oil in the ratio of 50:50 was used as preservative in this study. Sufficient quantity of this mixture was made and stored in the rueping tank of the treating plant and then surged for several hours for thorough mixing. Before each charge, the preservative was preheated in the rueping tank to about 85⁰C with a view to maintain its temperature at 82⁰C after it was transferred to the treating cylinder. Pre-dried pole samples were first weighed and then treated by Bethel Full-cell process (Findlay 1985, Hunt and Garratt 1967). In each treatment three pole samples were subjected to an initial vacuum of 508 mm mercury for an hour. Three treatment pressures such as 7.04 kg/cm², 8.80 kg/cm² and 10.57 kg/cm² and three treatment durations such as 1 hr., 2 hrs. and 3 hrs. were designed factorially, and the temperature was kept fixed at 82⁰C. On completion of the treatment, the samples were finally weighed.

Source of Information: Bangladesh Journal of Forest Science Vol. 28 (1) : 47-53, 1999.

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Eucalypts heartwood is typically difficult or very difficult to penetrate with preservatives applied by conventional pressure treatment. However, sapwood is not difficult to treat with preservatives to requisite levels of penetration and retention. Eucalyptus poles under study were found to have an average sapwood of 2.70 cm thick surrounding a heartwood of average 11.6 cm diameter, occupying 53.85 percent of its total volume on the average. Although the average thickness of sapwood was 2.70 cm, almost all the poles under study had sapwood zone of 2.50 cm thick. It appeared that if 2.50 cm was taken as the optimum depth of penetration for the poles, 100 percent poles would be treated as per specifications of Bangladesh Standard on Code of Practice of Wood preservation. An average penetration of 2.97 cm was achieved when treated with 7.04 kg/cm² for three hours.

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