Field Liners as physical barriers to prevent wooden utility pole decay in soil: An accelerated field simulation trial

IRG/WP 08-20384

A R Howgrave-Graham, L J Cookson, T Hale

Field Liners (FL’s), plastic sleeves used to protect in-ground wooden poles from fungal and termite damage, have been tested before as physical barriers to prevent contact between soil and wood and to retain wood preservative treatment. These earlier studies concentrated mostly on creosote preserved poles and early generation FL’s which were cumbersome in their application. The newer generation Field Liners were designed for simpler installation. Renewed interest in their application has emerged in Australia in light of dwindling supplies of suitable timber to use as utility poles. In light of this, and previous ‘hurdle theory’ publications, some Australian utility distribution companies commissioned a study to determine whether these new generation FL’s would work under Australian conditions. An accelerated field simulation trial using posts (with and without Field Liners and/or H1 retentions of ACQ preservative treatment) in fungus-rich soil was conducted in a purpose-designed facility maintained at constant high temperature and humidity. Posts were examined periodically for decay over 19 months. Decay was first noticed at the six month inspection, when a treated Eucalyptus cladocalyx and an untreated Eucalyptus globulus control (without Field Liners) had decayed slightly. No E. cladocalyx or E. globulus posts with FL’s had any decay. After 19 months, all eight untreated control posts had significant soft rot throughout their sapwood. All eight ACQ-treated posts without FL’s had 1-8 mm decay through their sapwood. All four ACQ-treated posts with FL’s had no evidence of decay while two of the four unpreserved posts with Field Liners had slight decay adjacent to the small hole/vent at the bottom of the FL’s where post-soil contact occurred. It is not recommended that FL’s be used as sole protection for untreated poles. Reduced preservative retentions in poles with FL’s may be considered in order to reduce the amount of preservative used, or poles which have lower natural durability in the heartwood could also be considered.

Keywords: field liners, ACQ, accelerated field simulator, utility poles, plastic wraps

Conference: 08-05-25/29, Istanbul, Turkey

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