Protection of utility poles

Transcription

1 Protection of utility poles Analyses of premature failures Risk of infection New protection systems Antje Gellerich, Holger Militz

2 Analyses of premature failure of utility poles

3 Introduction Service life of utility poles quality of preservative treatment soil conditions maintenance According to German electric power companies, wooden poles should have a minimum service life of years Within the last years failures of wood poles were observed before this predicted service life

4 Introduction Investigation of 18 utility poles of Scots pine treated with a copper-chromium wood preservative Poles from different lower voltage transmission lines in Germany (states Nordrhein-Westfalen and Rheinland-Pfalz) Service life was between 3 and 13 years Poles were replaced in 2010 because of their insufficient structural stability Investigations of sections from the ground line level

5 Experimental method Investigation of fungal decay Macroscopic and microscopic evaluation of decay and fungal identification Molecular diagnostics of fungi Analyses of Cu content Determination by sulphuric-nitric acid pressure digestion technique and ICP-AES

6 Results The macroscopic evaluation of the pole sections displayed two types of decay mechanisms: Strong decay in the sapwood area Strong decay in sap- and heartwood areas

7 Results Pole no. Type of decay Identified fungi 1 Brown rot * 2 Brown rot/soft rot * 3 Brown rot Antrodia spp. 4 Brown rot Antrodia spp. 5 Brown rot Antrodia vaillantii 6 Brown rot Antrodia vaillantii 7 Brown rot Antrodia vaillantii 8 Brown rot * 9 Brown rot Antrodia vaillantii 10 Brown rot Antrodia vaillantii 11 Brown rot Antrodia vaillantii 12 Brown rot/soft rot * 13 Brown rot * 14 Brown rot Antrodia vaillantii 15 Brown rot Antrodia spp. 16 Brown rot/soft rot * 17 Brown rot Antrodia spp. 18 Brown rot/soft rot * * - no genera or species of fungi identified

8 Results Pole no. Cu content <1,5 kg/m³ 1,5kg/m³<3kg/m³ 3kg/m³ 1 1 x 2 x 3 x 4 x 5 x 6 x x 9 x 10 x 11 x 12 x 13 x 14 x 15 x 16 x 17 x 18 x - No analyses accomplished due to initial material properties 1 a minimum of 3 kg/m³ copper content (in relation to the outer 3 cm of treated zone) are required according Technical Specification (introduced 2006) of the electric power company)

9 Results Determination of Cu content (undecayed areas) Fungal attack occured in a wide range of Cu content Below and above toxic values Results can give only a tendency and not an exact value during service life of the poles

10 Summary Most of the investigated poles were infested by copper tolerant brown rot fungi of Antrodia spp. The attack reduced the service life from predicted years to just 3-13 years The copper tolerant fungi seem to have preferred growth conditions which probably cause a selective fungal growth around the poles

11 Summary Recommendations to avoid fast infestation by copper tolerant fungi directly after replacement of an attacked pole: The impregnation quality (distribution and retention of wood preservative) must be guaranteed following the given rules The infested soil should be treated or removed Growth barriers around the pole will help to reduce the direct contact of the pole with mycelia

12 Investigations of the risks of infection

13 Project description Laboratory tests Adapted ENV 807 tests with different soil from field test sites Field tests Different test sites with different soil classes Possible solutions Treatment of soil Additional treatment of poles

14 Project description Laboratory tests Field tests Possible solutions Treatment of soil Additional treatment of poles

15 Results Selected test sites and soil showed different fungal activity very aggressive test sites with brown rot activity particularly in the area around the pole (mainly copper tolerant fungi) moderate aggressive test sites with combined brown and soft rot activity No relation between soil type and activity was found Activity is site-specific and not (only) soil specific

16 Results Treatment of soil is limited Use of fungicides is restricted particularly at agricultural areas Shift of ph-value due to soil treatment is limited Increase of fungal activity between ph 4 and 5.5 No influence of fungal activity until ph 7.5 Decrease of fungal activity at ph higher 9 Additional treatment of poles possible Physical barriers (bandage solutions) Envelope treatment

17 Fürstenberg Permadur - System Poles are protected with metal foil (brass) and a shrink sleeve in ground/air zone Protection against wood decaying fungi Reduced erosion of preservatives

18 Fürstenberg Permadur - System Investigation of poles in use No signs of decay after 3 years in use No visual signs No irregularities during sound test with a hammer Wood moisture content was above fiber saturation in the area of the shrink sleeve and metal foil Wood moisture content much lower in areas above the shrink sleeve Further monitoring necessary to clarify the influence of different wood moisture contents to fungal infestation and crack performance

19 Joint Research Project New protection technology to substitute creosote for the protection of railway sleepers, timber bridges and utility poles (CreoSub) Together with Norway and United Kingdom Investigations of oily and water based wood preservatives

20 Substitute products for creosote Substitute products for creosote Impregnation of utility poles in semi-industrial scale with oily products Impregnation with an empty cell process (adopted from creosote and optimised) Envelope treatment Impregnation with a water based product After fixation impregnation with an oily product Both treatments are possible also with new oily products

21 Durable LVL for Poles Project : LVL-Mast Partners: Funding: Fachagentur für Nachwachsende Rohstoffe e. V. (FNR) Sascha Bicke, Vladimirs Biziks, Holger Militz

22 Durable LVL for Poles Development of durable Softwood LVL Impregnation with wood preservatives Optimization of Impregnation process Structural development and testing of innovative pole-systmens (induo)