ScholarsArchive Community: College of Forestry

Conserving energy by environmentally acceptable practices in maintaining and procuring transmission poles for long service

Thu, 29 Jul 1993 22:58:59 GMT

Title: Conserving energy by environmentally acceptable practices in maintaining and procuring transmission poles for long service

Abstract: Evaluation of previously established field trials of internal remedial treatments continues to verify the excellent long-term protection afforded by these treatments. Field trials with gell encapsulated methylisothiocyanate (MITC) demonstrate that gelatin does not interfere with chemical release, nor is addition of supplemental moisture required for release. Field trials have been established to evaluate several new formulations including Basamid plus copper, boron/fluoride rods, and boron rods. Field trials of gelled and pelletized metham sodium indicate that both formulations are moving well through Douglas-fir poles one year after treatment. Evaluations of a copper naphthenate/boron paste for internal treatment indicate that the formulation has moved a short distance from the point of application 3 years after treatment. Boron rod field trials were not fully sampled for residual chemical level this past year; however, evaluation of cores removed from fused borate rod trials in New York indicate that some additional boron diffusion has occurred. Examination of treatment holes suggests that considerable amounts of the boron remain in rod form 2 years after application. In laboratory studies, we have evaluated the use of metham sodium/basamid mixtures and have found that these formulations provide enhanced MITC production over longer periods than either of the components alone. Both formulations were solid, creating the potential for development of safer formulations which provide a rapid release with long term protection. Field trials of these systems will be established in the coming months. Studies also continue with Basamid in an effort to enhance decomposition of this compound. Studies have shown that moisture addition has the most significant effect on decomposition followed by the presence of copper and increasing pH. Further studies on decomposition products are planned to better understand the activity of this molecule. Examination of Douglas-fir timbers treated with metham sodium indicate that MITC levels are similar to those found in poles at similar times after treatment. The presence increased surface area on timbers apparently did not adversely affect diffusion or chemical loss. Evaluation of the fungitoxicity of mixtures of MITC and carbon disulfide is underway in an effort better understand the activity of metham sodium. This compound decomposes to produce a wide array of volatile compounds with varying degrees of toxicity to fungi. Preliminary trials have shown the relatively low toxicity associated with carbon disulfide, a major decomposition product, particularly under acidic conditions. Trials with mixtures will begin shortly. Efforts to develop a three dimensional model of MITC movement are continuing. The model has been evaluated on data collected from small blocks and efforts are underway to verify these results. In addition, full pole grids have been prepared to evaluate the effects of treatment hole geometry and orientation on fumigant movement. Studies to identify alternative treatments for protecting western redcedar sapwood from decay are continuing. A variety chemicals have been shown to be effective 5 years after treatment; however, longer term trials of other formulations suggests that performance declines rapidly at longer time points. Field trials of remedial treatments for field drilled bolt holes continue to demonstrate the performance of diffusible boron and fluoride for preventing fungal attack. These trials will be evaluated again in the coming year. Inspection of the above ground region of Douglas-fir poles in the Pacific Northwest have shown that many poles are colonized by decay fungi far above the groundline. Fungal incidence was greatest in poles near the coast, but decay fungi were also isolated from poles in drier climates. Sampling of additional poles is planned to provide a more detailed analysis of the risk of above ground decay in this region. Efforts are also continuing to evaluate the performance of through-bored Douglas-fir poles to provide better data on the degree of preservative penetration required in the through-bored zone to achieve optimum performance. These trials have shown that most poles are well treated, but no decay has been detected in the through bored zone of poles with as little as 60 % of the through-bored zone treated. Efforts are also underway to evaluate penetration and retention of preservative in poles with various throughboring patterns. Studies to identify optimum conditions for sterilization of air-seasoned Douglas-fir poles are continuing. These trials have evaluated pentachlorophenol in oil treatments. The results illustrate the value of long treatment cycles which incorporate Boulton-seasoning. The data from these trials will be used to construct heating curves for this treatment. Trials of groundline preservative systems on Douglas-fir pole stubs continue to show that more recently developed formulations continue to move through the wood at rates which are similar to those found with older pentachlorophenol based systems. Trials in California on pine, Douglas-fir and western redcedar have provided similar results. Tests are now underway to establish thresholds for mixtures of groundline preservative formulations. Copper naphthenate treated wood continues to perform well in both field and fungal cellar trials. Unweathered western redcedar stakes have tended to perform better than stakes which were weathered prior to treatment. These differences may reflect an increased permeability which enhances leaching.

Conserving energy by environmentally acceptable practices in maintaining and procuring transmission poles for long service

Sat, 29 Oct 1988 22:58:59 GMT

Title: Conserving energy by environmentally acceptable practices in maintaining and procuring transmission poles for long service

Abstract: Evaluations of previously established field trials indicate that chioropicrin, and Vorlex continue to provide protection to Douglas-fir poles, although the degree of protection is diminishing. Reapplication of Vapam 18 years after the initial application eliminated fungi which had recolonized the poles. Methylisothiocyanate (MITC) continues to protect Douglas-fir poles 12 years after application. Gelatin encapsulation of MITC or chioropicrin appears to have no negative influence on fungitoxicity of these chemicals. Application of water to decompose the gelatin accelerated initial chemical release, but had no longterm effects on performance. A series of laboratory trials have been established to evaluate the performance of sodium n-methyldithiocarbamate (NaMDC), the active ingredient of Vapam. This chemical decomposes more slowly than the liquid formulations and a number of additives are being evaluated to accelerated decomposition. Along with the solid NaMDC, a pelletized formulation of Vapam was evaluated which contained 15 or 40 % NaMDC. These evaluations indicated that the addition of water accelerates release, but the fungal survival in these tests was more variable. The results suggest that a dosage 2 times greater than the liquid formulation is required for effective fungal control; however, further tests are planned to confirm these results. The evaluations of MITC-FUME in Douglas-fir and southern pine poles indicated that MITC has moved to a greater extent in Douglas-fir. Both closed tube bioassays and gas chromatographic analyses of ethyl acetate extracts of wood samples indicated that MITC was present at higher levels in Douglas-fir poles. Southern pine is far more permeable than Douglas-fir and MITC movement should be more rapid in this species. Further tests are planned to identify the nature of this delayed movement. 11 Evaluations of Dazomet, a crystalline solid which decomposes tO produce MITC in wood, indicate that detectable levels of this chemical are present in virtually all of the treatment groups. The decomposition rate of this chemical is normally too slow for effective fungal control and these trials are examining the ability of various additives to accelerate decomposition. Further evaluations of pole sections treated with Dazomet and selected additives are underway. A study to evaluate the effect of voids on fumigant effectivness suggests that voids do not adversely affect MITC movement through Douglas-fir pole sections. These results indicate that treatment of voids should be costeffective if the chemical is not applied directly to the void and if the pole retains a sufficient degree of strength. We continue to develop and refine a model for simulating the movement of MITC through Douglas-fir under varying temperature and moisture conditions. The model has been improved to permit three dimensional evaluations, but the times required for computation are still somewhat long. Further evaluations using a variety of environmental conditions are planned. Evaluations of potential replacements for pentachiorophenol for treatment of western redcedar sapwood and field drilled bolt holes have identified several promising alternatives. These chemicals are now under study in several modified field and laboratory tests. Field trials of several potential treatments for field drilled bolt holes indicate that Boracol 40, disodium octaborate tetrahydrate and ammonium bifluoride provided excellent protection over an 8 year period. These formulations all are relatively safe and can be easily applied in the field. 111 A laboratory trial to evaluate the effects of selected basidiomycetes on strength of Douglas-fir sapwood and heartwood has concluded. Fungal density, measured as the average number of fungi colonies per beam, gradually increased in all of the beams while longitudinal compression strength (LCS), modulus of rupture (MOR), and modulus of elesticity (MOE) slowly declined. Of the measurements, LCS appeared to be most useful, probably owing to the increased number of sampling sites per beam. The results indicate that the degree of colonization was not a good indicator of wood strength effects. The value of kerfing for decreasing post-treatment checking and improving the service life of Douglas-fir poles was evaluated using a series of inspection reports from a local utility. Kerfed transmission poles had substantially lower rates of internal decay and rejection, but there appeared to be little difference in the rate of decay between kerfed and non-kerfed distribution poles. The evaluation of disodium octaborate tetrahydrate for preventing colonization of air-seasoning Douglas-fir pole sections has been completed. Spraying with a 10 % boric acid equivalent solution (BAE) at 6 month intervals provided the greatest degree of protection, although dipping in a 20 % BAE solution at the start of air-seasoning produced a similar degree of protection. As expected, fungal colonization was far lower at the dryer Oroville site and borate treatment had little influence on the degree of fungal colonization at this site. The results indicate that borate treatment at the start of airseasoning is a viable method for limiting fungal colonization in moist airseasoning sites west of the Cascade Mountains. Evaluations of the tolerance of Stereum sanguinolentum and Peniophora spp. to elevated temperature exposures indicated that both of these fungi were extremely sensitive to elevated temperatures. The lack of long-term survival structures in these fungi probably accounts for this susceptibility to heat. iv A series of trials which measured internal temperatures in Douglas-fir pole sections during treatment with ammoniacal copper arsenate were used to develop a model for predicting internal heating during steaming. The results indicated that previous heating curves were overly optimistic in their prediction of heating. A series of heating curves for various pole diameters and starting conditions are presented. A number of externally applied groundline treatments are under evaluation in a field trial at Peavy Arboretum and a second trial will be established in the San Francisco Bay area. Seven formulations (including standards) are included. The Peavy site will be sampled in the next few months. The performance of copper naphthenate in western wood species is being evaluated in a series of small western redcedar sapwood stakelets which have been treated to a range of retentions and exposed in the fungus cellar. The results will be used to help confirm the performance of copper naphthenate in this species.

Conserving energy by safe and environmentally acceptable practices in maintaining and procuring transmission poles for long service

Mon, 29 Jul 1985 22:58:59 GMT

Title: Conserving energy by safe and environmentally acceptable practices in maintaining and procuring transmission poles for long service

Abstract: This fifth annual Cooperative Pole Research Program report outlines our progress in the six project objectives. Improved Fumigants Sampling of previously established field tests revealed that Vorlex and Chloropicrin continued to perform well after 15 years, while Vapam was slightly less effective. Solid methylisothiocyanate (MIT) also performed well in the field after 7 years. In additional tests, gelatin encapsulated MIT migrated through Douglas-fir heartwood with addition of moderate quantities of water to degrade the gelatin. However, in the presence of higher quantities of water or no additional water, MIT migration into the wood was slowed. In a previously established test, gelatin encapsulated MIT continues to inhibit reinfestation of poles 3 years after treatment. Pelletized MIT is a new formulation (65% active ingredient) that appears to have some promise. Preliminary tests indicate that up to 95% of the MIT is release in 24 hours, but a small quantity of MIT remains in the pellets after 63 days aeration and may pose a disposal hazard. The solid MIT formulations will permit aboveground applications, increasing the risk that MIT will come in contact with pole hardware. Preliminary tests indicate that MIT had little effect on corrosion of hot dipped, galvanized bolts attached to wood. This suggests that treatment in the crossarm zone with MIT or fumigants that produce MIT should not affect the integrity of attached hardware. i-i In addition to fumigant evaluations, we recently examined an earlier test of groundline treatments with Osmoplastic® and Hollowheart®. After 10 years, these treatments are performing reasonably well, with only a slight rise in the incidence of decay fungi in the past 4 years. We also reevaluated the effectiveness of kerfing for preventing decay and found that this process reduced the depth and width of checks, resulting in a decreased incidence of decay fungi. Kerfing appears to be a valuable method for preventing internal decay at the groundline. Cedar Sapwood Decay Control This past year, the second set of five chemicals applied to control sapwood decay were evaluated after 2 years of exposure. As in earlier evaluations using the Aspergillus bioassay, none of the chemicals approach pentachlorophenol in oil for ability to inhibit sporulation of Aspergillus niger; however, several samples from zones deep in the wood produced a slight zone of effect. This may indicate the presence of a reservoir for long-term protection against decay. Several of the chemicals including Fluor Chrome Arsenic Phenol and Ammoniacal Copper Arsenate (ACA) appear to bind to the wood and may be difficult to detect by the bioassay method. We expect to assess the effectiveness of these treatments using a soil block test. Investigations of the reliability of the Aspergillus bioassay under a variety of conditions indicated that quantity of spores, use of glass or plastic petri dishes, long-term cold storage, and the use of spray inoculum instead of flooding spores had little influence on the bioassay results with pentachiorophenol, Tributyl-tinoxide, or 3 iodo propynyl butylcarbamate; however, incubation temperature did influence assay results. The Aspergillus bioassay is a simple, effective means for estimating residual preservative levels. Bolt Holes Again this year, wood around the unprotected, control bolt holes in pole sections contained such low levels of decay fungi that evaluation of the treated poles will be delayed another year. In addition to the initial bolt hole treatments, we have begun a test to determine if gelatin encapsulated or pelletized MIT can prevent decay development in field-drilled bolt holes. The pole sections used in these tests had already begun to develop decay prior to treatment and will provide an ideal test material. Detecting Decay and Estimatin& Residual Strength of Poles Fluorescent labeled lectins used in our earlier studies detected decay fungi at low weight losses under laboratory conditions. We are currently evaluating this method for detecting fungi in increment cores removed from poles to reduce the need for culturing. Last year we identified a peak that was unique to infrared (IR) spectra of warm water extracts from decayed wood. This past year we attempted to identify the chemical responsible for this peak and found that carbonyl compounds, probably from oxidative lignin degradation, were responsible for the peak. Since brown rot fungi apparently do iv not completely metabolize lignin breakdown products, they accumulate in the decaying wood and can be readily detected by their IR spectra. Strength properties of beams cut front Douglas-fir pole sections, air-seasoned for 3 years significantly decreased although decay fungi could not be uniformly isolated from the beams. In addition, there were gradual declines in work to maximum load and modulus of elasticity, as well as increased Pilodyn pin penetration. These results suggest that some strength losses occurred during air-seasoning; however, the losses were not large and should not endanger pole users. We compared several test methods including the Pilodyn, radial compression tests, longitudinal compression tests, and the pick test for evaluating residual pole strength of the wood surface of Douglas-fir treated with combinations of funtigants or groundline wraps. The results indicate that only the pick test could accurately detect surface damage and illustrate the difficulty of detecting surface damage. This past year we evaluated several sections cut from ACA treated poles stored for a number of years to determine if they were worth salvaging. Static bending tests of beams cut from the ACA treated zone, the treated/untreated boundary, and the inner heartwood revealed ACA treated sapwood had lower MOR and longitudinal compression strength than the other zones. These results represent only a small sample, but they suggest that some strength loss occurs during ACA V treatments. More importantly, the results suggest that we could have reliably predicted beam MOR by testing small plugs removed from the poles. Small beams cut from decaying, pentachlorophenol treated Douglas-fir poles were acoustically tested for residual wood strength, then evaluated to failure in static bending. The acoustic test consisted of sending a pulsed sonic wave into the wood and recording this wave after it passed through the beam. As it moved, the wave was altered by the presence of any wood defects or decay, and these alterations create a "fingerprint" specific for that defect. Preliminary results indicated that signal analysis was highly 2 2 correlated with work to maximum load (r =.82) and MOR (r .88), suggesting that this approach to decay detection may prove more reliable than measuring of sound velocity. Initiation of Decay in Air-Seasoning Douglas-fir The results of the initial survey to determine the incidence of decay fungi in poles from widely scattered Pacific Northwest seasoning yards indicated that a variety of fungi were colonizing the wood. While most of these fungi do not pose a serious decay problem, two species, Poria carbonica and Poria placenta, became increasingly abundant with length of air-seasoning. These fungi are also the most conunon decayers of Douglas-fir poles in service. As expected, the number of fungi and the wood volume they occupied increased with seasoning time; however, this incidence varied considerably between yards, especially in poles air-seasoned for vi shorter time periods. In addition to the variation between sites, many of the decay fungi colonizing the wood appear to be monokaryons, indicating that spores landing on the wood are initiating the infestation. The distribution of fungi within the poles indicated that several of the more abundant decay fungi were present in the outer sapwood where they would be eliminated by conventional pressure treatment. The remaining fungi were most abundant in the heartwood but were more concentrated near the pole end. This suggests that exposed end grain was more readily invaded than lateral grain exposed in checks. In addition to identifying the fungi colonizing Douglas-fir, we examined the effects these fungi had on wood strength. Toughness tests indicated the presence of wide variation in decay capability of the isolates. Although there was no consistent pattern, most of the isolates did not cause substantial decay and, of those that did, only . carbonica and P. placenta were sufficiently abundant to have a large influence on wood strength. Due to the prevalence of P. carbonica and P. placenta in the inner heartwood, where they might not be eliminated in a short heating cycle, we evaluated the temperature tolerance of these two fungi in Douglas-fir heartwood blocks. These tests indicated that both fungi were eliminated by exposure to temperatures above 71°C for over 1 hour or 60°C for 2 hours. The results suggest that careful control of temperature during treatment should eliminate decay fungi and that wood treated at ambient temperatures should be heated to kill fungi that become established during air-seasoning. vii This past year was the third and final year of the decay development study. In this study, sterile pole sections have been exposed for 1, 2, or 3 years at widely scattered Pacific Northwest sites, then returned to the laboratory and extensively sampled. We are now in the process of identifying the fungi from the third year poles. In addition to examining poles prior to preservative treatment, we are also evaluating poles treated with waterborne chemicals (ACA or CCA) for the incidence of surface decay. This past year we examined twenty ACA-treated poles from a line installed in 1946. While a variety of fungi were cultured from the wood, none of the poles had evidence of substantial surface deterioration. A study was initiated on the fungal flora of fumigant treated wood because of the potential for fungi developing resistance to low levels of fumigant or the ability to actively degrade the chemical. Both of these developments could shorten fumigant retreatment cycles and increase maintenance costs. We have evaluated poles treated 7 and 15 years ago with fumigants and find markedly reduced fungal flora. Tests are continuing on the fungi isolated, and we hope to assess the effects of these isolates on long-term fumigant effectiveness.

Conserving energy by environmentally acceptable practices in maintaining and procuring transmission poles for long service

Sun, 29 Jul 1990 22:58:59 GMT