Robert W. Erickson, Professor Emeritus Department of Bioproducts and Omar Espinoza, Assistant Professor Biosystems Engineering

Improved Wood Utility Poles

Facts About Wood Utility Poles Technical Characteristics of Invention Benefits • Wood utility poles provide an This engineered wood pole will have the following benefits excellent support for overhead Creation of the Parent Flitch compared to conventional wood poles: transmission, distribution, and communications lines1,are • A hollow pole uses approximately reasonably priced, non-conductive, 60% of the material required for and easy to install. conventional wood poles. • There are approximately 135 • It is easier and more effectively million wood utility poles installed Boards of random-width and length are edge-glued to form treated against biological attack. in the United States, and are a parent flitch of the thickness and area required to produce • Wood of low moisture content replaced at a rate of 1.5 million per the octagon-shaped pole or portions thereof. contributes to higher dimensional year2. The average life span for a stability and much lower weight. conventional wood utility pole is Stave Retrieval • It’s weight is about half of that for its 30-40 years. conventional wood counterpart. www.nrel.gov • The most recognized standards for buying and designing This facilitates ease of manufacture, transportation, and wood poles is the ANSI O5.1. Most wood poles are 45ft. installation. in length and a butt-end diameter of 12 in.3. • Allows for more efficient utilization of our renewable • Common species for wood poles are Southern Yellow forest resource. Saw lines Pine, Douglas fir, Jack Pine, Lodge pole Pine, Pacific • An engineering approach creates greater flexibility in Silver Fir, Red Pine, and Western Red Cedar4 Staves are sawn as shown, with near zero waste of wood. designing for different shapes, sizes and strength • The most common chemical treatments for wood utility requirements. It also provides an opportunity for marrying poles are pentachlorophenol in heavy oil, chromated Assembly of the Staves into the Octagon-Shaped Entity a performance enhancing material, such as fiberglass, to copper arsenate, and creosote2. the structural wood components. Some disadvantages of conventional wood poles are: Remaining Work The following activities need to be carried out before • Prone to decay, especially at or near ground line. commercial-scale production of the octagon-shaped pole: • They are heavy. A typical 45ft Class 4 Red Pine pole weighs approximately 1,100 pounds. • Prototype construction. • Prime trees are required for conventional wood poles. • Testing according to ANSI standards. • Inadequate preservative treatment. Shrinkage during in • Further development of manufacturing process . line service will expose untreated wood that is subject to • Feasibility analysis of commercial-scale production. decay. • Due to the natural variability in the physical properties of References The staves, with adhesive applied, are nested into the trees, a high safety factor is required in conventional 1. Morell, J.; Clauson, M.; and Love, C. 2011. Forest Products Journal. wood poles. octagon shape. Modest pressure is applied to the nested 61(1):28–30. staves via a few strapping devices. An air-tight cap is 2. Anders Wood, A.; Reddy, D.; and Koganti, R. 2008. The Environmental applied to each end of the hollow pole, one of which Impact of Utility Poles. Value Proposition http://engineering.dartmouth.edu/~cushman/courses/engs171/UtilityPoles.p contains an air-line fitting through which a vacuum pump df “An engineered hollow wood pole, that meets evacuates the hollow core. The resulting difference in air 3. Wolfe, R. and Moody, R. Undated. Standard Specifications for Wood Poles. specifications, conserves wood, has a longer service life pressure applies uniform pressure to the glue-lines. For U.S. Department of Agriculture. Forest Service. Forest Products Laboratory. and a cost of manufacture that is equal to or less than that Madison, WI. http://www.fpl.fs.fed.us/documnts/pdf1997/wolfe97b.pdf example, at a 10 psi. differential, each square inch of the 4. Anonymous. 2011. Wood Utility Pole Life Cycle. The Environmental Literacy for its conventional counterpart” external surface area receives 10 lbs. of force. Council. http://www.enviroliteracy.org/article.php/1311.html