ANSI Wood Pole Specifications

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ANSI Wood Pole Specifications
Wooden poles are often used for telephone and electric wires. (telegraph pole image by green 308 from

The ANSI specification supplies criteria for pole acceptance in four basic classes: growth characteristics, pole shape, naturally occurring defects and processing defects. Although other wood products have numerous standards, only one stress-graded standard exists for poles. Poles must meet a minimum set of acceptance criteria in order to qualify for the ANSI 05 designated stress classification.

Pole Shape Considerations

Ten per cent of poles shorter than 55 feet in a given lot are permitted a sweep deviation of 1 inch for each 6 feet. For poles longer than 250 feet, up to 25 per cent are allowed the same deviation.

Growth Characteristics

Growth characteristics include the compression of wood, knots, slope of grain and rate of growth. Poles are divided in length classes in order to set knot size limitations. These length categories divide poles into those less than 45 feet or greater than 50 feet long. Knots are permitted in longer poles, and a single large knot is allowed in the top half of a pole, as both the cross-section and the wood strength decrease in proportion to height. The stress of a tree at mid height is typically considered to be half that at the base or ground line. As pole taper is relatively small, the stress encountered at mid height seldom exceeds 60 per cent of that at the base.

Naturally Occurring Defects

Bark inclusions and decay are classified as natural defects, as is any damage that has been caused by the activity of insects. Defects that occur in the outer 2 to 3 inches significantly reduce the bend properties of the wood and are considered defects under ANSI specifications. Inclusions in the bark that are less than 2 inches in depth are acceptable, as is any damage caused by insects that is less than 1/16 inch in overall diameter. Holes and depressions that have been caused by incipient decay are not permitted.

Processing Defects

Processing defects incorporate any damage that has been caused by handling and mishandling. These defects also include splits and checks, which are an unfortunate part of the drying process. Processing defects of this nature do not compromise strength but frequently allow insects access to the wood and eventually become port, from where the wood begins to decay. Splits in the wood of 12 inches are permitted, provided they are at the top of the pole extending downward. Splits that extend upward from the base of the pole are permitted to be twice as long.

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