General Order 64
Section VI
Detail Construction Requirements For Supply Lines
62 Crossarms, Pins Conductor Fastenings.
(a)
Strength
of Crossarms and Conductor Fasteners:
The minimum size of crossarms used to support conductors shall be 3 ¼
inches by 4 ½ inches of Douglas fir, or size to give equivalent strength if of
other material.
Crossarms shall have
sufficient strength (greater when necessary than that provided by the minimum
dimensions given above) to withstand, with the specified safety factor, the
loadings given in section V. In addition,
they must be able to withstand the application of an unbalanced pull of 700
pounds in the direction of the line at the outer pin.
Crossarms shall be securely
supported by bracing in order to withstand all vertical loads, including the
weight of the men working on them.
Pins, ties or clamp
conductor fastenings used in connection with pin insulators shall have
sufficient strength to withstand a tension in the conductor of 700 pounds per
pin or fastening as a minimum.
Note - A standard 1 ½ inch by 9 inch locust pin provides strength up to 1000 pounds tension in the conductor, with the conductor 3 ½ inches above the crossarm. Steel pins afford greater strength than wooden pins. Double crossarms may be used as crossings or at points of excessive stress, in order to provide sufficient strength. Special types of dead end construction may be necessary in order to provide the proper safety factor. Crossarm guys are sometimes used in connection with the above.
(b) Painting: All crossarms supporting supply conductors in excess of 750 volts shall be painted a bright yellow color or in lieu thereof there shall be placed on the face and back of each crossarm a sign showing in white letters not less than 3 inches in height on a green background “HIGH VOLTAGE.” The provisions of this paragraph shall not be held to apply to crossarms supporting supply conductors in excess of 17,000 volts, which are situated in rural districts.
(c) Low Voltage Racks: Where racks are used for the support of low voltage wires (0-750 volts) the clearances provided in Tables 1 and 2 must be maintained.