General Order 64-A
Strength Requirements For All Classes Of Lines
Supporting structures and other associated members shall be replaced or reinforced when their respective strengths are reduced to 2/3 of their values given in these rules for installation strength.
In Grades “C” and “F” construction such members shall be replaced or reinforced when their respective strengths are reduced below one half of the values given in these rules for installation strength. Excepted from this are guys in Grade “F” construction which shall be replaced when the safety factor is less than unity. (See App. D for Replacements Tables for poles in Grade “F” construction.)
The application of the two paragraphs above, when applied to Grades “A,” “B” and “C” construction, shall not be held to permit any structure or any member of any structures to depreciate in strength to the point where the safety factor is less than unity.
The advantage of wood treated with coal tar, creosote or other preservative of similar characteristics with regard to electrical resistance, has been demonstrated and is recommended for general use where wood members are involved.