Below-Grade Corrosion Control of Transmission, Distribution, and Substation Structures by Coating Repair Systems
|Publication Date:||10 December 2014|
This standard provides a procedure that shall be used to (1) identify electric transmission, distribution, and substation structures that may be at higher risk for below-grade coating degradation; (2) excavate and inspect the selected structure; (3) assess the level of risk to the structure in terms of corrosion attack and degradation to the existing coating system; (4) prioritize structures to be repaired based on those findings as to whether coating repair is needed and if so, to what extent; and (5) apply repair coatings to the structure, if applicable.
This standard is limited to assessment and repair of coating applied below grade and in the transition zone portions of carbon steel and galvanized steel electric transmission towers, grillage, and substation structures. It does not address assessment and repair of coatings above the transition zone. For the purposes of this standard, this area comprises of the below-grade portion, the transition zone, and is defined as that portion of the coating exposed up to 600 mm (24 in) above grade.
This standard does not address structural damage assessment, structural repairs, weathering steel, or structural integrity. This standard does not address concrete foundations or above-grade attachment points including anchor rods, attachment nuts, and noncoated ground sleeves. This standard does not address continuous immersion environments. This standard does not provide guidelines and repair procedures for coating systems for every specific situation because of the complexity and diverse nature of conditions to which buried structures may be exposed.
Purpose-This standard provides guidelines and repair procedures for coating systems most commonly applied to belowgrade electric transmission structures and typical of what inspection and coating repair crews most often find.