scope:

This standard explains the importance of pipeline electrical isolation in achieving and maintaining adequate, reliable, and economical corrosion control. The standard outlines the types of devices used for isolation; precautions to be observed; and selection of devices based on pipeline characteristics, site, and contents. The standard describes isolating flanges, gaskets, sleeves, washers, joints, unions, couplings, and spools, and discusses materials for pipeline casing isolation. Installation, field testing, and maintenance of isolating devices are also included.

This standard describes the application of isolating devices intended only for cathodic protection purposes when voltages across the isolating device are 1 to 2 volts direct current (DC) and the alternating current (AC) exposure does not exceed 15 volts root mean square (rms).(3)

This standard does not discuss situations in which isolating devices are incorporated purely for safety reasons; in those situations, reference should be made to relevant electrical safety codes. Isolating devices shall not be used in enclosed areas where combustible atmospheres are likely to be present.

Isolation of cathodically protected pipelines is recommended to minimize current requirements, facilitate testing and troubleshooting, and improve current distribution.