255.467 External corrosion control: electrical isolation.

(a)Each buried or submerged pipeline must be electrically isolated from other underground metallic structures, unless the pipeline and the other structures are electrically interconnected and cathodically protected as a single unit.#

(b)One or more insulating devices must be installed where electrical isolation of a portion of a pipeline is necessary to facilitate the application of corrosion control.#

(c)Except for unprotected copper inserted in a ferrous pipe, each pipeline must be either electrically isolated from any metallic casing that is part of the underground system or, if isolation is not achieved because it is impractical, must be treated by other measures to minimize corrosion of the pipeline inside the casing.#

(d)Inspection and electrical tests must be made to assure that electrical isolation is adequate.#

(e)An insulating device may not be installed in an area where a combustible atmosphere is anticipated unless precautions are taken to prevent arcing.#

(f)Where a pipeline is located in close proximity to electrical transmission tower footings, ground cables or counterpoise, or in other areas where fault currents or unusual risk of lightning may be anticipated, it must be provided with protection against damage due to fault currents or lightning, and protective measures must also be taken at insulating devices.#

(g)For any pipeline constructed after December 1, 1993 that is located parallel and in close proximity to or crosses underneath an overhead high-voltage (69 kV or higher) electric transmission facility, the step and touch voltages induced by magnetic fields of overhead electric lines under steady state conditions shall be limited to 15 volts or less at all points where a person could normally touch the pipeline or a pipeline appurtenance. This does not apply to buried pipelines or to locations where access is limited by use of fences or barriers to personnel that are trained in safe practices regarding step and touch voltages. The short term emergency loading condition of the circuit as defined by the New York Independent System Operator for the electric facility shall be used in determining the magnitude of such step-and-touch voltages.#

(1)Step voltage means the root mean square voltage difference between any two points on the ground surface separated by one meter (approximately the distance of one step) in the direction of the maximum voltage gradient.#

(2)Touch voltage means the root mean square voltage difference between any point on the ground where a person may stand and any point on the pipeline or its appurtenances which can be touched simultaneously by either hand.#