During a recent survey of cathodic protection requirements for a 1128-mile large diameter pipe line, it was noted that a very unusual stray current condition prevailed over the entire pipe line.
Stated briefly, a strong component of direct current was observed to flow with a behavior similar to the general run of pipe line stray currents that originate from electrified railway systems. The current would fluxuate in magnitude and direction, the usual amount of current being between 1 and 3 amperes but frequently attaining values greater than 4 amperes, and with momentary peaks of more than 5 amperes.
Variations in current flows were accompanied by corresponding variations in pipe-to-soil potentials, which would usually range from 1.5 volts negative to 0.6 volt “positive.” At times the stray current surges were sufficiently strong to completely reverse DC loads that were being applied to the pipe line in the course of conducting preliminary...
