Abstract
The problem faced by the engineer seeking to cathodically protect a buried pipe line is to find the best and most economical way to drain from certain selected points on the line sufficient current to give adequate protection. Three basic methods to this end are placing the line under full protection, placing the line under partial protection and calculating the requirements for complete protection, both using, temporary installations; and measuring the electrical characteristics of the line and calculating its behavior under various proposed systems.
The fourth method—an empirical estimate—is more important than its nature would indicate because certain assumptions based on observation and experience usually are helpful in arriving at a final conclusion.
Principal problems also faced by the engineer are those of securing electrical continuity where joints other than welded are used and insulating the line from other buried structures.
The author recommends a procedure involving steps such as: Determining static potentials, draining interrupted current from selected points and from data thus collected determining the relationship between polarization and driving voltage and attenuation of driving voltage; computing desired effect of combinations of drainage currents.
Also discussed are such questions as technique for making potential readings, various means of plotting data for best use, what constitutes “adequate” protection, where the electrode should be placed in making potential readings and other matters.
