Over the last three years, a new system for measuring the cathodic protection potential of subsea pipelines has been developed. The equipment consists of a dual silver/silver chloride electrode probe, mounted on a remote controlled submarine, a silver/silver chloride reference electrode which is maintained at a distance from the pipeline and support ship, and a monitor console. As the submarine moves along, over the pipe, the monitor console records the cathodic protection potential profile and radial field gradient on a continuous chart recorder and also on a strip printer. At intervals, contacts with anode bracelets or bare pipe are used to calibrate the system. A complete potential profile is obtained, together with measurements of current density on damaged areas, and anode output currents.
Typical results obtained from a number of North Sea pipelines are discussed.