Field Methods for Measuring Off-Potentials on a Buried Pipeline in Challenging Conditions

A literature survey was performed and several field methods that can be useful to measure the “off” potentials on a buried steel pipeline were found and summarized. These methods were developed prior to and evaluated in the 1980s. Field validation tests showed great performance of these methods. The advantage of these methods is that they can be used without the need of interrupting all current sources or when there is existence of stray current. Although this advantage may not be obvious when the -850 mV “on” potential criterion is used, it becomes very useful if an “off” potential criterion is required and the current sources cannot all be interrupted. This paper reports the theory behind each method, field validation results, and practical procedures for using the methods.