{"operation":"document","citation":"PI-72-033","title":"ADB 72-8 — Pipeline Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"1972-08-01","effective_on":null,"summary":"PI-72-033 response to ADB 72-8 concerning 192.457.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-72-033.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-72-033.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-72-033","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/Pipeline/1972/PI72033.pdf","body":"<<<PAGE 1>>>\n\nINTERPRETATIONS OF REGULATIONS\nRelates to 49 CFR, §192.457\nOPS has been requested to provide further clarification of an Interpretation on the two-electrode\nsurface potential survey method for locating areas of active corrosion, which appeared in the\nAdvisory Bulletin 72-8, August 1972.\nOPS Interpretation:...\"Your letter suggests that the \"leap-frogging' technique is no longer in use\nand that, therefore, it may not be appropriate to refer to it. However, the interpretation quoted in\nthe Bulletin was in response to a specific question, and, as indicated 'leap-frogging' is not useful\nfor Dresser-coupled pipelines with insulated joints. On the other hand, the 'leap-frogging' surface\npotential survey method is being successfully used for locating areas of active corrosion on\nelectrically continuous pipelines. As your letter recognizes, the purpose of 'leap-frogging' is to\ncompensate for electrode potential differences. While we recognize that there is equipment\navailable today which makes it unnecessary to use 'leap-frogging,' the leap-frogging technique\nremains available for use on electrically continuous pipelines.\n\"Your letter also states that the two-electrode surface potential survey method is the most\nsatisfactory approach for providing Dresser-coupled pipelines with adequate cathodic protection.\nTo the extent that you are referring to the use of two electrodes in continuous contact with the\nearth, we agree. The proper technique provides for a continuous voltage difference measured\nbetween one electrode placed over the pipeline and the other electrode located five feet from the\npipeline and perpendicular to the pipeline. The survey is normally conducted on both sides of the\npipeline to identify existing galvanic anodes.\"\nJoseph C. Caldwell\nDirector\nOffice of Pipeline Safety\nDB\nC:\\WP51\\INTERPRT\\192\\457\\72-08-01\n1","truncated":false,"body_characters":1859}