{"operation":"document","citation":"PI-81-009","title":"Florida Public Service Commission — Pipeline Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"1981-03-31","effective_on":null,"summary":"PI-81-009 response to Florida Public Service Commission concerning 192.755.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-81-009.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-81-009.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-81-009","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/Pipeline/1981/PI81009.pdf","body":"<<<PAGE 1>>>\n\nMarch 31, 1981\nMr. C. Edward Mills\nSenior Utilities Engineer\nElectric & Gas Department\nFlorida Public Service Commission\nFletcher Building, 101 East Gaines Street\nTallahassee, Florida 32301\nDear Mr. Mills:\nYour letter of February 26, 1981, to Mr. L. D. Santman, Director, Materials Transportation\nBureau (MTB), asks four specific questions relative to methods to be used to determine\ncompliance with 49 CFR Part 192, Appendix D, Criteria 1-A(5). Following are your questions\nand the MTB answers:\nQuestion 1. Does the current reversal technique of applying sacrificial anodes to corrosion\n\"Hot Spots\" on steel gas distribution pipelines meet the criteria for cathodic protection as defined\nin 49 CFR Part 192, Appendix D, Criteria 1-A(5)?\nMTB Answer. Yes! Any one of the five criteria listed in Appendix D may be used.\nQuestion 2. If the technique described in the above question is acceptable, is it also acceptable\nwhen the current reversal has been measured only on one side of the pipeline?\nMTB Answer. Measuring current reversal only on one side of the pipeline may not be adequate\nto show a net protective current from the electrolyte (soil) into the structure surface. Stray\ncurrents and the pattern of protective current flow could give false indications from measurements\ntaken on only one side of the pipeline that would show what appears to be adequate cathodic\nprotection when in fact the pipeline is corroding.\nQuestion 3. Is the same technique acceptable when the remote-from-pipe reference half-cell\nelectrode (two electrode method) is placed over, across or in the immediate vicinity of other\nunderground metallic structures?\nMTB Answer. MTB is now conducting a contract study that involves the conducting of electrical\nsurveys on pipelines located under paving and in areas with other underground structures. At this\ntime, we do not believe that the corrosion of other underground structures would produce enough\ncurrent to override the protective current unless the other underground structure is bare and\nunder high levels of cathodic protection.\ndal\\192.3\\Appx-D\\81-03-31 1\n\n<<<PAGE 2>>>\n\n2\nQuestion 4. Is the same techniques acceptable when conventional HRVM (high resistance volt-\nmeters) instruments are used to ascertain current reversal in lieu of the McCollum earth meter\nmethod of determining current flow to anodic areas of pipeline surface?\nMTB Answer. Yes! Several MTB staff members have experience using HRVM with the two\nelectrode method for measuring earth currents. Qualified personnel should be able to do this\nadequately.\nWe trust this information meets your needs relative to assuring compliance with 49 CFR Part 192.\nSincerely,\nMelvin A. Judah\nActing Associate Director for\nPipeline Safety Regulation\nMaterials Transportation Bureau\ndal\\192.3\\Appx-D\\81-03-31 2","truncated":false,"body_characters":2811}