{"operation":"document","citation":"PI-71-088","title":"Cathodic Protection Service — Pipeline Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"1971-12-20","effective_on":null,"summary":"PI-71-088 response to Cathodic Protection Service concerning 192.463.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-71-088.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-71-088.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-71-088","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/Pipeline/1971/PI71088.pdf","body":"<<<PAGE 1>>>\n\nDecember 20, 1971\nMr. Ted L. Canfield\nSenior Project Manager\nCathodic Protection Service\nP.O. Box 66387\nHouston, Texas 77006\nDear Mr. Canfield:\nIn reply to your letter of November 18, 1971, to Lance Heverly, following are our comments on\nyour interpretation of certain sections of Subpart I, the corrosion part of our Federal gas pipeline\nsafety standards.\nYour letter states:\n\"(a) Bare piping (distribution or transmission) under influence of impressed current\nprotective systems:\nInitial survey and resurvey to consist of acquiring structure-to-earth potential\nmeasurements at maximum 20' intervals over the entire length of line or system being influenced\nby a given impressed current system. This resurvey procedure to be conducted on an annual\nbasis.\n(b) Bare piping (distribution or transmission) under complete protection with magnesium\nanodes (i.e., supposed protection of entire surface area):\nInitial survey and resurvey procedure to be same as outlined above for bare piping\nunder influence of impressed current protective systems.\"\nIt is our position that when a bare distribution or transmission pipeline is under full cathodic\nprotection, regardless of whether the protection is provided by an impressed current type system\nor by galvanic anodes, the system must be checked at least once a year in accordance with Section\n192.465(a) and the level of cathodic protection must meet the requirements of Section 192.463.\nWe do not stipulate any distance intervals for making pipe-to-soil potential measurements.\nAlthough checking at 20-foot intervals may be appropriate in some instances, conditions could be\nsuch that no less than continuous inspection would be necessary. Our requirement is that the\ncathodic protection system must protect the pipeline in its entirety. It is the operator's\nresponsibility to determine what spacing is required between pipe-to-soil potential measurements\nto ensure that the pipeline is protected in its entirety. (If your firm is the consultant to a gas\ndal\\192\\463\\71-12-20\n1\n\n<<<PAGE 2>>>\n\noperator, the operator will be looking to you for advice as to what spacing frequency is necessary\nto comply with the regulations.)\n\"(c) Bare piping (distribution or transmission) which has been electrically surveyed to\ndetermine areas of current discharge and subsequently provided with galvanic anode installations\n(\"hot spot\" protection) at points or areas of previously determined current discharge.\nResurvey procedure to consist of resurveying annually 10% of a given system or\nline to determine that the structure is receiving a net protective current at the previously\ndetermined current discharge points. A different 10% is to be surveyed each year so that the\nentire system will have been resurveyed within a ten year period.\nFurther, that, at intervals not exceeding three years, a complete survey to be\nconducted over the entirety of a given bare line or system under \"hot spot\" protection to\nreevaluate unprotected portions and protect where active corrosion is detected. (This would\nappear to be somewhat in conflict with the 10% per year resurvey program). By way of\ncommentary here, we can see that this requirement as written could certainly prove to be very\nwasteful of scarce technical manpower. If the reevaluation survey is to be meaningful, so as to\npick up the possibly one newly developed \"hot spot\" areas every three (3) years for each 100\noriginally detected, it must still be conducted as thoroughly as the original survey.\"\nWith regard to the first two paragraphs of your statement (c), we wish to point out that the 10%\nresurvey per year applies only to separately protected service lines or to separately protected short\nsections of mains not in excess of 100 feet (Section 192.465). The 10% resurvey does not apply\nto \"hot spot\" protection. Monitoring tests of \"hot spot\" protected sections of electrically\ncontinuous pipelines must be made each year. (After all, this would require less work than\nchecking a bare pipeline that is cathodically protected in its entirety using galvanic anodes as\ndescribed in your statement (b).)\nWith regard to the third paragraph of your statement (c), when \"hot spot\" protection is involved,\nthe operator must resurvey his bare pipeline at intervals not exceeding three years, and provide\ncathodic protection in each area where active corrosion is found (Section 192.465(e)).\nYour letter also asked about the estimated date when the existing HM-6 code for liquid pipelines\nwill conform to the present natural gas code in respect to corrosion control. Although we may in\nthe future make those requirements essentially the same, we do not at this time have a schedule\nfor the necessary rule-making action. However, in regard to the questions which you have raised,\nthe two codes are quite similar. In the case of gas pipelines, complete resurveys are required\nevery three years instead of every five years as required for liquid pipelines.\ndal\\192\\463\\71-12-20\n2\n\n<<<PAGE 3>>>\n\nIn response to your question about gathering lines, the Natural Gas Pipeline Safety Act of 1968\nrequires that gathering lines in non-rural areas must meet our safety regulations. Section 2(3) of\nthe Act gives a detailed explanation of non-rural locations (copy of Act enclosed).\nI trust this information will be helpful to you.\nSincerely,\nJoseph C. Caldwell\nActing Director\nOffice of Pipeline Safety\nEnclosure\ndal\\192\\463\\71-12-20\n3\n\n<<<PAGE 4>>>\n\ncathodic protection service\nNovember 18, 1971\nOffice of Pipeline Safety\nDept. of Transportation\n800 Independence Ave., S.W.\nWashington, D.C. 20590\nAttention: Mr. Lance F. Heverly\nAsst. Chief, Technical Division\nGentlemen:\nOur present understanding of intent of contents of Title 49, Part 192, Subpart I -\nRequirements for Corrosion Control, with respect to survey and resurvey procedure for bare\npiping systems are set forth below. Your concurrence or correction of our interpretation is\nsolicited.\n(a) (b) (c) Bare piping (distribution or transmission) under influence of impressed\ncurrent protective systems:\nInitial survey and resurvey to consist of acquiring structure-to-earth\npotential measurements at maximum 20' intervals over the entire length of\nline or system being influenced by a given impressed current system. This\nresurvey procedure to be conducted on an annual basis.\nBare piping (distribution or transmission) under complete protection with\nmagnesium anodes (i.e., supposed protection of entire surface area):\nInitial survey and resurvey procedure to be same as outlined above for bare\npiping under influence of impressed current protective systems.\nBare piping (distribution or transmission) which has been electrically\nsurveyed to determine areas of current discharge and subsequently\nprovided with galvanic anode installations (\"hot spot\" protection) at points\nor areas of previously determined current discharge.\nResurvey procedure to consist of resurveying annually 10% of a given\nsystem or line to determine that the structure is receiving a net protective\ncurrent at the previously determined current discharge points. A different\ndal\\192\\463\\71-12-20\n4\n\n<<<PAGE 5>>>\n\n10% is to be surveyed each year so that the entire system will have been\nresurveyed within a ten year period.\nFurther, that, at intervals not exceeding three years, a complete survey to\nbe conducted over the entirety of a given bare line or system under \"hot\nspot\" protection to reevaluate unprotected portions and protect where\nactive corrosion is detected. (This would appear to be somewhat in\nconflict with the 10% per year resurvey program). By way of commentary\nhere, we can see that this requirements as written could certainly prove to\nbe very wasteful of scarce technical manpower. If the reevaluation survey\nis to be meaningful, so as to pick up the possibly one newly developed \"hot\nspot\" area every three (3) years for each 100 originally detected, it must\nstill be conducted as thoroughly as the original survey.\nIn addition, is there available an estimated date at which time the existing HM Code for\nliquids will conform to the present Code for Natural Gas Pipelines with respect to corrosion\ncontrol?\nIt would appear at this time that gathering system piping is excluded from Subpart 1 of the\nCode. Is this the intent or does the exposure to critical class location determine necessary\ncompliance?\nYour cooperation in providing the requested information will be greatly appreciated and\nwill enable us to better assist our clients in conforming to the code requirements.\nVery truly yours,\nCATHODIC PROTECTION SERVICE\nTed L. Canfield\nSenior Project Engineer\ndal\\192\\463\\71-12-20\n5","truncated":false,"body_characters":8627}