Interpretation Response #PI-70-0102
Below is the interpretation response detail and a list of regulations sections applicable to this response.
Interpretation Response Details
Equitable Gas Company
July 27, 1970
Mr. Lance F. Heverly
Office of Pipeline Safety
Department of Transportation
Washington, D.C. 20590
At the Harco Seminar held on June 23, 1970, at Cleveland, Ohio, it was stated that the gas servicing companies would be responsible for applying and maintaining cathodic protection to gas service lines, including those lengths of such service lines not installed and/or owned by the servicing companies. Please advise if this statement is still true and if the statement also includes other buried gas lines such as "house lines" that are installed and owned by the customer and are defined as such lines extending beyond the gas meter?
Since both the National Association of Corrosion Engineers Standard RP-01-69 and the office of Pipeline Safety's proposed Requirements for Corrosion Control (Notice 70-8: Docket No.OPS-5) do not satisfactorily discuss or define the effects of stray direct currents imposed upon gas pipe lines, will the Office of Pipeline Safety accept the controlled removal of such currents from effected pipe lines as a method of affording cathodic protection to these lines wherein such protection is being afforded only when such currents are being removed from the lines? As you know, there are locations where large amounts of such currents influence pipe lines wherein the requirement to provide continuous cathodic protection to such lines could be technically impossible, as related to the present manners and devices used today to provide continuous cathodic protection measures to pipe structures located in certain stray direct current area.
Very truly yours,
C. M. Rutter
111 South Commons
Pgh., Pa. 1521
September 24, 1970
Mr. Charles M. Rutter
111 South Commons
Pittsburg, Pennsylvanis 15212
In reply to your letter of July 27, 1970, Department of Transportation's jurisdiction would stop at the downstream side of the customers meter, if the meter is next to the customer's house. However, since our jurisdiction covers the distribution of gas, it is difficult to say just where it would stop if the meter should be at the property or curb line. Our General Counsel is currently studying this problem to determine just where our jurisdiction should end. As stated at Harco's Seminar, the gas company is really the only one that is in a position to know whether or not the service line from a meter at the property line to a house is protected. Obviously, the property owner ordinarily does not have the know-how or measuring equipment to check the corrosion condition of his service line.
As an example of the recognition of the seriousness of this situation, Tulsa, Oklahoma, has a City ordinance whereby a service line belonging to the customer has to be coated, electrically isolated at the house and separately cathodically protected. The work is done by a licensed plumber who has to make the installation in accordance with this city ordinance. However, it is the gas company, Oklahoma Natural Gas Company, that routinely checks the customer's service line and if the company finds that the service line is not protected, it reports its findings to the city inspector. You may wish to get in touch with Orville W. Everett, Chief Corrosion Engineer for Oklahoma Natural Gas Company, for further details.
So as to clarify paragraph 192.491, Control of Interference Currents, what would you think of adding a couple of sentences to paragraph (b) along the following lines:
"Joint interference testing either individually or through local electrolysis committees, must be made to determine if adjacent underground metallic structures are subjected to adverse interference currents. If adverse interference is found, appropriate measures must be taken to minimize such inference; yet maintain protection on the operator's structure in compliance with the protective criteria contained in paragraph 6.3 of the 1969 edition of NACE Standard RP-01-69."
Automatic potential control (APC) rectifiers, that is, solid state silicon controlled rectifiers (SCR), have immediate response (1/2 cycle) and are especially good in areas where a pipeline is subjected to rapid stray current fluctuations. If I remember correctly, the way to estimate the cost of APC rectifiers is 1.25 x base price of standard rectifier unit + $300. You may wish to get in touch with Tom P. Wilkinson, Marketing Manager, Good-All Electric, Incorporated, 201 S. Spruce Street, Ogallala, Nebraska 69153, for information on APC type rectifiers.
Lance P. Heverly
Assistant Chief, Technical Div
Office of Pipeline Safety
|External corrosion control: Electrical isolation