You are here

Interpretation Response #PI-76-026


Below is the interpretation response detail and a list of regulations sections applicable to this response.

Interpretation Response Details

Response Publish Date: 05-25-1976
Company Name: American Society of Mechanical Engineers' (ASME)    Individual Name: George L. Mocharko
Country: US

View the Interpretation Document


Response text:

May 25, 1976

Chief, Technical Division
Chief, Regulations Division
George L. Mocharko
American Society of Mechanical Engineers' (ASME)

Request to Revise Section 192.465

ASME has requested that the Office of Pipeline Safety Operations (OPSO) revise 49 CFR Section 192.465 by including the following as an alternate method for monitoring cathodically protected facilities:

"Where electrical test methods for evaluating and monitoring are impractical or are ineffectual in applying the criteria for cathodic protection in Appendix D of this Sub-Part; annual leakage surveys, and, corrosion and leak history studies, may be used to verify and monitor the effectiveness of cathodic protection and other corrosion control procedures."

Review:

Corrosion accounts for the largest number of repaired leaks each year. The minimum Federal safety regulations contained in Subpart I wee promulgated and became effective as of August 1, 1971, to provide the highest degree of protection for the public from leak incidents attributed or caused by corrosion. In that corrosion is the largest single problem which is controllable, within the operators capacity, from a technical feasibility and economic practicability standpoint; it would be an anomaly to revise Section 192.465 as stated by ASME. If safe operations is the goal as set by OPSO, corrosive control measures must be instituted before leaks occur. Monitoring is the only means by which the operator can prevent a hazard which can become detrimental to public safety.

Technical Summary:

  1. Cathodic protection is an electrical method of preventing corrosion on metallic structures (such as pipelines in electrolytes) and involves electro-chemistry. Therefore, it is illogical to monitor or verify whether or not cathodic protection has been installed to prevent corrosion or is at adequate levels to control corrosion with annual leakage surveys, and corrosion and leak history studies.
  2. There has been no systematic attempt to develop direct results or corrolation [sic] between gas leakage or leaks to cathodic protection or severity of corrosion, hence, electrical surveys, measurements, and tests are the only acceptable technology for monitoring or verification. It appears operators would like to just conduct post mortem leak surveys rather than any preventative surveys. This is supported by the contract studies OPSO had initiated, such as Technical report No. OPS-TR-71-001, "Ferrous Pipeline Corrosion Processes, Detection and Mitigation," and Contract DOT-OS-40190,"Study on Current Practices, Technologies Problems, and Recommendations Relating to Overall Safety of Gas Pipeline Distribution Systems," and NTSB accident reports. The TR-71-001 report stated, "At this time the best indicator of pipeline corrosion appears to be close monitoring and interpreting of pipe potentials. Since it is current leaving the buried structure that causes corrosion, the optimum measurement would be the determination of current leaving the structure." The DOT-40190 study stated, "Corrosion accounts for the largest number of repaired leaks each year. Improvements are needed in the overall understanding of the corrosion process and methods for better determination of active corrosion and assessment of applied cathodic protection. The methods now used by gas utilities to determine the physical condition and integrity of their pipelines are largely based on detecting and locating leaks. This procedure is essentially after the fact and largely precludes preventative maintenance. Efforts should be promoted to develop methods for identifying and locating deteriorating conditions before failure occurs and leakage ensues."

Conclusions:

  1. The ASME has not provided adequate supportive information to justify the statement that electrical surveys are ineffectual and impractical for determining the adequacy of cathodic protection in distribution system. In fact, they have only summarized the variables that knowledgeable corrosion control persons have worked with for many years.

    They have also strengthened the position that OPSO has taken in the requirements of Section 192.453. "Each operator shall establish procedures to implement the requirements of this Subpart. These procedures, including those for the design, installation, operation and maintenance of cathodic protection, must be carried out by, or under the direction of, a person qualified by experience and training in pipeline corrosion control methods."
  2. The proposed ASME revision is not technically sound and would have the effect of shielding imprudent operators for liability to the public as well as penalize the prudent operators who have met the monitoring requirements of Section 192.465. However, OPSO should consider some sort of relief for the distribution or transmission operators with regard to conducting electrical surveys. OPSO should take a serious look at the time requirements of all surveys in the Federal standards to determine priority of performance to enhance safety.
  3. Surveys--One area of particular concern to the operators involves the monitoring of"hot spot" cathodic protection in active corrosion areas. More Information is needed to determine whether or not using a statistical sampling - probability approach as a method of monitoring or some other type of risk analysis be used to monitor the effectiveness of cathodic protection.

'signed'

George L. Mocharko


Regulation Sections

Section Subject
§ 192.453 General