Interpretation Response #PI-98-009
Below is the interpretation response detail and a list of regulations sections applicable to this response.
Interpretation Response Details
Mr. David A. Hippchen
Gas Pipeline Safety Section
West Virginia Public Service Commission
PO Box 812
Charleston, WV 25323
Dear Mr. Hippchen:
This responds to your letter of July 13, 1998, regarding the gas pipeline safety standard on electrical isolation in 49 CFR 192.467(f). Our answers to your inquiries are set out below. Section 192.467(f) reads as follows: "Where a pipeline is located in close proximity to electrical transmission tower footings, ground cables or counterpoise, or in other areas where fault currents or unusual risk of lightning may be anticipated, it must be provided with protection against damage due to fault currents or lightning, and protective measures must also be taken at insulating devices."
Question 1. Is close proximity an absolute distance or some minimum distance at which interference with the pipeline corrosion control system or damage to the pipeline coating can be measured or calculated?
Answer. Considering the purpose of § 192.467(f), "close proximity" means near enough to the listed structures to reasonably expect that a lightning strike or fault current involving the structure might harm the pipeline's corrosion control system. Close proximity is not an absolute or minimum distance, and it could vary depending on site conditions. Under § 192.453, the distance must be determined by a person qualified in pipeline corrosion control methods who has knowledge of the circumstances. Thus, we have not determined whether the distances you listed in situation #2 are within a close proximity of the structures.
Question 2. Can an operator adopt an absolute distance standard to define close proximity?
Answer. Please refer to the answer to Question 1.
Question 3. What threshold voltage measurement/calculation is reasonable to determine if protective measures must be taken?
Answer. Section 192.467(f) does not specify a threshold voltage in connection with protective measures. This voltage would be determined by a person qualified in pipeline corrosion control methods.
Question 4. What constitutes an electrical transmission line (and thus, tower) for which this section applies?
Answer. Under § 192.467(f), the term "electrical transmission tower" is used in its ordinary sense to refer to tall aboveground steel structures that support cables used to transmit electricity over long distances. The term does not include poles that support cables used to distribute electricity throughout a community.
Question 5. Can this section be read to include protecting the pipeline from induced currents?
Answer. No, protection is required only against fault currents and lightning.
I trust you find this information helpful. If we can be of any further assistance, please call me at (202) 366-4565.
Richard D. Huriaux, P.E.
Office of Pipeline Safety
|§ 192.467||External corrosion control: Electrical isolation|