Interpretation Response #PI-20-0009
Below is the interpretation response detail and a list of regulations sections applicable to this response.
Interpretation Response Details
Mr. Darwin E. Farrar
Public Advocates Office
California Public Utilities Commission
505 Van Ness Avenue
San Francisco, CA 94102
Dear Mr. Farrar:
In a letter to the Pipeline and Hazardous Materials Safety Administration (PHMSA), dated March 10, 2020, you requested an interpretation of 49 Code of Federal Regulations (CFR) Part 192. Specifically, you requested an interpretation of § 192.113 as it relates to the longitudinal joint factor (E) for steel used under § 192.105 to determine a natural gas pipeline design maximum allowable operating pressure (MAOP).
You ask for clarification whether a value of E = 1.0 or E = 0.8 is used to calculate MAOP for steel pipelines with diameter of over four inches, installed after 1970, with an unknown longitudinal joint, and is used in the construction or replacement sections of natural gas pipelines.
You stated that the California Public Utilities Commission recently required its Safety and Enforcement Division to oversee an audit of the MAOP-related records of the Southern California Gas Company and San Diego Gas and Electric Company natural gas transmission Line 1600. You stated, in the Line 1600 case, the longitudinal joint type in certain segments is unknown. However, you stated an auditor who examined the records on the pipeline has stated that because the operator has represented there are no lap weld or furnace butt welds pipe in these segments, an E = 1.0 may be used. You stated this is in contradiction to the requirement under § 192.113 for a type of longitudinal joint that cannot be determined.
You stated that the Public Advocates Office seeks PHMSA's interpretation of the following questions based on the concerns set forth above. PHMSA's responses follow the questions.
Question 1: Are all Line 1600 segments installed after 49 CFR Part 192 was codified in 1970, that are over four inches, and that have an unknown longitudinal seam type, required to have a longitudinal joint factor of no greater than 0.8, assuming it is conclusively determined that such segments do not contain lap welds or butt welds (which would necessitate a longitudinal joint factor of no greater than 0.6)?
PHMSA Response: Yes, the table included in § 192.113 states that if the type of longitudinal joint cannot be determined, the joint factor to be used must not exceed that designated for "Other." For "Other" pipe over 4 inches (102 millimeters) the longitudinal joint factor E is 0.8. Methods for determining the pipe joint factor can be based upon factors, such as whether the pipe diameters, wall thicknesses, yield strength, and manufacturing period are applicable for that seam type. Also, the seam type can be determined based upon inspections of the pipe, such as excavations of the pipe or pipe removals.
Question 2: Given the applicable ASA [American Standard Code for Pressure Piping] standards establishing MAOP, dating back to 1955 and continuing until the codification of 49 CFR Part 192 in 1970, is it proper to assume a longitudinal joint factor of no greater than 0.8 for pipe segments installed during that period, which have unknown longitudinal seam types, and which are over four inches in diameter, even if it is conclusively determined that such pipes do not contain lap welds or butt welds?
PHMSA Response: If the longitudinal seam type of a pipeline is unknown, a value of E equal to 0.8 must be used in § 192.105 for determining the design pressure of pipelines with a diameter greater than 4 inches.
If the pipelines' MAOPs were established prior to 1970, under the § 192.619(c) requirements, the operators can operate them under those established MAOPs. However, a segment of pipeline that has been relocated or replaced cannot be returned to service without meeting the testing requirements under § 192.503, as well as the design and pressure test requirements in § 192.619(a)(1-2).
Question 3: Where the answer to question 1 or 2 is yes, does the resulting required reduction of the longitudinal joint factor from 1.0 to 0.8 also require that when the design is based upon MAOP required under 49 CFR § 192.105 to be reduced by 20%, assuming all other inputs into that formula are accurate and are otherwise unchanged?
PHMSA Response: Yes, since the MAOP is determined based on the design pressure requirements in § 192.105, and with E being a proportional factor in the equation in § 192.105, then a reduction of E from 1.0 to 0.8 is a 20% reduction in MAOP.
If we can be of further assistance, please contact Tewabe Asebe at 202-366-5523.
John A. Gale
Director, Office of Standards
|Longitudinal joint factor (E) for steel pipe