Determining MAOP

The current NPRM for Safety of Gas Transmission and Gathering Pipelines will likely change some of the processes for determining MAOP. However the following interpretation provides additional insight into establishing MAOP.

Interpretation 192.619, # 69

January 23, 2015

Mr. Joseph P. Como
Acting Director, Office of Ratepayer Advocates
California Public Utilities Commission
505 Van Ness Avenue
San Francisco, CA 94102

Dear Mr. Como:

In a letter to the Pipeline and Hazardous Materials Safety Administration (PHMSA) dated December 4, 2013, the Office of Ratepayer Advocates (ORA) requested a regulatory interpretation of 49 CFR 192.619 regarding the maximum allowable operating pressure (MAOP) for natural gas pipelines. Specifically, ORA asked if the consideration of design pressure in § 192.619(a)(1) is required for pipelines that were placed in service before July 1, 1970. ORA asked whether an operator must use the design pressure in§ 192.619(a)(1) as the MAOP for a segment of pipeline that was placed in service before July 1, 1970, if the design pressure is the lowest pressure from the methods set forth in§ 192.619(a). In addition, ORA informed PHMSA that the California Public Utilities Commission (CPUC) no longer permits gas operators within its jurisdiction to rely on the “Grandfather Clause” in§ 192.619(c).

ORA attached PHMSA’s letter objecting to the Oklahoma Corporation Commission’s (OCC) Waiver of Compliance, PHP-08-0074, dated March 17, 2008, and stated that it believes that letter to mean that an operator must calculate and consider the design pressure to determine the MAOP of pipelines installed prior to July 1, 1970, as well as after that date. ORA asked if its understanding is correct. ORA stated that the letter’s discussion was about distribution lines and asked PHMSA to confirm that a MAOP calculated under§ 192.619(a) cannot exceed design pressure for transmission pipelines installed prior to July 1, 1970.

ORA informed PHMSA that in a recent hearing held by the CPUC, Pacific Gas & Electric Company (PG&E) asserted that it is not required to consider design pressure for a pipeline placed in service before July 1, 1970, that has been subject to a Subpart J strength test. ORA stated that PG&E’s reasoning was that”§ 192.619(a)(l) is forward-looking and applies only to segments of new pipeline installed after 1970, the year the Federal regulations became effective.” ORA’s letter stated that PG&E believes that the regulations aVow it to operate a pipeline placed in service prior to July 1, 1970, at a MAOP based on its strength test pressure under § 192.619(a)(2) even if the design pressure is lower.

ORA stated that it disagrees with PG&E’s interpretation because:

Section 192.619(a) does not state the design pressure is inapplicable to pipelines installed before July 1, 1970;

The MAOP requirements under § 192.619 are part of Subpart L, which govern safe operating conditions, and the requirement in§ 192.619(a) appears to be a mandatory safety precaution; and

ORA believes the above mentioned PHMSA letter to the OCC confirms that the design pressure provision applies to lines placed in operation prior to July 1, 1970.

Section 192.619(a) does not state the design pressure is inapplicable to pipelines installed before July 1, 1970;

ORA asks the following questions, and PHMSA’s answers are below:

Question 1: When validating the MAOP of pipeline segments placed in operation before July 1, 1970, and still in operation today, is the operator required to calculate and consider the design pressure pursuant to§ 192.619(a)(1)?

Response: Section 192.619(a) states: “No person may operate a segment of steel or plastic pipeline at a pressure that exceeds a MAOP determined under paragraph (c) or (d) of this section, or the lowest of the following: …. ” Paragraphs (a)(1)- (a)(4) then specify four pressures which must be calculated in order to determine the MAOP. Therefore, the answer is yes.

The operator of a pipeline that was placed into service before July 1, 1970, must determine MAOP in accordance with§ 192.619. If§ 192.619(a) is used to determine MAOP, the operator must calculate the design pressure in accordance with§ 192.619(a)(l), and use the design pressure or a lower pressure as the MAOP if that is the lowest of the four pressures described in paragraphs (a)(l)- (a)(4). If applicable, an operator may also use the “Grandfather Clause” in § 192.619(c) to determine the pipeline segment’s MAOP.

Over time, changes in the population density surrounding a pipeline segment will affect the class location and MAOP of a pipeline. Section 192.613 requires operators to have a procedure for continuing surveillance of its facilities to determine and take appropriate action concerning changes in class location. When there are changes to population density along a pipeline segment, § 192.609 requires the operator to conduct a class location study, and § 192.611 details the requirements for confirming or revising the MAOP according to the new class location.

Paragraph (d) of§ 192.611 requires the operator to confirm or revise the MAOP within 24 months of the change in class location. If an operator fails to confirm or revise the MAOP within 24 months of the change in class location, then§ 192.611 cannot be used and the pipeline segment MAOP must be calculated in accordance with§ 192.619(a), using the design factor that appears in§ 192.111 for the new class location.

The CPUC may impose more stringent MAOP regulations by establishing them through state law. PHMSA does not interpret state regulations.

Question 2: If the answer to Question 1 is yes, must the operator use its design pressure as the MAOP when the design pressure is the lowest pressure calculation required by § 192.619(a)?

Response: Yes, if the Grandfather Clause in§ 192.619(c) or the alternative MAOP option in § 192.619(d) is not applicable. If the operator uses§ 192.619(a) to determine MAOP, the MAOP would be equal to the lowest value calculated according to paragraphs (a)(l)- (a)(4).

For a pre-July 1, 1970 pipeline segment, the operator must determine the MAOP in accordance with§ 192.619(a) unless the operator has documentation that meets the§ 192.619(c) requirements for the entire pipeline segment and elects to use it to establish MAOP.

If an operator uses§ 192.619(a) to determine the pipeline segment MAOP, the operator must have records to substantiate the calculations required in paragraphs (a)(1)-(a)(4), including the properties of pipe and pipeline components. Paragraph (a)(l) requires that the pipeline design pressure be determined in accordance with Subparts C and D, including§ 192.105 which states that the pipeline design pressure must be based upon the current class location design factor and the actual pipe properties which include yield strength (grade), wall thickness, longitudinal joint factor (seam type), maximum operating temperature and pipe’ diameter. If the pipeline segment contains pipeline components such as bends, fittings, flanges or valves, the operator would need to determine the design pressure of these pipeline components in accordance with applicable sections of Subparts C and D of Part 192.

If an operator uses the Grandfather Clause in§ 192.619(c) to establish the MAOP, the operator must have documentation of the pipeline segment’s condition and operating and maintenance history, including historical pressure records for the maximum operating pressure to which the entire pipeline segment was subjected during the five years prior to July 1, 1970. The Grandfather Clause in§ 192.619(c) cannot be used to determine the MAOP after a change in class location. Section 192.611 can be used to revise the MAOP within 24 months after a class location change; after that deadline, the MAOP must be revised according to§ 192.619(a).

Sections 192.517 and 192.603 require that all records regarding the pipeline MAOP determination be kept for the life of the pipeline segment, including records of pipe properties, pipeline component properties, pressure test records, class loqation studies, current class location designation, and operating history.

Question 3: Does § 192.619 apply to both transmission lines and distribution lines?

Response: Yes. The requirements in § 192.619 apply to both distribution and transmission natural gas pipelines. Section 192.621 contains different standards that apply only to high pressure distribution systems. States that regulate intrastate natural gas transmission pipelines and natural gas distribution pipelines have the right to implement state pipeline regulations that exceed the requirements in Part 192.

If we can be of further assistance, please contact John Gale, of my staff at 202-366-0434.


Jeffrey D. Wiese

Associate Administrator for Pipeline Safety

DMS ID# PI-14-0005

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