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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Interpretation Response #PI-18-0010

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

Interpretation Response Details

Response Publish Date:

Company Name: Michigan Public Service Commission

Individual Name: Mr. David J. Chislea

Location State: MI Country: US

View the Interpretation Document

Response text:

Mr. David J. Chislea
Manager of Gas Operations
Michigan Public Service Commission
7109 West Saginaw Highway
Lansing, MI 48917

Dear Mr. Chislea:

In an April 4, 2018, letter to the Pipeline and Hazardous Materials Safety Administration (PHMSA), you requested an interpretation of 49 Code of Federal Regulations (CFR) Part 192. Specifically, you requested interpretation regarding requirements for inspection and testing of relief devices under § 192.731(a).

You asked for clarification of the applicability of § 192.731(a) as it relates to §§ 192.201, 192.739, and 192.743 for the inspection and testing of compressor station relief valves and which compressor station relief valves must be inspected under § 192.731(a). In addition, you provided summary of some interpretations; regulatory history, and enforcement actions relevant to this request.

You asked for interpretations related to the following questions:

1. Are compressor station relief valves that protect downstream facilities, when a pressure control failure causes an exceedance of MAOP (maximum allowable operating pressure), the only relief valves required to be inspected under 49 CFR 192.731(a)?

PHMSA Reply:
No. Section 192.731(a) states that "each pressure relieving device in a compressor station must be inspected and tested ...." Therefore all relief devices (overpressure control devices) used for MAOP overpressure control for gas flow, thermal, and redundant purposes in gas carrying transportation pipeline facilities in a compressor station must be installed, maintained and inspected in accordance with the applicable paragraphs of §§ 192.201, 192.731, 192.739, and 192.743. The relief devices must be sized and have set pressures for all operating conditions that can lead to MAOP overpressure in accordance with §§ 192.201, 192.739, and 192.743.

2. If the answer to question #1 is "no," what relief valves must be inspected at a minimum, such as thermal relief or redundant relief valves that were not explicitly installed to comply with the inspection and testing requirements of 49 CFR 192.731(a)?

PHMSA Reply:
All gas carrying transportation pipeline facilities in a compressor station must have MAOP overpressure control and must be maintained and inspected in accordance with applicable paragraphs of §§ 192.201, 192.731, 192.739, and 192.743.

3. If the answer to question #1 is "no," what inspection intervals are required on non-MAOP protecting relief valves (such as thermal relief or redundant relief valves), specifically in regards to:

a. 49 CFR 192.739?

PHMSA Reply:
Section 192.739 requires each relief valve to be inspected and tested to determine that it is adequate from the standpoint of relief volume (capacity) and MAOP, and tested for reliability and correct pressure setting based upon MAOP at least once each calendar year with intervals not to exceed 15 months.

b. 49 CFR 192.743?

PHMSA Reply:
Section 192.743 requires each relief valve to be reviewed and determined to have sufficient capacity by testing the device in place or by review and calculations, at least once each calendar year with intervals not to exceed 15 months.

c. 49 CFR 192.201?

PHMSA Reply:
Section 192.201 specifies capacity requirements for pressure relieving and limiting stations, but does not specify additional requirements (based upon relief valve function - gas flow, thermal, and redundant purposes) for testing relief valves, when testing them to meet the requirements of §§ 192.201, 192.731, 192.739, and 192.743.

Section 192.743 requires each relief valve to be reviewed, inspected and maintained for relief volume and MAOP and tested for reliability and correct pressure setting based upon MAOP once each calendar year with intervals not to exceed 15 months.

4. If the answer to question #1 is "no," how are non-MAOP protecting relief valves expected to comply with the requirement of 49 CFR 192.739 in regards to being "set to control or relieve at the correct pressure consistent with the pressure limits of § 192.201(a)" if they are not installed to limit MAOP but for a different purpose, such as redundant relief valves or thermal relief valves in the case of ASME pressure vessels?

PHMSA Reply:
Thermal relief valves installed on ASME pressure vessels would need to protect the pressure vessels, when all valves and connecting piping used to isolate the vessels are closed. The ASME pressure vessel thermal relief valve settings should be based upon the compressor station piping MAOP. If the ASME pressure vessel, isolation valves, connecting piping, and fittings used to isolate the ASME pressure vessel have a documented higher MAOP than the compressor station piping, then a higher MAOP may be used for the thermal relief set pressure.

Thermal relief or any redundant relief valves for gas transmission pipelines must be tested and maintained in accordance with applicable §§ 192.201, 192.731, 192.739, and 192.743.

If we can be of further assistance, please contact Tewabe Asebe at 202-366-5523.

Sincerely,

John A. Gale
Director, Office of Standards
and Rulemaking

Regulation Sections

Section Subject
192.731 Compressor stations: Inspection and testing of relief devices