Interpretation Response #PI-20-0006
Below is the interpretation response detail and a list of regulations sections applicable to this response.
Interpretation Response Details
Mr. Marc S. Young
AC Engineering LLC
PO Box 1693
Sealy, TX 77474
Dear Mr. Young:
In a letter to the Pipeline and Hazardous Materials Safety Administration (PHMSA), dated February 10, 2020, you requested an interpretation of 49 Code of Federal Regulations (CFR) Part 192. Specifically, you requested an interpretation of §§ 192.195 and 192.197 as they relate to overpressure protection of a specific natural gas pipeline system.
In your capacity as a licensed professional engineer who has dealings with regulated municipalities and local distribution companies, you requested an interpretation of these regulations as they apply to a specific system where the normal operating pressure from a delivering pipeline is in the range of 250 pounds per square inch gauge (psig) (1,724 kPa gage) to a city gate inlet. You provided a drawing of the system to supplement your request for interpretation. You stated you are concerned because it appears some designers are selecting to eliminate relief valves or shutoff valves by assuming two regulators are sufficient overpressure protection devices without complying with all of the Part 192 overpressure protection requirements. You provided five statements and questions and asked PHMSA to respond to each one. PHMSA's responses follow your statements, which have been reproduced below:
Question 1: Confirm that if there is no high pressure distribution system (i.e. the custody transfer from the shipping pipeline at the inlet of a municipal gas utility or local distribution company's city gate) then the piping from the custody transfer receipt point and any manifold which handles one or more service lines to the city gate regulator, or regulators and a manual bypass line, if so piped, to the downstream flange of the first regulator or isolation valve is considered a high pressure distribution system for the purposes of the 49 CFR 192.197.
Answer: Section 192.3 defines a high-pressure distribution system as a distribution system in which the gas pressure in the main is higher than the pressure provided to the customer. Therefore, what you described meets the definition of a high pressure distribution system if the delivery pipeline is in the range of 250 psig as you indicated.
Question 2: If the normal operating pressure at the inlet to the 1st regulator is above 60 psig (414 kPa gage), then subpart (a) and (b) of 49 CFR 192.197 are not applicable and subpart (c) of 49 CFR 192.197 is applicable.
Answer: Section 192.197(c) is applicable for a distribution system that exceeds a maximum actual operating pressure of 60 psig.
Question 3: If the normal operating pressure at the inlet to the first regulator is above 125 psig (828 kPa gage), then 49 CFR 192.197(c)(1) or (2) must be used.
Answer: Section 192.197(c)(3) may not be used where the inlet pressure on the service regulator exceeds 125 psig (862 kPa gage). For higher inlet pressures, the methods in § 192.197(c)(1) or (2) must be used. Also, a service regulator and an automatic shutoff device that closes upon a rise in pressure downstream from the regulator and remains closed until it is manually reset can be used per § 192.197(c)(4).
Question 4: Confirm if either: a) the prescribed method in 49 CFR 192.197(c)(1) - an upstream regulating valve with a downstream regulating service valve that either operate a relief valve or a shutoff valve to prevent overpressure, or b) 49 CFR 192.197(c)(2) - a series of a primary regulator and a monitoring regulators, either alone or in parallel, and the piping contains a manual bypass line around the regulated service lines, even if locked closed and only utilized for limited periods during repair and maintenance, that a relief valve or quick acting shutoff is not mandatory to prevent overpressure of the downstream low pressure distribution system as required to satisfy 49 CFR 192.195. While it is not included in this regulation by reference, I would suggest that the caveats given in API Standard 521/ISO 232512 run counter to the suggestion of just applying a locking mechanism and to use administrative controls, e.g. to just instruct personnel to keep the bypass locked during normal operations. Does the Office of Pipeline Safety's Interpretation of 49 CFR 192.199 remain the same as it was almost 21 years ago?
Answer: With regard to overpressure protection for a manual bypass pipeline, there is a requirement for safety lock under § 192.199(h) that applies to gas pipeline valves installed between the system to be protected and relieving or limiting device. However, per §§ 192.619(b) and 192.621(b), no person may operate a segment of pipeline unless overpressure protective devices are installed on the segment in a manner that will prevent the maximum allowable operating pressure from being exceeded, in accordance with § 192.195. As for API Standard 521, PHMSA does not interpret this standard because it is not incorporated into the Federal pipeline safety regulations.
The rule in § 192.199(h) protects against unauthorized operation of a valve used for overpressure protection such as a valve in by-pass piping. The operator is required by § 192.605 to have detailed operating and maintenance procedures that are implemented by properly qualified operator personnel when valves in by-pass piping are being used for overpressure protection. By "operator personnel" we mean persons employed by an operator or working for a contractor engaged by an operator, including subcontractors and qualified in accordance with Part 192, Subpart N.
Question 5: Does 49 CFR 192.199 or 192.201 mandate a relief to protect a low-pressure distribution system, particularly if the system is to transition to polyethylene pipe, even if 49 CFR 192.197(c)(1) or (2) is employed upstream either with or without a manual bypass.
Answer: If piping meets §§ 192.197(a) and (b) or (c)(1) or (2), the maximum relief pressures must not exceed the maximum pressure limits in §§ 192.201 or 192.739, as applicable. Whether there is a steel to plastic pipeline connection or not, under § 192.619(a), no person may operate a segment of steel or plastic pipeline at a pressure that exceeds a maximum allowable operating pressure determined by the weakest element in the segment. Therefore, an operator with steel to plastic connection must design and operate its pipeline in accordance with Part 192 requirements.
If we can be of further assistance, please contact Tewabe Asebe at 202-366-5523.
John A. Gale
Director, Office of Standards
|§ 192.197||Control of the pressure of gas delivered from high-pressure distribution systems|