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Interpretation Response #PI-70-005 ([Public Service Commission] [F. M. Hoppe])

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

Interpretation Response Details

Response Publish Date:

Company Name: Public Service Commission

Individual Name: F. M. Hoppe

Country: US

View the Interpretation Document

Response text:

November 3, 1970

Mr. F. M. Hoppe
Director of Public Utilities
Public Service Commission
Seven Story State Office Bldg.
Lansing, Michigan 48913

Dear Mr. Hoppe:

Thank you for your letter of October 14, 1970, concerning construction of two Sections of Part
192, 49 CFR as issued on August 11, 1970. With regard to your first question concerning
Section 192.197(c)(4), it is not intended to permit the automatic shut-off device to be located
downstream of the service regulator. If this were done, it certainly could cause a ruptured
diaphragm in the service regulator which would be dangerous. What is intended is that the shutoff
device be located up stream of the service regulator, but controlled by excessive pressure
downstream of the service regulator by means of a control line connected from a point
downstream of the service regulator.

Section 192.197(c)(3), in its second sentence states "The relief valve may either be built into the
service regulator or it may be a separate unit installed downstream from the service regulator."

No mention is made of a shut-off device downstream of the service regulator. There are service
regulator diaphragm, and those would meet the requirements of this section. In regard to the
possibility of exceeding 60 psig or 125 psig, depending upon the design of the system, there are
requirements in Sections 192.199 and 192.201 for limiting pressures ar regulator stations
supplying distribution systems.

We are at present actively considering revision of several sections of Part 192 for clarification.
Section 192.197(c)(4) will be added to the list for such consideration.

With reference to your second question, Section 192.555 does provide an exception to the usual
test requirements of Section 192.619 . This exception was provided for in the previous minimum
safety standards, the ANSI B31.8 Code §845.23(3) and was apparently believed to be an
adequate safety requirement by the B31.8 Code Committee.

The exception, in Class 1 locations only, provides that a line may be operated at up to 80% of the
pressure allowed for a new line of the same design in the same location. Section 192.555(d)(2)(ii)
is subject to the further requirements of Section 192.555(d)(2)(i), which states that a test must be
impractical. Section 192.555(d)(2)(iii) places the burden on the operator to determine that the
new MAOP is consistent with the condition of the segment of pipeline and the design
requirements. A new line in a Class 1 location may not be designed for operation at more than
72% of SMYS, (Section 192.1110. Combining the limitations of those two sections leads to the
conclusion that a line uprated under the provisions of Section 192.555(d) could only be operated
at 57.6% of specified minimum yield strength.

Since you have raised the question of the safety of such a procedure the question will be
considered for future rulemaking procedures.

Sincerely,

/signed/

Joseph C. Caldwell
Director, Acting
Office of Pipeline Safety

Regulation Sections

Section Subject
192.111 Design factor (F) for steel pipe
192.197 Control of the pressure of gas delivered from high-pressure distribution systems
192.555 Uprating to a pressure that will produce a hoop stress of 30 percent or more of SMYS in steel pipelines