Public Service Commission — Pipeline Safety Interpretation

Page 1PI-70-0108 NOVEMBER 03, 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 shut-off 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 192.111). 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#

Page 2State of Michigan Department of Commerce Seven Story state Office Bldg. Lansing, Michigan 48913 October 14, 1970 Office of Pipeline Safety Department of Transportation 400 Sixth Street, S.W. Washington, D.C. 20590 Gentlemen: The review of Part 192 in Title 40, Code of Federal Regulations, by the Commission staff, has raised a number of questions in our minds regarding the meaning and intent of certain sections. We hope to be able to resolve most of these questions at the meeting in Kansas City, but we wish to direct your attention to two particular areas that we feel involve more than meaning and intent. 1. Section 192.197 (c) (4) This subsection does not appear to be compatible with subsection (c) (3). If the automatic shutoff device is located upstream of the service regulator, the pressure on the upstream side of the regulator could exceed 125 psig as long as the regulator maintained a pre-set downstream pressure. If the automatic shutoff device is located downstream of the service regulator, high pressure (60 +. psig) would be imposed on the downstream side of the regulator whenever the automatic shutoff device closed. Many service regulators are not qualified for imposition of high pressure on the low pressure side of the regulator. 2. Section 192.555 (d) (2) (i) & (ii) This subsection seems to negate the intent of Section 192.619 (a) (3) and (c). It could allow for upgrading the MAOP of a pipeline to a higher pressure than would be allowed by 192.619 (a)(3) and (c) even though the line had not been tested in the preceding 10-30 years and had never been operated at the proposed new MAOP. Accordingly, it appears to us the present provisions of the above- mentioned subsections should be revised to cover the points we have brought up. Yours very truly, F.M. Hoppe Director of Public Utilities#