Arizona Corporation Commission — Pipeline Safety Interpretation

Page 1PI-91-0103 Mr. Dan H. Weaklend Chief, Pipeline Safety Arizona Corporation Commission 1200 W. Washington Phoenix, AZ 85007 Dear Mr. Weaklend: I am responding to your letter of March 4, 1991, concerning the classification of pipelines under 49 CFR 192 as transmission lines or mains. You asked about four pipelines shown as #1, #2, #5, and #6 on enclosures. You also asked if pressure reduction points shown as #3 and #4 on the enclosures are pressure limiting or regulating stations. The Part 192 regulations contain the following definitions that re relevant to this discussion: Distribution line means a pipeline other than a gathering or transmission line. Main means a distribution line that serves as a common source of supply for more than one service line. Transmission line means a pipeline, other than a gathering line, that: (a) Transports gas from a gathering line or storage facility to a distribution center or storage facility; (b) Operates at a hoop stress of 20 percent or more SMYS; or (c) Transports gas within a storage field. Comprehension of the term, "distribution center," is essential to use of the transmission line definition. As we apply the term, it is the point where gas enters piping used primarily to deliver gas to customers who purchase it for consumption as opposed to customers who purchase it for resale. Line #1, which operates at less than 20 percent of SMYS, begins at a pressure limiting and metering station on an interstate natural gas transmission pipeline. From there the line extends to a series of pressure reduction points, beyond which the gas is distributed to consumers. Because there does not appear to be any transfer of gas to customers for resale beyond the pressure limiting and metering station, this station marks a distribution center under the above description. Line #1 is, therefore, a distribution line, or main, as it is a common source of supply for more than one service line. 192.3 DISTLINE 1#

Page 2Line #2 runs between the last pressure reduction point on Line #1 and another pressure reduction point. It is an extension of Line #1 and is, thus, a main. Lines #6 and #6 are like Line #1, except they extend to fewer pressure reduction points than Line #1, and, on Line #6, two of these points are on connecting laterals. Since these dissimilarities to Line #1 are not relevant for the purpose of classification, Lines #5 and #6 are mains. As for pressure reduction points #3 and #4, Part 192 does not define pressure limiting or regulating stations, though we have a rulemaking project to create a Part 192 definition for these terms. Terms used in Part 192 that are not defined in Part 192 have the ordinary meaning in the industry. We rely on the definitions in the B31.8 Code as indicative of the ordinary meaning of such terms in the industry. Based on the B31.8 definitions of pressure limiting or regulating station and of service regulator, point #3 is a pressure limiting or regulating station and point #4 is a service regulator. Please call me if you need any further help in this matter. Sincerely, /signed/ Cesar DeLeon Director for Pipeline Safety Regulatory Programs 192.3 DISTLINE 2#