New Hampshire Public Utilities — Pipeline Safety Interpretation

Page 1August 9, 1972 Mr. Bruce B. Ellsworth Gas Safety Engineer New Hampshire Public Utilities Commission 26 Pleasant Street Concord, New Hampshire 03301 Dear Mr. Ellsworth: This is in response to your letter dated July 26, 1972, and your telephone conversation with our Mr. Lance Heverly on August 2, 1972. Your letter indicates that there is a situation in your State in which two parallel transmission lines, one of which is 6" and the other 10" are operating at approximately 400 psig. The transmission company intends to shut down the 6" line and make permanent field repairs to some corrosion leaks that had been repaired with leak clamps in 1968. From your conversation with Mr. Heverly, you agreed that the hoop stress of 7.15 percent of SMYS was in error and that the pipe involved is Grade B,.188" wall thickness, and about 50 feet long. Your letter indicated that the company intends to x-ray all welds but questions whether a hydrostatic test is also required. If the operating company plans to pressure test the replacing section of pipe in the operating pipeline, then the pressure test would have to be made with air or water since the permissible test pressure in a Class III location using gas, as set forth in Section 192.503(c), falls just short of that required to comply with Section 192.619(a)(2)(ii). However, gas, air, or water could be used on the fabricated short section of pipe at some other location than in the pipeline, such as covered by Section 192.505 for pipe operating above 30 percent of SMYS, and then installed in the pipeline. We trust that this has answered your particular question. If we can be of further service, please let us know. Sincerely, /signed/ Joseph C. Caldwell Director Office of Pipeline Safety DB/dal/192.503 72-08-09 1#