{"operation":"document","citation":"PI-81-005","title":"Wisconsin Gas Company — Pipeline Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"1981-02-27","effective_on":null,"summary":"PI-81-005 response to Wisconsin Gas Company concerning 192.311, 192.703.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-81-005.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-81-005.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-pi-81-005","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/Pipeline/1981/PI81005.pdf","body":"<<<PAGE 1>>>\n\nFeb 27 1981\nMr. Keith A. Chen, P.E.\nDirector - Research\nWisconsin Gas Company\n626 East Wisconsin Avenue\nMilwaukee, Wisconsin 53202\nDear Mr. Chen:\nYour letter to this office of February 6, 1981, concerns the use of full encirclement\nstainless steel band clamps for permanent repair of damaged plastic pipe. We agree with\nyour interpretation that Subpart G of 49 CFR Part 192 (and, thus, 192.311) is only\napplicable during the construction of a transmission line or main. However, as further\ndiscussed below, even if the band clamp were considered a \"patching saddle,\" as intended\nby 192.311 (which it is not), its use to permanently repair plastic pipe either during\nconstruction or after operation may be prohibited under 192.703(b).\nIn regard to the term \"patching saddle\" as used in 192.311, these words were added to the\nfinal rule as a result of comments to the proposed rule stating that defective plastic pipe\nshould be permitted to be repaired. These comments clearly had in mind the use of a\nsaddle made of material similar to that of the pipe being repaired that would be joined to\nthe pipe by fusion, solvent cement, adhesion, or similar methods. Typical comments that\nprompted the Office of Pipeline Safety to permit use of a \"patching saddle\" were:\n\"We feel that patching of a plastic main should be allowed.\nShould be no difference between a patch over a gouge or the\ninstallation of a service tee.\" (Iowa Public Service Company)\n\"The use of solvent weld half-soles on polyvinyl chloride pipe has\nproven to be a safe, economical method of repair for scratches,\ngouges, and grooves on mains in service.\" (Central Telephone\nand Utilities Corporation)\nThus, a band clamp is inconsistent with the meaning intended by \"patching saddle.\"\nAnother reason why \"patching saddle\" does not mean a band clamp is that when 192.311\nwas issued, 192.281(e)(2) was also issued, requiring a rigid internal tubular stiffener to be\nused in conjunction with each compression type mechanical coupling. This requirement\nrecognizes the compressive forces of the sealing gasket used in a compression coupling\nand the fact that plastic materials under constant stress will tend to cold flow. A full\nencirclement stainless steel band clamp, like a compression coupling, subjects the plastic\npipe to compressive stress but does not provide internal support for the pipe that may be\nneeded to prevent cold flow of the plastic.\n\n<<<PAGE 2>>>\n\nBecause of the question of cold flow of plastic pipe, we believe that the safety of a\npermanent repair by use of a band clamp is questionable under some conditions, depending\non the stiffness of the plastic pipe involved. Where unsafe conditions would result,\n192.703(b) would forbid use of the band clamp as a repair method.\nIn your letter, you state that \"Wisconsin Gas conducted tests on the stainless steel clamp\nused as a patching saddle which determined that the performance met the required safety\nand serviceability tests of the code.\" We would appreciate your sending us these data and\nany other data available on the problem of cold flow of plastic pipe under continuous\ngasket pressure as discussed above.\nSincerely,\nMelvin A. Judah\nActing Associate Director for\nPipeline Safety Regulation\nMaterials Transportation Bureau","truncated":false,"body_characters":3271}