{"operation":"document","citation":"DCA04MP006","title":"Natural Gas Pipeline Leak, Explosion, and Fire","source_type":"incident","agency":"National Transportation Safety Board","status":"current","official":true,"published_on":"2026-01-30","effective_on":"2004-08-21","summary":"Accident. in DuBois, PA, USA. on 2004-08-21. National Fuel Gas Distribution Corporation. Leak/explosion/fire","machine_formats":{"json":"https://regulus.evalyn.ai/document/ntsb-case-dca04mp006.json","markdown":"https://regulus.evalyn.ai/document/ntsb-case-dca04mp006.md"},"app_url":"https://regulus.evalyn.ai/document/ntsb-case-dca04mp006","source_url":"https://www.ntsb.gov/investigations/Pages/DCA04MP006.aspx","body":"NTSB investigation DCA04MP006.\n\nEvent Type: Accident\n\nEvent Date: 2004-08-21\n\nEvent City: DuBois\n\nEvent State Or Region: PA\n\nEvent Country: USA\n\nPipeline Operator: National Fuel Gas Distribution Corporation\n\nPipeline Type: Distribution\n\nAccident Type: Leak/explosion/fire\n\nCompletion Status: Completed\n\nReport Number: PAB-06-01\n\nProbable cause: The National Transportation Safety Board determines that the probable cause of the leak, explosion, and fire in DuBois, Pennsylvania, on August 21, 2004, was the fracture of a defective butt-fusion joint and the failure of the National Fuel Gas Distribution Corporation to have an adequate program to inspect butt-fusion joints and replace those joints not meeting its inspection criteria.\n\nTier1Name: System operating\n\nTier2Name: Fire/explosion (post-release)\n\nTier1Name: System operating\n\nTier2Name: Product leak/release\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Support/oversight/monitoring\n\nFinding Tier3Name: Oversight\n\nFinding Modifier Name: State/Local agency\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Oversight - State/Local agency\n\nFinding Tier1Name: Organizational\n\nFinding Tier2Name: Support/oversight/monitoring\n\nFinding Tier3Name: Safety programs\n\nFinding Modifier Name: Other institution/organization\n\nFinding Report Text: Organizational - Support/oversight/monitoring - Safety programs - Other institution/organization\n\nFinding Tier1Name: Personnel\n\nFinding Tier2Name: Experience/knowledge\n\nFinding Tier3Name: Skill/ability\n\nFinding Modifier Name: Other company personnel\n\nFinding Report Text: Personnel - Experience/knowledge - Skill/ability - Other company personnel\n\nFinding Tier1Name: Pipeline\n\nFinding Tier2Name: Pipeline structure\n\nFinding Tier3Name: Joint/weld/seam\n\nFinding Modifier Name: Failure\n\nFinding Report Text: Pipeline - Pipeline structure - Joint/weld/seam - Failure\n\nOfficial NTSB investigation data. NTSB findings determine probable cause and make safety recommendations; they do not adjudicate civil liability or regulatory violations.\n\nWhat Happened\nOn August 21, 2004, about 8:54 a.m., a natural gas explosion destroyed a residence located at 48 Woodland Lane in DuBois, Pennsylvania. The two residents were killed in this accident.\n\nWhat We Found\nWe determined that the probable cause of the leak, explosion, and fire in DuBois, Pennsylvania, on August 21, 2004, was the fracture of a defective butt-fusion joint and the failure of the National Fuel Gas Distribution Corporation to have an adequate program to inspect butt-fusion joints and replace those joints not meeting its inspection criteria.\n\nWhat We Recommended\nAs a result of this investigation, we made the following new safety recommendations.\n\nTo the Pennsylvania Public Utility Commission: Require an analysis of the integrity of butt-fusion joints in National Fuel Gas Distribution Corporation’s gas distribution system and replacement of those joints that are determined to have unacceptable characteristics. (P-06-1)\n\nTo National Fuel Gas Distribution Corporation:\n\nRevise your butt-fusion procedures for plastic pipe to include a requirement for determining drag force in the field for each butt-fusion joint. (P-06-2)\nRevise your initial qualification and requalification procedures for plastic gas pipe to ensure fusers produce test joints made from coiled pipe with characteristics similar to those experienced in the field. (P-06-3)\n\nTo USPoly Company: Revise your butt-fusion procedures to include a requirement for the avoidance of mitering in plastic gas pipe joints. (P-06-4)\n\nTo the Plastics Pipe Institute: Revise your butt-fusion joining procedure for plastic gas pipe to (1) stress the importance of inspecting the finished joint, (2) include guidance on the joining of\ncoiled pipe, and (3) include a requirement for the avoidance of mitering. (P-06-5)\n\nPAB-06-01\n<<<PAGE 1>>>\n\nL\nT\nR\nA\nN\nS\nP\nA\nO\nN\nR\nU\nR\nI\nB\nU\nS\nM\nT\nO\nI\nA\nT\nA\nU N U\nP\nL\nE\nT\nI\nO\nN\nN\nS\nA\nF\nE\nT\nY\nB\nD\nO\nA\nR\nNational Transportation Safety Board\nWashington, D.C. 20594\nPipeline Accident Brief\nAccident No.: DCA-04-MP-006\nSystem Type: Natural gas distribution\nAccident Type: Leak, explosion, and fire\nLocation: DuBois, Pennsylvania\nDate: August 21, 2004\nTime: About 8:54 a.m. eastern daylight time1\nOwner/Operator: National Fuel Gas Distribution Corporation\nProperty Damage and Losses: $800,000\nFatalities: 2\nInjuries: None\nMaterial Released: Natural gas\nPressure: 50 pounds per square inch, gauge\nFailure Type: Butt-fusion joint leak\nComponent Affected: 2-inch plastic main line\nThe Accident\nOn August 21, 2004, about 8:54 a.m., a natural gas explosion destroyed a residence\nlocated at 48 Woodland Lane in DuBois, Pennsylvania. The two residents were killed in this\naccident. (See figure 1.)\nPostaccident Investigation\nNational Fuel Gas Distribution Corporation (National Fuel) probed the ground near the\nresidence for gas leaks. Combustible gas-to-air readings were found in two areas: one area was\nadjacent to the affected residence, and the other area was directly over the failed pipe on the front\nlawn. After the explosion, National Fuel excavated the front lawn. The excavation revealed a\nleaking butt-fusion joint in a 2-inch-diameter plastic main line pipe. (See figure 2.)\nA butt-fusion joint is made by the following process. A heater plate is inserted between\ntwo pipe ends, melting the material on each end. The heater is then removed, and the pipe ends\nare pushed together under applied force. The pipe ends remain under applied force as the pipe\nends cool and fuse together. The butt-fusion process forces excess molten plastic onto the inside\nand outside of the pipe surfaces. Because both sides of the pipe are molten, two visible beads are\nformed on the exterior and interior of the pipe joint. (See figure 3.) When this material cools and\nsolidifies, it is called a fusion bead.\n1 All times in this brief are eastern daylight time.\nNTSB/PAB-06/01\n\n<<<PAGE 2>>>\n\nFigure 1. Damage to 48 Woodland Lane.\nNational Fuel began excavating the accident site before National Transportation Safety\nBoard investigators arrived. During the excavation, National Fuel accidentally severed the plastic\npipe within a few feet of the butt-fusion joint. Because of this mishap, Safety Board investigators\ncould not determine the undisturbed position of the pipe to assess its bending. Only a small\nligament remained connected at the butt-fusion joint, making it impossible to directly test the\nstrength of the joint.\nThe Safety Board’s examination of the butt-fusion joint linked to the explosion indicates\nthat the bead widths were not uniform.2 The bead width on one side of the butt-fusion joint\nranged from 0.0535 inch to 0.1135 inch. On the other side of the joint, the bead width ranged\nfrom 0.0745 inch to 0.1060 inch. The total bead width ranged from 0.1315 inch to 0.2045 inch.\nThe joint was found to have been visibly mitered,3 having about a 2° angle. Mitering can\nconcentrate stresses. No evidence was found indicating that the joint was significantly\nmisaligned.4\n2 See butt-fusion criteria discussed in the section titled Butt-Fusion Procedures and Inspection Criteria,\nPreaccident.\n3 Mitered means a butt-fusion joint that is not joined with an 180° angle from each pipe. In this report, mitering\nrefers to a small angle made unintentionally in the field, not a large angle made intentionally as a pipe bend. A\nvisible miter is a joint that has an angle detectable by the unaided eye.\n4 Misaligned means a butt-fusion joint in which the two pipes are not evenly lined up relative to each other,\nexhibiting a high-low disjuncture at the point of fusion.\n2 NTSB/PAB-06/01\n\n<<<PAGE 3>>>\n\nFigure 2. Excavated butt-fusion joint.\n3 NTSB/PAB-06/01\n\n<<<PAGE 4>>>\n\nFigure 3. Optimal butt-fusion joint as illustrated in Uponor’s Heat Fusion Installer\nQualification Manual.\nAt the same location where the external bead width was thinnest, the bead was distorted.\nThe external bead on one side of the joint was larger than the bead on the other side. The\nboundary between the two beads was indistinct. The internal bead was also distorted, with the\nbead on one side of the joint higher than the other side. On one side of the joint, the internal bead\nhad numerous pockmarks.5 On the other side, small globules of plastic adhered to the bead,\nwhich is consistent with material being pulled from one bead and deposited on the other bead\nwhen the joint was made.\nThe fracture between the two pipe ends closely followed the plane of the center of the\nbutt-fusion joint. (See figure 4.) The external bead remained attached to one piece of the pipe,\nand the internal bead remained attached to the other piece of the pipe. (See figure 5.)\n5 Pockmarks may indicate a less than optimal butt fusion.\n4 NTSB/PAB-06/01\n\n<<<PAGE 5>>>\n\nFigure 4. Fractured end showing external bead and plane of fracture at center of\nbutt-fusion joint.\nFigure 5. View of fracture surface on one piece of pipe. Pipe is oriented as it was\nfound. Fracture origin was at 9 o’clock position as shown. Unlabeled arrows\nindicate crack propagation directions.\n5 NTSB/PAB-06/01\n\n<<<PAGE 6>>>\n\nThe fracture surfaces at the butt-fusion joint were examined using optical microscopy and\nan environmental scanning electron microscope. The fracture surface exhibited voids where the\ninternal and external beads were distorted. (See figure 6.) Fracture surface features indicated that\nthe crack initiated near the center of the pipe wall within the butt-fusion joint, followed by a slow\nprogressive crack growth.6 Ductile ribbons of plastic pipe material present at the inner and outer\nedges of the fracture surface indicated that the crack did not initiate at the notches7 of either the\ninternal or external beads.\nStudies of butt-fusion joints subjected to elevated temperature and high pressure indicate\nthat a fracture occurring in the butt-fusion area will normally start on the pipe wall surface at the\nnotch of the internal bead or, if bending is involved, the fracture would be expected to start at the\nouter pipe wall surface. However, the initiation of the fracture in the accident pipe near the center\nof the pipe wall is consistent with inadequate fusion of the joint.\nFigure 6. Voids in central portion of fracture surface.\n6 See National Transportation Safety Board Brittle-like Cracking in Plastic Pipe for Gas Service, Special\nInvestigation Report NTSB/SIR-98/01 (Washington, DC: NTSB, 1998), for additional information regarding\nprogressive crack growth.\n7 As the bead rolls back, a notch is formed between the bead and the wall of the pipe. Stress concentration\nincreases in the area of the notch.\n6 NTSB/PAB-06/01\n\n<<<PAGE 7>>>\n\nThe butt-fusion joint that joined the two coiled plastic pipes8 involved in this accident\nwas made on January 10, 1996, using a machine called the McElroy 14, which is manufactured\nby McElroy Manufacturing, Inc. (McElroy). The two plastic pipes were manufactured in\ndifferent years. One pipe was manufactured on May 16, 1995; the other was manufactured on\nOctober 5, 1994. Uponor Aldyl Company (Uponor) manufactured both medium-density9 pipes.\nAccording to written certifications from Uponor, the pipe met the requirements of ASTM\nD-2513, “Standard Specification for Thermoplastic Gas Pressure Pipe, Tubing, and Fittings.”\nLaboratory testing of the accident pipe determined that the dimensions, density, and melt index\nwere within Uponor’s production specifications.\nButt-Fusion Procedures and Inspection Criteria\nPreaccident\nUponor had a butt-fusion joining procedure, adopted in December 1991, for its pipe\nproduct. Uponor qualified its joining procedure in accordance with Title 49 Code of Federal\nRegulations (CFR) 192.283.10 As a service to National Fuel and other pipeline companies,\nUponor provided its procedure.\nNational Fuel had its own procedure for making butt-fusion joints. The butt-fusion\njoining procedures for National Fuel and Uponor were similar. The National Fuel butt-fusion\nprocedure was adopted in February 1993. National Fuel made butt-fusion joints using a variety\nof machines. The company inspected and certified its butt-fusion machines in accordance with its\nprocedures.\nUponor published a set of key visual inspection criteria for identifying an acceptable\nbutt-fusion joint. These criteria were in effect in 1996 at the time the fusion joint involved in the\naccident was made. As stated in Uponor’s inspection criteria (adjacent to photographs of\nbutt-joint fusions), key visual criteria for a good-quality fusion included the following:\n• Uniform bead development on both pipe ends\n• Bead rolled back to pipe\n• No misalignment between pipe ends\n8 Butt fusion of coiled pipe is considered more difficult than fusion of straight pipe because the residual\ncurvature makes it difficult to obtain an optimal alignment and reduce mitering. Proper procedures and equipment\nand extra care are necessary if high-quality joints are to be consistently produced.\n9 Medium density is characterized in ASTM D-2513. ASTM is now known as ASTM International, one of the\nlargest voluntary standards development organizations in the world. ASTM was originally an abbreviation for\nAmerican Society for Testing and Materials.\n10 Title 49 CFR 192.283 is issued by the U.S. Department of Transportation Pipeline and Hazardous Materials\nSafety Administration in Part 192, “Transportation of Natural and Other Gas by Pipeline: Minimum Federal Safety\nStandards;” Subpart F, “Joining of Materials Other Than by Welding;” Section 192.283, “Plastic pipe: Qualifying\njoining procedures.”\n7 NTSB/PAB-06/01\n\n<<<PAGE 8>>>\n\nIn addition, the Uponor procedure stated that joints not meeting these visual criteria had to be\nremade before being placed into service. The Uponor procedure further stated, “If the pipe ends\nare not aligned, adjust them in the shells and . . . [start over].” This procedure did not address\nmitering.\nNational Fuel essentially used Uponor’s inspection criteria. As part of its procedure for\nmaking a butt-fusion joint, National Fuel required the fuser11 to inspect the completed joint for\nconformity with its criteria. National Fuel’s procedure also stated, “If there is any reason to\nbelieve a butt fusion is defective, it shall be removed and replaced.”\nSafety Board investigators interviewed two current and two retired National Fuel\nemployees familiar with National Fuel’s fusion procedures and training at the time when the\nsubject butt-fusion joint was made. The four interviewees included two master trainers who\nconducted initial qualification training and two foremen who requalified personnel in the field\nbased on instructions from the master trainers. The interviewees stated that National Fuel had\nverbal instructions in effect in 1996 advising its fusers not to allow a visual miter; however, this\nguidance was not found in its written operating procedures.\nThe butt-fusion joint linked to the explosion was made with a 500-foot length of 2-inch\ncoiled pipe that was butt fused to a previously installed 2-inch coiled pipe using the McElroy 14.\nAccording to the National Fuel butt-fusion procedure, the fusion required the fuser to apply 15 to\n20 foot-pounds with the machine, which would have resulted in a joining force on the pipe ends\nof 165 to 215 pounds. A 500-foot roll of 2-inch plastic pipe weighs approximately 315 pounds.\nDepending on the placement of the pipe roll, the drag caused by the weight of the pipe roll could\nhave been negligible or significant. The written procedures of Uponor, National Fuel, and\nMcElroy did not account for drag force;12 however, McElroy’s onsite training program provided\ninstructions to fusers so that they could determine in the field the drag force for a butt-fusion\njoint. Among the four National Fuel interviewees, there was variation in the level of knowledge\nregarding drag force and the need to compensate for its effects.\nCurrent\nSince the accident, the PWPoly Corporation has acquired Uponor. The combined\nbusinesses of PWPoly Corporation and Uponor operate under the name USPoly Company\n(USPoly). Today, USPoly continues to manufacture medium-density pipe, but it no longer\nmanufactures the type of pipe involved in this accident.\nUSPoly’s March 5, 2000, pipe joining procedure addresses the methods for joining coiled\npipe using butt fusion and recommends that drag force be determined on a case-by-case basis. Its\nprocedure requires that the completed joint be inspected and prescribes that any joint not meeting\n8 NTSB/PAB-06/01\n11 A fuser is a person who makes fusion joints.\n12 The fusion of a long or heavy segment of pipe is different from the fusion of two small segments of plastic\npipe. Drag force is the force required to move the pipe to be joined. If this drag force is not added before applying\nthe joining force, the proper joining force may not be applied.\n\n<<<PAGE 9>>>\n\nvisual inspection criteria be remade. The USPoly procedure does not address mitering. USPoly’s\nkey visual inspection criteria for its medium-density pipe product include the following:\n• Complete and uniform beads\n• Bead rolled back to pipe\n• Alignment\nThe Plastics Pipe Institute (PPI) is the major trade association representing the plastics\npiping industry. The PPI publishes universal fusion procedures that are widely accepted\nthroughout the pipeline industry. PPI’s current butt-fusion joint procedure, published in late\n2005, recommends that the drag force be determined on a case-by-case basis. The PPI procedure\ndoes not address the joining of coiled pipe or the avoidance of mitering. The PPI procedure\nincludes an illustration of a properly made butt-fusion joint, but it does not specifically address\ninspecting the finished joint.\nIn November 2000, McElroy, the manufacturer of the McElroy 14, established\nbutt-fusion procedures that recommend determining drag force on a case-by-case basis. In\naddition, McElroy specifies using PPI’s fusion procedures or the pipe manufacturer’s procedures\nfor certain fusion parameters, such as joining force and holding time.\nASTM D-2657, “Standard Practice for Heat Fusion Joining of Polyolefin Pipe and\nFittings,” contains a general butt-fusion joint procedure. The ASTM procedure requires the use\nof PPI or pipe-manufacturer procedures to specify the fusion parameters. The ASTM procedure\nfurther prescribes inspecting the finished joint in accordance with recommended appearance\nguidelines. The ASTM procedure also addresses calculating and using a drag force.\nNational Fuel’s current butt-fusion procedure,13 published in May 2005, addresses joining\ncoiled pipe. This procedure adds a predetermined fixed drag force for some fusion machines. As\na part of its operating procedure, National Fuel requires the fuser to inspect the completed\nbutt-fusion joint. This visual examination of the butt fusion includes proper alignment, no miter,\ncomplete bead rollover, relatively uniform beads, and proper bead width. National Fuel’s current\nprocedure states, “If there is any reason to believe the butt fusion is defective, it shall be removed\nand replaced.” A butt-fusion joint made by a fuser in the field is subject to inspection by a\nforeman. Since January 1, 2000, National Fuel’s Quality Assurance/Quality Control department\nhas been performing periodic field audits that sometimes include inspections of butt fusions,\ndepending upon the subject of the audit. The fusers have been required to use a permanent\nmarker to write their employee identification number on their butt -fusion joints since\nJanuary 2001.\n13 National Fuel’s current policy does not permit two segments of coiled pipe to be butt fused; however, a\nstraight pipe can be butt fused to coiled pipe.\n9 NTSB/PAB-06/01\n\n<<<PAGE 10>>>\n\nQualification of Fusion Personnel\nPreaccident\nTitle 49 CFR 192.285 required that all personnel making plastic pipe joints be qualified\nunder the applicable joining procedure. To qualify, the applicant had to have appropriate training\nor experience using the procedure and had to produce at least one joint using it. These joints\nwere visually examined and mechanically tested by one of several approved methods, which\nincluded pressure testing, tensile testing, and cutting the joint into a minimum of three strips and\nbending them to failure. This testing was required for qualification and requalification.\nTwo qualified fusers were on the National Fuel work crew that installed the 2-inch plastic\npipe on January 10, 1996. One of these fusers signed a form indicating that he had made the\nbutt-fusion joint where the failure occurred. He also signed the chart of the final pressure test\nbefore this pipeline segment was placed in service.\nAccording to National Fuel records, both work crew fusers passed their original plastic\npipe butt-fusion qualification tests. Both work crew fusers requalified in 1994, 1995, and 1996.\nDuring their requalification tests, they used a variety of butt-fusion machines, including the\nMcElroy 14. Their requalification testing was performed in accordance with 49 CFR 192.285.\nTheir requalification records indicate that they received a review of procedures. The fusers were\nnot given a written examination, and records did not reflect whether they were requalified using\ncoiled or straight pipe. Neither crew fuser, according to National Fuel records, had a documented\nfailed joint.\nCurrent\nIn its fuser qualification plan, National Fuel has two levels of training and qualification:\ninitial qualification and requalification. New employees who produce plastic fusions and fitting\ninstallations are required to take an initial training course. The course reviews the National Fuel\nprocedures, best practices for plastic material installation, and fusion and mechanical coupling\ninstallation. Individuals performing plastic joining are requalified on an annual basis. Both the\ninitial and requalification programs include instructional videos, reviews of updated or changed\noperating procedures, and changes in materials or products. Both a written test and a practical\nexam are given. The trainee must be able to differentiate between acceptable and unacceptable\nfusions. The trainee is required to make test joints that may or may not be made from coiled pipe.\nThese joints are visually examined by the trainer and then evaluated by mechanical testing. To\nqualify an individual for the inspection of fused plastic pipe, National Fuel requires the\nindividual to pass either a written or an oral examination and to understand how to determine that\na joint meets National Fuel’s acceptance criteria. On March 8, 2004, two Pennsylvania Public\nUtility Commission (PUC) inspectors audited National Fuel’s program. No issue regarding\nNational Fuel’s butt-fusion operator qualifications was identified in the audit report.\n10 NTSB/PAB-06/01\n\n<<<PAGE 11>>>\n\nAdditional Fusions Removed from DuBois\nThe Pennsylvania PUC supervised the excavation and visual inspection of an additional\n40 joints from an area in the vicinity of the accident that were made in either 1994 or 1996.\nInspectors from the Pennsylvania PUC removed 24 of the joints and submitted them to the\nSafety Board for laboratory analysis.\nOf the 24 joints examined at the Safety Board’s Materials Laboratory, 5 were made from\nstraight pipe, and 19 were made from coiled pipe. The five joints made from straight pipe were\nfound to have sufficiently uniform beads, complete bead rollover, no visible miter, and proper\nalignment.\nAbout half of the 19 joints made from coiled pipe had visible variation in bead width, but\nall were relatively uniform. All of the 19 joints had complete bead rollover. The 19 joints had\nmiter angles that were greater than those on the straight pipe joints; the miter angles for the joints\nmade from coiled pipe ranged from 0.7° to 4.2°. The average angle of the miter for the 19 joints\nwas 2.08°. Thirteen of the 19 joints made from coiled pipe had a misalignment in excess of that\nallowed by National Fuel and Uponor. Two joints had an area that separated in the joint during\ntensile testing. These two joints had regions of poor bonding in the fusion area; one of the joints\nexhibited voids similar to those observed on the fracture surface of the accident joint.\nRecords to identify a specific fuser with any of the 24 joints examined by the\nSafety Board’s Materials Laboratory were unavailable. National Fuel records show that in 1994\nthere were nine qualified fusers and in 1996 there were seven qualified fusers who could make\nbutt-fusion joints in the DuBois Service Center area.\nGas System Performance Monitoring\nFederal regulations (49 CFR 192.613 and 192.617) require that gas pipeline system\noperators have procedures in place for monitoring the performance of their gas systems. These\nprocedures must cover surveillance of gas system failures and leakage history, analysis of\nfailures, submission of failed samples for laboratory examination (to determine the causes of\nfailure), and minimizing the possibility of future recurrences. National Fuel has reported that it is\nrevising its surveillance and analysis program to address the integrity of butt-fusion joints.\nProbable Cause\nThe National Transportation Safety Board determines that the probable cause of the leak,\nexplosion, and fire in DuBois, Pennsylvania, on August 21, 2004, was the fracture of a defective\nbutt-fusion joint and the failure of the National Fuel Gas Distribution Corporation to have an\nadequate program to inspect butt-fusion joints and replace those joints not meeting its inspection\ncriteria.\n11 NTSB/PAB-06/01\n\n<<<PAGE 12>>>\n\nRecommendations\nAs a result of its investigation of the August 21, 2004, DuBois, Pennsylvania, pipeline\naccident, the National Transportation Safety Board makes the following safety\nrecommendations:\nTo the Pennsylvania Public Utility Commission:\nRequire an analysis of the integrity of butt-fusion joints in National Fuel Gas\nDistribution Corporation’s gas distribution system and replacement of those joints\nthat are determined to have unacceptable characteristics. (P-06-1)\nTo National Fuel Gas Distribution Corporation:\nRevise your butt-fusion procedures for plastic pipe to include a requirement for\ndetermining drag force in the field for each butt-fusion joint. (P-06-2)\nRevise your initial qualification and requalification procedures for plastic gas pipe\nto ensure fusers produce test joints made from coiled pipe with characteristics\nsimilar to those experienced in the field. (P-06-3)\nTo USPoly Company:\nRevise your butt-fusion procedures to include a requirement for the avoidance of\nmitering in plastic gas pipe joints. (P-06-4)\nTo the Plastics Pipe Institute:\nRevise your butt-fusion joining procedure for plastic gas pipe to (1) stress the\nimportance of inspecting the finished joint, (2) include guidance on the joining of\ncoiled pipe, and (3) include a requirement for the avoidance of mitering.\n(P-06-5)\n12 NTSB/PAB-06/01\n\n<<<PAGE 13>>>\n\nBY THE NATIONAL TRANSPORTATION SAFETY BOARD\nMark V. Rosenker\nActing Chairman\nEllen Engleman Conners\nMember\nDeborah A. P. Hersman\nMember\nKathryn O’Leary Higgins\nMember\nAdopted: May 31, 2006\n13 NTSB/PAB-06/01","truncated":false,"body_characters":27098}