U.S. DOT/PHMSA - Presentation: Briefing Paper on Special Permits to Waive MAOP in New HL Pipe

Page 1Briefing Paper February 12, 2007 Consideration of Special Permit to Waive the Maximum Allowable Operating Pressure in New Hazardous Liquids Pipelines Advisory Committee Action: Briefing Project Contacts: Joy Kadnar and Alan Mayberry Past PHMSA action: PHMSA continues to seek ways to improve the safety and efficiency of the nation’s energy infrastructure and in doing so recognizes that improvements in metallurgical properties, pipeline manufacture, and life cycle management practices have improved the safety performance of these facilities. The Canadian standards and the National Energy Board allow hazardous liquid pipelines to operate at 80% of SMYS. The ASME B31.4 committee, unlike the counterpart ASME B31.8 (gas) committee, has not made changes to allow for higher operating stress levels. On November 17, 2006 TransCanada Keystone Pipeline, LP requested PHMSA to consider a waiver to allow them to operate at 80% of the specified minimum yield strength (SMYS) as opposed to 72% of SMYS, the current regulatory maximum stress level. The Keystone Pipeline originates at an oil sands supply hub near Hardisty, Alberta, and extends 1,845 miles to Patoka, Illinois. The US portion includes 1,023 miles of 36- inch, 55 miles of 24- inch and in the future may include a 291–mile long extension to Cushing, Oklahoma. TransCanada is not requesting a waiver for portions of the proposed pipeline operating in high consequence areas, stations and crossings of roads, railroads and navigable waterways. PHMSA met three times with TransCanada since last October to discuss the project. In January PHMSA hosted a technical meeting with TransCanada’s engineering staff to discuss all known technical issues related to pipe skelp, manufacture, coating, design, construction, testing, operations inclusive of leak detection, maintenance, and emergency response. PHMSA debated at length about pressure excursions and abnormal operations. We wanted to understand why the higher overpressure allowance is reasonable and would not exacerbate cyclic fatigue. Alternatively, we discussed if it would be reasonable to impose a lower limit. In researching overpressure and cyclic fatigue issue, PHMSA is also reviewing hazardous liquids pipeline accident caused by abnormal operations, specifically pressure excursions. However, because the affect of excursions on flaws is accretive, it may be very difficult to positively determine if pressure excursions caused flaws to fail prematurely.#