North American Oil & Gas Pipelines

SEP 2018

North American Oil & Gas Pipelines covers the news shaping the business of oil and gas pipeline construction and maintenance in North America, including pipeline installation methods, integrity management innovations and managerial strategies.

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Page 34 of 43 SEPTEMBER 2 018 | North American Oil & Gas Pipelines 35 pated. Therefore, all internal wall loss defects, external abra- sion or extremely high fatigue scenarios will be treated as temporary, requiring either a planned removal or an ongoing inspection plan. In the following case study, the operator de- sired a temporary repair to last until the affected system could be fully fixed. The operator was faced with a leak in a crucial fire water system, consisting of a 10-ft carbon steel fire water line with a 0.25-in. hole. The pipe could not be immediately cut out and replaced, and a repair option was desired that would last until spring. When the company discovered this anomaly, a MIS repair team was called with an ini- tial inquiry at 11 a.m. on one day, with design and quote completed and the order packed and shipped that same day. The following day, the team traveled to the site and completed the repair by noon the next day, finishing the repair in 25 hours from the initial call. Based on the leaking defect, MIS engineers recommended a hy- brid repair using EPRK (Emergency Pipe Repair Kit) and FormaShield. EPRK was used to stop the leak, while FormaShield was used to en- capsulate and reinforce the pipe. After the contractor prepped the pipe, the EPRK items were applied as a "stop- gap." A Butyl strip was clamped over the leak and clamp, then tented with filler putty. The team then waited 30 minutes to confirm a "drip-free" repair zone. A fast-curing, water activated wrap was applied over the clamp as an initial encapsulation, then 10 layers of FormaShield were applied to fully encapsu- late and reinforce the defected area. The re- pair was successfully completed within two and a half hours. To consider a repair "permanent", any thermal and cyclic fatigue should also be considered on the pipe as well as the repair itself. Additionally, specific repair systems with known longevity issues, such as unidi- rectional composites that circumferentially crack or systems that allow further corrosion growth under the repair, may need to be monitored more closely and not considered "permanent." The following case study con- sisting of general external corrosion could be considered "permanent" as the defect has been arrested and the repaired region is now in a static condition with no significant changes in the pipe or the composite repair anticipated. In a case study regarding an aging pipe- line in Patterson, Louisiana, MIS engineers considered the amount of corrosion it was experiencing and created a repair with an ap- propriate design life. A 20-in. OD horizontal gas pipeline in Patterson had been installed in 1956 and was starting to experience sig- nificant external corrosion. The damages, ex- isting at 9 o'clock and 3 o'clock on the pipe, were 17 in. long, 15 in. wide and 0.123 in. deep for the first grid and 15 in. long, 16 in. wide and 0.066 in. deep for the second grid. The repair of the pipe, with a nominal wall thickness of 0.281 in., would require facilitating a maximum operating pressure of 1,050 psi and a pipe temperature of 50 F. MIS engineers designed a 20-year design life solution using the A+ Wrap system consisting of 17 layers for three linear feet, which would re- store the structural integrity of the pipeline and bring it back to pristine conditions. The repair was completed in two hours by a MIS technician and contracted personnel. The repair area was grit-blasted and wiped clean with acetone, followed by an application of EP420 as filler material for load transfer at the corrosion site. The repair also in- cluded repairing a girth weld and long seam welds. The technician applied a PPR epoxy coating to the entire repair zone and the 12 in. wide A+ Wrap system was applied using the layer over layer with offset method. ILI markers were installed to allow for inspection and the application was finished by applying and curing perforated constrictor wrap, which was removed the next day, and a topcoat was applied. Years of field and third-party testing of composite repair products have shown that there are several options available that meet ASME and ISO engineering standards and are tested in accordance with ASTM and ISO. This testing shows that composites can withstand harsh elements, high pressure and the effects of long-time exposure in severe environments. Capable of providing repairs that can span decades, properly engineered composites can offer an extremely cost-effective solution. Casey Whalen serves as engineering supervisor at Milliken Pipe Wrap.

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