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Navy Engineers Oversee Examination of 63-year-old fuel line By Cynthia Greenwood
For 20 years, the Navy has run clean diesel fuel through a 32-inch pipeline encased inside a tunnel beneath Honolulu's volcanic hills. The 2.7-mile-long pipeline runs between the Red Hill Fuel Storage Facility's gargantuan tank farm and numerous fueling piers at Naval Station Pearl Harbor. Since it built the pipeline in 1943, the Navy has maintained it through visual inspections and external spot checks using ultrasonic testing methods. (See "Pigging the Diesel Pipeline between the Landmark Red Hill Facility and Pearl Harbor," CorrDefense, Oct. 2005. Click here) Naval engineering experts and a key contractor have begun finalizing the results of the first-ever "smart pig" inspection of the diesel line. They are working closely with directors of the Bulk Fuels division of the Navy Fleet Industrial and Supply Center (FISC), which is headquartered on base. Terri Regin, fuel facilities subject matter expert at Naval Facilities Engineering Service Center, oversaw the inspection, which is a critical supply line for the Pearl Harbor fuel depot. The depot supplies Navy warships headed to conflict zones in southwest Asia, as well as Oahu-based aircrews from Wheeler Air Force Base (AFB), Hickam AFB, and the Coast Guard. VECO Federal, Inc. (VFI), the Colorado-based contractor who carried out the inspection and supplied the equipment, developed a plan to address inherent challenges of pigging the line. Mike Denham, the VFI program manager, directed the overall project, while Brad Holm, the VFI project manager, directed the day-to-day activities, including the design, construction, pigging, processing, and final report gathering. The Navy also asked VFI to make necessary modifications to the line and install auxiliary systems needed to perform the investigation work. VFI handled all pigging operations, including cleaning and inspection runs, Holm said. "In addition, we received off-spec fuel generated by the pigging processes and returned acceptable fuel to the facility. We also developed the pigging and ultrasonic thickness scan completion reports that contained analyses and recommendations." Construction for the project occurred during October and early November of 2005. The pigging process took place in late November. Regin described a number of challenges that she and VFI's team experienced at the work site. "We sent ultrasonic pulses through the steel wall of the pipeline so we'd know where any anomalies from corrosion were located," she said. Finding a pig that would negotiate the miter joints, or pipe sections welded together at an angle that occur throughout the pipe, was not easy. Next, the team installed a temporary launcher/receiver and replaced a reduced-diameter valve with a full-diameter pipe spool piece. Because the pipeline rests inside a tunnel, it was not easy for inspection crews to access it. To install the pigs' launcher and receiver, Regin and her team had to transport their equipment through the tunnel using industrial golf-style carts. The team also took great pains to perform the necessary welding to modify the line.
It was also challenging for the team to locate a 34-inch, full-bore valve that would fit inside the tunnel. Eventually, the group found a 36-inch knife gate valve that was appropriate, but it took 30 minutes just to open it. Initially, the inspection crew ran two foam pigs through the line at 3 mph to remove the debris. Next, the crew pumped fuel slowly through the line to move the ultrasonic pig through the series of miters and pipe supports located every 40 feet, at each of the tunnel's 20 concrete walls. The process was difficult, Regin explained, because the ultrasonic pig ran very slowly. "During the planning phase, one of FISC Pearl Harbor's smaller pumps was tested to determine if it would provide the required flow rates," she said. "We also tested it to ensure that it would not burn out during the 18 to 24 hours of continuous operations." During the actual pig run, the pump temperature was checked every 15 minutes to ensure it operated continuously. In addition to using a small pump, a valve was throttled down so that the pig ran at its optimum speed. The type of pig used provided continuous real-time data, including the speed and location of the pig and the anomalies detected in the pipeline. Handling fuel during the receipt of the pigs also proved challenging, Regin recalled. As the pigs moved through the line, they disturbed the loose carbon and fine debris that were inside the pipe. "Approximately 40,000 gallons of diesel product became contaminated with this debris during each pig run," she explained. "The contaminated fuel could not enter the pump house, because it would damage the equipment, nor could it go directly into storage. Instead, the fuel quality was constantly monitored as the pig approached the receiver, and as the fuel changed color, it was diverted to four settling tanks. After the debris settled to the bottom of the tanks, the diesel was tested and then pumped back into active storage." To complete the project, Regin and the rest of the team had to spend Thanksgiving in Hawaii, rather than at home. "It was a choice between being away from home during either Thanksgiving or Christmas," she said. "As it was, the final walkthrough after removing the launcher/receiver was done on December 23, 2005." "In the end we found no corrosion where the pipe goes through the concrete wall or sits on supports," Regin said. "There was also no noticeable internal corrosion. However, we did find some areas of external corrosion where there is water dripping from the top of the tunnel." Editor's Note: Terri Regin provided reporting for this article.
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