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TAPS shuts down for summer maintenance Pipeline will be out of operation for up to 36 hours to allow crews to work at pump stations, Valdez Marine Terminal Alan Bailey Petroleum News
Alyeska Pipeline Service Co. is shutting down the trans-Alaska oil pipeline for maintenance on June 19 and 20 in the first of two maintenance shutdowns scheduled for the 2010 summer season.
“The event is designed to last up to 36 hours and begins Saturday morning,” the company said June 15.
The pipeline was closed down for more than 79 hours at the end of May while Alyeska responded to a contained oil spill at pump station 9, about 100 miles south of Fairbanks. But the complexity of the planning required for the June maintenance and the necessity to focus on dealing with the oil spill incident precluded the possibility of doing the maintenance work during the oil spill related outage, Alyeska spokesman Matt Carle told Petroleum News.
Annual maintenance Alyeska conducts line-wide shutdowns annually to provide maintenance crews with an opportunity to simultaneously work on a number of maintenance projects on the pipeline and at the Valdez Marine Terminal. The North Slope oil producers typically conduct routine maintenance on oilfield facilities at the same time.
Among a series of projects penciled in for the pipeline on June 19 and 20 is the final disconnect of the original turbine powered pumping system at pump station 4, Alyeska said. The company had converted the pump station to a new electrically powered pumping system in 2008-09 as a part of the strategic reconfiguration of the oil pipeline infrastructure.
Alyeska is also replacing the two large valves used at pump station 4 to receive the “pigs” sent down the line from pump station 1 to internally clean and inspect the line.
At pump station 1 Alyeska is rerouting the incoming pipeline connection from the Kuparuk field to a new above-ground line. The company will also conduct other maintenance projects at pump stations 5 and 7, and at the Valdez Marine Terminal, Alyeska said.
Strategic reconfiguration The strategic reconfiguration of the trans-Alaska pipeline, of which the disconnection of the legacy pumps at pump station 4 is but a minor part, is a multiyear project designed to enable the pipeline to flexibly handle lowering oil throughputs and to increase pipeline efficiency through the use of state-of-the-art pipeline control and monitoring technology.
A core component of the project is the replacement of the original pumping systems that drive oil through the pipeline by new electrically powered pumps with variable frequency drives that enable efficient adjustment of the pumping power. The installation of a bank of pumps at each operational pump station also enables individual pumps to be taken in and out of operation, thus further allowing great flexibility in handling different levels of pipeline throughput.
And, in recognition of reduced throughput in the pipeline, Alyeska has taken out of service all but five of the original 11 pump stations along the pipeline. Pump stations 1, 3 and 4 north of the Brooks Range now propel oil over the 4,739-foot Atigun Pass in the range. Pump station 5 on the south side of the Brooks Range acts as a relief station for oil flowing down from Atigun Pass and does not pump the oil. Pump station 9 drives the oil over the Chugach Mountains to the Valdez Marine Terminal, where the oil is loaded onto tankers.
Phased approach Alyeska established a phased approach to pump station upgrade, with the lessons learned from the modification of each pump station used to improve the upgrade plan for the next pump station. The company completed the conversion of pump station 9 in February 2007, with pump station 3 following in December 2007 and pump station 4 in May 2009.
Conversion of pump station 1, at the intake end of the line on the North Slope, is by far the most complex of the conversion projects because of the interconnects between this pump station and the North Slope oil infrastructure. Alyeska had planned to start upgrading this pump station in 2010, with the new systems coming on line in 2012. But in late 2009 the company postponed the upgrade by a year, along with a series of cost-reduction actions in a revised long-range plan for the pipeline system.
However, all of the pump stations, including pump station 1, are now controlled remotely from a control center that was moved from Valdez to Anchorage in 2008. New control and monitoring systems using state-of-the-art digital technology not only allow centralized pipeline control, they also enable the centralized collection of data for improved maintenance efficiency.
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