Technical details Trans-Alaska Pipeline System

map of trans-alaska pipeline system

oil going trans-alaska pipeline comes 1 of several oil fields on alaska s north slope. prudhoe bay oil field, 1 commonly associated pipeline, contributes oil, kuparuk, alpine, endicott, , liberty oil fields, among others. oil emerges ground @ approximately 120 °f (49 °c) , cools 111 °f (44 °c) time reaches pump station 1 through feeder pipelines stretch across north slope. north slope crude oil has specific gravity of 29.9 api @ 60 °f (16 °c). in 2008, pipeline carried approximately 700 thousand barrels per day (110,000 m/d), less theoretical maximum capacity of 2.14 million barrels per day (340,000 m/d) or actual maximum of 2.03 million barrels per day (323,000 m/d) in 1988. pump station 1 takes average of 11.9 days oil travel entire length of pipeline valdez, speed of 3.7 miles per hour (6.0 km/h).

the minimum flow through pipeline not defined maximum. operating @ lower flows extend life of pipeline increasing profit owners. 2012 flow of 600,000 bbd less pipeline designed for. low flowrates require oil move slower through line, meaning temperature drops more in high-flow situations. freeze in line block pig in line, force shutdown , repairs. 2011 engineering report alyeska stated that, avoid freezing, heaters need installed @ several pump stations. report noted these improvements bring flow low 350,000 bbd, did not attempt determine absolute minimum. other studies have suggested minimum 70,000 100,000 bbd current pipeline. alyeska replace 48 pipeline prudhoe bay fairbanks 20 pipeline , use rail rest of way, allow little 45,000 bbd.

pumping stations maintain momentum of oil goes through pipeline. pump station 1 northernmost of 11 pump stations spread across length of pipeline. original design called 12 pump stations 4 pumps each, pump station 11 never built. nevertheless, pump stations retained intended naming system. 8 stations operating @ startup, , number increased 11 1980 throughput rose. of december 2006, 5 stations operating, pump station 5 held in reserve. pump stations 2 , 7 have capacity of moving 60,000 gallons/minute (227,125 l/min), while other stations have capacity of 20,000 gal/min (75,708 l/min). pumps natural-gas or liquid-fueled turbines.

because of meanders , thermal , seismic accommodations, amount of 48-inch (1,200 mm) diameter welded steel pipeline between pipe stations , end of line 800.3 miles (1,288.0 km), while linear distance between prudhoe bay , valdez station endpoints 639.34 miles (1,028.92 km). pipeline crosses 34 major streams or rivers , 500 minor ones. highest point @ atigun pass, pipeline 4,739 feet (1,444 m) above sea level. maximum grade of pipeline 145%, @ thompson pass in chugach mountains. pipeline created in 40 , 60-foot (12.2 , 18.3-meter) sections. forty-two thousand of these sections welded make double joint, laid in place on line. sixty-six thousand field girth welds needed join double joints continuous pipeline. pipe of 2 different thicknesses: 466 miles (750 km) of 0.462 inches (1.17 cm) thick, while remaining 334 miles (538 km) 0.562 inches (1.43 cm) thick. more 78,000 vertical support members hold aboveground sections of pipeline, , pipeline contains 178 valves.

at end of pipeline valdez marine terminal, can store 9.18 million barrels (1,460,000 m) of oil. eighteen storage tanks provide capacity. 63.3 feet (19.3 m) tall , 250 feet (76 m) in diameter. average 85% full @ given time—7.8 million barrels (1,240,000 m). 3 power plants @ terminal generate 12.5 megawatts each. 4 tanker berths available mooring ships in addition 2 loading berths, oil pumping takes place. more 19,000 tankers have been filled marine terminal since 1977.