Equipment Specs
Content
Languages

Trans Alaska Pipeline System

From RitchieWiki

Projects > Pipelines
The Trans Alaska Oil Pipeline
At 800 miles (1,287 km) long, the Trans Alaska Pipeline System (TAPS) is one of the longest in the world. It stretches from Prudhoe Bay in Alaska to Valdez, the most northern ice-free port of the U.S. The pipeline was constructed by Alyeska Pipeline Service Co. for the purpose of transporting oil to refineries in the U.S. The project cost $8 million and took almost three years. Construction began in April 1974 and was completed in June 1977. Employing 2,000 contractors and 70,000 workers, it was the largest privately funded project of its time.

The project is unique not only for having one of the longest pipelines but also because it had to consider constructing in a variety of extreme temperatures. Typically pipes were laid beneath the ground; however, in some sections where permafrost was common or when the heat from the oil pipes would cause unstable thawing conditions of the soil, new methods had to be conceived.[1]

Contents

[edit] Construction History

[edit] Pre-construction Considerations

When the Atlantic Richfield Co. (ARCO) discovered oil in Prudhoe Bay in 1968, the idea of building a large pipeline to transport oil was first entertained. There were some obstacles to overcome, such as installing pipes in areas where permafrost was prevalent. In addition, negotiations had to be made with federal and state governments to ensure that the pipeline could cross wildlife habitats with little or no interference.

When the project was given permission, special materials were needed to build pipes for such harsh and extreme conditions. Cold-weather steel with a 48-inch (122-cm) diameter was ordered and shipped from Japan in 1969.

The permit, however, was not granted until 1974. Construction began shortly after, in April. Before excavators could start the digging process, the soil had to be surveyed throughout the area. This would determine how the pipes would be laid or buried. Where soil was thaw-stable, pipelines could be installed and buried as normal. Where they were not stable, the pipeline had to be insulated and kept above ground so that the heat from unstable, thawing soil would not corrode or destroy the pipes.[2]

[edit] Pipeline Types and Construction

[edit] Aboveground

There were three types of pipelines constructed. The sections of pipeline constructed above ground required vertical supports that were drilled into the earth’s surface. The pipes were designed to take on occasions when the soil would thaw and cause disruptions to the pipeline’s support. Heat pipes with two-inch (5.1-cm) diameters were installed in the supports to remove the heat from the ground when it exceeded a temperature deemed disruptive to the pipeline.

[edit] Belowground

The second type was the belowground, also known as conventional, pipeline. Typically, pipes are laid and covered with gravel padding and soil fill in ditches that are usually between eight feet (2.4 m) and 16 feet (4.9 m) deep, but can be buried deeper. Some of the pipes in the TAPS were buried as deep as 48 feet (15 m). Zinc ribbons, a device used to prevent corrosion of the pipes, were buried in conjunction with the pipes. The zinc returns potentially damaging currents back to the ground.

[edit] Special Burial

The third type of pipeline was buried in a way that required special conditions; this could be accomplished with refrigerated or non-refrigerated pipes. Sometimes, the pipe had to be buried because of highways or animal crossings, or in situations where there was a probability of rockslides or avalanches. In these situations, the pipes were buried with heavy insulation to protect against the harsh conditions of permafrost. Ditches also had to be refrigerated in some sections with six-inch (15-cm) brine pipes to keep them cool.[3]

Approximately 3,500 boreholes were dug using an array of machinery, including boring-machines, ditchers, and trenchers. Tractors and dozers were used to push soil that was excavated by hydraulic excavators, ditchers and trenchers. Each 40-foot (12.2-m) section of pipe weighing 75,000 pounds (34,019 kg) was laid by pipelayers on occasions when pipes had to be laid below the earth’s crust. At times, the pipes required bending, a process that could be completed with a pneumatic bending mandrel. As well, they sometimes needed to be welded to other pipes, a process that required welding truck rigs and welding tractors. Following the successful laying of the pipes, padding machines, dozers, or tractors were used to provide backfill for the holes.[4]

[edit] Sections of Pipelines and the Contractors Responsible

  • The first section reached 145 miles (233 km) long, from Valdez to Gulkana River and was constructed by Morrison-Knudson.
  • Section 2, at 157 miles (253 km), ran from Gulkana River to Salcha River and was completed by Perini Arctic Associates.
  • Section 3 consisted of 144 miles (232 km), from the Salcha River to Yukon River. This was completed by H.C. Price.
  • At 127 miles (204 km), section 4 stretches from the Yukon River to Midnight Dome and was constructed by Associated Green.
  • Section 5, at 98 miles (158 km) long, ran from Midnight Dome to Kuparuk River. Arctic Constructors completed this segment.
  • The final section was 125 miles (201 km) long. Arctic Constructors also completed this section, which ran from the Kuparuk River to Pump Station 1.[5]

[edit] Equipment Used

[edit] Unique Facts

  • More than 15 billion barrels of oil have been transported through the pipelines.
  • The pipe crosses about 800 streams and rivers from its point of origin to the oil refinery tanks.
  • Oil from Alaska contributes 17 percent of the U.S. crude oil production.
  • The companies that make up the ownership of TAPS are: BP Pipelines; ConocoPhillips Transportation Alaska, Inc.; ExxonMobile Pipeline Co.; Unocal Pipeline Co.; Koch Alaska Pipeline Co.
  • TAPS is headquartered in Anchorage, Alaska and employs 800 people. The largest camp was the Marine Terminal, with 3,480 beds. The largest pipeline camp is the Isabel Pass, with 1,652 beds, while the smallest is Sourdough with 112 beds. A total of 31 fatalities occurred during the course of construction.[7]

[edit] References

  1. Aleyska Pipeline Service Company: About Us, 2008-09-25.
  2. Trans-Alaska Pipeline. SolcomHouse, 2008-09-25.
  3. Trans-Alaska Pipeline. SolcomHouse, 2008-09-25.
  4. Aleyska Pipeline Service Company: Pipeline Facts, 2008-09-25.
  5. Aleyska Pipeline Service Company: Pipeline Facts, 2008-09-25.
  6. Pipeline Design and Construction: Step by Step, 2008-09-25
  7. Aleyska Pipeline Service Company: Pipeline Facts, 2008-09-25.