The Trans Alaska Oil Pipeline 2
The 48-inch diameter pipeline crosses three mountain ranges as well as forests, rivers, and plains. More than half the line is elevated in sections ranging from about 30 miles in length to the a few hundred feet. The remainder is buried underground.
The decision to elevate or bury the pipe depended primarily on soil conditions and the possible effects of the pipeline heat on the soil. Normal burial was used in stable soils and rocks, where thawing would not cause loss of soil support for the pipeline. Additionally, special burial techniques were used in some short sections for animal and highway crossings.
In places where melting permafrost might create soil stability conditions, the pipeline was insulated, jacketed, and installed above ground. Thawing around the aboveground supports in the most heat-sensitive areas was and is prevented by thermal devices that carry heat up through the pipes to radiators on top of the supports.
Aboveground sections were built in a flexible zigzag pattern in which longitudinal expansion or contraction of the pipe from heat or cold is converted into sideways movement. This also accommodates pipe motion induced by earthquake.
At more than 800 river and stream crossings, the pipe bridges the waterway or is buried beneath it. And, at 151 points along the line, valves are installed to stop oil flow, if necessary. In particular, valves are located near key stream crossings, population areas, and major uphill sections of the pipeline.
Throughout much of the life of the pipeline, crude oil was moved down the line by a series of ten operating pump stations. An additional facility provided oil control capability and could have become a pump station if expansion by the system had been required. A twelfth station site was also available. Today only six of the original ten pump stations are being used to move oil through the line. (Production of oil on the North Slope has been declining because of the age of the oil fields, thereby reducing the amount of throughput of oil in the line, and thus requiring fewer pump stations.)
The heart of each station is the main pump building that houses gas-turbine-driven mainline pumps. Most stations have three pumps, each of which can move 22,000 gallons of oil each minute, or up to 754,000 barrels a day (one barrel equals 42 gallons).
The Trans Alaska Oil Pipeline 2
The 48-inch diameter pipeline crosses three mountain ranges as well as forests, rivers, and plains. More than half the line is elevated in sections ranging from about 30 miles in length to the a few hundred feet. The remainder is buried underground.
The decision to elevate or bury the pipe depended primarily on soil conditions and the possible effects of the pipeline heat on the soil. Normal burial was used in stable soils and rocks, where thawing would not cause loss of soil support for the pipeline. Additionally, special burial techniques were used in some short sections for animal and highway crossings.
In places where melting permafrost might create soil stability conditions, the pipeline was insulated, jacketed, and installed above ground. Thawing around the aboveground supports in the most heat-sensitive areas was and is prevented by thermal devices that carry heat up through the pipes to radiators on top of the supports.
Aboveground sections were built in a flexible zigzag pattern in which longitudinal expansion or contraction of the pipe from heat or cold is converted into sideways movement. This also accommodates pipe motion induced by earthquake.
At more than 800 river and stream crossings, the pipe bridges the waterway or is buried beneath it. And, at 151 points along the line, valves are installed to stop oil flow, if necessary. In particular, valves are located near key stream crossings, population areas, and major uphill sections of the pipeline.
Throughout much of the life of the pipeline, crude oil was moved down the line by a series of ten operating pump stations. An additional facility provided oil control capability and could have become a pump station if expansion by the system had been required. A twelfth station site was also available. Today only six of the original ten pump stations are being used to move oil through the line. (Production of oil on the North Slope has been declining because of the age of the oil fields, thereby reducing the amount of throughput of oil in the line, and thus requiring fewer pump stations.)
The heart of each station is the main pump building that houses gas-turbine-driven mainline pumps. Most stations have three pumps, each of which can move 22,000 gallons of oil each minute, or up to 754,000 barrels a day (one barrel equals 42 gallons).