Studu of the Trans-Alaska pipeline

In warm permafrost and other areas where heat might cause undesirable thawing, the supports contain two each, 2-inch pipes called "heat pipes," containing anhydrous ammonia, which vaporizes below ground, rises and condenses above-ground, removing ground heat whenever the ground temperature exceeds the temperature of the air. Heat is transferred through the walls of the heat pipes to aluminum radiators atop the pipes. (Glass, Steel and Stone, 2003).
             Above ground sections of the pipeline are built in a zig-zag configuration to allow for expansion or contraction of the pipe because of temperature changes. The design also allows for pipeline movement caused by an earthquake. (Alyeska Pipeline Service Company, 2002).
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             (Fig.1 "the structure of the above ground pipeline).
             (http://www.alyeska-pipe.com/Pipelinefacts/PipelineEngineering.html) [2003, January 22].
             2.2. Conventional below ground, special burial, non-refrigerated and special burial, refrigerated pipeline (Fig.2).
             And the structure of the other three types of pipeline is basically the same. The pipe is underlain with a layer of fine bedding material and covered with prepared gravel padding and soil fill material, in a ditch from 8 ft. to 16 ft. deep in most locations, but up to 49 ft. deep at one location. Zinc ribbons, which serve as sacrificial anodes to inhibit corrosion of the pipe, are buried alongside the pipeline. The Atigun pipe replacement section, 8.5 miles in length, has four magnesium ribbon sacrificial anodes installed. Electrical currents in the earth's surface, called "telluric currents" and caused by the same phenomenon that generates the Northern Lights, can be picked up by the pipeline and zinc anodes. The zinc anodes act like grounding rods to safely return these currents back to the earth, reducing the risk of damage to the pipeline. .
             In areas of thaw-unstable soils calling for elevated pipeline construction, special burial, non-refrigerated will be used in the area where the pipeline had to be buried for highway, animal crossings, or avoidance of rockslides and avalanches, the line was insulated, to protect the permafrost from the heat of the pipeline, and buried.