Pipeline Engineering

Cost

Approximately $8 billion for construction of entire system, including Terminal and pump stations, at conclusion of initial construction period in 1977. Does not include interest on capital investment, or capital construction after 1977.

Concrete weights

• Pipe coating, river crossings — 75,000 lbs. per 40-ft. section
• Saddles, flood plains — 18,500 lbs. each
  

Mainline crossings

• Animal, elevated, minimum height — 10 ft.
• Animal, elevated, number — 554
• Animal, buried, number — 23
• Animal, buried, refrigerated, location — MP 645 and MP 649
• Bridges —
  • Pipeline, types and number —
    • Orthotropic box girder — 1
    • Plate girder — 9
    • Suspension — 2
    • Tied arch — 1
    • Total — 13
  • Road, number —
    • North of Yukon — 21
    • South of Yukon — 23
  • Road crossings, refrigerated — Glenn Highway at Glennallen
    

Design modes

Selection — Soil sampling and other means were used to determine soil types along the route. Where thaw-stable soils were found, the pipeline was buried in the conventional manner. In areas of thaw-unstable soils, and where heat from the oil in the pipeline might cause thawing and consequent loss of soil foundation stability, the pipeline was insulated and elevated above ground by means of a unique support system.

Basic types and miles of each —

• Above-ground — 420 mi.
• Conventional below-ground — 376 mi.
• Refrigerated below-ground — 4 mi.

Description —

• Above-ground — Specially designed vertical supports were placed in drilled holes or driven into the ground. 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.
• Conventional below-ground — 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.
• Special burial, non-refrigerated — In areas of thaw-unstable soils calling for elevated pipeline construction, but 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.
• Special burial, refrigerated — In some areas the line was insulated and buried in a refrigerated ditch. Refrigeration plants at each of these points circulate chilled brine through loops of 6 inch diameter pipe to maintain the soil in a stable frozen condition.
  

Insulation

• Elevated pipeline, thickness-3.75 in.
• Refrigerated below-ground pipeline, thickness-3.2 in.
• Under gravel workpad or road-2 in. to 4 in. (limited areas only)
  

Gabion & concrete mats

Used in Atigun Floodplain Pipe Replacement Project for scour protection of the new pipe because less cover on top of new pipe.

• Gabion mats, used 31,750 ft.
• Concrete mats, used 9,525 ft.
  

Land Ownership

Ownership, entire system, by area:

• Federal government-6.27 sq. mi. approx.
• State government-7.79 sq. mi. approx.
• Private-1.33 sq. mi.
• Owner companies-2.9 sq. mi.
• Total area-19.29 sq. mi.

Ownership, pipeline only, length

• Federal government- 376 mi. approx.
• State government-344 mi. approx.
• Private-80 mi. approx. (including 51 mi., Alaska Native Corp. land)
• Total –800 mi.

Pipeline in municipal jurisdiction, approx.

• Arctic North Slope Borough - 179.2 mi.
• Fairbanks North Star Borough - 89.1 mi.
• City of Delta Junction - 5.5 mi.
• City of Valdez - 20.8 mi.
  

Linefill

Definition - Amount of oil in pipeline from PS 1 to Marine terminal.

The linefill is 9,059,057 bbl.

Permanent facilities

Access roads, dimensions — 120 ft. to 7.5 mi. long; 28 ft. wide, minimum 3 ft. gravel base.

Access roads, number — 225, linking state roads with pipeline, pump stations and airfields.

Airfields, land status and length —

• Federal land subject to and operated under state leases —
  • Galbraith Lake — 5,200 ft.
  • Prospect — 5,000 ft.

Pressure Relief Station — 1 (PS 5, reinjects oil drained down for pressure relief, but does not have mainline pumps and does not boost total stream).

Marine terminal — 1 (Valdez).

Pig launching/receiving facilities — 3 (PS 1, 4, and Marine Terminal).

Pipe shoes, number — 39,000 approx.

Pump stations, operating — 11 (10 pump stations, 1 relief station)

Topping units — 3 (PS 6, 8, and 10.  PS 8 and 10 topping units placed in standby, summer 1996.  PS6 topping unit placed in standby summer 1997.)

Pipeline Valves, types and number —

• Check — 81
• Gate — 71
• Block — 24
• Ball — 1
• Total — 177
  

Thermal expansion

Definitions -

Thermal expansion - change in pipe length due to change in crude oil temperature

Tie-in temperature - actual pipe temperatures at the time when final welds were made which joined strings of pipe into a continuous line

Hot position - pipe at maximum oil temperature (145° F)

Cold position - pipe at minimum steel temperature
(-60° F) (pre-startup)

Each 40 ft. length of pipe expands .031 inches with each 10° F rise in temperature and contracts the same distance with each 10°F drop in temperature.

Longitudinal expansion of typical 720 ft. straight above-ground segment from min. tie-in temperature to maximum operating temperature - 9 inches.

Note: due to anchoring, the pipeline does not expand lengthwise but shifts laterally on the above-ground supports (See zig zag configuration , below)

Maximum above-ground lateral movement-

• Tie-in to hot position - 8 ft.
• Tie-in to cold position - 4 ft.

Thermal stress - maximum, 25,000 psi - where below ground pipeline is fully restrained by the soil, the maximum longitudinal stress due to change in temperature from pipe temperature at tie-in to maximum oil temperature

Zig zag Configuration

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.

Refrigerated Burial of Pipe

VSMs (Vertical Support Members)

Basic data —

• Number — 78,000
• Diameter — 18 in.
• Types — 16, to accommodate variety of soil and permafrost conditions.

Depth at which embedded — 15 ft. to 70 ft.

Distance between —

• Anchor supports — 800 ft. to 1,800 ft.
• Standard supports — 60 ft. approx.

Heat pipes, number fitted with — 61,000 (122,000 individual heat pipes, 2 per VSM, where fitted)

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