Glossary
At Alyeska Pipeline, acronyms abound. Some are used frequently, such as TAPS, which stands for the Trans Alaska Pipeline System; or SERVS, which is short for Alyeska’s Ship Escort/Response Vessel System. But some acronyms are more obscure and unfamiliar. This glossary should help in determining the meaning of those acronyms.
B
Block Valve
When closed, the valve can block oil flow in both directions. Block valves include manual gate valves, remote gate valves and station block valves (suction valves and discharge valves).
Breakout Tank
A tank used to relieve surges in a hazardous liquid pipeline system, or to receive and store hazardous liquid transported by a pipeline for re-injection and continued transportation by pipeline.
C
Check Valves
Operates one-way and prevents the reverse flow of oil. Check valves are designed to be held open by flowing oil and to drop closed automatically when oil flow stops or is reversed.
D
Discharge Pressure
Pressure of the oil as it exits a pump station.
DRA (Drag Reduction Agent)
A long chain hydrocarbon polymer injected into the oil to reduce the energy loss due to turbulence in the oil.
DWT
Dead Weight Tons, the weight of the cargo. DWT x 7 = bbl. (approx.)
L
Linefill
The amount of oil in the pipeline from PS 1 to the Valdez Marine Terminal.
M
Manual Gate Valve
Block valves that are operated manually; placed in check valve segments periodically to provide more positive isolation than can be provided by check valves.
Maximum Allowable Operating Pressure
A rating indicating the maximum pressure at which a pipeline or segment of a pipeline may be operated under the D.O.T. regulations in normal conditions. Also called pressure rating.
O
One Barrel
42 gallons
P
Packline
Oil flow that completely fills a pipline.
Permafrost
Any rock or soil material that has remained below 32½F continuously for two or more years.
Pressure Relief Valve
A valve designed to open automatically to relieve pressure and keep it below a designated level.
Pressure Spike
A sudden, brief rise in pressure.
Pressure Surge
A pressure spike/excursion moving through the pipeline at sonic velocity, produced by a sudden change in velocity of the moving stream that results from shutting down a pump station or pumping unit, closure of a valve or any other blockage of the moving stream.
R
Remote Gate Valve
A remotely controlled block valve for the primary purpose of protecting segments of the line in the event of a catastrophic pipeline break.
S
Slackline
Oil flow that does not completely fill a pipeline.
Station Block Valve
A gate valve installed at the inlet (suction) side and the outlet (discharge) side of the pump station to isolate the pump station from the pipeline in the event of an emergency.
Suction Pressure
Pressure of the oil as it enters a pump station.
T
Telluric Currents
Electrical currents in the earth's surface, caused by the same phenomenon that generates the Northern Lights.
Thermal Expansion
Change in pipe length due to a change in crude oil temperature.
Throughput
The amount of North Slope crude oil transported from PS1 to the Valdez Marine Terminal.
Topping Unit
A mini-refinery that draws crude off the line and produces turbine fuel to power the station. Three pump stations have topping units: PS 6, 8, 10. These topping units are currently shutdown.
U
ULCC
Ultra-Large Crude Carrier, Tanker more than 300,000 dwt.
Ultimate Strength
The stress level at which the pipe will fail/rupture or "break." The ultimate strength of the steel is determined by testing during the manufacture of the pipe.
V
VLCC
Very Large Crude Carrier, Tanker 150,000 to 300,000 dwt.
VSM
Vertical Support Member
Y
Yield Strength
The stress level above which the pipe will yield/bend/stretch.