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The trend of pipeline system design in recent
years has been toward Iarger-diameter, thinner-wall pipe operating at
higher stress levels, and toward increased automation of the pumping
plant and other operating, facilities. This was recognized and applied
when Tapline was conceived and built in the late 1940's; Tapline has
since continued to pioneer in the development of economic overland
transportation of oil.
Let us follow one imaginary barrel of oil -
Barrel X - through the maze of pipes, pumps and tanks from the
producing field in Saudi Arabia to a tanker berthed in the
Mediterranean Sea near Sidon. The story of its 1,600-kilometer
journey, which may be as short as eleven days, is unique because of
some of the methods and equipment used only by Tapline.
A LONG AND UNIQUE JOURNEY
Barrel X starts from a well, perhaps 7,500
feet underground. It then travels for about three days through
Aramco's gathering lines to Qaisumah, where it is gauged. Then it
enters Tapline for an eightday trip to the sea.
Barrel X's movements are determined by
Tapline's Beirut dispatching office. Through a radio communications
network, this office is only seconds away from any control point on
the pipeline or in the terminal. VHF (very high frequency) equipment
of the most modern "over-the-horizon" type is being extended
throughout Tapline, marking the first use of this type of VHF by
private enterprise.
At Qaisumah, the first of four community-type
pump stations, five electric-motor driven and six diesel-engine driven
centrifugal pumps are available to apply pressure to Barrel X to move
it westward. These units have a combined rating of 12,000 horsepower,
and normally operate at about 9,000
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horsepower. Oil from the line is used as fuel for all Tapline's pumping engines.
Since moving, oil by pipeline is an
around-the-clock operation every day of the year, operating crews are
on duty continuously. They work in alternate eight-hour shifts: from 7
a.m. to 3 p.m., from 3 p.m. to 11 p.m., and from 11 p.m. to 7
a.m.
Barrel X travels westward from Qaisumah faster
than it would if the pipeline were operated by conventional
methods. That is because it is traveling under Tapline's application
of a combined stress theory, sometimes called the "constant safety
factor" method of operation.
TEMPERATURES AFFECT LINE
Briefly, this theory takes into account the
fact that a pipeline operating under the pressure of the oil which it
is carrying is subjected, to other forces in addition to- those caused
by the pressure; for example, the force caused by changes in
temperature. Conventional practice is to ignore all but the forces or
stresses caused by pressure, and to operate the line at a constant
pressure which will always be safe regardless of temperature
change. But if proper account is taken of the cumulative effect of
several forces acting at once upon the pipe, higher operating
pressures are possible for periods of each day without reducing the
safety of the line.
So far Tapline is the only pipeline company
using this system, although its advantages are apparent. In Tapline's
instance daily capacity has been increased by more than 15,000
barrels.
Barrel X leaves Qaisumah in a buried line such
as is commonly used in most parts of the world. En route to Shu'bah,
142 kilometers to the west, it enters the first section
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