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of restrained, above-ground line, 604 kilometers of which were built
in accordance with methods first developed and used on a large scale
by Tapline.
A restrained, above-ground line is one which
does not include expansion bends to provide for changes in
temperature. Supports are provided at intervals to insure stability,
and anchorages are provided wherever there is a change in
direction. As temperatures increase or decrease, the line can not
move, but the steel pipe is subjected to stresses which must be
carefully calculated in advance so that the strength of the pipe is
not exceeded. This type of line should be built only in flat,
uninhabited areas underlaid with rock, where the cost and effort to
lay a buried line would be excessive. Much of the terrain across
northern Saudi Arabia provided an ideal opportunity for this unique
method of construction, and permitted Tapline to be built faster and
at lower cost.
At Shu'bah, Barrel X gets another pressure
boost from the first of three portable remote-controlled, gas-turbine
driven pumping units. Again, Tapline was pioneering when it developed
and installed this type of pumping unit, which is controlled by VHF
radio from the next main pump station to the east.
TURBINE UNITS: 5,000 HORSEPOWER
Each unit consists of a portable turbine van,
a control van and a communications van. The last two automatically
radio the needed information, such as pressures and tQmperatures, to
the controlling base station and in return receive radioed signals
which automatically control the operation of the pumping unit.
The turbine van contains a 5,000-horsepower
combustion gas turbine, the most powerful ever built for oil pipeline
use;
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and the main crude oil pump, driven at the gas-turbine speed of 5,000
to 6,000 revolutions per minute.
The gas turbine units were prefabricated in
the United States and packaged at an east coast shipyard. Weighing 125
tons each, they were shipped to the Persian Gulf, lowered onto a barge
at Ras Tanura, Saudi Arabia, and floated ashore. At a
specially-constructed pier they were skidded onto truck trailers
capable of supporting their great weight and then were hauled to their
locations on the line.
As its name implies, the control van houses
the various instruments needed to control the turbines. It also
contains equipment to filter the air supply to the turbine.
The radio van contains VHF transmitters and
receivers capable of transmitting and receiving all data necessary to
operate the unit from, the control center at the base station to the
east. Each van contains three 250-watt FM transmitters.
If a portable pumping unit requires major
repairs, a complete spare portable gas turbine unit with its control
van can be hauled out and connected to the pipeline to keep the oil
moving.
Barrel X is further helped to make a safe
journey along its way by a surge pressure control system developed by
Tapline's engineers. If a portable gas turbine driven pumping unit
suddenly stops, it causes a high-pressure surge wave to travel back
along the pipeline. Uncontrolled, this highpressure wave could rupture
the line. Tapline's system is so designed that the main pump station
to the east receives a radio signal from the turbine unit when it
stops pumping. This signal travels through the control system at the
base station and automatically reduces the base station discharge
pressure. Reduced pressure out of the base station offsets the effect
of the high-pressure surge coming back from the
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