Page 373 - Pipeline Pigging Technology

Pipeline Pigging Technology

relative to a theoretical horizontal line that would represent a point on a
circle. The plotted deviations from this line represent the magnitude of the
dent, ovality or other feature.
Round section: plots each set of sonar readings within a section of the
pipeline at a distance or time along the pipeline. The view is as if looking in
the end of the pipeline at the end of the section. Each sonar reading is plotted
as a residual from a circle.
Contour section: is similar to the Thermal section, except that the sonar
readings are contoured and a line of constant depth is determined and colour
plotted.
Gyro and diameter, plots the readings from the cross-track gyroscopes of
the inertial system. This is useful in confirming welds, as the gyroscopes will
see deflections as the front and rear cups of the pig cross the weld or any dent.
If, for example, there is some foreign matter clouding a particular sonar or
group of sonars instead of an actual dent, then there will be no perturbation
of the gyros. This helps to distinguish real features from measuring errors or
transducer problems. Also plotted is the best-fit of all the calliper sonars to
give a reading of the inside diameter of the pipeline.
3D plot: provides the ability to show the feature in a three-dimensional
view. The viewing perspectives in the horizontal and vertical can be changed
to give different perspectives. The vertical exaggeration is five times on the
vertical (depth) that on the horizontal to make the features more distinguish-
able.
Pig movement: a more quantitative correlation of the dents from the gyro
is possible using this display, which shows the horizontal and vertical
movement of the Geopig as it transits the pipeline. The movements are in
centimetres, and are related to the size and location of the feature.

Hardware requirements

Geodent requires a PC-compatible computer with the following minimum
requirements:

640K of memory
DOS 3.0 operating system
40Mb hard disk
1.2Mb floppy disc drive
math coprocessor
VGA or EGA colour graphics screen
2- or 3-button Mfcrosq/fr-compatible mouse driver

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