Page 374 - Pipeline Pigging Technology

High-accuracy calliper surveys

For production pipeline analysis, the following PC-compatible computer
is recommended:

1Mb of memory
extended memory manager
DOS 3.0 operating system
300Mb hard disk
1.2Mb floppy disk drive
math coprocessor
VGA (640 x 480) 16-colour graphics screen
2- or 3-button Af/croso/?-compatible mouse driver
SUMO read/write optical disk drive
HP PaintJet colour plotter

ANALYSIS OF FEATURES

Preliminary evaluation

The first step in determining the extent of the out-of-roundness problem
is to set criteria and determine the number of anomalies that exceed these
levels. Geodent provides two ways to do this. The dent-reporting utility can
be used to provide a hard-copy listing with dent numbers assigned to each
feature. The dent number can then be referred to in future analysis and
verification digs. The dent display portion of the main program with a suitable
window width can also be used to identify features that require further
analysis (Figs4-7).

Detailed analysis

Occasional sonar drop-outs, refraction from dent flanks, and reflections
from particles can cause a feature to appear or be much larger than it really
is. The redundancy of the Geoptg system provides several ways to verify that
there is a significant feature present and its size.
The gyroscopes in the strapdown inertial unit are affected even by the
slight movement the pig experiences in crossing a girth weld. The gyros will
be deflected by any dents. From the geometry of the tool (Fig. 1), it can be seen

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