Page 364 - Pipeline Pigging Technology

High-accuracy calliper surveys

Geoptg, and a storage device and power supply which allow independent
operation for long measurement periods.
Fig.l is a schematic of the Geopig for NFS 30-in sizes and larger. For a
detailed description of the development of the Geopig, see Adams etaL, 1989.
For detailed description of the applications, see Price etaL, 1990.

Background for feature reporting

In the initial stages of development, delivery of data was in hard-copy form.
A typical report would consist of several three-ring binders; for several
reasons, this was unsatisfactory. It was difficult and time-consuming to go
through the data, and analysis by manual techniques did not always result in
correct answers. With the large volume of data, many important features
could be missed. Storage of the information was expensive.
To solve many of these problems and provide a system that would allow
easy and precise analysis, Pigco developed a PC-based software package. By
using the new optical disk technology, the processed data from a 300-km line
section would fit on one cartridge. Although streaming tape could be used, it
would not allow random access of the data points. Access times for the optical
drive are only slightly slower than for the normal hard disks found on many
PCs.
By automating many of the search functions, the software allows rapid
screening or, if desired, afeature-by-feature step-through the line. Calculation
of effective dent height was made uniformly and consistently, and not subject
to interpretation error.
All the data is contained on the optical disk record; any point can be called
up and viewed. By interfacing with any of a number of hard-copy devices,
prints in colour or black can be produced as desired.

HARDWARE

Calliper sonar

The sonar devices are mounted in a ring and spaced at precisely-machined
constant angles around the ring on the pig. An accurate offset is added to these
ranges to give the actual distance from the centre of the carrier to the pipe
wall. These observations are in a polar coordinate system and are converted
to a rectangular coordinate system to form the pseudo-observations.
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