Page 276 - Pipeline Pigging Technology

Pig-tnto-place plugs and slugs

previously utilized was not considered reliable enough for subsea applica-
tions, requiring an acoustic interrogation system to be developed.
The pig consists of a series of brake shoes arranged around the packer
module and a sealing ring; on receipt of the command signal, the packer
pushes the brake shoes out against the pipe wall and also compresses the
sealing ring. The compressed ring is squeezed against the pipe wall and
therefore isolates the pipeline. Tests have shown that the tool is capable of
withstanding lOOOpsi differential pressure.
Nowsco is undertaking helium/nitrogen leak detection on the pressure
side of the packer to determine its long-term ability to resist by-pass of gas. A
34-in packer will be deployed in the North Sea for pipeline isolation during the
1990 season.

CONCLUSION

A number of alternatives are now available to operators requiring the
isolation of pipelines, each system being designed to be used independently
or in conjunction with others to safely isolate a pipeline. Work is continuing
on the refinement of these techniques.

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