Boring - Trenchless International
Boring - Trenchless International
Boring - Trenchless International
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Cleaning pipes with pigs<br />
by Lyndsie Mewett<br />
Pipeline Pigging and Integrity Management<br />
pipe cleaning<br />
April 2010 - <strong>Trenchless</strong> <strong>International</strong><br />
Cleaning pig uses<br />
Cleaning pigs have a variety of uses<br />
including the removal of debris, paraffin<br />
and millscale, the verification of the ovality<br />
of the pipe, corrosion control and dewatering<br />
during hydrostatic testing. During<br />
construction pigs are used to remove dirt<br />
or general construction debris that may be<br />
inside the pipe as it is being assembled.<br />
Pigs are used in the hydrostatic testing<br />
process, pumped through the pipeline<br />
with water, as a tool to expel air from the<br />
line. Following this, a cleaning pig is used<br />
to dewater and dry the pipeline before<br />
commissioning.<br />
During operation, cleaning pigs are<br />
extremely important because they are<br />
able to remove substances that may<br />
obstruct flow within the pipeline, or damage<br />
the pipeline itself, while still allowing<br />
continuous operation of the pipeline. In<br />
addition, through the removal of debris,<br />
cleaning pigs ensure that a pipeline maintains<br />
its maximum efficiency.<br />
Because of the pigs’ varied uses and<br />
the differences inherent in each pipeline,<br />
cleaning pigs are available in a number of<br />
different designs. The pigs can be of a light<br />
or heavy density, depending on the function<br />
of the pig. A pig of heavy density may<br />
be put through a pipeline first, followed by<br />
lighter density pigs.<br />
Foam and polyurethane pigs<br />
Foam or polyurethane pigs are available<br />
in various densities and shapes. They can<br />
be bullet shaped, have concave ends or<br />
flat ends, be jelly coated on the outside or<br />
sometimes have a silicone carbine coating.<br />
In addition, some foam pigs can have<br />
a crisscross pattern with silicone carbine<br />
implanted in the pig.<br />
Coated foam pigs are used for general<br />
cleaning, whereas the more abrasive coating<br />
of silicone carbine is used for cleaning<br />
lines with build-up. The crisscross pattern<br />
is also used for medium-length runs in pipe<br />
where extra abrasion resistance is required.<br />
The shape of the pig dictates how fast it<br />
travels while in the pipe. The travel speed<br />
in turn determines the force of the pig’s<br />
What’s in a name?<br />
Theories have abounded as to the meaning of the word ‘pig’. These days,<br />
many claim it stands for ‘pipeline inspection gauge’, however it seems that this<br />
term only came into being after the word pig was already in use in this context.<br />
A likely theory is the high-pitched squealing sound made by the early devices<br />
as they scraped the inside of a pipeline resembled the squeal of a pig. Other<br />
theories include the brushes resembling the hair of a pig, some early devices<br />
being made in part with pig skin and the appearance of the device once it had<br />
finished its job, covered in dirt like a pig.<br />
cleaning edge, with higher speed pigs<br />
being able to remove tougher debris.<br />
Foam pigs are flexible, enabling them<br />
to compress and expand so that they can<br />
travel through multi-diameter pipelines<br />
and navigate bends in the pipeline.<br />
Light-density foam pigs are used to<br />
pass through the pipeline first because<br />
their open-cell foam aids the drying<br />
of pipelines after hydrostatic testing.<br />
Medium-to-heavy density foam pigs are<br />
used during pipe construction, start-up,<br />
during operations, for maintenance and<br />
emergencies.<br />
Solid polyurethane pigs are designed<br />
to be used in batching or displacement<br />
of fluids in petroleum, chemical or process<br />
industry pipelines. Batching refers<br />
to when a pig is used between batches<br />
of product, such as between petrols and<br />
various other types of fuel. A displacement<br />
pig displaces one fluid with another and is<br />
used in the commissioning process.<br />
Mandrel pigs<br />
Mandrel pigs have a metal body with<br />
seals, scraper cups or discs on their<br />
exterior. The pigs can be used for an<br />
ovalarity check or for gauging the internal<br />
diameter of the pipe, to clean the<br />
line, as a sealing pig, as a combination<br />
cleaning/sealing pig, for batching,<br />
dewatering and drying after testing.<br />
Extra discs can be provided to attach<br />
to mandrel pigs to scrape extra debris.<br />
For example, crude lines can get a<br />
heavy wax build-up and sometimes<br />
require extra discs on the pig to clean<br />
the line. Additional cups and brushes<br />
can also be acquired.<br />
The world’s most respected<br />
pigging conference is coming to<br />
the Asia Pacific region<br />
www.clarion.org<br />
CONFERENCE • TRAINING COURSES • EXHIBITION<br />
8-11 November 2010 • Crowne Plaza Hotel • Kuala Lumpur<br />
April 2010 - <strong>Trenchless</strong> <strong>International</strong><br />
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