|
|
 |
|
Smart
Pigs
The Need
|
Smart Pigs are inspection
vehicles that move inside a pipe line pushed along by the flowing material. They have been
in commercial use since 1965, primarily for the detection of wall thinning caused by
ordinary corrosion. Until recently other types of defects - cracks, coating disbondment,
dents and gouges were not detectable with pigs (Willke; 1998). The industry is demanding
smart pigs that could pass along multidiameter pipelines and bends, that could detect the
precise location of any problem, and that does not interfere with or need the flowing
material to still be operational. |
CalScan Smart Pig -
Pipetronix Inc. |
The Technology
|
Smart Pigs use different
technologies to locate problems along the pipelines. Magnets have been used to detect
corrosion where the most common technology is the Magnetic Flux Leakage (MFL) that detects
corrosion on thinning walls. Another detection technology uses ultrasonic sensors to
detect coating disbondment, cracks, dents and gouges. The Global Positioning System (GPS)
technology is being adapted to smart pigs to obtain the exact location of any problem in
the pipe or to map the pipe itself. Some of these new Smart Pigs have a collapsing
characteristic that allows them to get into multidiameter pipes and gate valves (Willke;
1998). |
CalScan: Detecting dents
- Pipetronix Inc. |
|
Pipetronix Inc. offers several
Smart Pigs with different technologies: (Pipetronix web site)
- The CalScan pig that can locate and measure
geometric deviations. It works during the running operation of the pipelines, producing
only an insignificant throughput loss. The CalScan pig can detect deformations from 0.6%
up to 25%.
|
MagneScanHR Smart Pig -
Pipetronix Inc. |
|
- For detecting pipeline corrosion Pipetronix
designed the MagneScan HR system, which is based on the principle of magnetic flux
leakage. This Smart Pig can differentiate between internal and external corrosion and
detect changes in nominal wall thickness. A magnetic field is induced in the pipeline
steel. If a flaw is present, part of this magnetic field escapes the wall. Extremely
sensitive sensors detect and measure the resultant leakage field and allow the detection
and sizing of metal loss and corrosion.
|
MagneScanHR: MFL
technology - Pipetronix Inc. |
|
- An alternative to the MFL technology is the
UltraScan Pig, which also monitors pipelines for corrosion. It uses ultrasonics to
determine the pipe wall thickness. The UltraScan pig analyses the whole surface and length
of the pipeline for traces of corrosion. This technique can be applied while normal
operation of the pipeline is maintained without any significant reduction in pipeline
flow. The UltraScan system allow the determination of the extent, location, depth, and
internal/external position of the corrosion.
|
UltraScan Smart Pig -
Pipetronix Inc. |
|
Pipeline Integrity
International Ltd. has developed special crawler pigs capable of propelling themselves
through a pipeline when the product itself is unable to force the device through the line,
or when there is no flowing material (Puyear; 1998). Nowsco Well Service Ltd. offers the Geopig tool which measures
pipewall deformations using differential GPS surveying equipment. This provides pipeline
anomaly location (dents, buckles, wrinkles, and bending strain) within an accuracy of
1:2000 from any known reference point. It also allows the assessment of the dynamics
associated with slope instability, subsidence, overburden, frost heave, river crossings,
free spanning, overburden, and temperature and pressure changes. Comparison of repeat
Geopig survey data will determine pipeline movements as small as one inch and differential
bend curvature strain to +/- 0.02%. (P&GJ; 1997 and Nowsco web site) |
UltraScan: Ultrasonic
technology
Geopig Smart Pig -
Nowsco |
The Benefits
|
High resolution intelligent
pigs (smart pigs) can accurately detect, size, and locate corrosion or any other anomalies
in pipelines. Once the problem is detected the information can be used to develop a
pipeline de-rating schedule, implement a repair or replacement program, determine if
re-inspection is necessary, and evaluate effectiveness of a corrosion inhibitor program.
(Jones, Dawson, and Brown; 1995) Transcontinental
Gas Pipe Line Corporation (Transco) used a collapsible pig and realized an estimated
savings of about $2 million by avoiding the cost of replacing valves in a pipe line
section. "Transco believes a conservative estimate of its own savings over the next
10 years from use of this device could be $50 million." (GRI; 1997) |
Status
|
"The Gas Research
Institute (GRI), PRC International, the Canadian Energy Pipeline Association and British
Gas are sponsoring the improvement of a collapsiple pig called "Elastic Wave
Vehicle", for a 24-inch diameter pipe that could be resized for pipe diameters of 20
to 30 inches. Currently, the device exists only in sizes for 30 to 36 inches. T.D. Williamson Inc. and C.W.Pope & Associates
are developing smart pigs using electromagnetic acoustic transducers to detect stress
corrosion cracking along pipes. This technology uses ultrasonics to detect cracks but
employs a different method for generating energy into the pipe wall and interpreting
information.
The U.S. Department of Transportation is
working with the GRI and Tuboscope Vetco Pipeline Services to design an in-line inspection
device to detect and quantify mechanical damage to pipelines." (GRI; 1997) |
Points of Contact
-
Kiran Kothari, Principal Project Manager,
Gas Technology Institute
Phone: (847) 768-0893 Email: kiran.kothari@gastechnology.org
-
Stefan Papenfuss,
Tuboscope Pipeline Services, P O Box 808, 2835 Holmes Road, Houston,
TX 77001, USA
Tel: (713) 799-5433 Fax:(713) 799-5406 Email:spapenfuss@tuboscope.com
Web site: http://www.varco.com
-
Pipetronix Inc. 2207 Oil Center Court.
Houston, Texas 77073-3334.
Phone: (800) 324-7633.
-
The list of
manufacturers and distributors
http://www.piggingassnppsa.com/Consultancy-Services.htm
References
- Willke, T. 'Five technologies expected to
change the pipe line industry,' Pipe Line & Gas Industry, January 1998.
- Jones, D.G., Dawson, S.J., and Brown, M. 'Smart
Pigs Assess Reliability of Corroded Pipelines,' Internal Pipeline Corrosion
Assessment, Pipeline & Gas Journal, March 1995.
- Gas Research Institute (GRI) 'Smart Pigs
Latest in Technology R&D is helping to make Smart Pigs even smarter,' Pipeline
& Gas Journal, August 1997.
- Special to Pipeline & Gas Journal
(P&GJ), 'Intelligent Pigging - PSE&G Uses Geopig to Inspect Crown Central Gas
Pipeline,' Pipeline & Gas Journal, April 1997.
- Puyear, R., 'The Hub - Sophisticated
Monitoring used in Pipelines, Processing,' Pipeline & Gas Journal, March 1998.
Disclaimer Statement
|
Neither the Construction
Industry Institute nor Purdue University in any way endorses this
technology or represents
that the information presented can be relied upon without further investigation. |
LHM05
|
|
|
