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| The TesTex developed automated scanning
rig known as the Line-Cat is based on the
principles of the Low Frequency Electromagnetic
Technique (LFET). It was designed to quickly
and accurately scan piping of 6” or
greater diameter. This inspection is performed
from the pipe O.D. (outer diameter). |
About the Line-Cat
A remote controlled magnetic wheeled crawler
is used to propel the Line-Cat system making
it capable of traveling up to 10 feet per
minute. It has a contoured top shell that
supports and stabilizes the main sensor
array. The sensor array itself, is made
up of 16 individual 2” wide scanning
pods that contour to the actual geometry
of the pipe via a flexible coupling system.
The system is sufficiently designed to travel
around bends and over welds. All components
of the Line-Cat are designed to withstand
Artic conditions down to -40° Fahrenheit.
In addition, the Line-Cat is shippable via
overnight carriers. |
LFET vs. EMAT and A.U.T.
The Line-Cat system was field tested on
sections of two insulated crude transit
pipelines on the North Slope of Alaska,
during the fall of 2006. The insulation
was removed from both pipelines. One of
the pipelines was found to have anti-corrosion
tape, while the other was bare. These sections
were tested with the Electromagnetic Acoustic
Transducer technique (EMAT) and Automated
Ultrasonic Thickness (A.U.T.) as well as
LFET. Although A.U.T was able to give actual
thickness readings, it had a very slow scan
rate. EMAT displayed scan rates faster than
the A.U.T., but the LFET was by far the
most productive. Both EMAT and LFET demonstrated
a 100% POD (probability of detection) for
25% wall loss isolated pitting at a 3:1
aspect ratio. EMAT displayed a reduction
in the scan rate over the tape-covered section,
from 1000 ft per day on uncoated piping
to 500 ft per day on tape-coated piping.
The scan rate of LFET remained unchanged
over the tape-coated piping (approximately
10 ft per minute). Also, LFET has a false
positive overcall rate of less than 1%.
The results of the field test were such
that the Line-Cat’s LFET Technique
was the only method that could work efficiently
through the tape coating and had the highest
overall productivity for the job. The results
of the field test can be seen in the linked
article written by Mr. John J. Nyholt of
BP Americas. |
| Click to read
the TNT Article |
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Inspects piping of 6”
or greater diameter |
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Detects gradual wall loss, pitting,
gouging, etc. |
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Motorized to travel
at speeds up to 10 feet per minute |
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Sufficient clearance
to travel around bends and over welds |
| • |
Uniform coatings, rust and scale
have no effect on signal |
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Qualitative and quantitative multi-channel
high resolution 3-D graphics display |
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System components able to withstand
temperatures down to -40º Fahrenheit |
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