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LONG RANGE ULTRASONICS
The Wavemaker Pipe Screening System is designed for rapid screening
of long lengths of pipe to detect external or internal corrosion as well
as axial and circumferential cracking. It can be used on a wide variety
of pipes including those that are buried or insulated.
A wide range of innovative features has been incorporated into the
Wavemaker Pipe Screening System and a user-friendly interface ensures
that it is easy to use. The test can be done while the plant is
operating so disruption is minimised. Hundreds of metres of pipe can be
inspected in a day and 100% of the pipe wall is inspected during a test.
The Wavemaker Pipe Screening System is an efficient and effective method
of screening.
The Wavemaker Pipe Screening System uses a new two-ring array of probes
rather than three as used in earlier applications of this technology.
This has proven to be highly effective in terms of its ability to detect
the presence of corrosion but with reduced equipment capital cost. The
probe arrays can be attached to the pipe in less than one minute.
Two types of guided waves (longitudinal and torsional) are used to
broaden the range of possible frequencies and to adjust for different
situations, for example the presence of liquids. Axi-symmetric and non-axi-symmetric
waves aid in defect detection and interpretation of the results.
All aspects of the system, the electronics, software, probes and the
clamping arrangements are designed and manufactured in-house. |
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Applications
Rapid full coverage screening of pipes by the Wavemaker Pipe Screening System
makes it cost effective to inspect pipes in difficult to access locations. There
are a number of potential applications of the Wavemaker Pipe Screening System
with its ability to detect cracks and general metal loss (greater than 5% of the
cross-sectional area). Some of these applications are:
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The detection and positioning of
corrosion under insulation without removing lagging other than for the
application of the probes
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Screening of inaccessible areas
such as sleeved road crossings and wall penetrations
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Screening of on and offshore
pipework, even in tightly packed racks.
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Riser inspection
Classification
The following sections classify various test situations into four categories:
ideal, good, fair, and specialised. These classifications can be used to
separate jobs that will be relatively easy to perform (ideal) from those that
require operators with extensive experience (specialised).
| Test Classification |
Ideal |
| General description of application |
Long straight featureless. Butt welds with the average weld interval
being greater than 8 meters. Ease of visual access to pipe. Accurate
knowledge of pipe contents. Access can be gained at least 3 meters from
a prominent feature. |
| Examples |
Long pipe runs commonly found in pipe racks, transmission lines tank
farms interconnecting different parts of petro-chemical plants that are
in good to fair condition requiring screening to find isolated areas of
corrosion. |
| Typical Performance |
Test range typically 30 meters plus in either direction from
transducer ring. |
| Test Classification |
Good |
| General description of application |
Operating plant pipes. Average butt welds at intervals greater than
5 meters. Limited visual access to pipe. Some knowledge of pipe product
state. |
| Examples |
Pipes in pipe trenches and service pipes for storage tanks.
Inter-connecting pipes between production units. |
| Typical Performance |
At least 2.5 meters from closest feature. Tests range generally
between 20 and 30 meters in either direction from transducer ring. |
| Test Classification |
Fair |
| General description of application |
Operating plant pipes with the following properties: convoluted
geometry with short lengths before features; pipes with a lot of
corrosion (i.e. corrosion scale on surface or a high density of deep
pits); pipes coated with high density bonded insulation. |
| Examples |
Pipework within process units. Any pipe which already visually
exhibits severe corrosion. Pipes with factory applied polyurethane foam
insulation. |
| Typical Performance |
10 to 20 meters in either direction. Performance reduced as a result
of increased attenuation. |
| Test Classification |
Specialised |
| General description of application |
High general corrosion with more than 10% general wall loss caused
by pits and general corrosion. Pipes under road crossings. Sleeved or
buried pipes. Pipes with internal flaws (erosion and corrosion). Pipes
with a high density of T’s and bends, where the average distance between
features must be greater than 3 meters. Access can be close to a
prominent feature. |
| Examples |
Pipes wrapped with bitumen or Denso tape. Pipe sections through
concrete, bent header boiler type pipework, heat exchanger tubes and
coated riser pipes. |
| Typical Performance |
Test range dependent on application but can be between 3 to 15
meters in either direction from transducer ring. |
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