GWT - Guided Wave Testing
GWT - Guided Wave Testing is an NDT method that complements existing NDT methods and is widely used for screening pipelines
Originally developed for screening insulated pipelines because less insulation needed to be removed, this approach is now used in a wide range of applications, from screening pipes in pipe racks to inspection of buried and underwater pipelines.
Many refineries and plants are quite old and require maintenance. The presence at individual sites of kilometers of pipelines that must be controlled, monitored and maintained is a major task.
Standard NDT approaches provide solutions that target areas where initial conditions are most likely to deteriorate. In many cases, however, due to lack of information or the limitation of a specific technique or approach, piping may leak or even cause catastrophic failure.
Moreover, in many cases it is difficult to gain access to the part to be inspected. In all the above cases, guided waves provide the opportunity to obtain relevant and critical information that can prevent incidents and production losses.
Guided Wave system
A Guided Wave system consists of three main components..
- the transducer ring
- the instrument
- laptop on which the control software resides
The transducer rings are specific to the pipe sizes being tested. They use springs or air pressure to force piezoelectric transducer elements onto the pipe. The image below shows the instrumentation for an example where an inflatable ring is used.
The guided wave inspection equipment, set up for testing using an inflatable ring
Generally, little surface preparation is required because the operating frequency is low; usually below 100 kHz.
The transducers can pass directly through paint, thin layers of epoxy or a small amount of general corrosion. But any flaking paint, thick layers or loose corrosion must be removed.
It is not necessary to use coupling fluid. The transducer ring must be able to make contact with the pipe wall along the entire circumference of the pipe.
Once the inspection planning and preparation of the inspection areas are complete, the measurement process at each location is very fast.
In just a few minutes, the ring is attached, software settings selected and measurements recorded. In the process, the system performs a significant amount of operations, including a series of self-checking procedures, calibration and recording of all measurements and settings.
Reference(s).. www.ndt.net
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