Corrosion Mapping on Pipes above Supports Applus+ RTD addresses a high complex problem with an innovative testing system: corrosion mapping on uninsulated pipes above supports. With the RTD Compass an ultrasonic testing system has been developed that can be used for locations with difficult access without lifting a pipe. This without complicated preparation and without production interruption. The COMPASS System combines the highest level of efficiency and economy: the way to more plant safety, plant availability and environmental protection.
Due to linear expansions of the pipelines because of temperature fluctuations or proper motion caused by pumping operations, friction effects between pipelines and supports may occur. These effects were partly aggravated by penetrating dirt (abrasive effect) so that protective coating of the pipe will be destroyed over the years. Due to ever-changing climatic influences combined with aggressive and salty air and/or dirt accumulations the process of corrosion begins in the area of supports.
These areas under the pipelines are not easily visible from outside as the pipes partly run immediately above the ground and the corrosion spots are covered by supports, coats of pain or dirt. Recognition or Measurement of these corrosion spots was only possible so far by time-consuming lifting or rather cutting and subsequent rotation the pipeline by 180 degree, combined with additional non-destructive testing methods like ultrasonic, 3D-laser measurement or radiography.
A transmitter probe transmits into the examined pipe wall continously ultrasonic pulses which were captured by a receiver probe and displayed. On existing corrosion spots a part of the transmitted ultrasonic signal is reflected und is thus not captured by the receiver who is installed on the other side of the pipe wall. By means of a downstream electronic the recorded signals by the receiver were prepared, amplified, digitized and transferred to an analysis unit. This unit analyses the results and calculates the existing material removal in percent referred to the given wall thickness. An integrated algorithm can reconstruct the corrosion process in certain areas by means of the recorded signals.
The testing technology
The test procedure is based on the proven and in the technique recognised ultrasonic method. In theory it is an angle transmission with a specially by Applus+ RTD for the inspection problem adapted and optimized transmitter and receiver probe.
Calibration and interpretation
COMPASS is a comparative and qualitative inspection system for examination of changes in wall thickness of pipelines. In this case it is particularly important that the system is adjusted on a corresponding reference object in order to be able to subsequently compare the signals which were generated by real testing with the generated signals of the reference object. Because of a great number of disturbance and cause variable like different sound attenuation, coupling loss, nominal wall thickness, material loss etc. the residual wall thickness can only be presented in percent. Already performed inspections with additionally testing methods confirm the results achieved by COMPASS.
Quick, economical and reliable
- inspection during operations is possible (on-stream inspection)
- lifting of pipelines isn't required
- Because of the flat and narrow construction the system is applicable nearly everywhere 
- low own weight of the testing system
- testing with modern ultrasonic technique
- Documentation is an extensive and detailed report with graphical evaluation of measurement data
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