ZWP Anlagenrevision GmbH • Südstraße 1 • 66701 Beckingen • Germany
corrosion measurement on a test track of up to 20m per direction
testing of wall bushings
tube exposure only for coupling the probes
testing of pipe bends
testing of pipe bridges


In the chemical industry in particular, pipelines are subject to extreme conditions due to high pressures, high temperatures and the nature of the media.

For this reason, maintaining these pipeline systems is a major, but also complicated task for the operator and the responsible maintenance department. In many cases, corrosive material erosion or cracks have to be identified and inspected in inaccessible areas.

Defects, however, have to be located and evaluated at an early stage with the right effort and precision. This is important not only with regard to the availability of the systems concerned, but also in particular when it comes to minimizing liability for environmental damage as a result of leakages and in order to comply with legal operator obligations.

What testing methods are currently being used?
  • Cathodic corrosion protection
  • Intelligent pigging
  • Radiographic testing
  • Conventional ultrasonic testing
  • Surface crack testing
  • Visual inspection, endoscopy

When considering economic efficiency and effectiveness, however, these processes quickly reach their limits: For instance, when it comes to curved pipes of varying dimensions that have been fitted with flanges, branches or valves (e.g. armature casing on storage caverns), pig testing is out of the question. In addition to this, the amount of work required for pigging when carrying out a local inspection of the pipelines is in no way related to the associated costs.

Limits of conventional testing methods

Pipelines and pipeline sections that are not freely accessible are always particularly problematic:

  • Partially embedded in concrete
  • Joined to the masonry (wall ducts)
  • Heat insulated
  • Insulated with bitumen
  • Located in the ground

A major disadvantage of all the testing methods mentioned except for the pigging inspection method is that they are only capable of measuring corrosive material erosion locally.

This means that wall ducts have to be manually cut free, insulations have to be removed and soil has to be cleared away only then to use a conventional ultrasonic probe to locally inspect the pipe wall point by point to detect any unacceptable reduction in thickness resulting from corrosion or cracking. The results are then documented. Both casing spacers and pipelines on pipe bridges or in wall ducts can be inspected at random or not at all. To tackle this problem, we developed the CORRfinder test method. Once again, in cooperation with the scientists and engineers of the Fraunhofer Institute IZfP for Non-Destructive Testing in Saarbrücken, an ultrasonic testing system based on EMUS technology (electromagnetic ultrasound) was developed exclusively for us.

Description of the test system

In this method, a test probe consisting of one or more ultrasonic transmitters and receivers is attached to the pipe wall.
By superimposing magnetic fields and eddy currents – creating the Lorentz force and magnetostriction – these generate an ultrasonic wave in the pipe wall which then spreads as an impulse in one direction and detects the entire wall thickness. If there is corrosive wall erosion – either on the inside or outside – in the direction of testing, part of the ultrasonic energy is reflected back to the probe. This reflection is evaluated by a computer and displayed in the form of a scan. The intensity of the reflection is encoded in color. Within just a few minutes, the inspector then gains an initial overview of the condition of the pipe. The ability of guided ultrasonic waves to spread out within the pipe wall means that pipe inspections can be carried out regardless of the surface geometry. This means that it is possible to locate corroded areas at a distance of up to 25 m (50 m in two directions) and evaluate how they affect the functionality or durability of the pipe without completely exposing it.

Video CORRfinder

In this video you can see the modern CORRfinder testing method in action. It is particularly useful in places that cannot be reached from the outside using conventional testing methods.

Service provision
  • Computer-assisted monitoring and evaluation of the testing process by means of ongoing monitoring
  • The method delivers results that are fully reproducible
  • The testing method has been accredited as non-destructive according to DIN EN ISO/IEC 17025
  • The test method is recognized by the International Laboratory Accreditation Cooperation ILAC
  • Our employees meet the requirements of DIN EN ISO 9712 and ASNT
Testing result and documentation

Since this method delivers results that are fully reproducible, the corrosion rate can also be determined by comparing a repeat measurement with the previous measurement after some time. The finished scan is saved together with a digital image of the pipe to create a complete test report. In this context we are able to adapt the format of the documentation according to customer requirements.

Advantages of the method
  • Test up to a distance of 20 m (on both sides from where the probe is attached);
  • Testing of the complete pipeline (one hundred percent of the pipe wall inside and outside);
  • Dry testing – no coupling agent;
  • Testing of pipes with larger diameters;
  • Testing during operation (gaseous or liquid medium);
  • Can also applied for extremely bent pipelines;
  • Testing despite flange, branch, or valves (also suitable for sheet piling);
  • Testing in inaccessible areas (without exposing the pipes);
  • for monitoring changes (test can be reproduced as required).
Other potential applications of the CORRfinder test system

Due to its long reach, the method is also ideally suited for testing high masts such as:

  • Transmission masts
  • Stage masts
  • Wind measuring masts
  • For masts on sports grounds
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ZWP Anlagenrevision GmbH

ZWP Anlagenrevision GmbH
Südstraße 1
66701 Beckingen
Fon: +49 (0) 68 35 / 40 96
Fax: +49 (0) 68 35 / 6 88 11