ZWP Anlagenrevision GmbH • Südstraße 1 • 66701 Beckingen • Germany


In the transport infrastructure, prestressed concrete masts have been used extensively for decades for overhead lines for railways and trams.

Due to the combination of static and dynamic loads with a partially corrosive chemical environment, ferromagnetic prestressing steels can be damaged by stress corrosion. The area most affected is on the ground where corrosion is exacerbated as a result of animal waste, road salt or electrical leakage currents

Recently, there have been incidents where concrete masts have collapsed without any significant external impact. The damage images point to stress corrosion. Corrosion can only be detected with the naked eye once it has reached an advanced stage due to the concrete covering.


Current tests are associated with mechanical loads, which can lead to additional damage. X-ray testing is not possible without a great deal of effort to comply with radiation protection guidelines.

Magnetic flux leakage testing

Magnetic flux leakage testing is used to detect surface cracks in ferromagnetic materials. The method is based on the same physical effect that is also used in magnetic particle testing, which is widely used and standardized in the steel processing industry: If you apply an external magnetic field to sharp-edged gaps in the surface of a component, additional magnetic dipoles will form which cause a magnetic stray field close to the surface. This can be used to perform non-destructive failure tests on ferromagnetic prestressing steels.

BetoFlux – a mobile handheld testing system

The BetoFlux test system is a handheld device that is moved around the concrete mast in the peripheral direction. It has been developed for mobile use. A permanent magnet yoke integrated into the testing system magnetizes the prestressing steel in the concrete. The course of the magnetic field lines depends on how damaged the prestressing steel is and reveals areas that are affected by cracks. Magnetization by means of permanent magnets provides an energy-saving solution in mobile applications.
A sensor array consisting of 32 low-noise Hall sensors detects the magnetic stray field signals that are digitized in the test system and transferred to a notebook PC via a USB connection. The USB also provides power which means that the test system can be powered entirely from the notebook battery. Special filters make it possible to highlight the cracks and the prestressing steel arrangement. This means that the state and presence of the prestressing steel can be evaluated.

  • Quick testing
  • Intuitive representation of the arrangement and condition of the ferromagnetic prestressing steels
  • Designed especially for mobile use
  • Easy to adapt to various concrete mast diameters
  • Less time and effort required in comparison to alternative testing methods (e.g. X-ray)
  • No risk of causing additional damage to the mast

The BetoFlux research project is funded as part of the ZIM Program of the Federal Ministry of Economics and Energy (BMWi) on the basis of a resolution passed by the German Bundestag. It was developed in close cooperation with ZWP Anlagenrevision GmbH in Beckingen.

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