The FEMM is a potential drop technique called Transient Potential Drop (Transient PD). This technique, patented by Ferrx, is an electromagnetic method that combines features of different potential drop techniques that makes it highly versatile. FEMM measures the actual material degradation caused by stress and fatigue.

Years of testing of the method′s different measurement features with different types of specimens and structures has validated FEMM′s monitoring capabilities, and the results can be summarized as follows:

Stresses measured in ferromagnetic steel

Monitors elastic stress relative to a previous stress measurement. Calibration curves can easily be established which facilitate absolute stress monitoring.

  • Detects plasticity, permanent changes in the material caused by stress exceeding yield
  • Monitors changes in residual stresses due to external loads
  • Measures remanent stress, which shows the highest stress since the last measurement

Fatigue due to cyclic loads

Monitors the different phases of material deterioration until crack formation. The degree of fatigue can thus be monitored and, based on this data, remaining operational life of structures can be estimated.

Crack detection and crack growth monitoring

The initiation of cracks can be predicted, and crack growth can be monitored and crack size estimated.

Non-intrusive monitoring of internal defects in pipes

Monitor internal erosion, corrosion and cracks. Measure pitting and crack max depth directly with a new and patented technique which differentiates between inside crack and pit.

Monitoring outer surface corrosion

E.g. monitoring corrosion under insulation. Sensors on outside pipewall, same as used for monitoring internal corrosion.