Since the high risk of the high pressure urea equipment corrosion of the tubes is monitored non-destructively every scheduled shutdown of the plant.

In order to evaluate the remaining wall thickness of the CrNi-stainless steel tubes (AISI 316L urea grade or UNS N08310; diameter: 30mm, nominal wall thickness: 2.5mm) commonly used in high pressure urea strippers an accuracy of 0.05mm is required.

In order to do so an automated inspection technique has been developed based on the eddy current technique.

The remaining wall thickness and corrosion-rate of each tube tested is evaluated automatically on-line with an accuracy of better than 0.05mm (2% of the nominal wall thickness) without losing inspection speed (150 tubes tested per hour).

In this contribution the development of the software algorithm for analysing the eddy current data is discussed and the reliability and accuracy of the test method is demonstrated.