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Eddy current non-destructive technique of pipelines

A novel NDT technique for inspecting contaminated stainless steel welds in LNG plants has been successfully developed at TWI.

The technique is able to detect defective welds with wall thicknesses up to eight millimetres. To calibrate the system accurately, stainless welds were manufactured at TWI with known amounts of ferritic consumable in the weld root and an inspection procedure was developed.

Example of contaminated weld inspection using the Eddy current technique
Example of contaminated weld inspection using the Eddy current technique

The system was applied to stainless steel pipelines in a production plant in the Middle East. An inspection rate of approximately 100 welds per day was achieved. In addition, the performance of the system was found not to be affected by temperature variation of these pipelines.

This is one example of a number of applications of Eddy current techniques. Further examples are:

  • EC inspection of bridge stays.
  • EC inspection of vintage aircraft propeller hubs.
  • Inspection of Zircalloy welded tubes.
  • Detection and sizing of surface flaws in brake drums.
  • Boiler tube inspection.
  • Weld penetration depth measurement in stainless steel shafts.
  • Measurement of contamination levels in welds in titanium and zirconium.
  • Ultrasonic phased array inspection of storage tank annular fillet welds.

For more information, please email contactus@twi.co.uk

Example of Eddy current signal taken from Phasec 2200 system which indicates defective weld
Example of Eddy current signal taken from Phasec 2200 system which indicates defective weld
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