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Internal rotary inspection system IRIS

Boiler Tubes | Heat exchanger Tubes |Fin-Fan Tubes

Internal rotary inspection system (IRIS) is an ultrasonic method for the nondestructive testing of pipes and tubes. The IRIS probe is inserted into a tube that is flooded with water, and the probe is pulled out slowly as the data is displayed and recorded. The ultrasonic beam allows detection of metal loss from the inside and outside of the tube wall.

IRIS is commonly used in boilers, heat exchangers, and fin-fan tubes


IRIS testing has several advantages over others:

  • Works on all materials, regardless of properties.
  • Full sensitivity near tube support structures such as tubesheets.
  • Perfect as a backup to electromagnetic testing.
  • Very accurate wall thickness measurement results.


  • Field-proven and commonly used in boilers, heat exchangers, and fin-fan tubes.
  • Often used as a back-up to electromagnetic examination of tubes, to verify calibration and accuracy. Especially useful as a follow-up to remote field testing due to the full sensitivity near tube support structures provided by IRIS.
  • The IRIS probe must be moved very slowly (approximately 1 inch per second, or 2.5 cm/s), but it produces very accurate results (wall thickness measurements typically accurate to within 0.005 inch, or 0.13 mm).
  • Before the examination, tubes must be cleaned on the inside to bare metal.
  • A supply of clean water is needed, typically at a pressure of 60 psi, or 0.4 MPa. Dirt or debris in the water may cause the turbine to jam.
  • Works for tube diameters of ½ inch (13 mm) and up. Special centralizing devices are needed for larger diameters.
  • Works in metal or plastic tubes
  • Through hole is difficult to detect by using this method
  • Operates in temperatures above freezing.
  • Can pass bends, but will not detect defects in bends.
  • Not sensitive to cracks aligned with tube radius.
  • IRIS testing world wide.

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