Internal rotary inspection system (IRIS) ultrasonic test method is employed for testing of pipes and tubes in boilers, heat exchangers and fin-fan 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.
The IRIS probe consists of a rotating mirror that directs the ultrasonic beam into the tube wall.
The mirror is driven by a small turbine that is rotated by water pressure.
As the probe is pulled the spinning motion of the mirror results in a helical scan path.
The IRIS probe must be moved very slowly (approximately 2.5 cm/s) to produce very accurate results (wall thickness measurements typically accurate to within 0.13 mm).
Before the examination, tubes must be cleaned on the inside to bare metal.
Dirt or debris in the water may cause the turbine to jam.
A supply of clean water at a pressure of 400kPa is required.
Works for tube diameters of 13 mm and above.
Special centralizing devices are needed for larger diameters.
Typical smallest detectable discontinuity is through-hole of diameter 1.6 mm equivalent.
Can pass bends, but will not detect defects in bends.
Not sensitive to cracks aligned with tube radius.
Compared to conventional ultrasonic testing or eddy current testing,Internal rotary inspection system (IRIS) ultrasonic test instruments and probes are complex and expensive and requires highly trained, skilled and experienced technicians.