IRIS is an ultrasonic method for the nondestructive inspection of 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 can provide the location of flaw along the length. Defect detection capability for IRIS is better than RFET (in ferrous materials) but it is inferior to ECT (in non-magnetic materials). IRIS is not as capable of detecting smaller defects when compared to ECT. The major disadvantage is that it is very slow technique, but accurate in wall measurement of ferrous tubes in range of 0.15mm. IRIS inspection requires a better cleaning of surface than eddy current testing.
General Concept
A transducer located inside a turbine generates an ultrasonic pulse along the axis of the tube.
The ultrasound is reflected on a 45o mirror and oriented toward the tube wall.
The ultrasound is partially reflected by the tube ID, then transmitted through the wall, and finally reflected by the tube OD.
The ultrasonic velocity of the tube material allows the wall thickness to be calculated by using the time-of-flight difference between the OD and ID echoes.Water is pumped through the probe cable and the turbine.
The mirror, which is attached to the rotating part of the turbine, rotates at a speed of about 75 RPS.
This rotation enables a full inspection of the tube wall.
A small pin attached to the turbine body produces an ultrasonic reflection each time the mirror passes the pin.
The reflection from the pin is used to synchronize the screen display.
