The probe used in SIRIS examination is made up of a centering device, an ultrasound transducer and a rotating mirror (as pictured below). An ultrasound pulse is generated in the transducer that is mounted on the centre axis. A 45 degree rotating mirror in the probe guides the ultrasound towards the tube wall.
An ultrasound reflection (echo) takes place at the inner and outer walls of the tube. These echoes are reflected back and processed by the equipment. The time between the two echoes represents the wall thickness of the tube.
Knowing the sound velocity in the material under test, the wall thickness can be calculated. Water is used rotate the probe mirror and is also needed as a couplant between the transducer and the tube wall.
A calibration standard of the same material and dimensions as the tubes to be examined is used to check the IRIS system response.
After an inspection an on-site report detailing the condition of each tube is normally presented to the client, including a colour tube sheet map of tubes inspected.