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Internal Rotary Inspection System (IRIS) 3000/9000
Principles
IRIS is based on immersion pulse echo ultrasonic principles. The
test head consists of a high frequency, high resolution transducer,
mounted longitudinally to the tube axis, and a 45o mirror mounted
on a water driven turbine. The test head fits centrally into the
flooded heat exchanger tube. Ultrasonic pulses from the transducer,
emitted parallel to the tube axis, are reflected by the mirror and
strike the tube inside wall at normal incidence. Some of the ultrasound
will be reflected from the inside wall back to the transducer and
some will pass into the tube material. When the ultrasound within
the tube material strikes the outside wall, again a part of the
energy will be reflected back to the transducer. The time delay
between the echoes from the inside wall and the outside wall of
the tube is an indication of the tube wall thickness. As the turbine
rotates, the ultrasonic beam covers the full circumference of the
tube and by slowly withdrawing the test head 100% of the tube can
be inspected.
Presentation
Due to the digital nature of IRIS, the accuracy of calibration
and standard of presentation are of the highest level. The unique
feature of the IRIS is the method of display. The vertical axis
of the image represents 0 – 360 degrees around the tube circumference
and the horizontal axis represents the tube wall thickness. In effect,
the image is an expanded cross section of the tube at any given
position along its length.
Site Implementation
The equipment operates on 110 volts AC mains power. A fresh water
supply at 40psi (2.7 bar) or greater is also required. As with all
ultrasonic techniques, the effectiveness of inspection relies on
a high level of surface cleanliness and it is essential that all
deposits and scale are removed from the bore of the tube prior to
inspection. In ideal conditions, defects as small as 1.5 mm diameter
and 0.1 mm in depth can be detected. Tubes made of virtually any
material and in the range of 9 mm to 50 mm ID can be inspected.
Tubes outside this range can be appraised for suitability on request.
Production rates depend on factors such as tube cleanliness, tube
length and the number of defects encountered but are typically in
the region of 100 tubes per 12 hour shift.
Applications
Applications include the inspection of ferrous and non-ferrous
tubes found in heat exchangers throughout the oil, gas petrochemical
and power generation industries.
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