Tube Inspection Technologies
IRISNDT uses Eddy Current (EC), Remote Field Testing (RFT) and Internal Rotary Inspection Services (IRIS) to inspect tubes.
- Eddy Current is used to inspect non-ferrous tubes. We detect and size cracks, corrosion, erosion and mechanical damage in austenitic stainless tubes and in copper alloys.
- RFT is used to readily detect erosion losses in low alloy steels (ferromagnetic) and in ferritic stainless steels. Pits, corrosion and mechanical damage can be detected. RFT inspections should be followed by IRIS inspection if shallow pits or general thinning is suspected.
- IRIS is used to detect erosion, corrosion and baffle wear in heat exchangers. It is used to inspect boilers, and fin fan cooler tubes. for all tube materials (ferromagnetic and paramagnetic).
- The choice of which technique to use depends on the type of defect, tube material, cleanliness of the tubes and time available for the inspection.
- Tube cleanliness determines whether or not some of these inspections can be made. IRIS requires more extensive cleaning than EC and RFT.
- Small pits and cracks can be challenging to identify and size with EC and RFT. IRIS is not designed for identifying cracks.
- If needed, tubes may be Hydro Blasted, Abrasive Blasted, Slurry Blasted, and Bio Blasted
- After any type of abrasive cleaning, the tubes should be flushed with water or high pressure air to remove the abrasive particles prior to an inspection, or be chemically cleaned.
TUBE INSPECTION FUNDAMENTALS
EC AND RFT are electromagnetic techniques whereby a current carrying conductor (probe) in close proximity to the material (tube) induces a current in the tube wall, producing a magnetic field. Flaws or discontinuities disrupt the magnetic field. This produces a change in the current that is recorded and interpreted by the operator. The defect depth is estimated from amplitude and phase shifts referenced to the response from a calibration standard.
IRIS Testing uses an ultrasonic beam scanned around the tube ID by a water driven turbine probe assembly which is inserted into each tube.