Advanced Ultrasonic Inspection Techniques
Electromagnetic Acoustic Transducers (EMAT)
HIGH TEMPERATURE THICKNESS MEASUREMENTS USING EMAT
KAOTHEEM uses EMAT bulk waves to track piping metal losses while the part is in service at high temperature (up to 1200°F). This non-contact method does not need a couplant. It can inspect through coatings and needs minimal (if any) surface preparation. EMAT can generate longitudinal or shear waves to assess thickness. KAOTHEEM operators integrate different sets of magnets and radio frequency (RF) coils to obtain thickness measurements at various ranges.
• Ideal for dry (no couplant) thickness measurement applications
• Ideal for internal thinning wall measurements i.e. sulfidation corrosion
• Measures the thickness of parts up to 5 in.
• Does not need wedges and couplant making the inspection easy and fast
• Is less sensitive to surface conditions such as dirt or coating than traditional ultrasound tests
• Can display A, B and C scans
• Implements changes in sound velocity to correct for temperature changes
• Access to the inspection location is needed
• The insulation must be removed at the test location
• If the surface where the EMAT probe is placed has external corrosion/pits it must be ground flat
• Can only be used for thickness spot checks
• Surface preparation might be needed if external corrosion/pits are present. Rough surfaces can impede good sound transmission by attenuating the signal
EMAT Scope Displaying Ultrasonic Thickness Readings
KAOTHEEM Technician Performing EMAT High Temperature Piping Thickness Measurements While Using Rope Access Technology (Dual Trained Personnel)
Auto-Correlation Functions Algorithm (ACF): Echo-to-Echo Measurements
• These waves allow one to calculate thickness values based on multiple peak to peak echo measurements. Typical high temperature ultrasound thickness measurements are based on the information from the first two peaks. The information from multiple echo measurements makes EMAT more accurate for high temperature measurements than traditional ultrasound
• Based on this technique, at least two back wall signals are examined in the A-scan
Thickness Measurement – Auto-Correlation Algorithm Represented In Millimeters
EMAT – Bulk Wave.