Tandem technique
Tandem technique is an ultrasonic method with separate transmitter and receiver probes arranged in series. It is used to detect vertically oriented discontinuities in thick plates.
Physicochemical Mechanism of Action
The tandem technique uses two separate ultrasonic heads: a transmitter and a receiver. The transmitter sends ultrasonic waves into the test surface, and the receiver detects the returning echo signal. By positioning the heads in a row, the method can precisely catch vertical discontinuities or flaws.
Metallurgical Relevance & Welding Risks
This technique is especially useful for thin, flat parts or sheet metal thicker than 10 mm. It can precisely identify vertical discontinuities, coating defects, or other surface flaws. Wrong head spacing or lack of parallelism can give inaccurate results and miss potential defects.
Shop Practice & Procedures
• Head Setup: The transmitter and receiver heads must be parallel to each other and perpendicular to the test surface. Typical spacing is 10 to 20 mm, depending on material thickness.
• Calibration: Make sure both heads are properly calibrated and the ultrasonic wave direction is correct. Use a calibration block to check accuracy.
• Testing: Move the test surface slowly under the heads and watch for anomalies in the echo signal display. Mark any irregular signals or deviations for further inspection.