The use of ultrasonic thickness gauges can provide many advantages when a mill operator has to verify wall thickness of an extruded pipe or tube. In the mill, nondestructive wall thickness measurements of the pipe can be made to detect out-of-tolerance conditions. Concentricity of an extruded pipe can be monitored on a continuous and automatic basis with no need to cut the pipe or to shut down the manufacturing process. Similarly, when a machinist needs to accurately measure the thin wall of a tube, ultrasonics permits nondestructive thickness measurements along the total length.

Equipment: For manual thickness measurements, the Model 35DLand Model 38DL PLUS gages provide instant digital readings of most metal pipes and tubes to a calibrated accuracy of ±0.001 in. (±0.025 mm). This model used with an M112 contact transducer is capable of measuring most metal walls ranging from 0.020 to 1 in. (0.50 to 25.0 mm). The Model 35 can also be used in situations where data logging is not required.

If the diameter of a tube is less than 0.125 in. (3 mm), we recommend the Model 35DL or 38DL PLUS with an immersion transducer. The Model RBS-1 Bubbler System is a helpful tool in making ultrasonic thickness measurements that utilize immersion transducers. The 35DL and 38DL PLUS can be used with delay line transducers to make thickness measurements to a calibrated accuracy of ±0.0002 in. or ±0.005 mm.

Wall thickness measurements on metal pipes or tubes that are badly corroded on either the inside or the outside surface should, as a rule, be made with the Panametrics-NDT Model 38DL PLUS, or the MG2 series.