Ultrasonic thickness gages can provide advantages when a mill operator or end user has to verify wall thickness of a pipe or tube, since measurements are not limited to the accessible ends of the pipe. In the mill, nondestructive wall thickness measurements can be made to detect out-of-tolerance conditions. Concentricity of a continuously formed pipe can be monitored on a
constant and automatic basis with no need to cut the pipe or to shut down the manufacturing process. Similarly, when a process requires accurate measurement of thin walled tubing, ultrasonics permits nondestructive thickness measurements along the total length.
Equipment: For manual thickness measurements, the Model 38DL PLUS and 45MG with Single Element software gages provide instant digital readings of typical metal pipes and tubes to a calibrated accuracy of ±0.001 in. (±0.025 mm). These gages, used with appropriate transducers, are capable of measuring most metal tube and pipe walls ranging from less than 0.020 in. to greater than 2 in. (0.50 to 50 mm). Precision gages can also be used with delay line transducers to make thickness measurements to a calibrated accuracy of ±0.0002 in. or ±0.005 mm.
If the diameter of a tube is less than 0.200 in. (5 mm), we recommend the 38DL PLUS or 45MG with Single Element software along with an immersion transducer. The Model RBS-1 Bubbler System is a helpful tool in making ultrasonic thickness measurements that utilize immersion transducers.
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 Olympus Model 38DL PLUS or 45MG using dual element transducers. Corrosion gaging is discussed in detail in this application note.