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Ultrasonic NDT

Wall Thickness Measurements of Metal Pipes and Tubes

Published on 10th April 2021

Wall Thickness Measurements of Metal Pipes and Tubes

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.

Products used for this application


The handheld 45MG ultrasonic thickness gauge is packed with measurement features and software options. This unique instrument is compatible with the complete range of Olympus dual element and single element transducers, making this gauge an all-in-one solution for virtually every thickness gauge application.


The 38DL PLUS is an advanced ultrasonic thickness gauge. Uses dual element transducer for internal corrosion applications, and has features that include THRU-COAT technology and echo-to-echo. Uses single element transducers for very precise thickness measurements of thin, very thick, or multilayer materials.

Magna-Mike 8600

The Magna-Mike is a Hall effect thickness gauge that uses a magnetic probe to perform accurate measurements on nonferrous and thin materials such as plastic bottles.


The 27MG is a basic ultrasonic thickness gauge designed to make accurate measurements from one side on internally corroded or eroded metal pipes and parts. It is lightweight, durable, and ergonomically designed for easy, one-hand operation.`


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