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Factors Affecting The Indication Value Of Ultrasonic Thickness Gauge
Nov 12, 2018

Factors affecting the indication value of ultrasonic thickness gauge

Let's talk about the factors that affect the indication value of the ultrasonic thickness gauge.

(1) The surface roughness of the workpiece is too large, resulting in poor coupling between the probe and the contact surface, low reflection echo, and even failure to receive echo signals. For surface rust, in-service equipment, pipelines, etc., which have extremely poor coupling effects, can be treated by sand, grinding, frustration, etc. to reduce the roughness, and at the same time, the oxide and paint layers can be removed to expose the metallic luster, so that the probe A good coupling effect can be achieved by the coupling agent with the test object.

(2) The radius of curvature of the workpiece is too small, especially when the small diameter tube is thick, because the surface of the common probe is a plane, and the contact with the curved surface is point contact or line contact, and the sound intensity transmittance is low (coupling is not good). A small diameter probe (6mm) can be used to accurately measure curved materials such as pipes.

(3) The detection surface is not parallel to the bottom surface, and the sound wave is scattered by the bottom surface, and the probe cannot receive the bottom wave signal.

(4) Castings and austenitic steels are unevenly distributed or coarse grains. When ultrasonic waves pass through them, they cause severe scattering attenuation. The scattered ultrasonic waves propagate along complex paths, which may cause the echoes to annihilate, causing no display. . A low-frequency coarse-grained special probe (2.5mhz) is available.

(5) There is some wear on the probe contact surface. The surface of the commonly used thickness measuring probe is made of acrylic resin. The long-term use will increase the surface roughness, resulting in a decrease in sensitivity, resulting in incorrect display. It can be sanded with 500# sandpaper to make it smooth and ensure parallelism. If it is still unstable, consider replacing the probe.