Ultrasonic thickness in sensible applications, especially monitoring equipment in service, if indications of distortion of the actual thickness of the phenomenon, resulting in pipeline (gear) there is hidden, is primarily based on incorrect information to replace the pipe pieces, causing a lot of material waste. According to current years ultrasonic thickness of the track usage, to show the value of distortion and the reasons as follows:
1, shows no indication or indications of instability simply because of flash: this phenomenon in the field equipment and pipe detection typically occurs right after a large quantity of phenomena and information analysis, summarized for the following motives:
(1) through the big surface roughness, resulting in the probe contact surface coupled with the effects of poor echo low, can not even acquire the echo signal. In-service equipment, most of the surface corrosion of pipes, the coupling impact of really poor.
(two) workpiece radius is as well small, particularly in little diameter tube thickness, because of the probe used for the flat surface, and surface contact with the point make contact with or line get in touch with, the sound intensity transmission is low (poor coupling).
(3) detection of surface and bottom is not parallel to the scattering of sound waves generated bottom face, the probe wave signal can not accept in the end.
(4) casting, austenitic steels due to inhomogeneity or grain coarsening, in which the ultrasonic wave via the scattering attenuation when extreme, were scattered along the complicated path of ultrasonic propagation, has the potential to echo annihilation, outcome is not displayed.
(five) probe speak to surface has some wear and tear. Thickness probe surface employed acrylic resin surface roughness of long-term use will Qigongkangxian Sakura? Jia Lu aluminum lance fanny recognized be concerned? Commission? Fiji brake Sapporo let the floating net razor?
(six) measured object on the back of a massive quantity of corrosion pits. Because the other side of the measured object has rust, corrosion pits, resulting in attenuation, top to alterations in reading irregular and, in intense situations, even without having reading.
two, stated value is too huge or also tiny since of the actual test perform, frequently encountered thickness and design and style of indication worth (or anticipated worth) are obviously also huge or too modest, the factors as follows:
(1) the measured object (such as pipelines) inside the sediments, when the acoustic impedance difference between the sediment and the workpiece is tiny, showed a worth of wall thickness plus the thickness of sediment.
(2) when the material deficiencies in internal (such as inclusion, mezzanine, and so forth.) to show the value of the nominal thickness of about 70% (now use ultrasonic flaw detector further defect detection).
(3) temperature. Basic speed of sound in strong materials with the temperature decreased, and test data show that hot material for each additional 100 C, velocity decreased by 1%. High-temperature equipment in service for this circumstance is frequently encountered.
(four) layered materials, composite (non-homogeneous) components. To measure the cascading material without the coupling is not feasible, due to the fact ultrasound can not penetrate the space without coupling, and can not be in the composite (non-homogeneous) materials evenly spread. Produced by the multi-layer bandaging material for the gear (such as urea higher-stress gear), specific attention when measuring thickness, thickness of the indication that the probe only contacts of that layer thickness.
(5) the influence of coupling agent. Coupling agent is used to rule out the probe and the air among the measured object, so that ultrasound can successfully penetrate the workpiece to detect the purpose. If you select to sort or incorrect use will outcome in errors or coupled sign flashing, can not be measured. Actual use of coupling agent due to the fact of excessive use, causing the probe from the workpiece, the instrument showed a value of coupling agent layer thickness.
(six) speed of sound incorrect decision. Measuring workpiece before, according to material sort preset speed of sound or its block against the standard silent speed test. When, soon after instrument calibration with a material (utilised for the steel test block) went to measure one more material, will create erroneous results.