Basic principle of ultrasonic thickness gauge:
Ultrasonic Thickness Gauge is based on the principle of ultrasonic pulse reflection thickness measurement, when the ultrasonic pulse emitted by the probe through the measured object reaches the material interface, the pulse is reflected back to the probe, by accurately measuring the propagation time of the ultrasonic wave in the material to determine The thickness of the material being tested. Any material that allows ultrasound to propagate inside it at a constant speed can be measured using this principle. Thickness gauge designed according to this principle can accurately measure all kinds of plates and various processed parts. It can also monitor various pipelines and pressure vessels in production equipment and monitor the degree of thinning after being eroded during use. . Can be widely used in petroleum, chemical, metallurgy, shipbuilding, aviation, aerospace and other fields.
Use skills: (Using the ultrasonic thickness gauge sold by our company as an example)
1, the general measurement method:
(1) Use a probe to measure thickness twice at one point. In the two measurements, the split surface of the probe should be 90° apart, and take the smaller value of the measured workpiece thickness.
(2) 30mm multi-point measurement method: When the measurement value is not stable, take a measurement point as the center, perform multiple measurements within a circle with a diameter of about 30mm, and take the minimum value as the measured workpiece thickness value.
2. Accurate measurement method: Increase the number of measurements around the specified measurement point. Thickness changes are represented by equal thick lines.
3, continuous measurement method: using a single point measurement method along the specified route of continuous measurement, the interval is not greater than 5mm.
4. Mesh measurement method: Mark the grid in the designated area and record the thickness according to the point. This method is widely used in high pressure equipment, stainless steel lining corrosion monitoring.
5, the factors that affect the ultrasonic thickness gauge indication:
(1) The surface roughness of the workpiece is too large, which results in poor coupling between the probe and the contact surface, low reflection echo, and even failure to receive echo signals. For surface corrosion, the in-service equipment and pipelines with poor coupling effect can be treated with sand, grinding, and contusion to reduce the roughness. At the same time, the oxides and paint layers can be removed to expose the metallic luster. Coupling agent can achieve a good coupling effect with the test object.
(2) The radius of curvature of the workpiece is too small, especially when the small-diameter tube measures thickness, because the surface of the commonly used probe is flat, and the contact with the surface is point contact or line contact, the sound intensity transmittance is low (coupling is not good). Optional small diameter probe (6mm) can be used to accurately measure curved surface materials such as pipes.
(3) The detection surface is not parallel to the bottom surface, and the acoustic wave encounters scattering on the bottom surface. The probe cannot receive the final wave signal.
(4) castings, austenitic steel due to uneven microstructure or grain size, ultrasonic waves in which to pass through when there is a serious scattering attenuation, scattered ultrasonic waves along the complex path, there may be echoes annihilated, causing no display . A coarse crystal dedicated probe (2.5MHz) with a lower frequency can be used.
(5) The probe contact surface has a certain amount of wear. The commonly used thickness measurement probe surface is acrylic resin, and its long-term use will increase the surface roughness, which will result in a decrease in sensitivity, which may result in incorrect display. Optional sanding with 500# sandpaper makes it smooth and parallel. If it is still unstable, consider replacing the probe.
(6) There are a large number of corrosion pits on the back of the measured object. Due to rust and corrosion pits on the other side of the test object, sound waves are attenuated, resulting in random readings and no reading in extreme cases.
(7) There are deposits in the measured object (such as pipelines). When the acoustic impedance of the deposits and the workpiece are not much different, the thickness gauge shows the wall thickness plus the thickness of the sediment.
(8) When there are defects inside the material (such as inclusions, interlayers, etc.), the displayed value is about 70% of the nominal thickness. At this time, an ultrasonic flaw detector can be used for further defect detection.
(9) The effect of temperature. The sound velocity in general solid materials decreases as their temperature increases, and experimental data shows that the sound speed drops by 1% for every 100°C increase in hot material. This is often the case for equipment that is in service at high temperatures. Should use high-temperature special probe (300-600 °C), do not use ordinary probe.
(10) Laminated and composite (heterogeneous) materials. It is not possible to measure uncoupled laminates because ultrasonic waves cannot penetrate the uncoupled space and cannot propagate uniformly in composite (heterogeneous) materials. For devices made of multi-layered materials (such as urea high-pressure equipment), special attention should be paid to the thickness measurement, and the value of the thickness gage only indicates the thickness of the material in contact with the probe.
(12) Coupling agent effects. Coupling agent is used to eliminate the air between the probe and the measured object, so that the ultrasonic energy can effectively penetrate the workpiece to achieve the purpose of detection. If you choose a type or use it incorrectly, it will cause the error or coupling symbol to flicker and cannot be measured. Depending on the type of application, a low viscosity couplant can be used when used on a smooth material surface, and a high viscosity couplant should be used on rough, vertical, and top surfaces. High temperature parts should use high temperature couplant. Secondly, the couplant should be applied in proper amount and evenly applied. Generally, the couplant should be coated on the surface of the tested material, but when the measuring temperature is high, the couplant should be coated on the probe.
(13) The speed of sound is wrong. Before measuring the workpiece, preset its sound speed according to the type of material or reversely measure the speed of sound according to the standard block. When a material is used to calibrate the instrument (usually the test block is steel) and another material is measured, it will produce erroneous results. Requirements must be correctly identified before the measurement of materials, select the appropriate speed of sound.
(14) The effect of stress. Most of the equipment and pipelines in service have stress, and the stress state of the solid material has a certain influence on the sound speed. When the stress direction and the propagation direction are the same, if the stress is a compressive stress, the stress will increase the elasticity of the workpiece and accelerate the sound speed. If the stress is tensile stress, the speed of sound slows down. When the propagation direction of stress and wave is not the same, the vibration track of the particle in the wave process is disturbed by the stress and the wave propagation direction is deviated. According to the data, the general stress increases and the speed of sound increases slowly.
(15) Effects of metal surface oxides or paint overlays. Although the dense oxide or paint coating produced on the metal surface is tightly bound to the matrix material and has no apparent interface, the speed of sound propagation in the two materials is different, resulting in errors, and the error size varies with the thickness of the cover. Also different.
Ultrasonic Thickness Gauge is based on the principle of ultrasonic pulse reflection thickness measurement, when the ultrasonic pulse emitted by the probe through the measured object reaches the material interface, the pulse is reflected back to the probe, by accurately measuring the propagation time of the ultrasonic wave in the material to determine The thickness of the material being tested. Any material that allows ultrasound to propagate inside it at a constant speed can be measured using this principle. Thickness gauge designed according to this principle can accurately measure all kinds of plates and various processed parts. It can also monitor various pipelines and pressure vessels in production equipment and monitor the degree of thinning after being eroded during use. . Can be widely used in petroleum, chemical, metallurgy, shipbuilding, aviation, aerospace and other fields.
Use skills: (Using the ultrasonic thickness gauge sold by our company as an example)
1, the general measurement method:
(1) Use a probe to measure thickness twice at one point. In the two measurements, the split surface of the probe should be 90° apart, and take the smaller value of the measured workpiece thickness.
(2) 30mm multi-point measurement method: When the measurement value is not stable, take a measurement point as the center, perform multiple measurements within a circle with a diameter of about 30mm, and take the minimum value as the measured workpiece thickness value.
2. Accurate measurement method: Increase the number of measurements around the specified measurement point. Thickness changes are represented by equal thick lines.
3, continuous measurement method: using a single point measurement method along the specified route of continuous measurement, the interval is not greater than 5mm.
4. Mesh measurement method: Mark the grid in the designated area and record the thickness according to the point. This method is widely used in high pressure equipment, stainless steel lining corrosion monitoring.
5, the factors that affect the ultrasonic thickness gauge indication:
(1) The surface roughness of the workpiece is too large, which results in poor coupling between the probe and the contact surface, low reflection echo, and even failure to receive echo signals. For surface corrosion, the in-service equipment and pipelines with poor coupling effect can be treated with sand, grinding, and contusion to reduce the roughness. At the same time, the oxides and paint layers can be removed to expose the metallic luster. Coupling agent can achieve a good coupling effect with the test object.
(2) The radius of curvature of the workpiece is too small, especially when the small-diameter tube measures thickness, because the surface of the commonly used probe is flat, and the contact with the surface is point contact or line contact, the sound intensity transmittance is low (coupling is not good). Optional small diameter probe (6mm) can be used to accurately measure curved surface materials such as pipes.
(3) The detection surface is not parallel to the bottom surface, and the acoustic wave encounters scattering on the bottom surface. The probe cannot receive the final wave signal.
(4) castings, austenitic steel due to uneven microstructure or grain size, ultrasonic waves in which to pass through when there is a serious scattering attenuation, scattered ultrasonic waves along the complex path, there may be echoes annihilated, causing no display . A coarse crystal dedicated probe (2.5MHz) with a lower frequency can be used.
(5) The probe contact surface has a certain amount of wear. The commonly used thickness measurement probe surface is acrylic resin, and its long-term use will increase the surface roughness, which will result in a decrease in sensitivity, which may result in incorrect display. Optional sanding with 500# sandpaper makes it smooth and parallel. If it is still unstable, consider replacing the probe.
(6) There are a large number of corrosion pits on the back of the measured object. Due to rust and corrosion pits on the other side of the test object, sound waves are attenuated, resulting in random readings and no reading in extreme cases.
(7) There are deposits in the measured object (such as pipelines). When the acoustic impedance of the deposits and the workpiece are not much different, the thickness gauge shows the wall thickness plus the thickness of the sediment.
(8) When there are defects inside the material (such as inclusions, interlayers, etc.), the displayed value is about 70% of the nominal thickness. At this time, an ultrasonic flaw detector can be used for further defect detection.
(9) The effect of temperature. The sound velocity in general solid materials decreases as their temperature increases, and experimental data shows that the sound speed drops by 1% for every 100°C increase in hot material. This is often the case for equipment that is in service at high temperatures. Should use high-temperature special probe (300-600 °C), do not use ordinary probe.
(10) Laminated and composite (heterogeneous) materials. It is not possible to measure uncoupled laminates because ultrasonic waves cannot penetrate the uncoupled space and cannot propagate uniformly in composite (heterogeneous) materials. For devices made of multi-layered materials (such as urea high-pressure equipment), special attention should be paid to the thickness measurement, and the value of the thickness gage only indicates the thickness of the material in contact with the probe.
(12) Coupling agent effects. Coupling agent is used to eliminate the air between the probe and the measured object, so that the ultrasonic energy can effectively penetrate the workpiece to achieve the purpose of detection. If you choose a type or use it incorrectly, it will cause the error or coupling symbol to flicker and cannot be measured. Depending on the type of application, a low viscosity couplant can be used when used on a smooth material surface, and a high viscosity couplant should be used on rough, vertical, and top surfaces. High temperature parts should use high temperature couplant. Secondly, the couplant should be applied in proper amount and evenly applied. Generally, the couplant should be coated on the surface of the tested material, but when the measuring temperature is high, the couplant should be coated on the probe.
(13) The speed of sound is wrong. Before measuring the workpiece, preset its sound speed according to the type of material or reversely measure the speed of sound according to the standard block. When a material is used to calibrate the instrument (usually the test block is steel) and another material is measured, it will produce erroneous results. Requirements must be correctly identified before the measurement of materials, select the appropriate speed of sound.
(14) The effect of stress. Most of the equipment and pipelines in service have stress, and the stress state of the solid material has a certain influence on the sound speed. When the stress direction and the propagation direction are the same, if the stress is a compressive stress, the stress will increase the elasticity of the workpiece and accelerate the sound speed. If the stress is tensile stress, the speed of sound slows down. When the propagation direction of stress and wave is not the same, the vibration track of the particle in the wave process is disturbed by the stress and the wave propagation direction is deviated. According to the data, the general stress increases and the speed of sound increases slowly.
(15) Effects of metal surface oxides or paint overlays. Although the dense oxide or paint coating produced on the metal surface is tightly bound to the matrix material and has no apparent interface, the speed of sound propagation in the two materials is different, resulting in errors, and the error size varies with the thickness of the cover. Also different.
There are five general body styles of ball Valves: single body, three-piece body, split body, top entry, and welded. The difference is based on how the pieces of the valve-especially the casing that contains the ball itself-are manufactured and assembled. The valve operation is the same in each case.
In addition, there are different styles related to the bore of the ball mechanism itself.
Ball valves in sizes up to 2 inch generally come in single piece, two or three piece designs. One piece ball valves are almost always reduced bore, are relatively inexpensive and generally are throw-away. Two piece ball valves are generally slightly reduced (or standard) bore, they can be either throw-away or repairable. The 3 piece design allows for the center part of the valve containing the ball, stem & seats to be easily removed from the pipeline. This facilitates efficient cleaning of deposited sediments, replacement of seats and gland packings, polishing out of small scratches on the ball, all this without removing the pipes from the valve body. The design concept of a three piece valve is for it to be repairable.
Stainless Steel Ball Valves, Brass Ball Valves, Sanitary Ball Valves, Water Ball Valves
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