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You are here : Mechanical seal fluid film thickness testing technology
Fluid film thickness measurement is essentially a measurement of displacement and amplitude, but very thin film of fluid, measurement is difficult, generally such a small displacement sensor displacement is difficult to make an accurate response to changes in domestic and foreign workers over the years for this to do the sealing a large number of attempts and research. The commonly used measurement methods are capacitance and eddy current method.
BABatch capacitance method applied film thickness measurement, in the face away from the stationary ring 90 ¡ã installed three cylindrical probe, probe buried in cement in the stationary ring, the stationary ring with the grinding face flush with the probe, each probe as a plate capacitor a pole, the formation of the capacitor grounding ring to another pole, working between two poles separated by a membrane, through the electronic circuit to changes in capacitance into a voltage change, you can measure the thickness; JCarl face in the seal ring 5 installed on the probe, which measured 3 ring gap, and the other two measure the radial clearance, which can simultaneously measure the average thickness and thickness fluctuations; JDigard in the test device also uses a capacitive measurement end fluid film thickness.
Capacitance method is simple, sensitive, good output linearity and thermal stability characteristics, but the parasitic capacitance and dielectric permittivity on the measurement result will be the impact can not be ignored. In particular the common ground wire ring by way of fluid film bearing test device in the impact of changes in the thickness of fluid film bearings is possible to seal the fluid film thickness measurement face completely covered up. Li Baoyan such as film thickness using capacitance measurement, rotating ring-lead approach with a collecting ring to remove the fluid film bearing the impact of change, under the simultaneous measurement of the dynamic dielectric constant parasitic capacitance and dielectric, and the measurement results was amended to increase the accuracy and credibility.
Eddy current method uses a sensor --- inductive eddy current sensor. Eddy current sensor is an able machine displacement, amplitude and other parameters into electrical signals output power electrical measuring devices of non. It consists of the probe, converter, connecting cable and the test conductor, can also be used for static measurements of dynamic measurement, is a non-contact measurement to achieve an effective tool. Electric eddy current method has a linear range, high sensitivity, good dynamic response, simple structure, small size, can realize the advantages of non-contact measurement, in particular, the sensor from the fluid of its former, more suitable for mechanical seal fluid film thickness measurements. However, when the eddy current sensor using restricted by many factors, such as eddy current sensors work object must be metallic conductors, and the surface should be smooth; the measured area of the metal surface should be larger than the diameter of eddy current sensor 1183 times; Eddy Current Sensors induced magnetic field is weak, so the existence of the stray magnetic field around its sensitivity will have a huge impact, but also disturbances in the magnetic field of mixed signal components, so the need for screening measures; In addition, the ring of the material must have good permeability (tungsten carbide can be used.) Currently, the domestic use of eddy current thickness measurement of mechanical seal testing device more. Gu Yongquan, Hudan Mei, Chen Ming, and MinZou are measured using eddy current method of mechanical seal fluid film thickness were measured, and achieved good results.
BABatch capacitance method applied film thickness measurement, in the face away from the stationary ring 90 ¡ã installed three cylindrical probe, probe buried in cement in the stationary ring, the stationary ring with the grinding face flush with the probe, each probe as a plate capacitor a pole, the formation of the capacitor grounding ring to another pole, working between two poles separated by a membrane, through the electronic circuit to changes in capacitance into a voltage change, you can measure the thickness; JCarl face in the seal ring 5 installed on the probe, which measured 3 ring gap, and the other two measure the radial clearance, which can simultaneously measure the average thickness and thickness fluctuations; JDigard in the test device also uses a capacitive measurement end fluid film thickness.
Capacitance method is simple, sensitive, good output linearity and thermal stability characteristics, but the parasitic capacitance and dielectric permittivity on the measurement result will be the impact can not be ignored. In particular the common ground wire ring by way of fluid film bearing test device in the impact of changes in the thickness of fluid film bearings is possible to seal the fluid film thickness measurement face completely covered up. Li Baoyan such as film thickness using capacitance measurement, rotating ring-lead approach with a collecting ring to remove the fluid film bearing the impact of change, under the simultaneous measurement of the dynamic dielectric constant parasitic capacitance and dielectric, and the measurement results was amended to increase the accuracy and credibility.
Eddy current method uses a sensor --- inductive eddy current sensor. Eddy current sensor is an able machine displacement, amplitude and other parameters into electrical signals output power electrical measuring devices of non. It consists of the probe, converter, connecting cable and the test conductor, can also be used for static measurements of dynamic measurement, is a non-contact measurement to achieve an effective tool. Electric eddy current method has a linear range, high sensitivity, good dynamic response, simple structure, small size, can realize the advantages of non-contact measurement, in particular, the sensor from the fluid of its former, more suitable for mechanical seal fluid film thickness measurements. However, when the eddy current sensor using restricted by many factors, such as eddy current sensors work object must be metallic conductors, and the surface should be smooth; the measured area of the metal surface should be larger than the diameter of eddy current sensor 1183 times; Eddy Current Sensors induced magnetic field is weak, so the existence of the stray magnetic field around its sensitivity will have a huge impact, but also disturbances in the magnetic field of mixed signal components, so the need for screening measures; In addition, the ring of the material must have good permeability (tungsten carbide can be used.) Currently, the domestic use of eddy current thickness measurement of mechanical seal testing device more. Gu Yongquan, Hudan Mei, Chen Ming, and MinZou are measured using eddy current method of mechanical seal fluid film thickness were measured, and achieved good results.
