Eddy current sensor system is widely used in electric power, petroleum, chemical, metallurgical and other industries and some scientific research units. On-line measurement and protection of radial vibration, axial displacement, key phase device, shaft speed, expansion difference, eccentricity, rotor dynamics research and part size inspection of large rotating machinery shafts such as steam turbine, turbine, blower, compressor, air separation unit, gear box and large cooling pump are carried out.
Axial displacement measurement
For many rotating machinery, including steam turbine, gas turbine, water turbine, centrifugal and axial compressor, centrifugal pump and so on, the axial displacement is a very important signal. Excessive axial displacement will cause excessive damage to the mechanism. The measurement of the axial displacement can indicate the axial clearance or relative instantaneous displacement change between the rotating part and the fixed part, so as to prevent the damage of the machine. Axial displacement refers to the clearance between the internal rotor and thrust bearing along the axis. Some mechanical faults can also be distinguished by detecting the axial displacement:
Wear and Failure of Thrust Bearing Balancing Piston
Loosening of thrust flange and locking of coupling etc.
The measurement of axial displacement (axial clearance) is often confused with axial vibration. Axial vibration refers to the rapid change of the distance between the probe surface and the measured body along the axis, which is a kind of vibration of the axis, expressed by peak value. It has nothing to do with the average clearance. Some faults can cause axial vibration. For example, the compressor kicking and misalignment is.
Vibration measurement
By measuring radial vibration, we can see the working state of the bearing, the unbalance of the rotor and the medium mechanical failure. It can provide the necessary information for mechanical condition monitoring of the following key or basic machinery:
Industrial Turbines, Steam/Fuel Steam Compressors, Air/Special Purpose Gases, Radial/Axial
Expander, Power Turbine, Steam/Fuel/Water Conservancy
Electric motors, generators
Exciter, Gear Box
Pump fan
Blower, Reciprocating Machinery
Vibration measurement can also be used for continuous monitoring of general small machinery. It can provide important information for early identification of various mechanical faults.
Synchronous Vibration of Shaft and Oil Film Instability
Rotor friction and component loosening
Loose bearing sleeve, compressor kicking
Rolling element bearing failure, radial preload, internal / external misalignment
Babbitt wear of bearings, excessive bearing clearance, radial/axial
Balancing (blocking) piston wear/failure. Coupling "locking"
Shaft bending and crack
The air gap of electric motor is uneven. Gear occlusion problem
Resonance of turbine blade passage and impeller passage
Eccentricity measurement
Eccentricity is the measurement of the bending degree of an axis by an eddy current sensor system at a low speed. This bending can be caused by the following conditions:
The original mechanical bending, the bending caused by temporary temperature rise, must bend downward in a static state, sometimes called gravitational bending, the bending caused by external forces. The measurement of eccentricity is very important for evaluating the overall mechanical state of rotating machinery. Especially for steam turbines equipped with Turbine Monitoring Instrument System (TSI), eccentricity measurement has become an indispensable measurement item during start-up or shutdown. It allows you to see the magnitude of the axis bending caused by heat or gravity. The eccentric position of the rotor, also known as the radial position of the shaft, is often used to indicate the wear of bearings and the magnitude of loading. For example, in the case of misalignment, it is also used to determine the azimuth angle of the shaft. The azimuth angle can indicate whether the rotor is stable or not.
Differential Expansion Measurement
For turbogenerator units, due to different metal materials, different thermal expansion coefficients and different heat dissipation, the thermal expansion of the shaft may exceed the expansion of the shell, which may lead to the contact between the rotating and stationary parts of the turbine (such as the casing, nozzle, pedestal, etc.). The destruction of the machine. Therefore, the measurement of expansion difference is very important.
Speed measurement
For all rotating machinery, it is necessary to monitor the rotating speed of the rotating machinery axis. The rotating speed is an important index to measure the normal operation of the machine. The advantage of eddy current sensor in measuring speed is that no other sensor can measure speed. It can not only respond to zero speed, but also respond to high speed. The anti-interference performance is also very strong.
There are usually several kinds of sensors for rotational measurement: eddy current speed sensor, passive magnetoelectronic speed sensor, active magnetoelectronic speed sensor and so on. If you need to choose the type of sensor, you need to measure the speed according to the requirements of speed measurement, etc. (There are several kinds of speed generating devices: using standard involute teeth number (M1-M5) as speed generating signal, opening a key slot on the rotating shaft, opening holes on the rotating shaft, convex keys on the rotating shaft and other speed generating signal devices.
RS9000XL series eddy current speed sensor is suitable for measuring any speed above zero speed. It also has low requirement for the speed generator of the rotating shaft of the measured body. The number of gears of the measured body can be very small. The measured body can also be a very small hole, a convex key and a small concave key.
The eddy current transducer is usually used to measure the rotational speed with the probes of 3 mm, 4 mm, 5 mm, 8 mm and 10 mm. The frequency response of speed measurement is 0-10KHZ.
When the eddy current sensor measures the speed, the output signal of the sensor has high anti-interference ability (in the whole range of low speed and high speed).
Passive magnetoelectricity sensor is a power generation sensor (passive) designed for measuring gears. It is not suitable for measuring zero speed and low speed. Because of its small amplitude signal and poor anti-interference ability at low frequency, it does not need power supply.
Active magnetoelectricity sensor uses 24V power supply, output waveform is rectangular wave, with load driving ability, suitable for measuring speed signal above 0.03HZ.
Dynamic Monitoring of Rolling Bearing and Motor Commutator Rectifier
It is very important for predictive maintenance of machines using rolling bearings. The probe is mounted in the bearing housing to observe the outer ring of the bearing. Because when the rolling element is rotating, when the rolling element collides with the defective part of the bearing, the outer ring will produce slight deformation. The monitoring system can monitor the deformation signal. When the signal is deformed, it means that a fault occurs, such as the crack defect of rolling element or the defect of bearing ring. It can also measure the running state of bearing inner ring. After calculation, the slippage of bearing can be measured.
Compensated Differential Expansion Measurement of Double Inclined Surface Differential Expansion
Dynamic monitoring of rolling bearings and commutator rectifiers is very important for predictive maintenance of rolling bearings. The probe is mounted in the bearing housing to observe the outer ring of the bearing. Because when the rolling element is rotating, when the rolling element collides with the defective part of the bearing, the outer ring will produce slight deformation. The monitoring system can monitor the deformation signal. When the signal is deformed, it means that bearing failure occurs, such as the crack defect of rolling element or the defect of bearing ring. It can also measure the running state of the inner ring of the bearing, and the slippage of the bearing can be measured by calculation.
