Is the thrust bearing of the turbine vibration-monitored?
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Both radial bearings of the turbine are equipped with vibration sensors, but the thrust bearing does not have any. Why? Don’t the thrust bearings of centrifugal compressors also need vibration measurement?
The thrust bearing of a centrifugal compressor you are referring to must be that of a multi-stage compressor! In the case of multi-stage compression, vibration measurement is not required; instead, displacement measurement is necessary.
Normal critical equipment should all have axial vibration probes (sensors), only measuring displacement. There are three types of vibration probes: displacement, velocity, and acceleration. Vibration displacement reflects the magnitude of the vibration amplitude, vibration velocity reflects the amount of energy, and vibration acceleration reflects the intensity of the impact force. Below are the working principles and applications of these vibration sensors. 1. Eddy current vibration sensor: The eddy current vibration sensor is a vibration sensor that operates on the principle of the eddy current effect; it belongs to the category of non-contact sensors. An eddy current vibration sensor measures the vibration parameters of an object by detecting changes in the distance between the end of the sensor and the object being measured. Eddy current vibration sensors are mainly used for measuring vibration displacement. 2. Inductive vibration sensor: An inductive vibration sensor is a type of vibration sensor designed based on the principle of electromagnetic induction. An inductive vibration sensor is equipped with a magnet and a magnetic conductor; when measuring the vibration of an object, it can convert mechanical vibration parameters into electrical signal parameters. Inductive vibration sensors can be used to measure parameters such as vibration velocity and acceleration. 3. Capacitive vibration sensor: A capacitive vibration sensor generates a variable capacitance by changing the gap or common area, and then measures this capacitance in order to determine the parameters of mechanical vibration. Capacitive vibration sensors can be divided into two types: those with a variable gap and those with a variable common area. The former can be used to measure linear vibration displacement, while the latter can be used to determine the angular displacement of torsional vibrations. 4. Piezoelectric vibration sensor: A piezoelectric vibration sensor utilizes the piezoelectric effect of crystals to measure vibrations. When the vibrations of the object being measured exert pressure on the piezoelectric vibration sensor, a corresponding charge is generated in the crystal element, and this charge amount can be converted into vibration parameters. Piezoelectric vibration sensors can also be divided into piezoelectric acceleration sensors, piezoelectric force sensors, and impedance heads. 5. Resistance strain-type vibration sensor: A resistance strain-type vibration sensor is a type of vibration sensor that uses changes in resistance to indicate the degree of mechanical vibration of the object being measured. There are many ways to implement resistive strain vibration sensors, and various sensing elements can be used, among which resistive strain gauges are the most common.
Thrust bearings do not belong to the supporting equipment; seismic monitoring is not required – only the displacement of the thrust disc and the temperature of the thrust bearings need to be measured
The compressor’s radial bearings are bushing types, so there is no need to measure axial vibration. It is only necessary to monitor the axial displacement.
Axial displacement is generally measured to prevent the bearing shells from being damaged.
Vibration measurement of equipment: Acceleration sensors are generally used for equipment equipped with rolling bearings, while displacement sensors are used for those with sliding bearings.
Axial displacement can be measured; thrust bearings are designed to counteract axial movement, as long as the displacement value remains within the allowable range.
There is an axial displacement sensor that transmits the axial position of the shaft in real time.
Thrust bearings are not part of the supporting equipment; seismic monitoring is not required – only displacement measurement is necessary