Classification of fault diagnosis technology for rolling bearings

 

The fault diagnosis technology of rolling bearing mainly includes vibration diagnosis technology, ferrography diagnosis technology, temperature diagnosis technology, acoustic diagnosis technology, oil film resistance diagnosis technology and optical fiber monitoring diagnosis technology, among which vibration, iron shop and temperature diagnosis technology are the most widely used.

1. Vibration diagnosis technology

When fatigue peeling, indentation or local corrosion occurs on the working surface of bearing elements, periodic pulse signals will appear in the operation of bearings. This periodic signal can be received by a sensor (speed type or acceleration type) installed on the bearing seat, and the fault of the bearing can be diagnosed by analyzing the vibration signal.

Features: Vibration diagnosis technology is widely used; Online monitoring can be realized; The diagnosis is fast and the diagnosis theory is mature.

Application: It is especially suitable for fault monitoring of bearings in rotating machinery.

2. Ferrography diagnosis technology

Bearing wear particles are closely related to their working conditions. The lubricating oil with wear particles passes through a strong magnetic field, and under the action of the strong magnetic field, the wear particles are deposited on the ferrography according to certain rules, and the ferrography can be qualitatively observed on the ferrography microscope or tested on the quantitative instrument, so as to judge the working condition of the bearing.

Features: the machine does not need to be disassembled; Low investment and good effect; Can find the early fatigue failure of bearings; Wear mechanism can be studied.

Application: It is suitable for fault diagnosis of bearings lubricated with lubricating oil, but it is difficult for bearings lubricated with grease.

3. Oil film resistance diagnosis technology

A well-lubricated bearing has a great resistance between the inner and outer rings due to the action of oil film. Therefore, by measuring the resistance of the inner and outer rings of the bearing, the abnormality of the bearing can be judged.

Features: The same criterion can be used for different working conditions. The diagnosis effect of surface spalling, indentation, crack and other anomalies is poor.

Scope of application: suitable for occasions where the rotating shaft is exposed.

4. Optical fiber monitoring and diagnosis technology

Optical fiber monitoring is a diagnostic technology that directly extracts signals from the surface of bearing rings. The displacement sensor made of optical fiber bundle includes transmitting optical fiber bundle and receiving optical fiber bundle. The light is reflected by the transmitting optical fiber bundle through the gap between the end face of the sensor and the surface of the bearing ring, received by the receiving optical fiber bundle, and converted into an electrical signal by photoelectric elements. By analyzing and processing the electrical signal, the bearing working condition can be evaluated.

Features: high sensitivity of optical fiber displacement sensor; The signal is directly extracted from the bearing surface, which improves the signal-to-noise ratio; It can directly reflect the manufacturing quality, surface wear degree, load, lubrication and clearance of rolling bearings.

Application: Suitable for machines that can install sensors in bearing seats.

5. Temperature diagnosis technology

If there is some abnormality in the bearing, the temperature of the bearing will change. Therefore, according to the change of temperature, bearing faults can be diagnosed, but the ability to judge abnormalities is very low.

Features: simple diagnosis; It has a good judgment effect on bearing burn.

Application: Suitable for simple and routine diagnosis of bearings in machines.

6. Acoustic emission diagnosis technology

Metal materials need to release elastic waves due to internal lattice dislocation, grain boundary slip or the occurrence and development of internal cracks, which is called acoustic emission. When the rolling bearing peels off or cracks, it will produce different types of acoustic emission signals, which can be used to evaluate the working condition of the bearing.

Features: rapid and simple diagnosis; Can be monitored online.

Application scope: The new technology developed in recent years is seldom used in bearing condition monitoring.

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