Ball bearing fault diagnosis technology mainly has vibration diagnosis technology, iron spectrum diagnosis technology, temperature diagnosis technology, acoustic diagnosis technology, oil film resistance diagnosis technology and optical fiber monitoring diagnosis technology, etc., of which, vibration, iron shop, temperature diagnosis technology is commonly used. 

1.Vibration diagnosis technology When fatigue spalling, indentation or local corrosion occurs on the working surface of bearing components, a periodic pulse signal will appear in the operation of ball bearings. This periodic signal can have a sensor (velocity type or acceleration type) mounted on the bearing housing to receive it, and the analysis of the vibration signal is used to diagnose the bearing's fault.

Features: vibration diagnosis technology is widely used; online monitoring is possible; diagnosis is fast and the diagnosis theory is mature Applications: particularly suitable for fault monitoring of bearings in rotating machinery

2. Iron spectrum diagnostic technique Bearing wear particles are closely linked to their operating conditions. The lubricant with wear particles is passed through a strong magnetic field, and under the action of the strong magnetic field, the wear particles are precipitated on the iron spectrum sheet according to a certain pattern, which can be observed qualitatively on the iron spectrum microscope or tested on a quantitative instrument to determine the working condition of the bearing.

Features: no need to disassemble the machine; low investment, good effect; can find the early fatigue failure of the bearing; can do research on the wear mechanism

Application: Suitable for fault diagnosis of bearings lubricated with lubricating oil, more difficult for bearings lubricated with grease.

3. Oil film resistance diagnosis technology

Well-lubricated bearings, due to the role of the oil film, there is a large resistance between the inner and outer ring. Therefore, by measuring the resistance of the inner and outer ring of the bearing, the abnormality of the bearing can be judged.

Features: The same judging criteria can be used for different working conditions. The diagnosis of abnormalities such as surface spalling, indentation and cracks is poor. Application: Suitable for applications where the rotating shaft is exposed.

4. Optical fibre monitoring and diagnosis technology

Optical fibre monitoring is a diagnostic technique that extracts signals directly from the surface of the bearing collar. The displacement sensor made of optical fibre bundles contains a transmitting fibre bundle and a receiving fibre bundle. The light is reflected back from the transmitting optical fibre bundle through the gap between the sensor end face and the bearing collar surface, and is received by the receiving optical fibre bundle, which is converted into an electrical signal by the photoelectric element.

Features: optical fibre displacement sensor high sensitivity; directly from the bearing surface to extract the signal, improve the signal to noise ratio; can directly reflect the manufacturing quality of ball bearings, surface wear degree, load, lubrication and clearance situation.

Applications: Suitable for machines where the sensor can be mounted in the bearing housing.

5. Temperature diagnostic technology

The temperature of a bearing will change if the bearing produces some kind of abnormality. Therefore, based on the change of temperature, the ball bearing fault can be diagnosed, but the ability to determine the abnormality is very low.

Features: Simple diagnosis; better judgement of bearing burns.

Application range: Applicable to simple routine diagnosis of bearings in machines.

6. Acoustic emission diagnosis technology

Metal materials due to internal lattice dislocation, grain boundary slip or due to the occurrence and development of internal cracks, are required to release elastic waves, this phenomenon is called acoustic emission phenomenon. When a ball bearing is spalled or cracked, different types of acoustic emission signals are generated, from which the bearing condition can be assessed.

Features: quick and easy diagnosis; can be monitored online. Application: New technology developed in recent years, less used in bearing condition monitoring.