Causes of Damage to Generator Set Bearings or Rotor Systems

In this article, Starlight Power generator set manufacturer combines its own years of experience in the industry to explain in detail to the majority of generator sets users about the shaft current damage to the rotor parts during the production process of the generator set and the ultimate cause of damage to the bearing or the rotor system.

The rotating shaft must adopt a certain lubrication method to keep the rotor and the bearing in direct contact, that is, there is an oil film insulation between the entire rotor and the stator during high-speed rotation. Because the rotor has resistance to the ground, once it is charged, a voltage to the ground will be established. When the voltage rises to a certain value, it will break down in the area with the smallest resistance and spark discharge will occur. The main consequences of this discharge are as follows:

(1) Melt the metal particles in the discharge area, and form very tiny galvanic pits on the metal surface.

(2) The accumulation of pits makes the surface rough and loses its luster. If it occurs on the bearing bush, pure mechanical wear will occur.

(3) The molten metal particles enter the lubrication system, causing the lubricant to be contaminated, and the lubricating performance of the entire lubricating system deteriorates, and the lubricant containing a large amount of metal particles will reduce the oil film resistance and accelerate the progress of spark erosion.

(4) Localized high temperature is generated in the bearing area of the bearing, which destroys the oil film, burns the metal, increases abrasion, and finally causes serious friction damage.

In the rotor system of rotating machinery, the most prone to spark discharge is the bearing surface of radial bearing and thrust bearing, the working tooth surface of gear coupling and the sealing surface of floating ring. Changes in various conditions (such as load, temperature, lubrication conditions, and rotor vibration, etc.) may reduce the resistance of the oil film and the air gap, causing electric spark discharge in these parts.

For radial sliding bearings, the development of bearing galvanic pits will cause severe corrosion on the surface of the babbitt alloy, which will not only change the original clearance of the bearing, but also cause abrasion and scratches on the bearing surface due to the decrease in surface finish. Localized heat and burns.

The abrasion of babbitt on the surface of high-speed and light-load bearing will cause some of the bearing pads to lose their preload on the rotor journal, and the rotor is likely to induce oil film turbulence when rotating, causing the instability of the rotor system. The unstable oil film in turn will cause a sharp drop in the resistance of the oil film of the bearing, causing more shaft currents to pass through the area, aggravating the effect of electric sparks, mutually energizing each other, and ultimately causing damage to the bearing or rotor system.

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