The Working State of Sliding Bearing Affects the Service Lif
When the melt pump is stationary, the journal is at the bottom of the bearing, the two metal surfaces are directly contacted, and the clearance between the shaft and the bearing is not melted. At the beginning of starting, the bearing is in a dry friction state. The direction of the friction force between the journal and the journal is opposite to the circumferential velocity of the Journal surface, which makes the journal roll to the right and offset. When the melt transported increases continuously and the outlet pressure increases gradually, a part of the melt enters the bearing clearance from the outlet side along the bearing lubrication guide groove under the action of the differential pressure between the outlet and the inlet. With the rotation of the journal, a melt film on the bearing surface is formed. At this time, the friction between the two surfaces decreases and the journal moves to the left. When the melt film fully supports the starting shaft load, the friction resistance in the bearing is only the viscous resistance of the melt, so the friction coefficient reaches the minimum. At this time, the lubrication of the shaft and the bearing is between the mixed friction and the liquid friction, close to the liquid lubrication state. Obviously, under the limited load, it is impossible to achieve the ideal lubrication state, bearing temperature and melt temperature increase, resulting in the reduction of melt viscosity in the bearing, thus reducing the bearing capacity, temperature rise can also degrade through the melt of the bearing, reducing the overall quality of the polymer, so it is necessary to keep the lubricant film constantly updated.
The life of the melt pump mainly depends on whether the lubrication film between the journal and the sliding bearing can be maintained at all times. The pressure at the outlet of the pump, the speed of the pump and the viscosity of the melt all directly affect the bearing capacity of the lubrication film. In actual production, the installation, maintenance, operation and maintenance of the pump should take full account of the above factors, so that the sliding bearing and journal surface are always in a good lubrication state, reduce journal and bearing grinding, and achieve the purpose of prolonging the service life of the melt pump.
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