Vertical engines are a common type of engine installation. Previous articles have introduced many technical contents related to the selection, configuration and use of vertical motor bearings. Today, we discussed the issues of lubricating vertical engine bearings.
Lubrication plays a very important role in the use of bearings. In previous bearing failure statistics, almost half of the failures are related to inadequate lubrication. This correlation is not only present in horizontal engines, but is also prominent in vertical engines.
Bearings in vertical motors are used so that the bearing axis is perpendicular to the ground. Therefore, the force and state of motion at this time are different from those of horizontal motors. The following factors need to be considered in terms of lubrication:
First, the impact of gravity – the choice of grease viscosity.
For horizontal motors, gravity is equivalent to the radial direction of the bearing, but for vertical motors, all gravity is axial. In terms of lubrication, grease is affected by gravity and flows toward the ground. For horizontal motors, grease will flow to the bottom of the bearing. However, as the bearing rotates, the lubrication will be agitated and distributed throughout the bearing.
For vertical motors, the bearing rotation occurs in the radial plane and the direction of gravity is axial. Therefore, the grease inside the bearing will flow (or tend to flow) to one side of the bearing. Circumferential rotation of the bearing has a very limited effect on the axial distribution of bearing lubrication.
In this way, the fluidity of the bearing grease has a notable effect on the distribution of the grease. Therefore, in vertical engines in general, it is usually recommended to use lubricants with lower fluidity. This also means that when choosing the viscosity of the grease, it is advisable to consider a higher viscosity. For engines, this generally means that No.3 grease is often used in the bearings of vertical engines.
Secondly, the impact of gravity – grease life.
In the analysis above we mentioned that the rotation of the engine's vertical bearings in the radial plane does not contribute favorably to the circulation of grease within the bearing. In other words, the rotation of the bearing does not fully facilitate the agitation of the grease, which is not beneficial for the circulation of the lubricant within the bearing.
Consequently, generally speaking, for vertical motors, the internal bearing grease life is reduced by half based on standard grease life calculations. This directly results in halving lubrication intervals and increasing bearing lubrication frequency.
Third, the impact of gravity – lubrication path design.
For the selection of lubrication paths in horizontal engines, we have dedicated articles that explain this. However, for vertical engines, we must consider an important factor, which is gravity. For horizontal engines, we need to ensure that the engine bearing oil path inlets and outlets are on both sides of the bearing, with the engine outlets normally the same.
These aspects also require attention in vertical engines. But even though the bearing lubrication paths are distributed on both sides of the bearing, we must consider that the best direction for oil to enter the bearing is from above, and oil drainage should ideally be from below.
This way, gravity will help circulate the lubricant. If designed otherwise, it could lead to unfavorable oil drainage, which could cause various problems, such as excessively high bearing temperatures.
Fourth, the Impact of Gravity – Motor and Bearing Storage.
For electric motors and bearings stored vertically, gravity causes internal lubrication to flow downward. This, over long periods, can lead to an excess of grease in the lower part and a deficiency in the upper part of the bearing. For the same gravitational reasons, we recommend equalizing pre-start lubrication for engines stored horizontally.
However, this radial rotation method of lubrication equalization is limited for vertical engines. Therefore, we recommend supplementing lubrication prior to operational deployment of vertically stored motors that have been stored for long periods to avoid poor lubrication on one side of the bearing.
It is easy to see from the above analysis that the main difference between the lubrication of vertical engine bearings and horizontal bearings is the directional impact of gravity on lubrication. By paying attention to these aspects, the lubrication status of the engine's vertical bearings can be properly safeguarded.
