Do stainless steel ball bearings have to be placed horizontally?

Stainless steel ball bearings do not necessarily have to be placed horizontally, but the installation direction can affect performance and lifespan, and should be carefully selected according to the design. The following are key considerations:

The sealing structure determines directional sensitivity:
Rubber contact seal ring bearings (commonly RS and 2RS types), when installed vertically, lubricating grease may slowly seep out due to gravity, and the upper ball bearings are prone to oil shortage after long-term operation.
Non contact sealing rings (ZZ metal dust cover) or specially designed lip seals have low directional dependence.

The retention ability of lubricating grease is affected by gravity:
When installed vertically or obliquely, lubricating grease is prone to deposit towards the bottom of the bearing under the action of gravity, resulting in insufficient lubrication of the upper raceway and exacerbating wear.
When installed horizontally, the distribution of grease is relatively uniform, which is more friendly to bearings lubricated with ordinary grease.

Feasibility differences in re lubrication operations:
For bearings that require regular manual grease addition, the grease injection port is usually located on the side or top during horizontal installation, making it easy to operate and allowing grease to easily enter the raceway.
When installed vertically, if the grease injection port is facing downwards, it is difficult to add grease and new grease is difficult to effectively replace old grease; If facing upwards, grease may accumulate under the top cover plate.

The type of axial load affects the design:
A thrust ball bearing that can withstand pure axial force must have its axis perpendicular to the installation plane (i.e. placed horizontally), otherwise it cannot function properly.
Although deep groove ball bearings can withstand certain axial forces, when installed vertically and subjected to unidirectional axial heavy loads, the lower ball bearing experiences greater stress and may have a lower lifespan than when installed horizontally.

Internal clearance fine tuned by gravity:
When installed vertically, the weight of the internal components of the bearing will slightly change the radial clearance (especially for large or high-precision bearings).
For precision equipment sensitive to clearance, it is necessary to evaluate the impact of direction on preload or clearance.

The risk of external pollutant intrusion varies:
When installing the horizontal axis, the sealing ring is subjected to uniform force around its circumference, ensuring stable dust and water resistance.
When installed vertically, the lower sealing ring may come into contact with more deposited liquids or particles, which requires higher sealing reliability.

Common directional designs under specific operating conditions:
Allow horizontal installation: for most common applications such as motors, conveyor pulleys, fan impeller shafts, etc.
Vertical installation is allowed: the main shaft of the water pump, the shaft of the mixer, the vertical lifting mechanism, etc. need to be optimized with sealed lubrication design or combined with auxiliary structures such as oil slingers.
Must be installed horizontally: thrust ball bearings, some ultra precision machine tool spindle bearings.