Hydrodynamic Aid Designs
The subject of installation represents an area commonly overlooked when selecting a radial shaft seal for application. Improper installation methods are a major cause of premature seal failure. The most expertly designed and manufactured seal will not function properly if the axial and radial alignment are not correct. Refer to Shaft and Housing Assembly on pages 23 and 24 for further discussion on proper alignment.
An installation tool should always be used when installing a radial shaft seal. The use of a tool improves ease of installation and reduces the possibility of seal cocking (non-perpendicular to shaft). A hydraulic or pneumatic press is advised to supply necessary force to install the seal.
When painting, be sure to mask the seal. Avoid getting paint on the lip or the shaft where the lip rides. If the paint is to be baked on or the mechanism otherwise subjected to heat, the seals should not be heated to temperatures higher than their materials can withstand. In cleaning or testing, do not subject seals to any fluids or pressures that could damage them. When in doubt, check the fluid compatibility section.
- Bore: Verify the proper chamfer, remove any
- Shaft: Verify proper lead in chamfer on end of shaft. Remove any burrs nicks, grooves or lead that could come in contact with the seal. burrs or nicks
- Splines and Keyways: Sharp edges should be covered with a lubricated assembly sleeve, shim stock or tape to protect the seal lip.
- Component Specifications: Check all components that come in contact with the seal and verify proper dimensions within tolerances, surface roughness and hardness.
- Part Interference: Verify that other machine parts do not rub against the seal, causing friction and damaging heat.
- Radial Shaft Seal: Visually inspect seal for cuts, nicks or other damage.
- Seal Direction: If replacing an existing seal, face in the same direction. Otherwise, generally, the lip faces the media being sealed.
- Pre-Lubrication: It is common practice to use lubrication to aid in installation for both the I.D. and O.D. of a seal. This is also beneficial for initial startup for the primary lip in application.
- Correct installation tool: Pressfitting tools should have an outside diameter approximately 0.010” (0.25mm) smaller than the bore size. For best results, the center of the tool should be open so pressure is applied only at the seal outer edge.
- Improper Driving Tool: Use proper driving tool such as a soft-face tool arbor press or soft workpiece (wood). To avoid cocking the seal, apply force evenly around the outer edge.
- Avoid Cocking: Bottom out the tool on the shaft, the housing or bottom out the seal in the housing counterbore.
Acceptable Installation Methods
Press-fitting tools should have an outside diameter approximately 0.010” (0.25 mm) smaller than the bore size. Never press directly against the sealing element to seat it in the bore.
|Housing Surface Stop Installation: Machined face of installation tool bottoms on machined housing face.||Housing Stop Installation: Seal bottoms on interior shoulder of bore.|
|Surface Stop Installation: Installation tool bottoms on machined housing face.||Installation of Seal Over Splines: A thin walled lubricated assembly sleeve prevents damage to seal lip from splines, keyways and unchamfered shafts.|
|Strike Plate Installation: Face of strike plate bottoms on machined housing face. Care must be taken to insure proper seal to bore alignment while seal is being installed.||Shaft Stop Installation: Installation tool bottoms on shaft.|
Unacceptable Installation Methods
Following are schematics of common improper installation procedures. These methods are presented because they are commonly seen and not recognized as being incorrect in the industry. Proper seal installation is of utmost importance. If a seal is improperly installed, it could be deformed or severely damaged, greatly reducing its life . Typically, when a seal is not properly installed, it will be cocked in the bore. This causes one side of the sealing lip to have greater interference with the shaft, leading to uneven wear and premature radial shaft seal failure.
|Improper Driving: Always use a type of driving ring to install the seal. Without it, localized seal deformation may occur.||Undersized Installation Tool: Driving diameter of installation tool is too small, seal deformation may occur.|
|Poorly Engineered Installation Tool: Seal deformation may occur. In this situation the installation tool should be designed similar to the Surface Stop Installation tool.||Misalignment Errors: Centerline of tool and bore do not coincide, causing seal to deform or to be cocked in the bore, providing a leak path for the media being sealed.|