Have you found the right oil seal for your application? The next step is a precise and error-free assembly, so that the oil seal is fitted without being damaged. If you are replacing an existing oil seal, you must first disassemble it with the same care and precision. In this article, you will read all about the different steps of an appropriate (dis)assembly process that contributes to optimal operation within the application.
Successful assembly first requires careful preparation. By following a few simple steps, you significantly increase the chances of a flawless assembly.
When it involves a repair, you must first remove the old oil seal. To remove an oil seal, it is important to use the right tools to avoid damaging the shaft and bore. The best solution is therefore to pull out the oil seal without having to completely dismantle the shaft. This can be done by making a few holes in the oil seal with an awl and a hammer. You can then use a hook to pull the oil seal out of its seat. You could also screw some screws into the holes and then slowly pull out the screws to extract the oil seal from its housing. Be careful not to damage the shaft or housing in the process.
If the shaft or housing gets damaged, it must be repaired. If you replace only the oil seal, but the shaft or bore remain damaged, then there is a chance of premature failure or leakage. You can easily repair the shaft, for example using an SKF Speedi-Sleeve.
By first finding out the dimensions of the inner and outer diameters and the height of the bore, you have all the data for the correct size of the oil seal. Of course, the oil seal must also be able to withstand the pressure, temperature and medium it is exposed to within the seal during the manufacturing process. You can read more about this in our oil seal selection guide.
Before installing the oil seal, it is essential that the oil seal, shaft and bore are not damaged. So, ensure that the surfaces the oil seal comes in contact with do not have any sharp points or burrs. The sealing lip is fragile, so any minor damage to it can cause leakage. Also, make sure the oil seal is clean. Even a small amount of dirt can cause a leak. Therefore, never use a pre-used oil seal for the assembly.
Assembling the oil seals is only possible with the right assembly tools. Due to the high risk of damage during assembly, it is important that you have tools with which you can work carefully. A bearing fitting tool set is ideal.
Because the inner diameter of the oil seal must be stretched during assembly, it is necessary for the shaft to possess a ramped edge. The angle at which the ramped taper should be chamfered is 30° a 50°. If a flange or keyway is present on the shaft, it is best to use a bushing. The bore should also have a chamfer of 30° over at least 1 mm on the ramped side. Be sure to round off the edges properly in the process.
A final step in preparation for assembly is to lubricate the shaft, sealing lip and bore with sufficient oil. This will allow the oil seal to slide more easily over the shaft and prevent dry running after the first rotation. Always use oil or grease that is compatible with the oil seal material. In addition, when sliding over the shaft, the oil seal comes into contact with the keyway, threads and grooves. By taping or covering the shaft at the location of these irregularities with oil-soaked paper, the oil seal can be mounted without damage to the sealing lip.
If you have prepared the assembly properly, then you are already largely on your way to a successful installation. The assembly of the oil seal itself is not complex. It is, of course, important that it is done properly in view of the longevity and reliability of the seal.
When you start the actual installation make sure that the oil seal is always facing the right direction. So, not facing outwards, but always with the spring facing the side of the medium to be sealed. The oil seal must then be pressed into the bore. Use appropriate tools, such as a bearing fitting tool set, to ensure that this is done evenly. The oil seal must never be forcefully hammered into the bore.
It is quite common for a groove to develop at the sealing lip at some point due to long-term use. As a result, the new oil seal no longer fits and seals properly. It is not strictly necessary to replace or repair the entire shaft. Take a closer look at the dimensions first. It may be possible to fit with a slightly narrower or wider oil seal next to the groove. Alternatively, using the Speedi-Sleeve repair kit, repair the running surface under the seal.
Below is a list of other problems you may encounter when fitting oil seals.
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Stijn de Cnop
Product Manager of Sealing & Polymer Technology
Product Manager of Sealing & Polymer Technology
The oil seal should undergo thorough inspection to ensure there are no flaws or deformities. A very small scratch on the OD can cause leakage in the seal. Evaluate the bore to confirm no abrasions or residue are present. The seal and shaft should be lubricated, to ensure the lip protection during its first run.
Oil seal installation tools are recommended for use when installing rotary shaft seals, to facilitate proper engagement and decreases the likelihood of seal cocking. When using a press fitting tool (preferably pneumatic or hydraulic press), make sure the tool has an OD .01″ (.25 mm) smaller than the size of the bore.
Seal cocking is when one side of the sealing lip has greater shaft interference, which can negatively impact the oil seal’s function. This causes higher heat generation and makes the sealing lip harden and crack. In worse cases, this may dislocate the spring from the sealing lip.
When using a rubber-covered OD, the seal could spring back after installation. The rubber OD of the seal and the bore produce friction and can cause the seal to withdraw from the installation point, after being pressed in.
Described below, are incorrect ways to install an oil seal. These mistakes are seen rather frequently, however are not necessarily understood nor condemned within the industry. Incorrectly installed oil seals can be dented and contorted, thus diminishing its function. Improper installation, it will be cocked in the bore and fail in service.
Use a suitable driving ring while installing a seal. Utilizing an inappropriate driving ring can cause deformation and misalignment of the seal.
If the installation tool’s driving diameter is too small, this could cause the seal to deform during installation.
If the installation tool is not correct for the seal, this may cause deformation.
If the tool and bore do not meet evenly, the seal can become deformed and/or cocked in the bore. Thus, creating a leak path for the matter being sealed.