Mounting instructions are supplied with most SKF bearing housings, or with the corresponding seal kit. For additional information about mounting, refer to the SKF bearing maintenance handbook or skf.com/mount.
Preparations prior to mounting
Mounting housings (and bearings) requires care, accuracy and the appropriate tools. Prior to mounting, do the following:
- Make sure that the work area is clean.
- Study any drawings or instructions to determine the correct order in which to assemble the various components.
- Make sure that all the necessary components and tools are at hand.
- Clean the support surface.
- Check that the support surface meets the requirements for flatness (→ Specifications for shafts and housing support surfaces).
- Check that the shaft seats and seal counterfaces meet the requirements for dimensional and form accuracy, roughness and hardness (→ Specifications for shafts and housing support surfaces).
- Chamfer or round any shaft edges over which a seal lip will pass.
SKF tools and products
The SKF assortment of mounting tools and products includes mechanical tools, hydraulic tools, heating equipment and gloves. For additional information, refer to Maintenance products.
Many SKF bearing housings are supplied with eye bolts for safe and easy handling. The eye bolts are designed to support the weight of the housing only, and not the incorporated bearing or shaft.
When lifting, make sure that the eye bolts are only subjected to load in the direction of the shank axis. The load should be evenly distributed across the number of eye bolts.
Attachment bolt tightening
Applying the specified torque to a bolt during installation is extremely important. Improper torque values can lead to machinery movement during operation. This can cause misalignment between machine parts, which will eventually lead to premature damage to bearings and other components.
Recommended tightening torque values are provided in the product tables and are based on bolt manufacturers’ recommendations.
All bolts should be tightened with an accurate torque wrench (in at least two stages) or a hydraulic bolt tensioner. SKF recommends using a HYDROCAM hydraulic bolt tensioner in applications where the attachment bolt has an end protruding above the tightening nut. These tensioners reduce the risk of over tightening and enable bolts to be installed accurately without the need of a torque wrench. The tensioners also provide uniform assembly preload or uniform bolt elongation.
Shims can be used to raise the centre height of a housing. SKF recommends using shims made of stainless sheet steel with sufficient strength and the ability to withstand corrosion from several media. Shims made from soft metals like copper or brass typically compress over time, causing looseness, which can eventually lead to misalignment. Whenever possible, use only one shim and never stack more than three shims.
Make sure that the shim covers the complete contact surface between the housing base and the support surface (fig. 1). If shims are placed under the housing feet only, the bearing seat can distort.
Using locating (stabilizing) rings
A bearing in the locating position must be secured axially in the housing. If the bearing seat in the housing and the bearing width do not match, locating (stabilizing) rings (fig. 2) are required. Typically, two locating rings are required per housing. One ring should be placed on each side of the bearing. If only one locating ring is required, it should be installed on the same side as the lock nut. When placing a locating ring in position, make sure that the open end of the locating ring is facing up.
CARB toroidal roller bearings, which are used exclusively in the non-locating position, require locating rings when the bearing seat in the housing and the bearing width do not match. For information about which locating rings are required for a bearing in a particular housing, refer to the relevant product section.
The seal counterface should meet the specifications for surface roughness and roundness (→ Specifications for shafts and housing support surfaces), and should be clean. If the counterface shows any signs of wear, repair it. This can be done easily with an SKF SPEEDI-SLEEVE or a large diameter wear sleeve (LDSLV). If repair is not possible, replace the shaft.
In general, the seal and counterface should be coated lightly with the lubricant used in the application.
When installing seals, make sure that the seal is oriented correctly. Many seals are not symmetrical and can be installed to either exclude contaminants or retain the lubricant.
Split seals consist of two halves, which can be installed around the shaft. They are easier to replace and can ease mounting.
Felt seals should be soaked in hot oil prior to installation.