23 Sep 2019

3 Expert-Approved Practices for Mounting and Dismounting Bearings

Improper mounting accounts for nearly 20% of all premature bearing failure. According to leading bearing manufacturers, a minuscule change (0.01/10 mm) in alignment can contribute to load imbalance and improper load distribution.

This can result in increased vibration and excessive or uneven heating of the bearing. It may also introduce heavy wear, leading to unacceptable operating conditions. Using incorrect assembly will cause early deterioration that results in a catastrophic bearing failure.

Choosing the correct fitting and mounting method according to the bearing supplier’s specifications will provide a long service life.

However, mounting these heavy-duty machine elements requires a right amount of knowledge, experience and precision. A clean assembly site, correct working methods, and the appropriate tools will reduce the risk of damage and will preserve the service life of the bearings. This will ensure that you can get value for your money by utilizing the maximum life of your bearings by following certain practices

The information below will help facilitate a properly conducted mounting and dismounting process. This will ensure bearings are mounted and removed correctly, safely and reliably, without causing damage to the bearing and its high-precision components.

Before mounting

Before bearing assembly or disassembly, ensure that the assembly site is clean.

Utmost cleanliness is necessary to prevent foreign contaminants from penetrating the bearing itself and the location where it will be mounted. Cleanliness and orderliness are paramount as even the smallest particle can potentially damage the application itself by causing premature bearing failure.

The work area should be dry, dust-free, and relatively kept away from machine operations that may introduce foreign contaminants during the mounting process.

If the assembly site is in an unprotected area, bearings should be protected and be placed in a safe location free from dirt, water and other forms of contaminants.

This can be done by keeping bearings preserved in their original package until immediately before mounting. Similarly, the bearings can be preserved by using plastic or foil as a covering to prevent exposure to contaminants.

Associated components should also be inspected for contamination and damage. This is necessary as substances of previous machining operations may have been left behind.

Required tools for mounting and dismounting

Mounting and dismounting bearings require specially designed tools and equipment. There are many tools available to ensure a more efficient installation and removal process. This ensures a faster and safer way of executing the process. However, it’s also necessary to know the bearing type and size, as well as the method used for mounting as this will determine which tools must be used.

Below is a list of the most commonly used tools and equipment according to bearing type, size, and mounting method:

Cold mounting

Hot mounting

Dismounting

  • Internal gripping kit
  • Puller kit
  • Pulling plate

Hydraulic mounting and dismounting

  • Hydraulic nut and pump
  • Hydraulic puller
  • Hydraulic oil
  • Extension tubes and adapters

Using the proper tools and personal protective equipment not only enhances safety but also prevents potential contamination, maximizing the bearings’ service life and to easily get the job done with guaranteed perfection and precision

Mounting

The dimensional and geometrical tolerances of each assembly piece must be checked before mounting. This ensures that all components correspond to manufacturer drawings and specifications. This is important as it will minimize the likelihood of improper mounting during assembly.

Once the prerequisite checks have been confirmed, mount the bearing according to the specified method.

1. Cold mounting

Also known as mechanical mounting, this procedure is recommended for small- to medium-sized bearings. Bearings with a diameter under 80mm and up to 200mm can be cold mounted.

In traditional cold mounting methods, the bearing is mechanically pressed onto the shaft using a hammer and a pipe. This is an incorrect practice as the pipe could impact the rolling element, or damage to the raceway can occur.

This increases the risk of contamination entering the bearing and it might cause additional damages on it upon mounting.

Rather, perform assembly using the right fitting tools. Assembly paste will facilitate a smooth insertion and prevent rusting. The mounting kit and fitting tool will aid in a more reliable installation and will ensure the proper force is applied to the bearing.

2. Hot mounting

While hot mounting can be used for small- to medium-sized bearings, this assembly method is preferred for fittings that call for a large press force or has a high interference fit. Large bearings such as those with a diameter larger than 200mm will require the use of hot mounting as the force required for mounting cannot be achieved mechanically.

Several techniques can be used to heat large bearings. This includes oil bath, hot plate or oven. These methods, particularly an oil bath, increase the risk of contamination. A hot plate or oven will require the bearings to be turned over several times, potentially damaging the bearing.

To ensure safety, cleanliness, and speed, an induction heater is recommended.

Different bearings require different heating temperatures. Sealed bearings are typically heated to 100 °C while open bearings are heated to 130 °C. To avoid compromising the bearings and their components, the heating temperature should not exceed 130 °C.

Refer to the manufacturer’s specifications for the recommended heating temperature.

When hot mounting, precautions must be taken. Heat resistant gloves must be worn at all times during the hot mounting procedure considering the temperature currently present during the process. An anti-fretting paste should be used to assist with the mounting process it’s best for bearing service and maintenance operations. For heavy bearings, additional handling support may be required.

3. Hydraulic mounting

The installation of bearings with a tapered bore, especially very large bearings, requires considerable force. Mechanical mounting does not exert the amount of force required to achieve correct and efficient bearing mounting in this instance.

Hydraulic mounting is particularly suitable for this type of application.

With the hydraulic method, three techniques are available:

  • Oil injection
  • Hydraulic nut and pump
  • A combination of the two

The combination of oil injection and the use of a specialized hydraulic nut and pump is the best practice for hydraulic mounting large bearings.

High-pressure oil is injected via ducts and distribution grooves, which reduces friction. Once the oil film is applied, the hydraulic nut and pump allow for substantial forces to physically mount the bearing into the shaft.

This method ensures more control, precision, repeatability, less manual effort, and greater operator safety.

Dismounting

During the disassembly process, care must be observed in order to avoid damage to the bearings or other machine components such as the shaft or housing. This will prevent costly breakdowns and maximize machine efficiency and lifetime.

Operator safety must also be a priority to reduce the risk of personal injury.

1. Cold dismounting

To effectively dismount bearings mechanically, an extractor is required. There are several puller kits available varying in diameter, accessibility, reach, and extraction method. Ensure that the appropriate tool is used by defining scope, spacing, and extraction force required.

When using a mechanical tool, the bearing can be dismounted from a shaft by engaging the claws of the mechanical puller to the inner ring or an adjacent component.

2. Hot dismounting

Needle roller bearings or cylindrical roller bearings can be dismounted using a heating method. Induction heaters or heating rings can be used to rapidly heat a bearing’s inner ring without increasing the temperature of the shaft. The heat will cause the ring to expand, allowing easy removal.

Induction heaters will be used on dismounting inner rings with different diameters. A heating ring is preferred for infrequent dismounting applications or on large bearings as they are more cost-effective.

3. Hydraulic dismounting

Hydraulic dismounting should be used on bearings that have been in service for a long period or require considerable dismounting force. Certain dismounting difficulties such as fretting corrosion may also call for the hydraulic method.

There are two extraction methods available via hydraulic dismounting: bearings fitted on a tapered shaft seat and bearings fitted on an adapter or a withdrawal sleeve.

Avoid injury by attaching a provision or stop at the shaft end. This will limit the bearing travel during extraction.

Conclusion

Despite of their heavy-duty nature, bearings are susceptible to shocks and heavy impacts. Care and precautions must be observed during mounting and dismounting procedures to avoid compromising the integrity and precision of the bearing itself.

Any type of bearing damage during installation may jeopardize the service life of the bearing, and a damaged bearing demands costly services for correction and replacement.
Using the appropriate tools and equipment as well as the correct installation and removal methods will keep bearings well maintained during use. Without the use of proper practices, risk of bearing damage and serious injury can occur.

Learn more about the importance of having basic or in-depth technical knowledge about bearing diagnosis by getting in touch with our in-house technical experts.