MRO Today - Handling bearings

Handling bearings

Simple bearing handling procedures can provide significant performance improvements.

Here are some techniques and tools help to maximize bearing life.

Regardless of the industry or application, proper bearing handling techniques are required in order to maximize bearing life and performance. From shipping and receiving to unpacking, installing, disassembling and rebuilding, a bearing is exposed to a variety of handling techniques. Done incorrectly at any stage, handling may reduce the life of the bearing.

However, understanding and following proper techniques reduces bearing damage and downtime, providing significant productivity gains for the customer.

Common handling mistakes
Incorrect bearing handling often occurs during installation. To avoid such mistakes, it is important to closely follow the instructions and recommendations provided by the bearing manufacturer.

The most common mistakes at installation are improper bearing setting and adjustment. Set or adjusted incorrectly, the bearing is at risk for conditions such as misalignment, nicking or spalling, all of which may lead to premature failure.

Aside from the initial installation, it is advised to consult manuals provided by the original equipment manufacturer (OEM) for proper technique and procedure when rebuilding equipment. During a rebuild, it is critical that the entire system is properly cleaned and relubricated to ensure the system is free of any damaging debris or particles. If not cleaned properly, replacement bearings and components still may be at risk for damage because the contamination might remain in the system. When the system is properly cleaned, it is equally important to be sure to handle replacement bearings and components in a clean environment so dirt or contamination is not transferred into the system during the rebuilding process.

Other common mistakes that can diminish bearing life include denting the cup during installation and not pressing the cup correctly. In addition to carefully handling the bearing itself, it is important to remember that the bearing is affected by its surrounding components such as lubricants and seals. That’s why careful inspection of these elements as well will help with the overall performance of the bearing system.

Handling solutions
To alleviate these problematic situations, manufacturers offer a variety of proper bearing handling tips to assist users in maximizing bearing life.

First, ensure that the work area is clean and free of debris. Clean out the machine or equipment with a clean rag and gloves. Remember, sometimes solvents can help to loosen up any hardened grease and air hoses can clean out air holes or castings. Although an excellent method to clean out a bearing, if using an air hose, be sure to use proper safety equipment and take care to not blow any debris into or onto the clean work area.

Lastly, before final installation, check the seals and use an application-appropriate lubrication to provide additional security and ensure better system performance.

Bearing handling tools
Beyond these general handling tips and guidelines, the next step is selecting the right tools for the job. Remember, with any tools, it is important to exercise proper safety techniques and use the recommended safety equipment.

Induction heaters
Induction heating is a superior, fast, clean and controlled heating method for bearings, gears and other products requiring a press fit. It is a safer and more environmentally friendly alternative to traditional heating methods such as oil baths, or blow torches.

Heating the bearing with an induction heater increases the diameter of the bearing slightly to allow easy placement over a shaft. This tool will eliminate any damage to or debris from the bearing when moving over the shaft. If the user attempts to place an unheated bearing over the shaft, microscopic particles may break off and get into the machine, causing premature damage to the bearing and other components.

Once the bearing cools down, it grabs the outside diameter (OD) of the shaft enabling it to have a proper fit so it doesn’t move or spin in place.

When using an induction heater, make sure the heater has an automatic demagnetizing feature. An extremely magnetic bearing may collect unwanted debris. Also use a feeler gauge to make sure the backface of the bearing does not move away from the shoulder on the shaft.

Finally, take care not to overheat the bearing as this may damage, soften or misshape the bearing. Temperatures of 200 to 250 degrees F will generally allow the bearing to overcome most fitting conditions.

Feeler gauges
Because it is difficult for the naked eye to see if the bearing is sitting against the shoulder, feeler gauges can be used to measure thousandths of an inch between the two surfaces to ensure proper seating.

Dial indicators
Dial indicators are used to check the end play (amount of movement of the shaft axially, relative to the housing) in Tapered Roller Bearings only. To make sure there is proper clearance (end play) the following procedure should be used. After mounting a dial indicator on the housing with the indicator point on the end of the shaft, move the shaft in one direction axially, while rotating or oscillating. Set the indicator to read “0.” Move the shaft in the opposite direction, while once again rotating or oscillating. The indicator will read the amount of end play in the system. Consult your equipment manufacturer for the proper amount of end play for your application, since each application is unique, resulting in an end play tolerance that is unique for that particular application.

For spherical, cylindrical and ball bearings, clearance is measured in a radial direction and is affected by the class of bearing ordered and the fits. Critical applications should be checked by feeler gauges or dial indicators. It is important to follow the design engineers’ requirements when installing all bearing types. Some bearing manufacturers offer classroom and hands-on training in all of these methods as well as all aspects of bearing maintenance.

Bearing or gear pullers
If planning to reuse a bearing or gear, pullers can be a useful tool for removing them safely and properly. Compare the “reach” and “spread” of the puller with the product to be removed and select a puller with dimensions larger than those of the job. Make sure the jaws do not interfere with the free movement of the cage. One of the most common mistakes is to attach the jaws to the cage and begin the pulling operation. For proper removal the jaws must engage the backface of the bearing.

When properly handled, bearing damage can be greatly minimized, ultimately saving your company time and money.

WARNING

Proper bearing maintenance and handling practices are critical. Failure to observe the following warnings could lead to a risk of serious bodily harm.

► Never spin a bearing with compressed air. The rollers may be forcefully expelled with great velocity.

► If a hammer and bar are used for bearing removal, fragments from the hammer, bar or the bearing can be released with high velocity. Note: a mild steel bar is preferred since it is less susceptible to fragmenting.

► When installing or removing bearings, always wear safety glasses or goggles.

► Cleaning solvents may be toxic or flammable. Ensure adequate ventilation and wear protective clothing.

► Remove oil or rust inhibitor from parts before heating to avoid fire or fumes.

This article was provided by The Timken Company. For more information on bearing handling techniques, training programs or tools to maximize bearing life, contact 330-438-3000; Web site: www.timken.com.

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