What Causes Bearing Failures and Preventative Measures ...

As we've stated already, bearings do not last forever. They can be damaged and have a shortened lifespan if the right preventative measures aren't followed through in the facility.

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How do you know if a bearing is about to fail?

For starters, bearing failures are sorted into four unique stages.

Source: ACOEM AB, Conditioning Monitoring Basics: 4 Stages of Bearing Failure

These stages are based on the types of frequencies produced by the bearing's rolling elements impacting defects in the inner and outer races. 

Let's dive into the four stages of failure...

In the first stage, you will see small pits begin to appear in the bearing race as well as impacts of rolling elements that show up at ultrasonic frequencies in the spectrum.

It's important to note that this stage is still considered within the normal operation, so here your bearings are functioning normally. 

According to Vibralign, defects appear around 20,000-60,000 Hz and while this isn't a cause for replacing a bearing, Stage 1 may indicate a lack of lubrication between the races and rolling elements.

Once you reach stage two of failure, you will commonly find that the bearing's defects begin to ring at its natural frequencies, which ranges from 500 to 2,000 Hz.

Often these frequencies are actually the resonances of the bearing's components (like the races or rolling elements) or the bearing support structures.

It's important to note that repairs should be put on the schedule for critical machines at this stage.

At the third stage, the bearing defect frequencies levels become much more apparent and harmonics show up on the spectrum. 

You would clearly see defects on the raceways if you were to remove it, and it's key to determine a deterioration rate at this point.

Furthermore, bearings (in both critical and non-critical machinery) that reach this stage of failure should be replaced, if they're not already.

Bearings reach this stage when they're at the end of their lifespan, and you will notice that the noise floor is increased at all levels, which in turn produces a random, broadband spectrum. 

"Amplitudes of both high-frequency noise floor and HFE may actually decrease, but this is a sign that the bearing is about to fail." [source]

In short, the goal is to prevent bearings from reaching this stage, but if they do, it's imperative that they're replaced immediately.

Utilizing these four stages and identifying which stage a bearing is in is critical because not only will it help you foster an accurate predictive maintenance plan, but it will also help you keep your machines operating efficiently and prevent costly, unplanned downtime.

Speaking of failures, let's move on to discussing in detail the most common reasons why bearings fail that you should keep in mind... 

Chapter 3

13 Most Common Reasons Why Bearings Fail

When there is a bearing failure, that means that the bearing motion becomes ineffective. Without proper bearing motion, the machine shaft can ultimately fail, therefore, the machine itself can be damaged and break down.

Regardless if your facility has experienced bearing failure recently, it's not a surprise to say that bearings are being worn down every minute of active process operation. 

There are a handful of causes of bearing failures you can experience, and some are more common than others.

In fact, over 70% of bearing failures are due to poor fitting, poor lubrication, or contamination. [source]

Here's a chart that better displays the statistics behind common causes of bearing failures.

Let's dive into further detail about these 13 common reasons why bearings fail as they relate to your manufacturing process. 

1. Improper Lubrication

This should be one of the first reasons considered when inspecting a bearing that has failed. To ensure proper lubrication, adequate viscosity at operating temperature is a must. 

Look for highly polished or discolored bearing raceways when troubleshooting to determine if working surfaces are lacking adequate viscosity at operating temperature. 

Over-lubricating can be just as detrimental as under-lubricating.

"Under-lubrication risks metal-to-metal contact, over-lubrication causes heat build-up and friction as the rolling elements continuously try to push extra grease out of the way." according to IBT.

2. Cage Damage

There are numerous causes for cage damage. Some of the more common ones include vibration, excessive speed, wear, or blockage.

3. Contamination & Corrosion

There are many contaminants that can cause problems with a bearing. Dirt, sand, and water are the most common ones that you run into, but chemicals and corrosives can also damage bearings. 

These contaminants reduce viscosity which causes corrosion to the bearing surfaces, disrupts the oil film, and causes erosion, leading to the creation of countless abrasive particles.

Be sure to keep work areas, tools, fixtures, and hands clean, as this prevents and contamination failures. [source]

4. Electric Arcing

Also known as "Electric Arc Erosion," this failure occurs when an electric current passes through the bearing and is broken at the contact surface between races and rolling elements, producing high temperatures at localized points. [source]

This can damage the bearing by creating pits on the raceways and rolling elements.

5. Poor Fitting

It's vital that the bearing is properly mounted to an accurately sized shaft. If it isn't, it can cause issues in two ways:

1. If the shaft is oversized or expands, it will result in too tight of a fit, reducing the bearing's internal clearance (see more on this below).

2. If the shaft is undersized or has too loose of a fit, the bearing will creep on the shaft and will wear and create heat, which eventually will result in vibration and runout problems. 

6. Fatigue

Often referred to as "spalling," fatigue failure occurs when there's a fracture of the running surfaces, which leads to the removal of tiny, detached particles of bearing material.  

Since this type of fatigue is progressive, once it begins, it will continue to spread as the bearing operates. A key indicator of fatigue to keep an eye on is an increase in vibration.

While fatigue may occur at the end of the bearing's normal life expectancy, it frequently occurs before then due to an excessive loads, according to AST Bearings.

7. Brinelling

This type of failure occurs when loads exceed the elastic limit of the ring material and can be identified as permanent indentation marks in the raceways, which cause increased vibration. 

Brinelling falls into two categories:

1. True brinelling - caused by exposure to loads that exceed the elastic limits of the bearing material.
   
   
2. False brinelling - caused by vibration or swaying between rolling elements and the races. This type of failure takes the form of a depression around the race.

8. Misalignment

Misalignments lead to excessive vibration and loads. Some bearings (not all, though) can handle minor misalignments. 

According to Bearing Failure: Causes and Cures, the most commonly found causes of misalignment include: bent shafts, dirt or burrs on shaft or housing shoulders, shaft threads that are not square with shaft seats, and locking nuts with faces that are not square to the thread axis.

To prevent misalignment, there are a few best practices you can keep in mind...

Ensure you inspect shafts and housing regularly, use precision-grade locknuts, and shim the housings as needed. 

9. Path Patterns

To gain a better idea of the conditions a bearing was operated, it is best to examine the wear path pattern of the dismantled bearing that's already been in service. 

Through failure analysis testing and the understanding of normal/ abnormal wear path, one can correctly assess if the bearing has been run under the ideal conditions.

10. Seal Selection & Maintenance

Adequately sealed bearings guard against contamination and ensuring the lubrication isn't destroyed. 

Here are some guidelines for selecting and maintaining seals from Flow Control Network:

• Utilize seals that can withstand the chosen environmental/operating conditions of the facility.

• Install external shields to prevent the build-up of debris on and around seals, when possible.

• Be sure to schedule routine checkups on the radial lip seals for flexibility, hardening, cracking, and shaft contact.

• Inspect for leaks and replace damaged seals quickly.

• Steer clear of purging excessive grease past the lip seals. This can cause them to lose contact and their effectiveness and in some grave cases, can be dislodged from the housing.

• Proceed with caution if you're using water, steam, or compressed-air sprays when cleaning. It's easy to accidentally damage seals and force contaminants into otherwise clean equipment.

• If you're taking large machinery apart, avoid lifting with chains, wire ropes, or dirty slings that can score sealing surfaces. If the seal contact surfaces are worn down, be sure to resurface and grind them to meet their original specifications for finish and diameter. 

11. Overload

Putting too much load on a bearing is a common cause of failure.

You can troubleshoot overloading by reducing the load on the bearing or considering using a bearing with a greater capacity.

12. Improper Handling & Storage

Simply put, improperly storing bearing causes issues later on because they're exposed to outside elements like dampness, dust, and varying temperatures.

Handling becomes an issue when boxes are opened, or wrappings are torn prematurely because it can expose the bearings to dirt and corrosive elements.

Reliable Plant says to be sure to watch out for dampness and temperatures that could cause rust or uncovered bearings in the storage area.

13. Inadequate Internal Clearance

Last but not least, this failure impacts friction, load zone size, and fatigue life of a bearing. If the clearance of the bearing is inadequate, excessive heat will build up. 

As we've discussed already, high temperatures do not fare well for bearings and can cause other problems already listed as in lubrication and internal friction. 

Now that you know more about the most common types of bearing failures you can witness in your facility, how exactly can you prevent a bearing failure?

Keep on reading to find out about our top preventative measures that you can implement at your facility today!

Chapter 4

Preventative Measures for Bearing Failures To Keep in Mind

Under normal operating conditions, bearings have a substantial service life, but  since they do have a fixed lifespan, it's inevitable that a bearing will eventually fail. 

Actually, less than 1 percent (0.35 percent specifically) of rolling bearings do not reach their expected life. [source]

The key to preventing downtime and lost productivity in your facility is to prevent premature failure, which stems from damage that occurs to the bearing that usually could have been halted.

Doing so can not only help you prevent premature failure, but it can also help keep your process moving smoothly as well.

The majority of bearing failures we've discussed above (think pitting, spalling, unusual wear patterns, rust, corrosion, etc.) trace back to a small group of causes that are not only interrelated but are fixable too.

These causes are mounting/ alignment, lubrication, operational stress, environmental influence, and improper storing.

Let's dive in...

Why Proper Mounting and Alignment of Bearings Matters

It's imperative that the proper tools, ovens, and induction heaters are used during the mounting and installation process of bearings.

Be considerate of avoiding misalignment or shaft deflection, as this is significant in mounting bearings with separate parts. Without proper alignment between components, the bearings will end up experiencing abnormal wear.

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Once you've completed installation based on manufacturer's instructions, a best practice to keep in mind is giving the bearing a solid flushing and cleaning out with lubricant. Additionally, be sure to apply the final proper amount of lubrication before the machine is used. 

This leads us to the next preventable measure... lubrication!

Lubricate According to Manufacturers' Guidelines

Lubrication is used on bearings to cover the rolling completely and sliding surfaces with a thin oil film to prevent metal-to-metal contact. 

Grease is more commonly used because it's easy to handle, while oil lubrication is frequently used with high-temperature or high-speed applications. 

Common lubrication failures occur due to:

• Using the incorrect type of lubricant
• Too little grease/oil or too much grease/oil
• Mixing grease/oil
• Contaminating the grease/oil by objects or water

According to Machinery Lubrication, when applied correctly and effectively, lubrication helps reduce issues like friction and abrasion, transports heat generated by friction, prolonging service life, prevents rust and corrosion, and keeps foreign objects and contamination away from rolling elements.

Prevent Operational Stress

Operational stress on a bearing can impact bearing life. 

• If the load is too low on a bearing, it will result in skidding and improper loading of the rolling elements.

• If the load is too high, it could result in overloading and early fatigue.

Normally, the first sign of issues like these is unusual noises and/or elevated temperatures. The desirable bearing temperature is somewhere below 100 degrees Celsius.

It's important to note that bearing temperatures usually increase with start-up and level off at a temperature slightly lower than the start-up (ranging from 10 to 40 degrees Celsius higher than room temperature). 

That is why it's crucial to make sure vibrations are isolated in associated equipment because if they're not isolated, they can cause unusual noises and uneven running.

Source: Machinery Lubrication "5 Ways to Prevent Bearing Failures"

Take Environmental Influence Into Consideration

If not taken into consideration, there are numerous operating environments that can bring down even the best bearing and cause a failure. Here is a list of the primary issues you should have on your radar...

Dust and dirt, which can contaminate a bearing at an aggressive rate. Be sure to use proper sealing techniques to prevent this type of contamination. 

Aggressive media or water - This is another instance where proper sealing is crucial. 

External heat - Ambient operating temperature mandates many choices in radial internal clearance, high-temperature lubricants, intermittent or continuous running and other factors that affect bearing life. [source]

Current passage or electrolytic corrosion - Sparks can create pitting or fluting on bearing surfaces if current is allowed to flow through the bearing's rolling elements. You can fix this by using insulation on or within the bearing or creating a bypass circuit for the current.

Store Your Bearings Actively

Present-day, a majority of facilities keep the number of spares they have in stores a minimum.

Why?

Thanks to preventative maintenance (like the other measures we've mentioned above), facilities can detect potential failures earlier.

This means facilities can order and replace the damaged bearings before an entire machine breaks down, making the need for spare bearings to sit on shelves practically obsolete.

When you need to have bearings being stored in your facility and sitting on shelves, be sure to store them actively. This can be accomplished by rotating or spinning them frequently.

If bearings don't receive occasional rotations, it can cause false brinelling to occur, which is a premature failure we discussed in Chapter 3.

Conclusion

Bearings are typically very reliable, even under the most rigorous conditions, and under normal running conditions, a bearing's service life is substantial. 

When a bearing does fail prematurely, it's often due to causes that can be avoided. For this reason, it's crucial to be able to identify the root causes to prevent future failures with preventative measures and the issues that follow them.

Accurately diagnosing and troubleshooting bearing failures in order to get ahead of them will help prevent repeat failures and additional pain-points your facility might be experiencing, such as decreased operating efficiency, increased downtime and lost revenue. 

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The wheel bearings in your vehicle play a very important role in ensuring a smooth and safe ride. They enable the wheels to rotate freely while supporting the weight of the vehicle.

Over time, however, these bearings can wear out and fail, leading to potential hazards on the road. It's essential to recognize the signs of failing wheel bearings and know when to replace them. 

In this article, we'll explore the common indicators of worn-out wheel bearings and provide insights into when it's time to seek professional assistance to replace your wheel bearings. 

Replacing Your Wheel Bearings with Goodhood

Once you recognize wheel bearing problems, you must take action quickly and have your vehicle serviced.

At Goodhood mobile auto repair services, our experienced technicians can inspect your wheel bearings and replace them if needed. We use only high-quality parts and offer the best customer service available.

Signs Your Wheel Bearings Need to Be Replaced

Unusual Noises

One of the most prominent signs of failing wheel bearings is unusual noises coming from the wheels. As the bearings wear down, you may hear a grinding, growling, or humming sound, especially when you're driving at higher speeds. These noises are typically more pronounced when making turns. If you notice any of these sounds, it's crucial to have your wheel bearings inspected promptly.

Vibrations

Failing wheel bearings can cause vibrations in your vehicle. You may feel a pulsating sensation in the steering wheel or even throughout the entire vehicle when the bearings are worn out. 

These vibrations can negatively impact your driving experience and may indicate a need for immediate attention to prevent further damage.

Uneven Tire Wear

When wheel bearings start to fail, they can affect the alignment of the wheels. As a result, you may notice uneven tire wear. If you observe that the tread on one or more of your tires is wearing out more quickly than the others, it could be a sign of a failing wheel bearing. Regularly inspecting your tires for uneven wear patterns can help you catch potential problems early on.

Steering Instability

Worn-out wheel bearings can lead to steering instability. If you feel that your vehicle is drifting or pulling to one side while driving in a straight line, it may indicate a problem with the wheel bearings. This can compromise your ability to maintain vehicle control and pose a safety risk.

A damaged wheel bearing can also affect the wheel hub assembly, so it's important to have the entire system inspected and replaced if needed. This assembly connects your wheel and axle, providing structural support and allowing it to rotate.

If you experience any steering-related issues, it's essential to have your wheel bearings checked by a professional mechanic.

Excessive Play in the Wheel

Another sign of failing wheel bearings is excessive play in the wheel. If you notice a noticeable amount of play or looseness when you try to wiggle the wheel by hand, it could indicate worn-out bearings. This play can be felt horizontally and vertically and should not be ignored.

Knowing when to replace your wheel bearings is crucial to prevent further damage and ensure your safety on the road. While there isn't a specific mileage and/or time frame for replacing wheel bearings, having them inspected regularly is recommended, especially during routine maintenance checks.

Additionally, consider the following factors that may accelerate wear and require earlier replacement:

Driving Conditions

If you frequently drive on rough or uneven terrain, your wheel bearings may wear out faster. Off-road driving, potholes, and bumpy roads can put additional stress on the bearings, leading to premature failure.

Improper Installation or Maintenance

Incorrect installation of wheel bearings or insufficient maintenance can contribute to premature failure. It's crucial to have your wheel bearings installed by a qualified technician and follow the manufacturer's recommended maintenance guidelines.

How a Professional Mechanic Fixes a Worn-Out Wheel Bearing

If you recognize the signs of a worn-out wheel bearing, it's essential to have them checked and replaced by a professional mechanic. A qualified technician will inspect your vehicle for any issues and determine whether you need to replace the bearings.

The repair process typically involves removing the wheel from the car, taking out the old bearing, cleaning all components, and installing new bearings. Following this process requires specialized tools and experience; therefore, it's best to leave it up to experienced professionals rather than attempting a DIY fix.

Conclusion

If you notice any of the signs, such as unusual noises, vibrations, uneven tire wear, or steering instability, it's essential to have your wheel bearings inspected immediately. Ignoring them can lead to further damage to your vehicle and compromise your safety

In conclusion, recognizing the signs of failing wheel bearings and knowing when to replace them is essential for maintaining a safe and smooth ride.

When it comes to replacing your wheel bearings, it's always best to consult a professional mechanic for expert advice and assistance.

At Goodhood, our experienced technicians can inspect your wheel bearings and replace them if needed. We use only high-quality parts and offer the best customer service available.

Frequently Asked Questions

How often should I replace my wheel bearings?

It's generally recommended to have them inspected regularly, especially during routine maintenance checks. Additionally, consider the following factors that may accelerate wear and require earlier replacement, such as driving conditions and improper installation or maintenance.

Why do a car's wheel bearings fail?

Wheel bearings wear out due to several reasons, such as wear and tear due to age or excessive load. They can also fail due to improper installation or maintenance, as well as driving conditions like frequent potholes or rough terrain.

What happens if I don't replace my wheel bearings?

Ignoring the signs of bad wheel bearings can lead to further damage and compromise your safety. It's essential to recognize the signs and take action quickly by having them inspected and replaced as needed.

How do I know when my car requires a wheel bearing replacement?

Common indicators of worn-out wheel bearings include unusual noises, vibrations, uneven tire wear, or steering instability. If you notice any of such signs, it's best to get your vehicle serviced by a professional mechanic right away. At Goodhood mobile auto repair services, our experienced technicians can inspect and replace your wheel bearings if needed. We use only high-quality parts and offer the best customer service available.

How much does it cost to replace a wheel bearing?

A wheel bearing replacement cost can vary depending on the type of vehicle, the location of the wheel bearing, and other factors. On average, it can cost between $200 - $400. At Goodhood, we offer affordable and transparent prices on all of our services. Contact us for a free quote today!

What are roller bearings?

Roller bearings are a type of bearing that utilizes rolling elements to reduce friction. These bearings typically consist of rows of rollers, rings, cages, and washers. They're used in various applications such as automotive, industrial, and aerospace applications.

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