When it comes to regreasing bearings, more is not always the better option and actually can be a costly mistake. Instead, greasing should be set on a frequency with proper calculations used to determine the amount of grease needed at each relubrication. The determining factor for the amount required is based on the dimensions of the bearing or the bearing housing.
Overgreasing can lead to high operating temperatures, collapsed seals and in the case of greased electric motors, energy loss and failures. The best ways to avoid these problems are to establish a maintenance program, use calculations to determine the correct lubricant amount and frequency of relubrication, and utilize feedback instruments.
Too much grease volume (overgreasing) in a bearing cavity will cause the rotating bearing elements to begin churning the grease, pushing it out of the way, resulting in energy loss and rising temperatures. This leads to rapid oxidation (chemical degradation) of the grease as well as an accelerated rate of oil bleed, which is a separation of the oil from the thickener.
The heat that has been generated over time along with the oil bleed eventually will cook the grease thickener into a hard, crusty build-up that can impair proper lubrication and even block new grease from reaching the core of the bearing. This can result in accelerated wear of the rolling elements and then component failure.
Seal damage is another negative side effect of overgreasing. Grease guns can produce up to 15,000 psi, and when you overgrease a bearing housing, the lip seals can rupture, allowing contaminants such as water and dirt to gain access into the bearing housing. Keep in mind that lip seals usually fail around 500 psi. ReadLip Seals - A Practical Guide for more about this topic.
This excessive pressure can also damage single and double-shielded bearings, causing the shields facing the grease supply to collapse into the bearing race and leading to wear and eventually failure. When too much pressure is generated from a grease gun due to overgreasing, it is easy for the hard, crusty grease formed from heat (high operating temperatures) to be broken apart and sent directly into the bearing track.
Overgreasing electric motor cavities has the same effect as with any bearing application except that grease can reach the motor windings. When filled completely with grease, an electric motor bearing will generate excessive heat due to churning. This results in energy loss as well as an accelerated rate of oil bleed and hardening of the grease thickener.
Again, the high pressure applied from a grease gun can result in grease finding its way between the shaft and inner bearing cap and pressing into the inside of the motor. The result over time is the coating of the electric motor windings with grease, which leads to both winding insulation and bearing failures.
Setting up a maintenance program is key to solving the problem of overgreasing. Each lube point, whether it be a bearing housing or electric motor, should be tracked as an asset, and records kept for scheduling planned maintenance or inspections of the asset. While the initial setup of a maintenance system may take some time and hard work, the end results will have a major impact.
Once you have planned the scheduling of the assets, you will need to determine the timing and amount of grease (volume) that should be applied at each point. The volume can be calculated with a simple equation (ref. SKF):
G = 0.114 x D x B
Where G = the amount of grease in ounces
D = the outside diameter of the bearing in inches
B = the bearing width in inches
| 70% | of lubrication professionals believe overgreasing is a problem at their plant, according to a recent survey at machinerylubrication.com |
Next, calibrate all grease guns in use and train the technicians on the proper procedures of usage. Calibrating a grease gun is very simple. All you need are the grease gun and a postal scale. Determining the weight in ounces per full stroke (shot) of the grease gun will allow you to identify the number of shots it takes to equal 1 ounce of grease. This will help you establish the right volume needed to ensure you are delivering the precise amount at each use.
After you have determined the correct volume, it’s time to establish the proper frequency. There are several methods for estimating a regreasing frequency, including multiple calculators, tables and charts. Use our handy regreasing volume and frequency calculator for help. The major factors in determining frequency are load, operation time, type of bearing, speed, temperature and environment.
Feedback tools can also be beneficial for fine-tuning your frequency. For example, ultrasonic instrumentation is one of the best ways to optimize the correct frequency and help you set up your maintenance program.
Establishing appropriate procedures and inspections during relubrication is another important part of a maintenance program. Some basic steps include:
Cleaning areas around the fill and relief fittings.
(Video) Rollix tutorial #5: Maintenance of your slewing bearing - Re-greasingEnsuring the grease relief valve moves freely or the drain plug is removed.
Checking to be sure the relief passage is clean from any hardened grease that may be blocking grease from exiting.
Greasing the bearing cavity with the correct calculated volume of grease while slowly adding each shot to minimize excessive pressure build-up.
Allowing the motor to run during and after greasing to expel any excess grease. This should be done before re-installing the purge port or bottom grease relief valve and cleaning the area of any excess grease.
Tips to Control Overgreasing
Discontinue greasing when you feel abnormal back pressure.
(Video) How to plan your car repair - Central door lock repairAlways make sure exhaust ports are cleaned out from any debris or old, hard crust that could be blocking the passageway.
Consider installing grease guns with pressure gauges, shut-off grease fittings or relief-type vent plugs.
Slowly pump grease into bearings every few seconds. Using a quick-lever action could cause seal damage and not allow the grease to distribute throughout the bearing correctly.
Read more about motor bearing regreasing best practices:
FAQs
What are the dangers of over greasing bearings? ›
In instances where bearings are in an electric motor, over-lubricating those bearings can cause serious damage. If the excess grease reaches the motor windings, the windings will get insulated with grease, causing inefficient performance, overheating, and bearing failure.
What are the problems with overgreasing? ›EFFECTS OF OVER GREASING
An abundance of grease in a bearing cavity will cause rotating bearing elements to begin churning and pushing the grease out of the way, resulting in energy loss and increased temperatures.
Overgreasing by applying too much grease to a bearing at one time can result in a seal failure and generate heat in the bearing housing. When too much grease is pumped into a bearing cavity, it eventually will become full. If there is no relief port on the housing, the grease will blow through the seals.
What is the effect of over lubrication? ›Lubrication in excess also has a negative impact on the state of the joints. When there is an excess of lubricating oil, the pressure rises in the seals, which makes them deteriorate and break. When this happens, both water and dirt can find their way into the mechanical system.
Can you overpack a wheel bearing? ›If too much grease is “packed” into the bearing and the cavity, this grease will be pushed out when the wheel spins, and could easily ruin the brake shoes. In addition, the wheel bearing could actually overheat. Repacking wheel bearings is an easy job, and should be part of the routine maintenance of the vehicle.
Can you put too much grease in a wheel hub? ›Too much grease causes churning and higher temperatures. Semi-fluid grease must be used with a vented hub cap. It cannot be packed around the bearing as it will slump.
What happens if you over grease a motor? ›Having too much lubrication, also known as over greasing your motor can lead to higher operating temperatures and seal failures. This is because excess grease in a given bearing cavity will cause those bearing elements to churn and push the extra grease out of the way.
Can you over grease a grease fitting? ›Too much grease will damage bearing seals allowing contaminants to enter and grease to escape. Adding the wrong amount of grease can be as harmful as not greasing bearings at all.
What problems can develop if too much grease is used in lubricating an electric motor? ›Overheating Due to Excess Grease -Too much volume will cause the rotating bearing elements to churn the grease, trying to push it out of the way. This results in parasitic energy losses and high operating temperatures, and increases the risk of oil separation and bearing failure.
Does lube make you more wet? ›In another study, women felt positively about lubricant use and preferred sex to feel more “wet” and were able to orgasm more easily using it. This insight is very helpful for those women who have difficulty orgasming during sexual intercourse!
What will happen if the viscosity of lubricant is too low or too high? ›
This can lead to an increased mechanical friction and wear due to film loss. At lower temperatures a lubricant with low VI might have a viscosity that is too high, resulting in low oil flow, oil starvation and dry start-ups.
How often should bearings be packed? ›How often should you repack your trailer bearings? The axle manufacturers recommend that you repack your trailer bearings once annually or every 12,000 km.
What makes a wheel bearing worse? ›Impact damage or poor road quality – all impacts from driving through a pothole, driving over speed bumps or hitting the curbstone can damage a wheel bearing and reduce its lifespan. Poor quality wheel bearing – a wheel bearing is continuously under enormous pressure.
How much grease do you put in a sealed bearing? ›Sealed bearings are filled with a high grade, low viscosity grease that fills ~ 15% of the free space in the bearing.
Is lithium grease good for bearings? ›A lubricating grease such as white lithium grease works by lowering the coefficient of friction at the interface between 2 or more parts. It is often used as a gear grease and to protect bearings.
Can you use silicone grease on bearings? ›Applications of silicone grease
Figure 3: Silicone grease can be used to lubricate gears, valves, or machinery components such as bearings.
With a larger travel trailer, you should grease your trailer wheel bearings every 10,000 miles or once a year, whichever comes first. If you have a smaller travel trailer, however, you'll need to grease your wheel bearings every 2,000 miles.
What happens if you put too much grease in a ball joint? ›One concern about greasing ball joints is not wanting to overfill it and bust the seal between the ball joint and the dust boot, which leaves the joint open to contaminates that can potentially lead to failure.
Can you over grease gears? ›A sufficient amount of grease must be used to ensure gear teeth are lubricated, but excess grease can result in power losses and viscous drag.
How much grease should you add to a motor bearing? ›30% to 50% fill — Typically used. For very high speeds the lower limit should be used in order to reduce churning and overheating of the grease. Overpacked bearings tend to overheat, and to overheat even more at higher speeds.
What is the most common cause of premature bearing failure? ›
The most common cause of bearing failure is fatigue, with 34% of all premature bearing failures being attributed to fatigue. This could be that the bearing is at its natural lifecycle end, but it can also be caused by using the wrong bearing for the application.
What does Zerk mean? ›zerk in American English
(zɜrk ) noun. a small metal fitting through which grease can be inserted into a mechanical joint that requires periodic lubrication.
If this is the case, the best tactic is to “feel” the grease into the bearing cavity until slight resistance or back pressure is felt against the trigger, or lever, signaling the bearing cavity is now full.
What is the main effect on lubricating oil of operating for long periods at excessively high temperature? ›Lubricating oils in machines operating at elevated temperatures for a long time will have higher degradation rates. Therefore, keeping the lubricants at the lowest possible temperature helps extend their service life while reducing degradation rates.
Can you grease a motor while it's running? ›Consult your lubricant supplier and analyze the bearing operational conditions. In cases of excess heat, be mindful that greasing best practices suggest to re-grease when the motor is running and to remove the lower drain plug while introducing new grease.
What are the most common causes of lubrication system maintenance problems? ›- Over-lubrication. You can have too much of a good thing. ...
- Under-lubrication. A lack of lubricant is likely one of the easiest problems to spot. ...
- Using the wrong lubricant. ...
- Mixing lubricants. ...
- Lubricant contamination.
While higher viscosity oil causes issues in frigid weather, lower viscosity oil can cause issues in warmer weather. The hot weather can prevent the oil from properly lubricating the engine, which in turn causes the oil to burn. Excess friction between the metal parts of your car can cause long-term damage.
What happens if a liquid has high viscosity? ›Fluids with low viscosity have a low resistance and shear easily and the molecules flow quickly; high viscosity fluids move sluggishly and resist deformation. Some liquids, like pitch, glass and peanut butter, have such high viscosity they behave like solids.
What problems can low viscosity cause? ›Low viscosity increases the risk of internal leakages and negatively affects the efficiency of pumps and motors. High viscosity can cause problems such as sluggish movement, increased mechanical friction, heat generation and cavitation.
Can a bearing be over 90 degrees? ›A bearing describes a line as heading north or south, and deflected some number of degrees toward the east or west. A bearing, therefore, will always have an angle less than 90°.
How much tolerance should a bearing fit? ›
| Load type | Shaft diameter dimensional tolerance | |
|---|---|---|
| lower | ||
| Rotating inner ring load | Low speed Light load | －7.5 |
| Rotating outer ring load | Low to high speed Light load | －7.5 |
| －7.5 | ||
Misalignment is a frequent cause of rolling bearing failure. It can cause cage fracture, which will result in seizure of the bearing, pump failure and costly downtime. It can also cause edge loading, which will result in early bearing failure.
What causes bearing overheating? ›The issue of overheating is related to fluid friction, which is a result of fluid churning. This is a secondary effect of overfilling the cavity at the time of relubrication. Installing a relief vent port can help in this situation, but this would be only addressing the symptom rather than the cause.
What are the 3 rules of bearings? ›- Always measure the angle in a clockwise direction.
- Always measure the angle from north.
- Always give a 3-figure bearing (E.g. 030° instead of 30°)
Bearing Temperature Conditions
A bearing temperature that is less than 180 degrees F is typically considered acceptable (see the chart below). Of course, there may be other consequences for operating in this “good” range. A higher operating temperature will cause the bearing lubricant to deteriorate at a faster rate.
A simple rule for troubleshooting bearing temperatures: No more than 180 degrees Fahrenheit (82 degrees Celsius) on the housing. The bearing outer ring can be up to 20°F (11°C) hotter than the housing.
How much wiggle should a wheel bearing have? ›Check wheels for side-to-side looseness – There should be a very slight amount of play in the wheel, typically 1/8-inch or less. If the wheels are loose or spin with a wobble, the bearings must be serviced or replaced.
How much clearance do you need between bearing and shaft? ›For instance, internal radial clearance of a deep-groove ball bearing mounted on a solid steel shaft with an interference fit of 0.013 mm (0.0005 in.) may be reduced as much as 0.010 mm (0.0004 in.)
How much end play should a wheel bearing have? ›ACCEPTED PRACTICE. For decades, the heavy duty truck industry has accepted a recommended wheel end bearing setting of 0.001-inch to 0.005-inch of endplay.
What is the most common cause of bearing failure? ›While it may seem like common sense, standard wear and tear is one of the leading causes of bearing failure. Eventually all bearings fail due to wear, however, excessive load, vibration or force can cause a bearing to wear out long before it should. Most of this excess force is caused by improper installation.
What is one of the first signs of bearing failure? ›
Vibration. A sure sign that your bearing has failed is vibration. If the raceway surface of the bearing becomes damaged by abrasion, the rolling elements (the balls or rollers) will bounce around on the raceway surface during operation, causing high levels of vibration.
How do I know if my wheel bearing is about to fall off? ›- A humming, rumbling or growling noise that increases with acceleration or as the vehicle turns.
- A loud constant whining or grinding noise when the vehicle is in motion.
- Clunking noises when driving over uneven road surfaces.
Overheating Engine. The excessive build-up of heat in the engine can lead to crankshaft sensor damage by melting the plastic covering. Circuitry Problems. Faulty voltage or loose, worn-out, or damaged wiring can disrupt the signals sent to and from the crankshaft sensor, causing it to have issues.
Can overheating cause a spun bearing? ›A spun bearing is usually the end result of a chain of unfortunate events. These include high operating loads, excessive heat and a loss of lubrication.