…and 5 ways to avoid it!
Mae West famously said, “Too much of a good thing can be wonderful.” Although we don’t know just what she was referring to, chances are pretty good it wasn’t lubrication of bearings, because in this case, too much is just as bad as not enough.
Over-lubrication of bearings is dangerous for a number of reasons. Read on to learn more!
- Lubricant churn
- Seal failure
- Electric motor failure
Many people believe that if some lubricant is good, then more must be better. In fact, excess lubricant requires a machine to produce extra torque in order to move bearings or gears at the required speed. (Why is this? Ask yourself which is easier: walking through mud up to your ankles, or up to your knees?) Extra torque results in the generation of excess heat, and heat destroys lubricants before their time.
Every 10°C (18°F) rise in temperature above 65°C (150°F) cuts the service life of lubricant in half. This means lubricant that would normally last one month at 150°F will last only two weeks at about 168°, one week at 186°, and just three or four days at 204° before it needs to be replaced or rejuvenated. If an application is unknowingly over-lubricated, this means your lubricant might be offering little or no protection for days or weeks without you even knowing about it. The result: possible equipment failure, resulting in expensive maintenance, replacement, and downtime.
Just how does excess heat destroy lubricant? One way is to cause the oil to begin to separate from the thickener, which results in runout of the oil and hardening of the thickener that remains.
As we explained in our article “What is the difference between oil and grease?”, grease is oil with thickener added. The majority of lubrication (depending on the type of thickener) is done by the oil. Imagine the oil running out, carbonizing, or evaporating, leaving a stiff thickener behind. Lack of lubrication from the base oil, plus the presence of the stiff thickener, will cause major problems for your application. Imagine chunks of solid matter knocking around inside your bearing, clogging up the track, and you’ll get the idea.
Traditional wisdom has always been to apply grease from a gun until you see it start to emerge from the other end of the application, or when you feel the pressure pushing back too hard to add any more. In fact, this method practically ensures over-lubrication. In addition to the above-mentioned issues, the pressure generated by too much grease can cause seals on bearings to rupture, which in turn causes leakage, and ultimately failure due to lubricant starvation. Grease guns produce 2,000 psi or more, with high-pressure grease guns delivering as much as 15,000 psi. The typical seal, meanwhile, ruptures at a much lower pressure.
Electric motor bearing cavities are subject to the same vulnerabilities as other bearings. Excess heat will cause separation, thickening, and runout. In addition to this, the excess grease will end up between the stator and rotor of the electric motor. There is simply no room for the excess grease to leave the motor, which will cause damage.
Larger motors will have a purge hole opposite the grease nipple. Make sure you check these holes and remove any protective cap.
So, how to avoid over-lubrication? We recommend the following techniques:
- Calibrate your grease guns
- Keep lubrication records
- Use a vibration analyzer
- Use condition-based maintenance techniques
- Use Math
Knowledge is power. The first thing you should do is make sure you know just how much grease each gun emits per pump. You can do this by simply measuring the amount of grease that comes out. If you want to take an average, you can do ten pumps into a container and then divide the result by ten. You can measure either by mass (weight) or volume, but ideally you will do both.
For future applications, apply only the recommended amount of lubricant, rather than simply adding until you can’t add any more. Your machine manual will likely tell you just how much lubricant is required per application. Since you know how much each gun produces per pump, you have removed the guesswork and greatly reduced the likelihood of over-lubrication.
It can be time-consuming to make notes on every single thing you do all day, especially when you’re running from machine to machine with hardly enough time for a lunch break. But this is a really important step, so it shouldn’t be overlooked… and don’t forget, the end result is actually going to make your life easier, not harder. We recommend that you set aside a segment of time for lubrication checks, during which you focus exclusively on this task. Carry a clipboard with you and record lubrication data as you go. Keep your clipboard by your lube cabinet, and make sure all maintenance or lube techs at your workplace know they must use it.
If you don’t have time to create your own lubrication log, just download ours and print out as many copies as you need.
Interflon USA recommends the use of analyzers that measure both heat and noise to gauge whether an application has been suitably lubricated. These precision instruments can tell immediately when your lubrication has reached the optimum level, and provide you with instant feedback so you know when to stop pumping. You can also use these tools to measure current lubrication levels, so it’s easy to tell whether you need more lube or if you can hold off on this round of scheduled lubrication. This is the most scientific and precise way to avoid over-lubrication, so the expense of the analyzer is quickly offset by how much money you’ll be saving on bearing replacements and lost production.
For more information on our vibration analyzers, please call us at 877-FIN-LUBE. We’ll be happy to connect you with a Technical Advisor who can meet your needs in this area.
Condition-based maintenance (CBM) is part of predictive maintenance (PdM), and is a method of decision-making that relies on real-time performance data, rather than a fixed timetable. Although CBM is a much older method than PdM, it lends itself very well to new technologies. Sometimes CBM refers to monitoring rather than maintenance. It is more scientific than reactive maintenance (fixing things when they break) or preventive maintenance (trying to guess when it will break and fixing it beforehand). There is necessarily some overlap between CBM and PdM.
To learn more about how PdM works, check out our post called “What is Predictive Maintenance?”
The following formula can also be used to determine just how much grease your bearing application requires:
G = 0.114 x D x B
G = amount of grease in ounces
D = bore diameter in inches
B = bearing width in inches
G = 0.005 x D x B
If you don’t care to crunch the numbers yourself, use this handy calculator from Machinery Lubrication.
How can Interflon help?
Interflon manufactures high-performance lubricants with MicPol®, our unique lubricant technology that provides the lowest possible friction, repels water and particles, and possesses outstanding penetration. Our lubricants last up to ten times longer than ordinary lubricants, and are known to increase chain and bearing life by many times. This is no idle boast… check out our case studies! Interflon products reduce your costs for lubrication, maintenance, replacement, downtime, and energy.
To find out how Interflon can help your business save money and improve performance, contact a Technical Advisor in your area or call us at (877) FIN-LUBE.
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