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Lubrication Advice for Electric Motor Bearings

Lubrication Design & Engineering

If you work in an industrial environment then you'll know how aggravating, time consuming and costly inefficient machinery can be.  Down time is to be avoided at all costs and this means proper care needs to be taken of all equipment including lubrication of electric motors.  Making roller bearings last is of paramount importance, but of course you want to make sure you're lubricating properly to prevent it back firing and actually hampering productivity.  Below is a summary of a few opinions on whether lubrication is necessary at all, and if it is; the best way to go about it.

To lubricate or not to lubricate?

The first protocol which needs to be established in any plant or factory is whether ball bearings will be lubricated at all.  A lot of companies may decide to adopt a no lubrication policy as the result of lubrication damaging a machine.  It's true that correct lubrication can be tricky to get right, since so many variables can effect when and how much grease should be applied, so overall it can be easier to get hold of bearings which are manufactured to not need lubrication.  Sealed bearings have an elastomeric seal which prevents contaminants getting into the bearing.  These are especially useful in particularly harsh environments such as very moist atmospheres but the seals can fail when exposed to high heats or simply from mechanical stress.  Generally sealed bearings are useful in smaller machines but may fail within as little as two years in larger machines. 

The main problems relating to lubrication are failing to achieve a sensible lubrication practise.  Two much grease can be applied, the wrong type of ball bearing lubrication can be used or it is applied too late to have enough impact.  In itself lubrication has many advantages reducing friction, protecting surfaces from rust during idle periods, transferring heat and protecting the bearing from dirt.  This is why, when you get a system in place which works, lubrication will prolong the life of your electric motor bearings. 


If you do decide to lubricate one thing you must check out is whether the type of grease you are using is compatible with grease which may have been used before on the bearing.  If incompatible they two types can react with each other and become obsolete.  A lot of suppliers will give you some sort of chart which indicates compatibility, but it's always best to get in touch with the manufacturers of both types of grease and establish whether they can be used in conjunction.

How Much and When?

One of the trickiest elements of lubrication is how often to apply grease and how much to apply.  This can be influenced by factory conditions, such as heat and humidity, the dimensions of the ball bearings or roller bearings, RPM, frequency of use and duration of running time when in use of, as well as the type of grease you're using.  Inconveniently, every single bearing will need to be greased at different times according to their age and type.  Ultrasonic equipment and vibration analysis can help determine when a bearing may need lubrication.  Some workers tend to go on an "aural" instinct and only apply grease when a machine gets extremely noisy, but this can often be way too late.
You can get hold of guidelines in the form of tables which try and make the task of lubrication more comprehensible but the best advice is be willing to adapt the rules to a specific situation and keep a vigilant eye on bearings. 

Handy Tips

A good tip is keeping in mind that a 10°C degree increase in temperature cuts a bearing's life expectancy in half.  So make sure your lubrication won't crank up the temperature of the machine whilst working, as this is likely to be counterproductive.

Similarly, be wary of greasing a bearing which hasn't been used in two or three years.  The old grease will have hardened and can prevent even distribution of the new grease, sometimes forcing the new grease through a seal. 

Lubricating bearings can seem a bit of nightmare, but with thorough research, attention to detail and the right experts in charge of maintaining lubrication it can really enhance the productivity of machines, so may well be worth all the hassle in the long run. 

Article contributed by:
Acorn Industrial Services
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