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What would be the ideal greasing frequency for motor (90kW-1500rpm) and fan (2 bearing blocks-overhung - belt driven) bearings and how much grease to add?
Here is one article which describes a relatively simple set of rules developed by EPRI that apply to motor bearing regreasing intervals and quantities, and I think it is reasonable for fans also if they are ball bearings:
http://www.machinerylubricatio...il.asp?articleid=749For your situation >100hp, 1500-1800rpm, belt drive, assuming ambient temperature <140F, that article table will tell you to add grease every 12-18 months for the motor. Quantity of grease to be added depends on shaft size which we could figure out if you tell us the bearing type.
Of course each of the bearing manufacturers has recommendations that will differ from above. Generally the bearing manufacturers will recommend adding smaller quantities of grease at more frequent intervals than the EPRI approach described above.
The equipment OEM may also have recommendations for each individual each piece of equipment which in an ideal world trumps either of the above, but that is not always easy or practical to keep track of all of those recommendations for different OEM's and different equipment
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Is it better to open the bearing blocks and replace old grease with new? Or is it beter to use a greasing-pump?
Most people just add grease periodically without ever opening the cavity until they see some evidence the cavity is full. I think this works in most cases but you get in trouble faster with high D*N bearing machines as the cavity gets full.
The bearing manufacturers recommend also periodically changing the grease (opening the cavity, removing old grease, adding new to a level somewhere around half full). For example SKF recommends I think no more than 3 intervals of addin grease before the grease is repacked. But not many people do this. Two reasons we don't do it: 1 - it is more work; 2 - I think there is serious risk of contamination during this process which could do more harm then good.
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Is there a type of grease for motor and fan bearings that you would recommend to all?
I think Mobil Polyrex EM is the most universally used general purpose motor grease. Of course there are always possible special application requirements that may apply here and there, but if you're looking to standardize on one good one for the majority of your motors, that's a good one to start with.
