Shell Grease Compatibility

All,

Need your expertise and advice..

We are currently using Shell Gadus S3 V220 2 to lubricate our electric motor bearings (motor rpm in 1400s range), however, it seems that this lubricant not really fit for the application. We found Shell Gadus S2 V100 2 that seems to be a better fit hence we want to replace to this grease. However, we are worried are these two greases compatible to get mix?

Thanks

Original Post

Both of these greases are lithium based greases so compatibility should not be an issue. The S3 V220 2 grease is a good product but is probably overkill in routine motor bearing applications. The V100 2 will suit most any "normal" application for roller bearing motors.

 

rgf12 posted:

Both of these greases are lithium based greases so compatibility should not be an issue. The S3 V220 2 grease is a good product but is probably overkill in routine motor bearing applications. The V100 2 will suit most any "normal" application for roller bearing motors.

Does that mean ISO VG220 is suitable for motor bearings? cause from what I know typically ISO VG100-150 is preferred. What are the consequences if higher viscosity base oil chosen?

What do you mean by overkill? pricy? and can you please define "normal" application?

MOST motor bearings are greased with a high temperature non-EP polyurea grease with a base viscosity right around 95-100, NOT lithium based. So right off the top I'm suspicious that you're using the wrong grease system, not just an odd viscosity. The vast majority of motor manufacturers and motor rebuild shops as a consequence use Mobil Polyrex EM or Polyrex EM 3 and nothing else. Once in a while this gets them in trouble with the high pressure roller bearings where a high temperature lithium grease is appropriate but that's rare. Either way, lithium greases and polyurea greases are in general NOT compatible although the reality is that this prohibition references older lithium formulations which is no longer really an issue, but the stigma against mixing greases has lasted for decades.

The EP additive is specifically added when bearings experience high thrust loads (where a thrust bearing is not used). That's not the case for most motor applications...we avoid this condition like the plague. The EP additive seriously decreases grease life so motor applications specifically call for non-EP greases. However obviously if your motor is under high thrust loads, then you need the EP additive because the grease life is already seriously impacted so in that case you'd be going back in that direction. But the general motor industry tribal knowledge is to specifically avoid EP additives. In general it should be the rule with everyone else too for the exact same reasons as to whether or not to use an EP additive but its just that with motors it is the exception rather than the rule as far as its use.

Some large motors do use high pressure roller bearings though and that's where some manufacturers switch back to a high temperature lithium grease, which is where your choice comes in. But keep in mind that's the exception, not the rule. The Shell equivalent to what 90% of motors use (Mobil Polyrex EM) would be Shell Gadus S2 T100 2, but you will run into serious problems with warranty issues. Same problem comes up with certain compressor manufacturers that standardize on Mobil Rarus oils to the point where switching manufacturers runs afoul of warranty issues. And your Shell distributor should know this and have access to this information. Granted the fact is that Gadus S2 T100 2 SHOULD be a drop in replacement for Polyrex EM but since manufacturers give a very specific make/model for the grease in their warranties, you are normally highly limited in your choices. This is done for a reason...if the spec was opened up to just any polyurea non-EP grease, who knows what garbage will get put into a motor, not necessarily a reputable manufacturer like Shell.

I work for a motor shop so we have to abide by the industry rules whether or not alternatives might make sense for individual cases.

PAULENGR-very well stated. I agree that the Mobil Polyrex product is the most universally used motor grease and is suitable for all but the most extreme applications. As for compatibility I agree that the newer formulations have better mixing properties and the old grease compatibility charts might not reflect current practice but in JAXN14's case I'm not sure if he is willing to take a chance. If it was me I would gradually switch to the Polyrex product when changing bearings and/or motors and make sure my motor shop only uses Polyrex.

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