We have some 3 Hp 3600 rpm fan motors, which run all the time, that are lubricated with Dow Corning 33 silicone grease. I'm uncomfortable with this grease as the product information sheet states its uses are for such things as caster wheels, clock motors, instrumentation, etc., while not mentioning high speed electric motor bearings. Does anyone have experience with DC33 in industrial electric motors?

Looking at the tech sheet http://64.242.109.170:8080/1/doc?id=3790 I would say that no, this is not suitable for electric motor lubricantion. Looks like a very low load clean enviroment lubricant that is more suitable for lubricating rubber then bearing's.

if you get a couple years out of motors do not worry about it that grease is plenty good for motors.

If motor bearing fails to soon (how Long is a good question) then look for a different type, be advised that silicone grease may not be compatible with other types if changeing I would stick to a Lithium soap type, same as the Dow to minimize any compatibility problems.
bruce

bye the way it IS recomended for light loaded BALL or roller bearings such as small electric motors.
bruce

Would you consider a 3HP motor a light load? From what I gathered from the tech sheet it is used for lubricating very small components like water meters, clock parts and so on.

look, how is it working now?? yes a 3 hp motor is a light load with roller bearings.
Moly,EP and AW are NOT needed for a motor bearing on a 3hp motor.

bruce

Thanks for your replies. The reason I started this discussion was that we had a recent bearing failure in one of our 3 HP motors with DC33 grease after about 1 year service, in which it appears the balls disintegrated. We are still trying to determine if the grease type was a contributing factor, or if it was lack of lubrication, or a defective bearing. The OEM told us the bearings were double-shielded, permanently lubricated, when in fact we found they were single-side shielded with a grease nipple. Still a bearing packed with grease shouldn't fail after only one year. The course of actions we are considering are to grease these bearings with Dow Corning 44, which appears to be more suited to fan motor operation and is compatible with DC33, or to change out all bearings to double shielded bearings with permanent Polyrex/SRI lubrication.

I agree the DC44 sounds more suitable. The DC33 is a extreme cold temperature grease and unless your motors are inside a refri***ator the DC44 would probably be a better choice.

The permanent lubrication bearings are another good choice. My brother works at the SKF bearing plant in Hanover, PA and has worked with there permanent solid lubricated bearing line for a couple of years. According to him they are a very dependable bearing. Permanent lubrication bearings are great for those applications where a regular bearing might be forgotten and not lubed, like small electric motors.

quote:

The OEM told us the bearings were double-shielded, permanently lubricated, when in fact we found they were single-side shielded with a grease nipple.

maybe they are not help here are all?
we use grease lubed bearings on all out 5-15hp motors and just about never lube them they run 8 hours day and last falure which was electrical motor had run for many years.
then just went to grain***s bought a new one and put it in.
bruce

Hi

DC 44 is used for small electric motor bearings. New products include the polyurea based G-0100 multi-purpose motor bearing grease has been developed to meet the increasing demands of the industry.

It’s a mineral oil grease thickened by an urea system that offers a wide temperature range, low noise performance, with excellent corrosion and oxidation preventive properties. With a service temperature range of +338ºF and drop point in excess of 482ºF, the product was tested for the application for over a decade before its commercial introduction. It can extend relubrication intervals vis-à-vis the conventional greases used by the industry for electrical motor bearings, and extend bearing life by preventing prevent premature failures.

Along with its high temperature performance, Molykote G-0100 provides all key requirements that is required by an electric motor bearing greases: excellent low torque characteristics, low oil separation, high speeds capability (DN value 600000 = bearing avg.dia x rpm). low evaporation loss, etc. The product is available in 1 kg and 25 kg packs from Dow Corning.

Andrew, While you might get away with using this product I would not recommend it in that application. Phenyl methyl-silicone has a low pressure-viscosity coefficient which makes it a poor choice for rolling contacts where EHD conditions exist. I believe this product is normally intended for applications operating in low temperatures environments. That being said you may run into compatibility issues with conventional electric motor greases.

Please try URETHYN RANGE WHICH ARE REAL GOOD

HI ANDREW.

I THINK SO YOU NEED TO TRY SOME POLYUREA COMPLEX GREASE, MOLYKOTE HAVE ONE THE GREASE G0100 EM, IS MUCH BETTER IN THIS APLICATION.

There could be more than one issue here. First, I am not a huge fan of silicon based greases for motor bearings unless there is a specific reason for its use and I do not know of any. Also not all small motors are lightly loaded. In fact many might have minimial bearings to cut cost and size. Plus, is yours horizontal or vertical, does it take any axial load from the driven equipment and what are the ambient conditions? Hot and cold extremes or temperature cycling can be issues.
First, double check what bearing you were supposed to have and the clearance. Some motor bearings are a C3 with a bit more internal clearance. Also, double shielding with a sealed for life bearing is a bit odd. Normally lube for life has double seals not shields and not just one. Was it something like a 6204-Z? This has one shield. If one shield make sure that it was installed with the shield on the right side. As a comment if the bearing failed after greasing then using too much grease and/or too high a pressure can push the shield into the cage causing eventual failure. An early failure after greasing could also indicate other problems with grease compatibility. This has to be checked. Breaking the balls is a bit unusual as well because with inadequate lubrication the cage can wear first and then frosting and damage on the races. I am also not a huge fan of the polyurea greases being proposed by some because those that provide adequate rust protection seem to have poor mechanical stabilty. Have not seen one yet with both. Lithium complex or calcium sulfonate choices might work. If proper relubrication is an issue consider the sealed for life bearings with greases although some bearing supplies also offer variations with oil impregnated plastic cages.

Ken