Lubricant additive - EP

A corrosion inhibitor and rust inhibitor will largely perform the the job as suggested by their name. A corrosion is a acid attack of matal and rust is specific to Iron components.
Preventing the formation of Iron Oxide.

Generally EP Greases can be used in Motor bearings without problems if they are compatible with the bearing material. As some bearing manufactures may use a bronze cage where an sulphur phosphorus EP System might react. Or else there is no problem.

Again two greases are interchangible if they are compatible to one another- that is they either dont harden or soften on mixing. If they are not compatible they may cause noise becuse of the dry area they may generate be cause of incomaptibility. Of course you need to look at the base oil viscosity and hence the DN factor of the grease.

The heat that can be subjected on a deep grove ball bearing on a metal cage is roughly 90 deg c and after that there is a thermal stress and hence a detoriation of the shapes and components of berings take place fast and you will not get a desired life and you need additional a colling arrangement

What is he temp. range you are talking about and if you opt for a high temp grease also you need to look into the regreasing cycles to see the lubricant is effective, to do its job.
regards

Dear Mr.Mukherjee,
Thanks for your valuable response.

Yes, you are quite right. The cage is brass and may be that's the reason the manufacturer had recommended a grease without EP.

For both greases thickeners are of the same -lithium and the NLGI factor is 2. But how can I know the base oil viscosity, as the MSDS does not specify the same? DN factor- you mean the mean dia x rpm or the grease speed limit mentioned by the bearing manufacturer?

Can the rough temperature limit of 90 deg.C apply arbitrarily to all metal cages (pressed steel and brass)? Is there a restriction to polyamide cage too?

The temperature range I mentioned was, eg: Can a multipurpose mineral oil+lithium grease with EP ,NLGI 2, having an op. temp. limit of 120 , be replaced with a grease of same bases, but NLGI 3 with an op. temp. limit of 150 deg.C - if the machine had consistent complaint of high bearing temp. at 106-108 deg.C on the plummer block casing?

Regard,Sajeev

Sajeev,
You need to look at the Product Specification Sheet to find information such as base oil viscosity. The MSDS does not contain this information. Your lubricant supplier should have Spec. Sheets for the products they supply or you can search the manufacturers web site which should also have them.

Using a high temp grease will not increase the temperature rating of the bearing itself as grease does not change the property of the metal. Your bearings need to be selected on the basis of the service expected. High temp grease is selected to offer protection at higher temperatures by resisting thermal breakdown, drop out and maintaining adequate film thickness.
If you need a higher temp option you should be able to find a grease in the same NlGI thickness grade.