We have had less than satisfactory grease life on our grease-lubricated 100hp 3600rpm motors with type 80BC03 (6316) single-shielded bearings. On several occasions we had poor lubrication indicated by vibration within a few years after bearing replacement, and inspection showed overheated/degraded grease.

I realize there may be several causes (misalignment, grease technique, grease quantity). We have looked at these but are now focusing on the grease type.

Generally grease suppliers identify a maximum D*N where D = bearing bore in mm and N speed in rpm. We use Mobilith SHC100 which is a fairly general purpose high temperature (180C) motor grease. The maximum D*N number is 250,000. I believe most general purpose greases are similar since several references mention a maximum D*N number for greased beairngs somewhere in the range 200k - 300K.

This application has D*N number of 288,000 which is fairly high. Inboard bearing housing temperature runs 150F-180F.

Does anyone have recommendations as to a good grease for this type of application (relatively high speed based on D*N)?

Mobilith SHC 460

Walt

We use Mobile also with good sucess someone recommended Royal Purple to use the other day does anyone have any expirence with this grease?

Do you mean SHC460 or SHC46 ?

Changing from SHC100 to SHC46 involves reduction of base oil viscosity from VG100 to VG46 which makes sense to me (high speed rolling elements don't need high viscosity so there is needless heat generated with vg100).

SHC 460 is being used on shipboard machinery on hot gas fans with 3600 rpm with very good results.

Walt

Moboil POLYREX EM works great at our site.
Just remember if you try this it has a Polyurea thickner.

I sometimes wonder about single sided shielded bearings. If the shield is to back-up the seal and add sealing where normally the OEM calls for a non-shielded bearing why take it upon yourself to re-design the bearing's application? Why loose the extra cavity for additional lubrication and heat loss. Plus it changes the 'natural pump' characteristics of the bearing itself.

I'm under the impession that many have gone to this method to avoid pushing out the seal from over greasing! A vented plug can remove this problem along with a good calculated program. Sorry for getting somewhat off topic on lubrication.

Most OEM motor manufacturers ship motors with bearings shielded on both sides. If you want something different, it has to be special ordered. I can't figure why they have grease fittings when you can not grease the bearing. They should just plug them.

We use Chevron SRI grease in our motors with shielded one side deep groove ball bearings with good success. Most of our motors are 1800 rpm, but we have many that are 3600. Have not seen any issues with bearing lubrication.

Gary B

Thanks guys. We have good luck with most of our 3600 rpm machines and most of our large bearings, but the 3600 rpm large bearings are kicking our butts (6313 through 6316). Any specific experience with those?

We use polyrex em in all our motors and fan bearings, in some very hot places on the papermachine. Have had great results.

For your 3600 RPM units just make sure you are not using a # 2 grease that is tacky. # 1 is OK. But to do this right we need to start with the OEM specs and then we can tweak it for the best answer with the L.E.T.S.
Load , environment , temp. and speed.

quote:

Does anyone have recommendations as to a good grease for this type of application (relatively high speed based on D*N)?

I worked in a shop where we made high-speed spindles (like, 10,000RPM, up to and in some cases over 250,000 by your D*N equation) and we only used Arcanol L75. Pricey stuff, but nice.