How many of you feel that couplings require the special coupling grease? I understand the concept, and it makes sense to me that having the soap at a lower or equal density to the oil would be a Good Thing in a coupling, but that doesn't mean it's always _necessary_. I've been trying to streamline my greasing by using a high-end synthetic grease which I can use in _almost_ everything. Right now I have two greases - one for electric motors and one for everything else. I need to add an extreme high-temperature grease (600F) for one particular application, meaning I will have another grease gun (painted red) for just one pair of pillow blocks, which annoys me, but if it's necessary then I guess I'll have to have another one just for this coupling. It's a Lovejoy Sier-Bath gear coupling. Reasonable size... 4"-ish bore on a 500HP DC drive.
Any thoughts?

http://www.lovejoy-inc.com/uploadedFiles/Catalogs/hp.pdf

Check it out; may help?

On many gear type coupling I've used EP 1 and after 12 yrs continueous service the coupling looked as new.

Typically bearing greases are for bearings. The coupling under good alignment has little movement but high loading.

quote:

Originally posted by Sam Pickens:
http://www.lovejoy-inc.com/uploadedFiles/Catalogs/hp.pdf

Check it out; may help?

On many gear type coupling I've used EP 1 and after 12 yrs continueous service the coupling looked as new.

Typically bearing greases are for bearings. The coupling under good alignment has little movement but high loading.

I didn't see anything in that PDF about lubrication, but that is the type of coupling that I'm talking about (a close-coupled one).
I have _heard_ that the reason coupling greases exist is because a 'normal grease' has a soap base that is denser than the oil, so when you spin it for long enough in a coupling the soap tends to gravitate to the outer edge (where the teeth are) and the oil heads for the middle (where it doesn't do anyone any good). Again, I see how this could be an issue, but I'm not sure that it's a big enough issue to be worried about.
It sounds like you've had good luck with normal grease, so I'm taking that as a vote for the 'don't worry about it' side.

I thought Seir-bath couplings were lubricated with oil. When the sels failed and they would no longer hold oil, we greased them until a motor or refiner was changed.

Gary B

The need for special coupling grease increases with increased speed and coupling diameter.

You can probably get away with not using special coupling grease on smaller couplings at 1800 rpm and below.

We had used standard bearing grease on 3600 rpm gear coupling about 6" diameter. Teeth eventually stripped out, and the pump just stopped turning. And there had been no warning on vibration and no unusual grease or oil ejected from the coupling. Needless to say the scenario of pump stopping without warning is usually not a good thing! We were not 100% sure of the cause (ruled out misalignment by measurement), but the grease type may have contributed. We now use coupling grease on several of our machines and have beefed up our inspection requirements.

AGMA has a standard that provides recommendations based on speed and diameter. That document is copyrighted, and I don't have it handy. But here is a useful link:

http://www.emerson-ept.com/EPTRoot/public/Kopflex_tech_papers/MMC11.PDF
Page 6 of this link discusses grease selection for couplings. Of course they recommend you listen to the manufacturer. In absense of manufacturer's guidelines, they provide a rough guideline that special coupling grease should be used for gear couplings when RPM > 2800/sqrt(d) where d is shaft diameter in inches.

This message has been edited. Last edited by: electricpete,

quote:

Originally posted by Gary B:
I thought Seir-bath couplings were lubricated with oil. When the sels failed and they would no longer hold oil, we greased them until a motor or refiner was changed.

The engineering data that comes with them says to use grease. Specifically Lovejoy's own brand of coupling grease, of course.

Mind you, there are a bunch of different kinds... including a nylon-sleeved one that doesn't get lubricated at all, so there might be some that are oil-lubricated.

quote:

Originally posted by electricpete:
We had used standard bearing grease on 3600 rpm gear coupling about 6" diameter. Teeth eventually stripped out, and the pump just stopped turning. And there had been no warning on vibration and no unusual grease or oil ejected from the coupling.

That's what happened to me. Just up and stripped out all at once. There was 500HP going through that coupling. The upside is that it made a really cool noise when it failed. VROOOOOOOOMMMMMMMMmmmmm.....

It was a pain to install a new coupling, and I lost a few days (24 hours each) of production, so I'd like to avoid it happening again. From now on I'm pulling the thing apart yearly to check on it, and I'm topping up the grease every six months. The drag with topping up the grease is that it gets awfully messy when you run it the first two times afterwards. The expanding grease oozes out and coats the inside of the guard. This winter (slow season) I'll pull the coupling apart and give it a good looking-over. If I see any indication that the grease is separating then I'll clean it out and switch to coupling grease.