I'm after opinions and reasonings behind them as to wether its better to grease motors with small amounts of grease frequently, or large amounts infrequently.
at our plant there has been a regime of big quantities every six months or so, but the equipment being driven is done weekly or fortnightly, I'm going to have the motors done this way as well but i thought I'd run it by you guys for a second opinion as to wether I'm doing the right thing

Addding small amounts of grease frequently is better for the equipment than large amounts infrequently.

you may consider trying automatic greasing. i was introduced to one product named GreaseMAx. i am yet to discuss with my motor team for a tryout.

Have you tried using ultrasound and let the bearing tell you when and how much grease to add?
We used auto-lubers for years with poor results.(IMO) The lubers wouldn't work, they would run empty, or the grease lines would choke off. We looked at greasing according to the manufactures specs. but we use several brands of motors and it seems that each one has a different set of recommendations. Then on top of that are all of the rebuilt motors with a different brand of bearing in it that says to use an even different set of specs!
That's why we started trying ultrasound. So far it seems to be the best fit.

if the bearing is running with inadequate grease, is it true this will lead to creation of vacuum within the bearing vicinity?

e-pete
the little and often approach I agree with
Valve
we have been down the track of using auto lubes on our fans and as paul2007 says they are unreliable and we are going back to manual greasing, (Vacuum in the bearing vicinity?)a tackified grease will get flung out of the bearing and stick to the housing where as a tackified grease will "flow" back into the bearing
Paul2007
we will soon be getting an ultrasound kit but at present are using grease gun with headphones attached

quote:

Originally posted by Jonesy:
I'm after opinions and reasonings behind them as to wether its better to grease motors with small amounts of grease frequently, or large amounts infrequently.

Just the throw a wrench in the works, I don't bother greasing motors at all, with the sole exception of our large DC motors, which are 100-500HP.
As far as the smaller ones go, I am currently of the opinion that unless you have some swanky lubing gear, you are too likely to cause big problems. I've got never-greased motors that have been running happily for 15 years, and I've had motors die after a couple of years because of a greasing mis-hap. When the motor finally dies (actually, I'm still waiting for a never-greased motor to die of lube-related causes), I replace it, and the replacement motor is sufficiently more efficient that it easily pays for itself in power savings during its lifetime.

I first heard of the notion of just saying 'no' to greasing motors in an article about an oil refinery that was sick and tired of replacing motors, so they stopped greasing and their world became a much better place. It seemed reasonable to me, and that's what I do. I replace the grease nipples with plugs, and don't even think about them.

The DC drives I pull the grease caps off of so that I can clean them out as thoroughly as possible without pulling the bearing, and re-pack with grease by hand - not with a gun.

Mike

My two cents: The life of the grease is related to the D*N number of the application. (Look up regreasing intervals on a chart). D=bearing bore in mm. N = speed in rpm.

Below D*N = 80,000: the life is long enough that sealed bearings are almost always good enough for the life of the equipment. Bearings are usually supplied in a sealed or double-shielded configuration by the OEM in this size range.

In the range 80,000 - 120,000 - a grey area.

Above 120,000, you will need to regrease or you won't get satisfactory life (perhaps failure in 5-10 few years?). Especially true as you get up beyond 200,000 or 300,000 - the bearing won't last more than a few years continuous run without regreasing. Even with regreasing it can be a challenge. Above 300,000 or so oil-lubricated bearings are preferred.

So the balance as to the best strategy swings with the size and speed and duty of the equipment. As was stated, for small motors, no greasing is often best. Also intermittent run motors are better candidates for no-lub even in higher size and speed ranges.

The above comments based in part on an article by Heinz Bloch and review of Fortshoffer's Handbook.

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

quote:

Originally posted by electricpete:
My two cents: The life of the grease is related to the D*N number of the application. (Look up regreasing intervals on a chart). D=bearing bore in mm. N = speed in rpm.

I'm assuming that the 'bearing bore' is the ID of the bearing, is that correct? If so, then a 1750-ish RPM motor would be ignorable for sure up to a 45mm shaft size, and a 3600-ish RPM motor would be ignorable up to about a 22mm shaft size. Correct? And the 'gray area' would be up to half again those sizes, or something like 67mm and 33mm.
That would cover a whole heck of a lot of motors. However! It would indicate that I am ignoring a few motors that perhaps I shouldn't be ignoring, like a couple of 100HP AC motors, and some 30HP high speed ones. They haven't died yet, but it's food for thought.