Gear Grease Installation Standard

[SwaggingIt]

Hi,

Wondering if anyone can point me to a standard that covers the application of grease on gears. I've looked at AGMA 9005, AGMA 911, MIL-PRF 23827, but they all speak more to composition than installation. I'm looking for best practices for grease coating on gears. Any ideas? Thank you.

 

[mfgenggear]

Swag
This agma link has the ref. Specifications at the end of the page.
But can you give us a little background why you want to use grease. And what application.

https://members.agma.org/MyAGMA/MyA...aspx?iProductCode=9005_F16&Category=STANDARDS

 

[geesaman.d]

Is grease being discussed as a preservative or as the operating lubricant?

If it's operating, what's the PLV?

 

[mfgenggear]

Here is a link to types of grease

https://www.valvolineglobal.com/en-ksa/grease-101-different-grease-types-and-when-to-use-them/

In past there has been issues with grease application on splines. From my research
Low rpm or none, high contact stress
Grease is preferred.
High rpm lube oil is preferred.

And follow the viscosity recommendations of Iso
Agma, and Sae for viscosity, temperature, rpm,
And contact stress.

 

[SwaggingIt]

Thanks for the replies. The use of technical forums is so very underrated (as long as you adhere to 'trust, but verify').

Grease is the operating lubricant. My firm designs actuators for aerospace/defense. Grease has always been our go-to such as Braycote 601 or Aeroshell 7 or 33, because our actuators are not continuous duty so temperature is not a concern, and we dont use seals unless required (i.e. environmental testing). Additionally, grease stays on the gear surface so we dont need to recirculate it as oil would require. I'm sure there's more I'm missing, but the use of grease on gears has a very long history at my company, and the much larger company from which all our senior engineers came from (not to say that they must be right, and I'm always open to ideas down the tribology path).

That said, our drawings simply state "apply light coat of grease on gears". I feel that leaves much to be desired since proper lubrication is critical for gear longevity. So if there's a standard or industry best practice of applying grease to gears for operation, then I'd love to interpret that into an internal standard here. Thanks.

 

[geesaman.d]

In my experience of gears operating in grease, you want to fill the entire cavity with grease so that there is some heat transfer and lubrication is assured. With high enough rotating speed the grease will be pushed aside and the teeth will become lubricant starved. So we use a #0 or #1 NLGI consistency to help ensure to keeps flowing into the teeth. On the other hand, too low of an NLGI will tend to leak past the seals.

Applying a light coat of grease might work for low velocity / minimal operating hours but my gut says that sounds inadequate.

The oil carried in grease can have different additive packages and viscosity grades so ensure that your base oil is optimized for gears instead of standard bearing grease. AGMA 9005 should be very helpful w.r.t. these details.

 

[mfgenggear]

From my experience as a part time mechanic
Would add just enough on wheel bearings, then pack the end caps full of Greeace. As specified by the manufacture.

During my research skf has a formula
I will add it in few. To little or to much grease according to the mfg is both bad

 

[mfgenggear]

This link

https://www.machinerylubrication.com/Read/31524/calculate-grease-quantity

 

[SwaggingIt]

Thanks again. All great info. We typically fill bearings 10-15% of grease. Anything more would cause too much heat. But that SKF formula will be looked into and documented. As part of the next gen of engineers here, I'm really trying to move away from tribal knowledge where possible.

We're careful about packing housings full of grease because every ounce counts in aerospace. In the absence of any standard or industry best practice, I think I'll rely on our internal practice of applying globs of grease around the gears, then running them in to create a thin film of grease, and whatever little amount the spills into the housing is bonus.

Appreciate the discussion!

 

[mfgenggear]

My favorite is bath or sump by splash.
It worked in standard transmissions for decades.
Second best would be spray. Last is grease.
Yet grease definitely has its place.
And works well, for enclosed systems. Like wheel
Bearings.or electric motors

 

[geesaman.d]

When it comes to lubrication and tribological issues, nothing beats testing and real-world experience. I only apply guidelines and book knowledge when there is no real-world tested configuration or when there is substantial reward for taking the risk.

 

[Tmoose]

Did I miss the information about stuff like rpm, load, continuous vs intermittent operation?

https://www.crcindustries.com/extreme-duty-open-gear-and-chain-lube-12-wt-oz/

https://webaps.ellsworth.com/edl/Actions/GetLibraryFile.aspx?document=2782&language=en

 

[mfgenggear]

I would say from my research that grease is great for certain situations and it is contained in a certain manner. In any case contamination has disastrous detrimental effects. So there's this fine line of having this very thin film of lubrication. So lack of, or contamination, and in some cases as bearing to much can have bad results. If wanted to do more research and create an internal procedure I would educate myself.
A) the proper lubrication , for the condition and application. Proper application or incase of bearing packing or lubing correctly.
Visual aids with few as possible words would be very helpful for mostly new or young technicians.
I would say that most experience technicians and mechanics have been trained and have experience under their belts. And have valuable advice from their experience.
It's interesting in technical books possibly the lack of lubrication science.

 

[mfgenggear]

It is possibly as an engineer and or a technician
I think more emphasis should be on lubrication as well as the science and properties of metals, plastics an processes such as heat treating and coatings. Reminds me that a coating of silver copper or dry lube help with break Ins an prevent intial scuffing or fretting. Something done on gears before I was born.

 

[TugboatEng]

For open gears you want a grease with a tackifier to help pull the grease back onto the contact area as the tooth unmeshes.