How do i test grease to determine whether it can withstand high temperature

Hello,

Can you be more specific?
How much high?
Do a simple test? or a lab test.but as far as I know you can not judge by heating up the grease and seen when it starts to drop.

Dear Enduser,

Please access the website http://www.practicingoilanalysis.com and reference the article;
"Grease Analysis - Monitoring Grease Servicability and Bearing Condition" by
Bill Herguth, Herguth Laboratories

I am not sure if it will give you an answer cast in stone but will point you in the right direction.

Here are some quotes out of the article to wet your appetite;
"...Thermal Gravimetric Analysis (TGA). TGA analysis measures the mass of a substance in relationship to temperature and is used to determine the loss of material with increasing temperature. The analysis can be carried out in an inert atmosphere such as nitrogen or a reactive atmosphere such as oxygen. Typically, a few milligrams of the sample is weighed and heated under controlled conditions. The weight loss at specific temperatures allows the technician to evaluate the oil/gelling agent ratio as compared to new (unused grease), as well as the presence of volatile compounds such as water, allowing any significant change in gelling agent chemistry to be determined..."

and
"...Rheology is the study of the deformation and/or flow of matter when it is subjected to strain, temperature and time. A rheometer only requires a few grams of sample to perform the analysis, yielding much more information than the cone penetration or the apparent viscosity measurements. This makes the rheology measurement an ideal test for small amounts of used grease..."

Have fun.

G'day Eduser

I would ask.."why would you want to test a grease to determine whether or not it can withstand high temperature?"

Would it not be better to determine the temperature involved, and then approach a lube supplier to provide a grease that will do the job?

I have been in a situation where I was asked if I could possibly provide a grease for an unusual high temp application, and I went straight to my Lubrication Engineers (USA) Australian boss and he put us right into the game with one of their excellent products, straight off the shelf. Easy. No fuss.

quote:

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Originally posted by Enduser:
How do i test grease to determine whether it can withstand high temperature

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You do not need to test the grease for with standing high temperature. What you need to do are: 1)Look at the machine/equipment service manual for the grease recommendation
2)Ask the lube supplier technical rep to provide the suitable equivalent for the grease recommended.
3) The Lube supplier will be glad to help you.

For high temperature applications Bentonie/Lithium Complex/ Urea base type of grease available but you need to follow the above procedures.

Kumar

kumartr2@yahoo.com

Advices posted by Peter Berner and Kumar suggest the correct approach. I would just add that you need to be as specific as possible when describing your application. Indicate type of operation, operating temp, nature of application (above or underwater application), grease delivery system used (farval or manual), environment (possible exposure to acidic, basic, or oxidative materials) type of grease you are currently using (important to determine compatibility), and the reason you are not satisfied with it. Such approach will ultimately result in you getting the product you need.
For best results: a) do your homework before you talk to grease manufacturers by getting more familiar with the machine/equipment service manual and its recommendation for grease (Kumar’s advice); and b) if possible, query personnel at similar industries regarding their experiences in similar or identical operational conditions.

John

Sandman,

The simple test drop point will answer
your question

Bala.

Not neccessarily high drop point grease is always good for high temperature application. The more important is the base oil in the grease properties and thickener type. Some high temperature applicationsrequire non soap grease based on bentonite. Some applications require Li - complex greases. Many high temperature applications require synthetic base oils instead mineral type. All the above products charecteristics may not reflect in drop point alone.

To test the suitabilities before the grease is applied on the bearing of a kiln cart that goes into a tunnel for baking bricks.The thickner usually hardenered and jammed the bearing after the addtives melted.

Sandman,
You have been provided some very sound advice.
I'd just like to add that I ran into a similar problem a few years ago. The pallet cars in an Iron Ore pelletizing machine, that travel through a large furnace. Everyone (yes everyone, furnace OEM, pallet supplier, maintenance superintendants, mechanics etc) told me that we had to use a high temp grease the one in use was specific type of bentonite clay based grease thickener because of the "high" temperatures associated with the application. Me being too stupid to understand why we had so many failures when we were using the right lube started to assess the application. Because I couldn't see how the flames above the cart could effect the wheels and the bearings, I ended up placing a thermo coupling and a chart recorder adjacent to a wheel and let that go through the machine. Wern't we surprised when the strip charts were read and the temperature averaged ~ 130F throughout it's journey. So we ended up selecting a lube that did not have the nasty tendency of drying out and seizing up our bearings. We are now getting some 4X life from this application. Thanks to understanding the actual operating conditions and then working with several different lubricant suppliers to find a workable solution.
An alternative for you might be to use some welders paint sticks of varions temperatures to try to find out what temperatures the wheels are actually seeing.

One additional thought is that your application is a very slow moving very heavily loaded situation. If this is correct then a very thick base oil (minimum 1500 cst @ 40C) with some solid additaves is essential to trying to get some life out of your bearings.


hope this helps....

regards.........

Alan
You are right. I had the Identical experience in this application in Sinter pallet wheel Brg.

I've had a bit of experience with bearings exposed to very high temperatures. I always try to remember two things in these applications: 1. The regreasing interval decreases as the temperature increases. 2. Oil is not necessarily the only ingredient in grease that can lubricate. For a kiln cart application, where the cart bearings were exposed to 450F for periods of at least 3 hours, I used Castrol's Molub-Alloy 1000. The oil dropped out in a hurry, but the moly stayed in. And when it was time to replace the bearings or regrease, what was left was not hardened and did not prevent regreasing and wiped off for bearing replacement. Bearings lasted about 6 times longer than when they were using a conventional high temp grease.

G'day Sandman,

All the previous replies make good sense and to add another simple test we often place a sample of the grease being considered in a small clean metal container, a teaspoon or two, couple of oz's, not too much,
Then leave exposed to the same heat source area as the application, length of time decided by your self, then check physical appearance and consistancy over the time period required,
if the grease sets like concrete or there is other detrimental changes, what ever then it's use would be questionable,
Rob S