"microgel" thickener in Aeroshell grease

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The MSDS for Aeroshell 22 which has the microgel thickener lists it as a inorganic clay,probably bentonite, the clay type greases hold up to heat very well but as far as I know don't hold up to water very well.
 
The only truly inorganic substances I am aware for grease thickeners is a silicon-based gel.

Clays are organic in nature, since they contain quite a few varieties of sodium- , potassium-, and phosphorus-carbonates.
 
quote:

Originally posted by RB Shannon:
The MSDS for Aeroshell 22 which has the microgel thickener lists it as a inorganic clay,probably bentonite, the clay type greases hold up to heat very well but as far as I know don't hold up to water very well.

I have seen wheel bearings pitted from corrosion after using Aeroshell 5, but only on aircraft that see little use and are tied down outside. This would seem to imply poor water resistance. I will try mixing it with water per the advice on this board the next chance I get. Thanks for the reply

I just emailed Shell via the "Ask Shell" feature on their website. I will post back when/if I get their reply.

[ August 11, 2003, 07:20 PM: Message edited by: ralan ]
 
I emailed and received a reply from Aeroshell about this, here it is....

"Microgel is a modified clay based thickener. Thank you for your interest
in Shell products.

Richard Moore
Staff Engineer
Shell Global Solutions (US) Inc.
Westhollow Technology Center, PO Box 4327, Houston, TX 77210, United
States of America
1-800-782-7852 option 3"

I guess I should have asked them first!! Now I will comb the archives here on BITOG and learn the goods and bads about clay thickeners. This is a great site.
 
Oh,ralan by the way
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With that said, I was wrong about the water resistance of the clay type greases
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NLGI's Guide to Grease states that clay based thickeners have good to exellent water resistance(but doesn't call them water proof),I'm not sure why I thought otherwise,sorry about the misinformation,it also calls them organo clay. It doesn't sound like the Aeroshell 5 has much in the way of corrosian inhibitors though.

Here's a good place to start Functions Of A Grease

[ August 12, 2003, 11:37 PM: Message edited by: RB Shannon ]
 
A clay base grease will NOT mix with any complex and will have to be completely cleaned out before putting in any other. That type of grease is normally designed for higher heat applications than a what a normal vehicle bearing would ever create. Not sure why they'd use such on a plane. IMO, not a good choice for that application.

If this type of grease is what was normally used on that plane that went down due to grease, then I can see why it happened as it doesn't mix well with other greases.
 
The plane went down due to lack of grease, not grease incompatibility. Alaska airlines was trying to blame Boeing for for the problem. That part had not been greased in something like 2500 hours.

Almost all aviation greases are clay thickened and there are interchanges within the same MIL spec from mulitple suppliers such as Aeroshell, Mobil, Royco and Braycote. Clay-thickened greases, like Aeroshell 5, are specified for wheel bearings and engine accessories at temperatures up to 350F.

Aeroshell 33 is a new lithium complex thickened, Diester/PAO based grease developed specifically for Boeing to replace multiple older greases except for wheel bearings and high temp apps.
 
Jimbo, thanks for the update about the grease on the aircraft failure. I didn't stay up on that so didn't know.

Most all automotive applications will come and use a lithium complex. Clay is a specialized grease normally used in higher temp areas.

As for synth base oils, many are using synth's for oxidation stability but the real catch isn't the base oil, it's the type of additives and base complex used that makes the difference. One of the biggest problems is reversibility with greases.

Reversibility - during normal operation of a bearing, it is the function of the thickener to release its base oils and additives to lubricate. Once released, the grease must have the thickener must have the ability to recapture the oil to return to its original consistancy. Think of it like a sponge, when the grease is under pressure, it squeezes out oil, but when cooled backdown and such, it act's like a sponge and re absorbs the oil back in.

The greases reversibility characteristics are dictated by the type and amount of thickener used.

Here are some numbers...
REVERSIBILITY
PERCENTAGE OF REVERSIBILITY
DIFFERENT GREASE THICKENERS

code:

THICKENER TYPE % REVERSABILITY



Aluminum Complex 95 -100%

Barium 30 - 55%

Barium Complex 0 - 30%

Bentone(clay) 50 - 95%

Calcium 12-hydroxysterate 10 - 30%

Calcium Complex 10 - 30%

Calcium Sulfonate Complex 75 - 90%

lithium 30 - 65%

Lithium 12-hydroxysterate 45 - 65%

Lithium Complex 70 - 80%

Polyurea 20 - 60%





[ August 14, 2003, 03:43 PM: Message edited by: BOBISTHEOILGUY ]
 
I'm glad that someone else changed the subject to grease reverseability, compatability and base oil.
Lately we have been losing rail car timkin roller bearings on two types of cars.
The gross weight of each car is 143 tons (286,000 lbs). One axle carries 36 tons, one bearing 18 tons.
There are about 3,000 cars affected.
I'm wondering if the journal failure, now showing up in the hot weather is caused from:
1. The wrong base lube viscosity for our Canadian climate or a base lube with insufficient VI:
A. we have -40C cold starts when the cars are loaded and not picked up for a day or three.
b.+45C summer time track temperatures.
2. The wrong thickener type
3. Car design
4. Dynamic forces
5. Addition of a non-compatable grease with the original during service.
6. A grease manufactured from a poor quality base oil, thickener or faulty EP additive package.
7. More than one of the above
 
This is interesting,What type of grease are they using,and do they use a different type of grease for winter conditions,I would also think you would need a good barrier additive due to the fact the car can set motionless on the track and the vibrations could cause false brinelling of the race.The cold weather starts after sitting would rely heavily on the barrier add's IMO and a lower cSt oil base to shorten the time to get on a oil film.How big are the bearings,are they tapered roller. This should be a good discussion
 
I wish I knew more. The cars were built in Mexico and the place went bankrupt.
Not tapered rollers and no end cap bearings either.
When running on a warm day loaded, you can put your hand on the outside of the shell, but not leave it there for long.
When slightly overheated, trackside heat detectors will pick up the axle number say # 342 of 510. The journal will melt a crayon or wax candle. If another hour went by.....the train could end up in the river.
Or worse yet the journal could burn off and the car could bounce along riding on the ties and clip a passenger train.
Very serious stuff.
 
Wow, this turned into a pretty good discussion! While Aeroshell basically answered my question, they really didn't explain the "inorganic" part. Molakule's reply did, but I think its just a marketing term for A/S.

Bob's mandate of flushing out the old clay based stuff before going with anything new is what I have always done. Of course, this is pretty easy with wheel bearings anyway.

*REVERSABILITY*

This is an important characteristic, as I understand it. I glad that The Oil Guy agrees
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However, I cannot find any specs on it at the two manufacturer's websites that I am interested in. Could this characteristic have another name? I posted a link to Aeroshell's grease spec page, and as everyone can see, and it doesn't say anything about reversability
grin.gif
Same story with Mobile. We currently use Mobile 28 grease at work, and I would really like to know more about it. On a hot day, red oil drips from the grease gun
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Is this a sign of low reversability?
dunno.gif


Anyway, thanks for the welcome. I am reading more and more from this site and am learning alot.

[ August 15, 2003, 06:19 PM: Message edited by: ralan ]
 
userfriendly,here's some info I dug up,there's a grease spec for railcar bearings AAR M-942.
It's interesting they found that a softer grease performed better reducing corrosion and water etching over a stiffer grease(Canadian Railroad) and an EP grease showed less wear(which I think would be expected) and less corrosion over a non EP grease. Brenco,Journal Roller Bearing Grease Technical Developements

They go on to suggest a higher bleedability and the developement of polyurea greases to reach EHD quicker.
I'll have to go down to the railside where they bring in our soybean oil at the plant on monday and take a look at some wheels.

[ August 16, 2003, 02:29 AM: Message edited by: RB Shannon ]
 
PA, the railroad state. Thanks. the article was written in 1995, but adresses my concerns about cold starts.
Perhaps the synthetic (organic?) plastic thickener polyurea, poly means more than one, (like PAO) with a modern high VI base oil is the answer.
Metalic soaps scare me except for high temp applications.
I wonder if the ep additives are active like GL-5s or inactive organics like GL-3s.
I heard that shell was active in the journal lubricant research business.
For the now, we are not exceeding 30 mph, when loaded with the affected cars until the problem is rectified.
Once again thanks for the info, it could save a life.
 
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