Difference in four balll test

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So I'm looking at different spec sheets for ISO 46 compressor oil. LE, OEM Kaeser (ie.RP), Amsoil and a Noname. It seems they, if they list the four ball test, are each different. Two run the ASTM D-4172 but at different weight, rpm, and temp, and another shows a different ASTM D2783 test all together.

So what am I looking at and does it even matter in a rotary screw application? I tried looking up the ASTM spec/test but it seemed like I'd have to subscribe to find out what they meant.

Hoping you guys could shed some light.
 
wouldnt worry about 4 ball wear test.

Pert plus shampoo passes that one great.
 
Read the directions that came with your air compressor.
Find a name brand that fits your application.
Then you are done.

The problem with all these "tests" is that they are marketing hype. They can be manipulated to show the outcome that the marketers want.

Not much to compressors. It's a sealed unit that is there for lubrication, and distributing heat from friction.
There are no combustion blow-by contaminates, and it doesn't have the wear and tear from shifting gears like a transmission.
 
OK I guess I could stick with or go back with the Kaeser oil which is again repackaged RP but its real expensive compared to other oils out there. So trying to compare one brand against another to see if there is really any difference. [censored] if its ISO-46 its ISO-46, Seems like all the Viscosity is very much equal through out the temp ranges which seem consistent. So other then anti-wear packs like LE is over 700 Phosphorus (Virgin oil tested) compared to Amsoil 200+ (claimed). Seems like any will do the job.

Just saw manufacturers using different parameters for the four ball and was curious. I figure I'll be giving LE a chance to figure out whats going on with theirs before I give up on them and just start comparing by price.
 
The 4-Ball test is irrelevant for a rotary screw compressor - all hydrodynamic lubrication, mostly just a coolant. Key parameters for fluid life are oxidative stability and hydrolytic stability. The RPVOT test (ASTM D 2272) would be more meaningful. Follow the manufacturer's recommendations for viscosity.

Tom NJ
 
If for any reason your equipment loses full or mixed hydrodynamic lubrication and is left with boundry lubrication only, that is when a lubricant's 4 ball wear test ability could make a difference.
 
In a perfect world your compressor would not need EP/AW protection, but a quality fluid will have those properties to protect drive gears and anti-friction bearings. 4-ball wear and weld are decent and affordable tests to approximate these properties, but are sometimes manipulated to show a particular strength of a lubricant for marketing purposes (e.g. changing temperature, force, speed, etc.)

It is a small piece of the lubricant performance - sludge/oxidation protection, demulsibility, air release and corrosion protection are all probably more important for your compressor.
 
RPVOT is the "rotating pressure vessel oxidation test" and it is a bench test for oxidation stability in oils. TOST or "turbine oil stability test" may also be reported and measures oxidation stability, but that test is less severe and a high-quality fluid will have a result of over 10,000hr.

Air release is measured by the amount of foam entrained in a fluid-filled cylinder when air is diffused into the fluid. The test number is ASTM D3427 and there is a DIN test number also, but I can't recall the test number.
 
Originally Posted By: small
Oh tomNJ what's this "RPVOT test (ASTM D 2272)" none of the oils I'm looking at show this test.


The RPVOT test measures oxidation stability at 150°C in the presence of water and copper. Hence it also measures hydrolytic stability and yellow metal corrosion properties. Screw compressors subject the oil to a highly oxidative environment (thin film of oil on a hot metal surface against concentrated oxygen) and the water that falls from the compressed air can cause hydrolysis in some oils. Wear protection can be meaningful for some designs, but for the most part the oil serves as a coolant and hydrodynamic bearing lubricant. I agree with Jake88 that demulsibility and air release are also important, as is rust protection.

Tom NJ
 
Thanks guys. Looking at the spec sheets For example Amsoil states Copper strip corrosion test w/results 1A, Rust test as Pass, Foam after 10 min at 0 and demulsibility [oil/water/cut off (minutes)] 40/40/0 (10) LE shows the same results calling it Emulsion test is 5 minutes?? 40/40/0 (5). Only LE is listing there specs for the Rotary Pressure Vessel Oxidation in minutes @ 1300. I guess I could ask the other manufactures what their numbers are for that.

These oils all look good on paper. To me. We ran the RP for years until LE came in. Oil analysis haven't been good, so I'm looking hard at different oils. Trying to get a handle on it without having to become an actual tribologist. Its been over 12 years since we had a failure on the large Compressor and it was "Catastrophic" when it did go. Oh and very expensive by the time we were back online. We aren't having issue of any kind I just want to start to balance the cost of maintenance. Whether it is less expensive oil changed more often or pay more and get more?

If those test are the "important ones" for air compressors what then should I be looking for in my oil analysis when they come back? I notice that on my sample reports Oxidation (abs/cm) isn't tested or Nitration. And for whatever reason there are two "Water by Karl Fischer" test, one (D1744) was done and then the next sampling they ran a 6304c test. So there isn't a way for me to compare side by side for that.

Thank you guys for the help so far, once i get this nailed I'll be asking you about filters!
 
jake88, I just reread you post and see your calling over 10,000 hours a good measure for the RPVOT, the LE is only 1300 minutes!! Huge difference, what does that mean?
 
Originally Posted By: small
jake88, I just reread you post and see your calling over 10,000 hours a good measure for the RPVOT, the LE is only 1300 minutes!! Huge difference, what does that mean?


Sorry that was confusing the way I wrote it.

The RPVOT is a severe test, and a fluid with over 1,000 hours has very good oxidation stability

The TOST is less severe, and the test is only ran until 10,000 hours. Any quality R&O fluid will make it to the end of the test, so this test is less useful for comparing multiple fluids.
 
Originally Posted By: small
So I'm looking at different spec sheets for ISO 46 compressor oil. LE, OEM Kaeser (ie.RP), Amsoil and a Noname. It seems they, if they list the four ball test, are each different. Two run the ASTM D-4172 but at different weight, rpm, and temp, and another shows a different ASTM D2783 test all together.

So what am I looking at and does it even matter in a rotary screw application? I tried looking up the ASTM spec/test but it seemed like I'd have to subscribe to find out what they meant.

Hoping you guys could shed some light.


The primary purpose of the 4-ball wear test is to determine the relative wear rates and friction coefficients of competing formulations during lab testing.

If the 4-ball tests are listed they are generally used for marketing purposes.
 
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I'd give the guys at SumOil (http://www.sumoilcorp.com/) a shout. They got quite the line of compressor oils.


One thing I haven't seen mentioned here is that in a rotary screw - the oil is also used to seal the chambers of the screw. Better oils with lower volatility can actually improve the volumemetric efficiency of the compressor.

Don't buy the expensive OEM stuff - there are plenty of awesome aftermarket oils that can even extend your oil change intervals.
 
OK so I read a "White paper" put out comparing Comp Oils and have decided to go and give Amsoil a try. I just got another analysis back for my smaller comp and it's starting to show some Aluminum in the wear metals category. I'm changing it out this morning less then 4 months run time. Very disappointing. Funny though had the salesmen not sold me on sampling I'd have never known! I'll try the Amsoil and see how that holds up.
 
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