I work in a nuclear plant and we have EMD diesels with Mobilgard 450 NC oil for emergency back up power. The industry has had a couple of bearing failures in these diesels and the experts are searching for the root cause. The latest probable cause is foaming of the oil. My opinion is our diesels have a very large sump (350 gallons) and any foaming that takes place would dissipate before the lube oil pump would pick it up. The questions I have, if I start having ASTM D 892 foaming test performed what acceptance criteria should I apply to used oil before I recommend a change? How often should I request a foam test? Should the foam test been a test that I should have been requesting all along? And the last question, is my assumption of the large sump and the oil dissipating correct?
Foaming Diesel oil
- Thread starter D C Anderson
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MolaKule
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Do the bearings show cavitation or foaming of the oil? Bob has some excellent photos of bearing failures and root causes.
I'm with you on your assement. I would think the bubbles would have dissipated by the time the oil returns to the sump, and with such a large sump capacity.
When you say EMD, I assume you mean that these 2-cycle diesels are now used to generate AC. As I recall, these engines have to have stright-grade viscosity oils and Ashless additives.
Just guessing, but I would bet that what they will find are acids attacking the bearings.
I'm with you on your assement. I would think the bubbles would have dissipated by the time the oil returns to the sump, and with such a large sump capacity.
When you say EMD, I assume you mean that these 2-cycle diesels are now used to generate AC. As I recall, these engines have to have stright-grade viscosity oils and Ashless additives.
Just guessing, but I would bet that what they will find are acids attacking the bearings.
Has an oil analysis been performed?
I think you can rule out that Cl theory.
I think also contacting labs and Mobil - could tell you how much foam and how rapidly it dissipates - will get you closer to criteria you need.
I think you can rule out that Cl theory.
I think also contacting labs and Mobil - could tell you how much foam and how rapidly it dissipates - will get you closer to criteria you need.
With that large a sump the foam should be able to pop before returning. mibil might be able to furnish more additive.
The root cause might be not running enough when you fire up for testing so moisture builds up. It takes a long time to get the oil temperature up in engines of this size. I know the CAT 3416 takes about 90 minutes to get it's 160 gallons up to temp.
I've seen a lot of trouble with bearings in stand-by engines for not running them enough.
The root cause might be not running enough when you fire up for testing so moisture builds up. It takes a long time to get the oil temperature up in engines of this size. I know the CAT 3416 takes about 90 minutes to get it's 160 gallons up to temp.
I've seen a lot of trouble with bearings in stand-by engines for not running them enough.
We run these diesels (EMD 16 Cyl series 645 turbo charged) once a month for about 90 minutes. The oil is sampled every month for metals, vis @ 40 & 100c, TBN, FTIR and water and sediment test. I have no experence with the foam test and am trying to draw from the experience of my Peers. The oil analysis on my diesels has always looked good. From what I gather is I might want to add a Karl fisher test and check for moisture. What would be an acceptable limit here? The FTIR has never shown a trend for moisture.
DC,
Foaming is more of an issue with some of the newer diesel engines that use the "HEUI" injectors, where the injectors are actuated using engine oil as a hydraulic fluid under very high pressure. In fact the foaming test that is performed as part of the CH-4 and CI-4 test matrices is done with a 7.3L Ford Powerstroke engine. So I'm not really sure this is the problem in this case ....
I would generally flag moisture if it is > 0.1% in a sample of used oil. With enough moisture you will tend to deplete the additives and get sludging, along with more rapid sulphuric acid formation.
As I recall, these EMD engines use bearings that contain silver, so the additive chemistry of the oil has to be compatable with that metallurgy.
Foaming is more of an issue with some of the newer diesel engines that use the "HEUI" injectors, where the injectors are actuated using engine oil as a hydraulic fluid under very high pressure. In fact the foaming test that is performed as part of the CH-4 and CI-4 test matrices is done with a 7.3L Ford Powerstroke engine. So I'm not really sure this is the problem in this case ....
I would generally flag moisture if it is > 0.1% in a sample of used oil. With enough moisture you will tend to deplete the additives and get sludging, along with more rapid sulphuric acid formation.
As I recall, these EMD engines use bearings that contain silver, so the additive chemistry of the oil has to be compatable with that metallurgy.
For the foam test, what acceptance criteria should I apply to used oil before I recommend a change or some sort of action? How often should I request a foam test? The diesels that have failed we outsiders believe it was because of foreign material. They failed after a rebuild of the engines. Some want to contribute the failures to the new oil not containing chlorine. Fingers are being pointed in all directions.
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