Granted, this is mainly geared for turbines (hey Shannow!
) and hydraulic systems, but it has a bunch of information and what testing will give you a better idea about what's going on inside.
Varnish white paper
Varnish white paper
All about varnish
- Thread starter SubieRubyRoo
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so tl;dr use a good filter, don't short trip, change regularly?
Back when they changed to GrII (and didn't tell us), we got caught.
membrane patch colorimetry was not at that stage an ASTM standard, so I sponsored an engineering thesis on seeing if we could do same on a decent, calibrated flat bed scanner...
https://drive.google.com/file/d/0B72RMQAMdx4iejZwcHBRT3ZPZl9hWFdILWFSaENxQ3Y1SGJR/view?usp=sharing
membrane patch colorimetry was not at that stage an ASTM standard, so I sponsored an engineering thesis on seeing if we could do same on a decent, calibrated flat bed scanner...
https://drive.google.com/file/d/0B72RMQAMdx4iejZwcHBRT3ZPZl9hWFdILWFSaENxQ3Y1SGJR/view?usp=sharing
So Shannow, when using the desktop scanner, did they simply add the worst-case underreporting of ~2.37 to the results to determine which grade it fell in?
And you're essentially saying the decreased polarity of GrII oils is what allowed the varnish to begin precipitating because the metal of the turbine was more polar than the molecules in the oil itself? With GrI and higher polarity, the varnish would remain suspended until it agglomerrated and was removed by the filtration? This must be how old-school ICEs didn't get really varnished or sludged up unless completely neglected.
Makes you wonder how many times "technological advancements" (hydrocracking etc) resulted in previously unseen mechanical issues. Thanks for your one-pager!
And you're essentially saying the decreased polarity of GrII oils is what allowed the varnish to begin precipitating because the metal of the turbine was more polar than the molecules in the oil itself? With GrI and higher polarity, the varnish would remain suspended until it agglomerrated and was removed by the filtration? This must be how old-school ICEs didn't get really varnished or sludged up unless completely neglected.
Makes you wonder how many times "technological advancements" (hydrocracking etc) resulted in previously unseen mechanical issues. Thanks for your one-pager!
Makes you wonder how many times "technological advancements" (hydrocracking etc) resulted in previously unseen mechanical issues.
I guess so. A book of the 'unintended consequences' of so many 'advancements' would be a great read. The addiction to our smart phones is one that comes to mind!
I guess so. A book of the 'unintended consequences' of so many 'advancements' would be a great read. The addiction to our smart phones is one that comes to mind!
suby,
it was well known in the industry that PAOs had very poor solvency...for both additives and contaminants...Mobil used GrI "Carrier" oil in the '80s to get the additives into suspension. Got razzed badly, and sort of defended it to the hilt without saying why their additives needed GrI…
They are very very high in terms of oxidation stability...but can't hold the varnish in suspension.
The varnish is formed somewhere (hot, electrical discharge zones, high temperature atomised oil exposed to air), but the place that they are formed, isn't the place that they deposit. Video here shows how the varnish solubility changes with temperature...
So I'll use my turbine stuff...
It was formed somewhere (my guess the generator hydrogen seals), and made it to the main oil tank.
* some of that went to the centrifuge. As the centrifuge was water sealed, and varnish is very polar (water and caustic detergents are the best to remove it), the varnish that came into contact with the water formed a big sludge ball, locking up the centrifuge monthly.
* the stuff that returned to the turbine was cooled to 45C, and sent to turbine bearings, hydrogen seals, and the turbine valve gear hydraulics.
The bearings ran at 90C
The hydrogen seals at 85C
The hydraulics, they ran at ambient oil tempertures, had no heat from motion of components.
So that's where the varnish plated out...all through the hydraulics.
Industry wide, many many turbines have been lost due to failure of the hydraulics to trip the machine and close the valves.
So look at an engine...the heat is in the crank, and motion of the pistons, plus some under piston temperature. The crankcase is full of nasty blowby, with reactive species like CO, NOx, water vapour, half combusted fuel...THAT's where the varnish is formed.
But where do we usually detect it ?
Top end, where it's relatively cooler, not much more than coolant temperature.
In plant, we can remove it from circulation, and the machine will clean up over time...but you've got to get the oil at the coldest point below it's saturated level so that it can start to harvest the deposits.
it was well known in the industry that PAOs had very poor solvency...for both additives and contaminants...Mobil used GrI "Carrier" oil in the '80s to get the additives into suspension. Got razzed badly, and sort of defended it to the hilt without saying why their additives needed GrI…
They are very very high in terms of oxidation stability...but can't hold the varnish in suspension.
The varnish is formed somewhere (hot, electrical discharge zones, high temperature atomised oil exposed to air), but the place that they are formed, isn't the place that they deposit. Video here shows how the varnish solubility changes with temperature...
So I'll use my turbine stuff...
It was formed somewhere (my guess the generator hydrogen seals), and made it to the main oil tank.
* some of that went to the centrifuge. As the centrifuge was water sealed, and varnish is very polar (water and caustic detergents are the best to remove it), the varnish that came into contact with the water formed a big sludge ball, locking up the centrifuge monthly.
* the stuff that returned to the turbine was cooled to 45C, and sent to turbine bearings, hydrogen seals, and the turbine valve gear hydraulics.
The bearings ran at 90C
The hydrogen seals at 85C
The hydraulics, they ran at ambient oil tempertures, had no heat from motion of components.
So that's where the varnish plated out...all through the hydraulics.
Industry wide, many many turbines have been lost due to failure of the hydraulics to trip the machine and close the valves.
So look at an engine...the heat is in the crank, and motion of the pistons, plus some under piston temperature. The crankcase is full of nasty blowby, with reactive species like CO, NOx, water vapour, half combusted fuel...THAT's where the varnish is formed.
But where do we usually detect it ?
Top end, where it's relatively cooler, not much more than coolant temperature.
In plant, we can remove it from circulation, and the machine will clean up over time...but you've got to get the oil at the coldest point below it's saturated level so that it can start to harvest the deposits.
OVERKILL
$100 Site Donor 2021
Originally Posted by Shannow
https://www.machinerylubrication.com/Read/1027/varnish-potential-analysis
https://www.machinerylubrication.com/Read/29768/varnish-levels-monitoring
Thanks for those links Shannow, good reads
Question for you: Why is POE not used? It's polar and I would thus expect it to have a positive impact on the varnish situation?
https://www.machinerylubrication.com/Read/1027/varnish-potential-analysis
https://www.machinerylubrication.com/Read/29768/varnish-levels-monitoring
Thanks for those links Shannow, good reads
Question for you: Why is POE not used? It's polar and I would thus expect it to have a positive impact on the varnish situation?
80,000L of oil per turbine, an about 15,000L of usage per annum.
Conoco tried to sell me GrIII turn of the century...I didn't bite, for the solubility issues...then they switched.
For steam trubines, GrI with an R and O inhibitor did the job just fine.
Conoco tried to sell me GrIII turn of the century...I didn't bite, for the solubility issues...then they switched.
For steam trubines, GrI with an R and O inhibitor did the job just fine.
OVERKILL
$100 Site Donor 2021
Ahhh, so it's a cost thing. Makes sense.
There's probably other reasons as well.
Seal and gasket compatibility are well known with the GrI (and GrII)
The generators have an oilf flooded hydrogen seal to keep the 60psi of hydrogen in the generator. That's got to remain dry (to avoid wetting the hydrogen), and esters as you know have an affinity for water...which the steam turbine tends to introduce into the oil, so you want fast separation of the water/oil.
Seal and gasket compatibility are well known with the GrI (and GrII)
The generators have an oilf flooded hydrogen seal to keep the 60psi of hydrogen in the generator. That's got to remain dry (to avoid wetting the hydrogen), and esters as you know have an affinity for water...which the steam turbine tends to introduce into the oil, so you want fast separation of the water/oil.
OVERKILL
$100 Site Donor 2021
Yes, that'd be another potential issue for sure. Kind of reminds me of Mobil's fault-plagued foray into blending piston aircraft engine oils that, being PAO-based, didn't handle the lead from fuel dilution well.
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