Oil is dark, smells like half cooked ATF, and has good RBOT tests ?

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Probably the right forum.

At work, I look after a half dozen voith fluid couplings, each transferring around 9000 shaft horsepower.

The oil temps are high, as the plant cooling water is struggling in the current high temps. Working oil temps are 90 degrees C plus. (Rule of thumb is that every 10 over 80 degrees halves oxidation resistance)

The oil (Bartran HV32) looks dark, smells like half burned ATF, and I desperately want to switch to hydrocracked because of the operating temps.

But the RBOT tests read 150mins time after time (baseline around 250-300), indicating oxidation isn't an issue. Wear is good (herringbone gearsets help). The things aren't clagging up their hydraulics.

What gives ?

How can I justify changing to "better" oil, when the old stuff looks and smells like a problem, but tests OK ?

Guess I'll have to find something else to play with. Anyone good with grease lubricated 10" diameter roller bearings ?
 
You're probably smelling the sulfur additives and base oil sulfur. Economics say if the fluid is testing ok, stay with it.

You might see some friction reduction with a more refined oil, which would tranlsate to less energy being used, but the energy reduction and reduction in energy cost would have to compensate for the increased cost of the more expensive fluid.

10" bearings? Thick moly grease with high drop points!

Edit: I read a recent paper that showed AW additives, especially ZDDP, turns ATF and hydraulic brown with high temperatures.

[ February 05, 2003, 07:50 PM: Message edited by: MolaKule ]
 
Molakule,
thanks for the info re zinc and temperature. Was really hoping to do a controlled lubricant test, as all we seem to do these days is fix broken stuff.

The 10" bearings are causing us some grief. They're 1500 RPM, and quite lightly loaded. Used to be oil lubricated (ISO32). Due to temperature, the shaft grows 1/8 inch, and wipes seals, dumping the circulated oil on the floor and starting fires. Used to run 60 degrees C on oil.

So we rejigged the system for grease.

Went through the SKF lube selection procedure, and decided that I wanted a little more than 20 cst at operating temp. Settled on Mobilith SHC100.

Temps go all over the place, 50 to 100 degrees C. I reckon it's grease falling back into the race, and heating it up like an overload of grease. Average is about 70, which is OK, but the variability scares operators at 2AM in the morning.

SKF are blaming the grease - recommending a grease with a base oil of 26cst at 40 degrees. Falls to 9cst@our operating temp. Lubrication engineers blamed the grease, then specified one with 120cst at 40, crossing the mobil at 70 degrees.

I believe that the grease we're using is OK, but the shaft is too lightly loaded for the bearing size. SO we're putting continuous (every couple hours) greasers on to see.
 
The greaser should work. I had originally assumed a heavily loaded, slow turning shaft. Seems like the bearing probably needs a light aluminum complex grease.

Let us know how the auto-greaser works.
 
Jury is still out on the auto greaser.

Keeps failing on no grease flow.

Manufacturer is now Blaming Mobil SHC100 grease, as being "too good", and dissolving air, which causes the piston pumps to compress and expand the bubbles without pumping grease.

Will update one day or another when there's some results to compare.
 
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