"I have an industrial gearbox operating at 200F (casing temperature) with a synthetic, non-EP, ISO 220 gear and bearing oil in use. This seems to be hot. Any comments?"
If the casing is 200F, the oil inside is likely about 220F or hotter. This is much hotter than I would prefer. We would like to see the oil temperature at about 150F or lower, so something is wrong.
A viscosity-temperature plot of your oil suggests that it has a viscosity at your operating temperature of about 22 - 25 cSt. This is well below the 33 cSt minimum viscosity recommended for most industrial medium speed gears (excluding worm gears). I believe some of your high temperature is being caused by metal-to-metal contact from an oil that does not have enough viscosity.
I would suggest that you immediately add some thicker oil (ISO 460) or do a complete oil change to the 460. I would continue to use a synthetic non-EP oil until you see what happens to the temperature after you have completely converted to the synthetic 460. Some fine tuning of the oil type (EP vs. non-EP) and grade (320 vs. 460) may be needed later. There may also be a different root cause of the high temperature and gear speed (pitch-line velocity) should be checked.
Bob Scott, Noria Corporation
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