Pulsafeeder Pulsalube 8 GS Ultra, Operation & Maintenance Manual

Page: 165 / 198

DRIVESYSTEMS
MINICASE
®
(SM SERIES) WORM GEAR
LUBRICATION GUIDELINES
RETAIN FOR FUTURE USE U10790 - 2 of 2
www.nord.com/docs 04.24.13
NORD Gear Corporation
Toll Free in the United States: 888.314.6673
NORD Gear Limited
Toll Free in Canada: 800.668.4378
6. Oil Viscosity
The viscosity rating determines the operating oil’s resistance
to shear under load conditions. Some important viscosity
considerations include the following:
• Lightly loaded gears require lower viscosity oils than highly
loaded
gears.
• Lower viscosity will provide thin oil fi lm, lower friction,
higher mechanical effi ciency, and better heat removal
conditions.
• Higher viscosity will provide thicker oil fi lm, and better
resistance to sliding wear, scuffi ng wear, and galling at
high
pressure.
• Higher operating temperatures will cause a reduction
in viscosity and lower operating temperatures, cause an
increase in viscosity or a thickening of the oil.
The standard oil-fi ll is considered acceptable for most applica-
tions. In certain situations an oil viscosity change may be ben-
efi cial.
• If the gear unit is exposed to frequent high load condi-
tions. A higher viscosity oil will have a higher fi lm thickness
offering better overall resistance to oil shear, sliding wear
and
scuffi ng wear in gears and roller element bearings.
• An oil viscosity correction or lubrication change may
improve the overall performance when operating the gear
unit at very low or high ambient temperature conditions.
IMPORTANT NOTE
The user should consult with their primary lubrication sup-
plier before considering changes in oil type or viscosity.
7. Viscosity Index
Viscosity index helps quantify the rate of oil viscosity change
with respect to temperature changes. Oils with a reasonably
high viscosity index tend to be more stable in a changing tem-
perature environment. The ability of an oil to maintain a small
viscosity differential over the operating range of the gearbox
provides a more consistent lubricating fi lm and better wear
performance.
Synthetic oils typically have a higher viscosity index than min-
eral oils and polyglycol oils tend to have an exceptionally high
viscosity index compared to other synthetic oils like polyalphao-
lefi n or ester based products.