NORD Drivesystems B1000 - Manual (Page 16)

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INTRODUCTION
G1000 – Subject to Change Without Notice
Gear Reducer Ratings
The permissible continuous power limit of gear re-
ducers is limited by both the mechanical rating and
the thermal rating. The mechanical rating depends
upon the material strength of the gear reducer’s
gears, bearings, housing, shafts, etc. The mechanical
input power limit to the reducer is also a function of
the mechanical power rating divided by the relevant
reducer service factor.
The thermal rating or thermal limit depends upon
the amount heat generated within the reducer and is
infl uenced by a variety of factors including:
• Churning or splashing losses in the lubricant which
depend upon reducer type, ratio, input style,
mounting position or oil fi
ll-level, and the
circumferential travel velocities of the gear wheels.
• The actual speed and load conditions. These
factors determine load-dependent losses in the
gears and frictional losses in the gears, bearings
and seal areas.
• Ambient Conditions:
- Ambient Temperature.
- Amount of free air circulation around the drive.
- Possible near-by heat sources.
- Heat dissipation or the ability of the reducer to
transfer heat through the housing, shafts, and
the mating sub-structure or mounting surface.
Observing the Reducer’s Thermal Limit
When to Contact NORD
Through computer program analysis NORD can evalu-
ate application conditions and the impact they have
on a reducer’s thermal capacity.
When applying helical in-line, Clincher™ shaft mount,
& helical-bevel gear units of case sizes 6 & larger (SK62,
SK6282 and SK9072.1 and larger), consult NORD if any
two or more of the following conditions apply:
• Gear ratio, i
total
≤ 24:1or ≤ 48:1 for helical-bevel units
• Input power, P
1
≥ 60 hp (45 kw)
• Input speed, n
1
> 1800
• Vertical positioning (mounting position M2 or M4)
• Input
confi guration: NEMA C-face, IEC, servo adapter
or solid-shaft input (Type-W)
• Elevated ambient temperature ≥ 86° F (30 °C)
When applying helical worm or worm gear units, please
consult NORD if one of the following conditions applies:
• Input speed, n
1
> 1800
• Vertical positioning (mounting position M2 or M4)
• Input
confi guration: NEMA C-face, IEC, servo adapter
or solid-shaft input (Type-W)
• Elevated ambient temperature ≥ 86° F (30 °C)
Advise NORD of any special application considerations:
• Confi ned space or limited air circulation
• Exposure to other near-by radiant heat sources
• Dirty or dusty environments
• High altitude operation > 3,280 ft (1000 m) a.s.l.
Dangers of Reducer Overheating
The following problems may result when a reducer’s
thermal capacity or maximum oil sump temperatures
are exceeded:
• Lubrication oxidation, breakdown & deterioration.
• A decrease in lubrication viscosity & fi lm thickness.
• Loss of critical bearing and gear clearances required
for proper lubrication.
• Increased contact pressures & increased operating
temps. in the critical load zones of the gearing
and
bearings.
• An increased possibility for metal-to-metal contact
and premature component wear.
• A signifi cant reduction in the lubricant’s ability to
prevent
scuffi ng, pitting, and in extreme cases
galling or welding.
Maximum Oil Sump Temperature Limit
To prevent reducer overheating, the reducer’s maxi-
mum oil sump temperature limit must not be exceed-
ed for prolonged periods of operation (up to 3 hours
continuous operation, depending upon reducer size).
Oil Type Maximum Oil Temperature Limit
NORD AGMA 9005-D94
Mineral 80-85 °C (176-185 °F) 95 °C (203 °F)
Synthetic 105 °C (220 ° F) 107 ° C (225 ° F)
Measures to Expand the Application Range
There are a variety of measures that may be taken
in order to protect against thermal overload and
expand the application range of the gear reducer.
Common examples include the following:
• Recommending a change in lubrication viscosity
and/or a specifi c synthetic lubricant type.
• Applying high-temperature seals.
• Increasing air fl ow around the gear unit.
• Protecting the reducer from high heat sources.
• Considering an integral motor instead of the bolt-on
input assembly covers. In many cases the motor
fan will substantially increase air-fl ow around the
gear
unit.
• Add an Oil Expansion/Overfl ow Chamber (Option
“OA”) or an Oil Reservoir (Option “OT”).
• Oil Cooler (Option “OC”).
• Water Cooling Cover (Option “WC”)
Selection
Information