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Running torque

The grease characteristics (viscosity penetration, etc.) and grease quantity can influence the bearing running torque; further to influence the bearing running speed and result in an increase of bearing temperature.
Generally speaking, if the lubricant quantity is increased, the running torque increases, which may result in temperature generation and being speed fluctuation. Also, with the same grease volume, bearing with high viscosity will come out more running torque than those with low viscosity.

Following table lists some frequent problems which are caused by increased running torque.

Types Description Causes Countermeasures
Bearing temperature is going to be higher and higher. Churning from several lubricant couplings. Churning type lubricants cause temperature generation because of the shearing effect. Reduce the lubricant
quantity. Change to a channeling type of lubricant.
Failure to
Reach Speed
Sometimes motors cannot reach the designed nominal speed. Excessive grease quantity. Selection of a soft churning type of lubricant.
Excessive Power
The motors or engines are higher consuming the power than that was estimated. The reasons for this are the same as "Failure to Reach Speed" above. Lubricants with high worked penetration can also add to the problem. Reduce the grease quantity. Change lubricant type.
Excessive Reach
Running Current
The high running current of the motors during operation. Grease quantity. Worked penetration of lubricant softness level of a churning type of lubricant. Selection of a soft churning
type of lubricant. Reduce the grease quantity.
When bearing is within high rotating condition, speed fluctuations come. This is caused by grease "slumping" into the pathway of the ball. Reduce grease quantity.
Use a channeling type grease. Use a much softer type of churning grease.

The speed factor n·dm for lubricating greases
The attainable speed factor of lubricating grease depends largely on its base oil type, viscosity, thickener type, and of course the bearing type used. Under high-speed bearing operating conditions it is important to achieve a constant oil supply.

Grease types Base oil viscosity
at approx, 40℃
[ mm2/s ]
Speed factor
Mineral / lithium / MoS2 1000 to 1500 50,000
Mineral / lithium complex 400 to 500 200,000
Mineral / lithium / MoS2 150 to 200 400,000
Ester / polyurea 70 to 100 700,000
Ester / lithium complex 15 to 30 1,600,000
Ester / polyurea 15 to 30 2,000,000

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