Hydraulic motors Technical Information Series V12 Bearing life

Bearing life calculation General information An application is usually governed by a certain duty or work cycle where pressure, speed and displacement vary with time during the cycle.Bearing life is also dependent on external shaft loads,case fluid viscosity and fluid contamination.Parker Hannifin has a computer program for bearinglife calculation and will assist in determining life for specific V12 load conditions; refer to MI 170, ‘V12 bearing life’, available from Parker Hannifin. Bearing life can be calculated for that part of the load/ life curve (shown below) that is designated ’Bearing fatigue’. ’Fatigue of rotating parts’ and ’Wear’caused by fluid contamination, etc., should also be taken into consi- deration when estimating the service life of a motor/pump in a specific application.In reality, bearing life can vary considerably due to thequality of the hydraulic system (fluid condition, cleanli- ness, etc.) Bearing life calculations are mainly used when com- paring different motor frame sizes. Bearing life, desig- nated B Required information When requesting a bearing life calculation from Parker Hannifin, the following information (where applicable) should be provided:-A short presentation of the application -V12 size and version -Duty cycle (pressure and speed versus timeat specified displacements)-Low pressure -Case fluid viscosity -Life probability (B
10 (or L
10 ), depends of system pressure, opera-ting speed, external shaft loads, fluid viscosity in the motor case, and fluid contamination level.The B
10 value means that 90% of the bearings surviveat least the number of hours calculated. Statistically, 50% of the bearings will survive at least five times the B Î± ) as defined below.
10 life.
WearBearingfatigueFatigue ofrotating partsSystem pressure 10 , B
20 , etc.)-Direction of rotation (L or R) -Axial load -Fixed or rotating radial load -Distance between flange and radial load -Angle of attack (
Life expectancy (logarithmic scale) Hydraulic motor life versus system pressure.

F Î± F

20
Parker Hannifin Mobile Controls DivisionTrollhättan, Sweden