allowable speed

14
ALLOWABLE SPEEDS V.GOPI KRISHNA 13MCD1053

Transcript of allowable speed

Page 1: allowable speed

ALLOWABLE SPEEDS

V.GOPI KRISHNA

13MCD1053

Page 2: allowable speed

TIME

•WE KNOW THAT TIME IS MORE valuable FOR US AND WE RUN FOR IT.•THE ENTIRE WORLD IS AUTOMATED NOW A DAYS•WITH THIS AUTOMATION WE MAKE OUR MACHINES RUN ALONG WITH US.

Page 3: allowable speed

LIFE TIME

• one of the important characteristic that the life time of any particular machine decides is its speed.

ex. bikes

Page 4: allowable speed

ALLOWABLE SPEED

• As rotational speed of the bearing increase, the temperature of the bearing also rises due to heat produced inside the bearing by friction.

• The bearing can’t maintain stable operation.• The maximum speed at which it is possible for

the bearing to continuously operate without the generation of excessive heat beyond specified limits, is called the allowable speed (min-1).

Page 5: allowable speed

category

• The allowable speed of a bearing depends on the type of bearing are:

Bearing dimensions Load Lubricating conditions and Cooling conditions.

Page 6: allowable speed

• Bearing size - Higher speed will result in higher axial and radial thrust  loads. The existing bearings may become inadequate to carry the increase  in thrust loads.

• Maximum allowable working pressure (MAWP) - Increasing the RPM will increase differential pressure by the square of the speed ratio. The maximum RPM will be limited to a point where pressure will not exceed the  MAWP.

Page 7: allowable speed

• Bearing lubrication requirement - The bearing lubrication requirement increases with RPM. At higher RPM oil-ring lubrication may no longer be sufficient, and forced-feed lubrication may be required.

• Cooling

A quality lubricant must be used. The lubricant must be replenished and changed when necessary.

Page 8: allowable speed

calculation

Page 9: allowable speed

• If rotational speed is to exceed allowable rotational speed given in the dimensions table, it will require special considerations such as using a bearing for which cage specifications, internal clearance and precision have been thoroughly checked.

• It will also require adopting forced circulation, jet oil or mist oil lubrication as the lubrication method.

Page 10: allowable speed

• when radial bearings are mounted on vertical

shafts, lubricant retentions and cage guidance are not favorable compared to horizontal shaft mounting.

• Therefore, the allowable speed should be reduced to approximately 80% of the listed speed.

Page 11: allowable speed

• For bearings to be used under heavier than normal load conditions, the allowable speed values listed in the bearing tables must be multiplied by an adjustment factor.

Page 12: allowable speed

Adjustment factor on bearing load

Page 13: allowable speed

Adjustment factor on combined bearing load

Page 14: allowable speed