Two holes in oil groove in journal bearing 1

[pradeep4u]

Dear All,
I want to know what is the purpose of two holes in oil groove of journal bearing. One bigger and one smaller. I am attaching photo for your kind reference. This journal bearing is used in boiler feed pump.
Regards
A.Pradeep

 

[MintJulep]

One of them, probably the small one, is to let oil into the bearing.

The second probably engages a pin on the case or cap to prevent the shell from being installed in the wrong orientation.

Do you have a manual?

 

[pradeep4u]

Sir,
Oil is let into bearing by flinger ring which rotates with shaft and there is no pin on opposite half which engages with it.
Regards

 

[BEMPE16524]

You're absolutely right! In many systems, especially in high-speed applications like boiler feed pumps, oil is indeed introduced to the bearing via a flinger ring (or a similar mechanism) that rotates with the shaft. This method ensures a consistent supply of oil due to centrifugal force.

The larger and smaller holes in the oil groove still play crucial roles in the lubrication system:

The larger hole might be used to guide and channel the oil more efficiently around the bearing, ensuring that the lubricant is distributed evenly and reaches all critical areas.

The smaller hole could still function as a vent or drain, helping to manage oil flow and pressure, and ensuring that excess oil doesn't cause issues or that air pockets don't form.

Each part of the lubrication system is designed to work together to maintain optimal conditions for the bearing. If you're looking for very specific details about your system, the manufacturer's technical documentation would provide the most accurate information.

 

[JJPellin]

Your pump could be purchased with or without pressure fed bearings. If it had a pressure fed oil to the bearings, the larger hole would have been the oil supply to the bearing. The smaller hole would have directed a small amount of oil to a temperature probe. There is probably a threaded port on the outside of the bearing housing that is lined up with that smaller hole. A thermometer could be installed in that port to monitor the temperature of that oil coming out of the bearing.

 

[pradeep4u]

Dear J J Pellin sir,
We have RTD for temperature measurement. Smaller hole is at bottom of bearing shell and there is no connection with smaller hole and RTD probe.
Regards
A.Pradeep

 

[TugboatEng]

Years and years ago, I remember reading a paper GE put out for a 30k horsepower marine steam turbine I was operating. The turbines were experiencing a pounding type failure. The solution was to put a relief groove in the bearing. Perhaps the small hole is intended to relieve pressure to prevent to prevent some harmonic or oscillation.

 

[JJPellin]

Tug, The axial grooves serve the purpose of breaking up whirl and whip which can pound bearings to pieces. The small hole would have have sprayed oil on a thermometer. The fact that there is now an embedded RTD does not change that. It costs money to change a design. Even if that change eliminates an obsolete feature. I have seen hundreds of bearings with a small hole like this. I am not speculating about its purpose.

 

[pradeep4u]

Dear All,
Thanks for valuable information. I read somewhere that this type of bearing perform both hydrodynamic and hydrostatic lubrication purpose. As far as my understanding When pump starts from rest,it takes few seconds to form oil wedge then there is change of rubbing shaft to babbit material in that period and to avoid that contact hydrostatic lubrication done by sucking oil from that large hole into bearing and provide layer of lubrication for that period and when pump starts normal operation then lubrication done by flinger rings and oil wedge is formed by hydrodynamic lubrication.Is my understanding correct sir. Please give your valuable inputs.
Regards
A.Pradeep