Babbitt thickness on plain journal bearings on centrifugal compressors

[sinectica]

Good morning guys,
I would be very grateful if someone could give me an idea, about his own experience, regarding the recommended babbitt thickness in plain journal bearings for a centrifugal compressor with these carachteristics:

Power 300 kW (max electric motor power)
Rotor weight 40 kg (aprox)
speed 13000 rpm
shaft diameter 70 mm

We have radial bearings (lemon bore) with a babbitt thickness of 1 mm. As I have recently read in some publications, this is so much in the fatigue point of view, and maybe I could increase the fatigue resistance by a coating with less qauntity of babbitt. The problem is that our bearing manufacturer says that with less than this 1 mm is not feasible to guarantee the bonding between the base metal and the antifriction.

Which is your experience about the coating thickness in this kind of bearings? is it feasible to reduce it into less than 1 mm?

If someone knows where to manufacture them in Spain, better

Thank you so much for your kind help,

Marc

 

[sinectica]

Hello guys,
does anybody have a light about this issue?

Thank you so much for your help!
Marc

 

[romke]

is the fatigue resistance the limiting factor in the bearing life right now? if not, i would not change the design, or even might want to increase it somewhat.

remember: one of the good things from a babbitt bearing is the fact that when overheated it melts and the fluid babbitt material can act as a temporary lubricant preventing catastrophic failure of the rotor and the shaft.

if the loading is such that fatigue is a problem, there are only two ways to solve the problem: increase the bearing surface area or change to another type of bearing material. the first solution calls for a costly redesign, the second option is cheaper but you will loose the "babbitt induced safetynet" in the process: when the bearing goes, the resulting damage to the shaft will problably be prohibitive for further use.

 

[GregLocock]

Your babbitt needs to be at least as thick as the biggest grit or swarf you expect to see.



Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.