Hydrodynamic Bearing Design Data

[smckennz]

Hi there

can anyone refer me to some freeware or similar for the design of a journal bearing.

Approx scantlings are:
Load: around 200T
Diameter: 1.5m
Width: 0.6m
Surface speed: 1 m/s
Lube: ISO 220 cSt (I hope)

Its a 180 degree bearing on an old ball mill that we are putting back in service. I want to do a check on heat, lube flow, and to estimate the runnning lift.
Can do by hand/spreadsheet, but it takes an age.

Thanks in anticipation,

Steve McKenzie

 

[balu1]

have a look at this:

http://www2.latech.edu/~mcorley/me462/bearing/Bearing.htm

 

[PaulJuhnke]

The previously mentioned web-site is a good one, but it’s focused primarily on normal high speed journal bearings, using relatively light oil. The thick oil you need at slow speeds is not allowed in the calculator.

Your lift will only be a few thousands of an inch, approximately 0.002” to 0.010” depending on your bearing design and oil characteristics. More important than the amount of lift is the bearing lead-in taper. Trust me; I’ve fought with bearing problems on several old ball mills and kilns, with good and bad journal conditions.

Whatever you do, don’t’ use less that 0.0015” radial clearance measured across the diameter, per inch of journal diameter. So in your case the journal bearing should be machined 0.090” larger in diameter that the journal (minimum). Then you can adjust the lift as needed using oil viscosity and oil type. Surface roughness and radial run-out are also important considerations in old ball mills.

Also, be sure to NOT allow the installing contractor to scrape your new bearing to get “100% contact”. Most installers don’t know how to measure bearing contact, and they end up ruining a new bearing during the installation process.

If you need more information, feel free to call me at 641-423-9363 with more details about your application. Good Luck, Paul Juhnke, Maintenance Engineering Services.

 

[smckennz]

Hi Paul

thanks for that. We stayed with the manufacturers recommended clearances of 0.030" each side (0.024" measured 8" down from the top of the 180 deg slipper bearing). Kept a 40 degree non-clearanced bed at the bottom. /getting around 0.008" static lift at 30 deg C, although I think the running lift is higher. The oil feed horns are staying full of oil and there is no sign of distress to the bearing or lube system.
The web site suggested by Balu gave a fairly good approximation of the operating conditions. Used SAE 50 oil which is not too far away from VG220. I also worked it out by hand using the correct parameters for a 180 deg slipper bearings. Reasonably good correlation.

Cheers

Steve McKenzie

 

[PaulJuhnke]

Glad everything worked out, and thanks for all the info. The manufacturer's specs (1/1000" per inch and 220 weight oil) work well if your journals are in good condition. I guess I assumed your mill was old and possibly in rough condition, as many are. With bad journals (out of mfg spec), some added bearing clearance and a thicker oil will often allow an old mill to operate without scuffing (and heating) at the bearings. Do you have a temperature sensor riding on the journals? Paul

 

[smckennz]

Yes I modified the temperature sensors, from one per end to three PT100 per end. Temps are within about 2 deg C across each bearing. Drive end runs a little hotter probably because it has a bit more weight on it.

Cheers

Steve McKenzie