Journal Bearings Clearance Calculation

[Osvaldo]

TL;DR Summary

Clearance calculation

Would need to know radial clearance, recommended viscosity of oil and babbit alloy of the journal bearings of a gear reducer of following dimensions and specifications:

1400 HP
22300 RPM input
6400 RPM output
Journal diameter of input bearings 2 in, length 3 in, 2 bearings
Journal diameter of output bearings 3.25 in, length 3.5 in, 2 bearings
Babbitt metal tin base

 

[jedishrfu]

Isn't this information something you could get from a parts supplier or the manufacturer?

 

[Baluncore]

Is this a rebuild of an old machine from last century, or a new design? Make and model?
22300 RPM is too fast for an oil bath. Will the lubrication oil be pumped to the journals?
What temperature range is expected in the oil? Is there an oil cooler?

 

[jrmichler]

While there are published recommendations for journal bearing clearance, viscosity, and alloy, you will not find anything applicable to your situation because this is a high speed, high load application. Your best source is the reducer manufacturer. If that information is not available, and because of the high speed and load, a detailed bearing analysis is needed. An analysis of the detail necessary is beyond what we at PF can do for you.

If you really want to work on this problem, get a book on machine design. It will have a chapter on journal bearings. Study that first. Then, if you still want to work on it, and because this is a high speed high performance application, get a copy of Fundamental of Fluid Film Lubrication by Bernard J. Hamrock and study that. Since you have a master's degree, this is within your abilities.

And no, there are no shortcuts. Not for these loads and speeds. If you were designing babbit bearings for a 2000 RPM 1/2 hp grinder like the one in the foreground below, there would be shortcuts. But not for your speeds and loads.

 

[Osvaldo]

Below the reply to the questions posted about the equipment.
1. Lubrication is by a pressurized system
2. The gear reducer is Westech model 301-3 S/N 3302 Solar P/N 50583-8
3, This is a rebuilt reducer.
4. At this time, getting parts from abroad is very difficult, and so repair if of utmost importance.

 

[Baluncore]

@Osvaldo
Can you please confirm that the input drive rotates at over 22 thousand RPM ?
What type of gas turbine drives the reducer ?
If not driven by a gas turbine, what is the source of input drive ?

 

[Tom.G]

I checked the Westech website and found the contact information for them; e-mail, telephone, mailing address.

I did not find any technical information, maybe you will have better luck.

http://www.westech-inc.com/contact-us

Cheers,
Tom

 

[Osvaldo]

Baluncore:
Input RPM are 22300. The gas turbine is a Solar one. Do not know model. The gear reducer is driving a split multistage centrifugal pump.

 

[OCR]

The gas turbine is a Solar one. Do not know model.

FWIW, and that's not much, but it should be this model. . .

SATURN 20

Turbine Speed: 22,300 rpm.Carry on. . . . .

 

[Osvaldo]

jrmichler I was looking for advise from experienced people in the Mechanical Engineering area of journal bearings. Your post is not only unuseful but also improper. If you do not have the required experience, keep your advise for your self. I appreciate the other post the at least try to help.

 

[Tom.G]

RANT:
Considering that @jrmichler is among the top mechanical folks on the site, that seems a bit harsh. He even told you that you have a specialized/rare application and gave you two sources with the information you need.

If you are not willing to do the specialized research and learning you need, why do you think that volunteers here will do the work for you?
End Rant

If you can show significant effort in this specialized area, there is a much better chance of finding others here that can contribute in specific aspects.

Have Fun, and learn much!
Tom

 

[Joe591]

If the advise you get is wrong and that bearing set decides to seize after two weeks of operation, who is to blame? The problem with questions like this is always liability.
I worked for a boiler company for a long while. Maintenance was a big part of what we did.

A boiler has something called a induced draught fan. Its a big centrifugal fan that sits on top of the boiler. Its impeller weighs 300-400 kg. It spins at close to 1440 rpm. This particular one was driven by a 20 odd kW motor via a belt drive. One day the motors bearings decided to seize at full speed. The motor came to an abrupt halt and put such a harsh braking force on the fan impellor that it ripped off all four heavy duty v-belts on the v belt drive.
When high speed bearings go they tend to fail catastrophically and they tend to inflict severe damage on other components. Luckily Id fan impeller blades are made rough and strong and luckily the v belts snapped, otherwise we would have had to buy another impellor at great cost.

I doubt that your gas turbines blades are as rough and strong and they might take severe damage from a seized bearing along with other components. Depending on how badly things go, you might have to replace a lot of components. If things go badly enough the whole unit might be written off. And then who is to blame?Who has to pay? The people that advised you?

Nobody with any level of sanity is going to answer this question. You really are better of phoning the manufacturer...