Bearing selection for pump/compressor rotors...

[coteesh]

I am investigating what type of bearings I should use on a new rotary pump/compressor that I am helping to design. We require bearings for the shafts of the rotors. The rotor shafts range in size from 2 cm up to 30 cm in diameter. Each shaft will require 2 or 3 sets of bearings. The bearings will experience both radial and axial forces. Normal (radial) force on a single bearing is expected to range from a few hundred pounds (small rotors) up to around 100,000 lbs for the big rotors in the high-torque applications. The axial forces (along the shaft direction, perpendicular to radial) is expected to range from a few hundred pounds (2 cm rotor) up to 400,000 lbs (30 cm rotor) in high torque applications. We want bearings that can handle the following conditions: 1) “high speed / low torque” (minimal forces on bearings) and 2) “high speed / high torque” … and for each of these, be able to handle unsteady RPM. We expect there to be some vibration, but not too significant. We are interested in the temperature and lubrication requirements also.

We are in the early stages of development, but my best guess is that the rotational speeds may get as high as 1000 RPM for the big rotors, and up to 10,000 RPM for the little ones.

I am a only a recent Mechanical Engineering graduate, so I don’t have a lot of experience with selection of bearings, I do have a textbook that walks me through some of it, but I would like to get some reassurance before I rely on my book (Fundamentals of Machine Component Design, 3rd Edition - Robert C. Juvinall). I believe that roller element bearings would probably be desirable for this application. I would greatly appreciate guidance!!

One last question ... are there numbers that describe terminology such as “high speed, low torque” , “low speed, low torque” , etc. ?? These terms seem to be commonly used in practice, but I don’t know what they mean besides just a general feel. Actual numbers would be useful.

Regards,
Curtis Patterson

 

[sprintcar]

Contact your bearing vendors FIRST -
What they don't teach you in school is resource utilization.
Why spend weeks calculating what bearing you think you need when SKF, Timken, etc can look at your design and hand you the part numbers, fits, loads, L10 life, lubrication, etc. in a day or two.
Keep the wheels on the ground
Bob
showshine@aol.com

 

[dgallagher]

Agree with Sprintcar - once you've gotten information from a manufacturer, then a good tool to use is a software program called the Bearing Expert.

The Bearing Interchange is a database of over 1 million bearings and reports match up substitutes you may have in stock by providing all possible alternatives and can select best fit based on materials needed, durability and cost. Program also provides Vibration Fault Frequencies and harmonics for bearing diagnostics.

Link to info:

http://www.reliabilitydirect.com/vibrationmeterproducts/vibfrequency.htm

 

[vanstoja]

The maximum bearing loads for the 15cm rotor of 100,000 radial and 400,000 lbs axial seem rather huge for the shaft size and I wonder if rolling element bearings are even feasible. If you were using for the pump application, process fluid lubricated bearings (say water)a typical 50 psi specific bearing load limit would need roughly a 90 inch OD thrust runner and three 56 inch long radial bearings to support the maximum loads. Oil-lubricated bearings with typical specific load limits of about 400 psi would make the sizing problem somewhat more tractable but then you would need a separate oil supply and cooling system for the machines. Are you planning to provide a separate bearing lubrication system? vanstoja

 

I want information about the selection of the bearing for the expert system.
please reply me on my email address
shantaram_kasar@yahoo.com