Bearing High Heat Application

[Geomar]

Hello Guy's
Please help concept design new product.
Application is a shaft with a 12" dia. impeller on the end extending into a hot oil at 375 deg. F. The shaft is 1"-1 1/8" in dia. at 700- 900 RPM. Seal is no problem avaliable from Parker, but the bearing is. What do I use as a bearing which should be close to the impeller to reduce the overhung load that will take the heat? Heat treatment stabilized ball bearings are only good to 125 deg. C which fall a little short of 190 C/375 F. Fan shaft bearing coolers can be used but it's not going to reduce the heat enough at the bearing due to conduction.

 

[dvd]

Look at Graphalloy or Dodge Solidlube bearings.

 

[Geomar]

I believe both of these are a bushing type bearing, what clearance is going to be required when the shaft is cold (rooom temp.)? The shaft can not be allowed to flop around at cold start-up.

 

[EdDanzer]

Have you looked at ceramic ball or roller bearings? You may be able to derate a larger standard cylindrical bearing if you know the radial load. I think SKF has a way to do that.

 

[savithri]

CERAMIC BUSH HOUSED INSIDE STAINLESS STEEL CASE CAN BE USED AT THE TEMPERATURE INDICATED.

SAVITHRI.

 

[Geomar]

Thank-you, for advise.
How much is the shaft going to grow in size from cold to hot?

 

[dvd]

The shaft is going to grow on the order of .002" in diameter. But the bearing will also grow and that amount is going to depend on the bearing you choose. The shaft is going to grow longitudinally from the temperature gradient and cause a thrust load on the bearings. Regardless of the type of bearing you choose you will need fixed and expansion type bearings on the shaft. It's really not all that hot. Why don't you just use a larger diameter shaft and move your inboard bearing outward some and add a heat slinger?

 

[Geomar]

Thanks dvd:
Coming to that conclusion, its not worth the hassel, move the bearings further outboard, make the shaft a little bigger for the extra load and put a heat slinger on the shaft, then the bearing lub. is not a problem.
Thanks every one for the help
Regards,
Geomar (George)