7313 BECBM housing inner diameter abutment limit? What is the max?

[Mech5656]

Hello All,

We are repairing a pump and bearing housing bore against which two thrust bearings sit (7313 BECBM bearings) was machined oversized by 0.030 diametrical. SKF recommends that bore to be max 133 mm (5.236 inches) , as shown in attached picture. That bore is machined to 5.266”. My question is: is it still acceptable? Can it still be used?

 

[Mech5656]

If you can suggest reading technical papers and perform calculations, please guide me. I am willing to do that.

 

[TugboatEng]

My guess for the MAX abutment diameter is that the contact stresses become very high at rated load. If you're operating below rated load you may be able to get away with less support from the abutment. You may be able to compare the loss of abutment area in proportion to your load factor. Don't forget to subtract the bearing race corner radius when calculating contact area of your abutment.

 

[geesaman.d]

Agree with Tugboat - it will be fine if you're expected bearing life is in the ,000's of hours rather than the static load rating.

Also depends on thrust load - if this bearing is loaded in pure thrust, or the other end of the bearing is clamped down via a threaded device, it could generate very high axial forces that would distort the bearing.

If you think you need the thrust capacity you might bore out to full diameter for a few mm and install a step spacer that has the Db for its ID. I'd make the spacer thickness = (Db-D)

 

[Mech5656]

Hello TugboatEng:

Thank you for replying to this post. I really need to come up with some calculation to confirm this will actually work (in oppose to intuition based decision). So please guide me in that direction.

I can calculate the area using A= pi X (r^2-R^2)
I will subtract the radius. Can you help in finding the load factor? Is this a value that comes from bearing OEM or I can calculate it?

“You may be able to compare the loss of abutment area in proportion to your load factor”

 

[TugboatEng]

If your bearing has a maximum load rating of 100 and your system only loads it to 20 then I would assume you need 20% of the abutment area to maintain the same maximum pressure as called out by the bearing manufacturer.