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Sr. Member / Supporter
Posts: 310
Reply with quote  #1 
Axial Thermal Growth


I'd like to learn from you the practice followed at your sites when you install small-medium horizontal machines and there is decent thermal growth. My interest is primarily related to the axial expansion and how you handle it assuming acommon coupling type (e.g. spacer with shim packs) and basic thrust bearing arrangement.

Horizontal and vertical growths are taken care usually by the alignment. For large machinery, DBSEs is carefully measured and adjusted.

How frequently do you encounter issues related to this subject?

Regards- Ali M. Al-Shurafa

Sr. Member
Posts: 647
Reply with quote  #2 
Sleeve bearing motors typically have 0.5" endplay and are held axially somewhere near the center of that endplay (and near magnetic center) by the driven equipment thrust bearing, via the coupling.  Thermal growth might move the rotor a wee bit off from stator magnetic center, but it's typically not a big deal.

Rolling bearing motors come in a lot of varieties... depends on the bearing configuration.   

Many motors  have fixed coupling-end bearing and floating opposite-end bearing... that opposite end bearing floats in the housing (with or without wavey washer).  We generally assume the growth between the fixed coupling-end bearing and the coupling is neglibible. 

Motors for belt drive may have fixed bearing on the outboard end and floating cylindrical roller on the inboard. But a small axial movement of the shaft extension due to growth is typically much less than sheave axial alignment tolerances.

We do have one family of motors (200hp 1800rpm Westinghouse) that has a cross locating arrangement of deep groove ball bearings with 0.050" endplay on the shaft extension (unusual).  I don't remember what type of coupling (gotta look that one up)

Sr. Member
Posts: 670
Reply with quote  #3 
in my experience is just like electricpete said, fixed bearing coupling/pulley side and 

for sleeve bearings, our procedure is to make marking of the magnetic center on unloaded condition, during the alignment keep this axial position during alignment and follow the manual for coupling axial play.

Sr. Member
Posts: 1,917
Reply with quote  #4 
In ships i have found generators connected by shafts to the main gbx and in the generator the outer bearing was the fixed one so thermal expands the shaft in to the gbx. no flexible couplings or expansion joints and after some years they had axial damage in the main gbx to the tune that they opened the top of the ship by cutting and pulled out the gbx for repair but it was supposed to be like that and could not be modified as it was stated in the generator OEM design..... So I guess they still keep doing that.
Good Vibrations since early 1950's, first patented vibrometer 1956 in the US.
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