Why do we have large coupling floats when the compressor barrel maximum end float is 0.8 mm ??
Why do we have large coupling floats when the compressor barrel maximum end float is 0.8 mm ??
(OP)
Hi everyone, We have a couple of steam turbines in our plant that are used to run multi-stage compressors. Now there are gear/spline couplings between each barrel of a compressor. My question is that what is the purpose of having large coupling floats of around 15 mm or more when the axial float of a barrel's shaft could be max 0.8 mm due to its thrust bearing. Is there a reason behind having such large coupling floats??
Thanks in advance!!
Thanks in advance!!

RE: Why do we have large coupling floats when the compressor barrel maximum end float is 0.8 mm ??
If you add a second compressor case driven off the back end of the first one, you have a challenge. The thermal growth of the first compressor is all directed at that second coupling. Depending on the length of the first compressor and the temperature it runs, this can easily be several millimeters. To accommodate this movement you either have to pre-stretch the coupling, or use a gear or spline coupling that allows for that much movement.
Provide the configuration of your machine train with the locations of the thrust bearings and the case keys and pins along with the process temperatures if you want a more detailed explanation.
Johnny Pellin
RE: Why do we have large coupling floats when the compressor barrel maximum end float is 0.8 mm ??
So as I understand from your post, the rotor of each barrel expands depending on the temperature along with the casing. This is why the couplings have large axial floats. But does this thermal expansion not affect the relatively smaller thrust bearing clearance of each barrel?
Thanks again!!
RE: Why do we have large coupling floats when the compressor barrel maximum end float is 0.8 mm ??
Johnny Pellin
RE: Why do we have large coupling floats when the compressor barrel maximum end float is 0.8 mm ??