Gearbox labyrnith seal melted
Gearbox labyrnith seal melted
(OP)
Hi.
When we were overhauling a centrifugal compressor which is connected to a motor through a speed increaser (gearbox), we noticed when we opened the gearbox cover that there as some melted metal on the shaft just underneath gearbox labyrnith seal of the high speed shaft (5800 rpm). Why would the seal melt ?!
Regards,
When we were overhauling a centrifugal compressor which is connected to a motor through a speed increaser (gearbox), we noticed when we opened the gearbox cover that there as some melted metal on the shaft just underneath gearbox labyrnith seal of the high speed shaft (5800 rpm). Why would the seal melt ?!
Regards,





RE: Gearbox labyrnith seal melted
Not so obvious is why it got hot. A labyrinth seal should be non-contacting. You have to figure out if you have alignment issues, not enough clearance between the shaft and seal, or some other reason why the shaft would rub against the seal. I am assuming you saw rub marks on the shaft. If no rubbing was seen, did someone do welding on the gearbox without proper grounding?
RE: Gearbox labyrnith seal melted
Just a question, do you think that misalignment between the compressor and the gearbox might be the root cause ?!
RE: Gearbox labyrnith seal melted
It probably melted shortly after it seized from galling. Like PeteDB mentioned, get the alignment fixed and make sure you're not side-loading that seal. It may be as simple as adding a spider coupling in line if the motor doesn't face mount directly to the gearbox. Again I don't know what's already there.
James Spisich
Design Engineer, CSWP
RE: Gearbox labyrnith seal melted
To see the system configuration, please have a look at the attached image.
RE: Gearbox labyrnith seal melted
Have you measured this with your current setup?
James Spisich
Design Engineer, CSWP
RE: Gearbox labyrnith seal melted
Max axial misalignment (in) = 0.08
Max parallel misalignment (in) = 0.024
Max angular misalignment (degree) = 0.50
When we did the laser alignment we didn't record the amount of misalignment, we only corrected it.
RE: Gearbox labyrnith seal melted
James Spisich
Design Engineer, CSWP
RE: Gearbox labyrnith seal melted
RE: Gearbox labyrnith seal melted
Russell Giuliano
RE: Gearbox labyrnith seal melted
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Now you are faced with Quite a few "if"s, and they are all un-answerable now that repairs are made. A careful autopsy is important if a reasonable root cause is to be ascertained. A list of "coulda-beens" is not all that useful in preventing it happening again.
I'd use a feeler gage to probe around the labyrinth seal gap and test for fairly equal gap. If the g'box housing machining was done badly ( new or rebuilt) the labyrinth bore may not be so concentric with the bearing bores, and will rub even with nicely aligned shafts.