High temperature in the thrust bearing of the centrifugal compressor?
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During the last maintenance check, carbon buildup was found on the main thrust pads; the manufacturer recommended enlarging the return hole in the thrust bearing oil control ring (copper ring)； After reinstalling it and turning it on, the temperature remained very high, at 90°C, with an interlock threshold of 110°C. The pre-tension value of the coupling is a bit high (the standard pre-tension is 2.4 mm); could this affect the temperature of the main thrust bearing?
Is there anything wrong with the oil, such as viscosity or the right type?
The oil has not been tested; no one thought of a problem with the oil – it’s Great Wall 46# turbine oil
The pre-tension value of the coupling is too high; the gap left during installation was not correct. In my opinion, as the temperature of the unit rises, the expansion of the coupling continues to exert force on the main thrust component, resulting in a very small gap between the thrust plate and the main thrust element. This prevents lubricant from entering properly, thus preventing the formation of an adequate oil film. Another point is that lubricant inspections usually involve checking those five key items; carbon buildup occurs when the oil temperature is too high, causing the additives in the lubricant to precipitate out. If possible, change the oil. I hope this helps you.
The thrust bearing of this compressor is primarily supported from the outside. If excessive pre-tensioning is the cause, then it should be the secondary thrust pads that are overheating; but currently, it’s the primary thrust pads that are overheating? How to explain this? Is my understanding correct?
By \"the main thrust stop being on the outside,\" do you mean it is located near the coupling? If that’s the case, then when the coupling was first installed, the clearance might have been set too small, which continues to pull on the rotor
By the outer side, I mean the side that is not adjacent to the coupling, while the inner side is the side that is adjacent to the coupling. If it is the temperature of the inner thrust pad that is high, then pre-stretching could be a possible issue; but currently, it is the temperature of the main thrust pad that is high. I have encountered situations before where the pre-stretch was too large, but there were no issues with high temperatures in the thrust bearings. It seems there’s no way out now; the manufacturer sent a young guy who knows nothing about it, so there’s no hope
The axial thrust is too high; it’s a mounting issue – check the bearing shells at both ends
The reserved clearance was too small; once the temperature of the unit increased and the coupling expanded due to heat, it stretched. I have heard of this situation before. When installing the coupling, what is the gap in its free state compared to that of the coupling itself? Generally, the coupling allows for a variation of plus or minus 15 microns
I also want to ask this question: when we measure the gap between the couplings, do we push both rotors to the position of the main thrust pads? Or another location?