Regarding the axial movement issue in multi-stage pumps
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For multi-stage pumps with semi-axial installation, after everything is set in place, the bearings are installed. The relative position between the balance disk and the shaft is fixed, as is the position of the inner ring of the bearings relative to the shaft. So what is the actual clearance for the movement of the balance disk? Is it the bearing clearance? Is it possible to balance the axial force relying only on bearings without installing a balance disc? The wear of the balance disc and balance sleeve is caused by a small clearance; but if the half-thrust clearance is large, can the clearance between the balance disc and balance sleeve be increased using bearings?
I would be grateful if experts could offer their guidance; the image is not related to the question. . .
The actual operating clearance of the balance disk is 0.1–0.2 mm. If there is no balance disc, the impellers must be arranged symmetrically; it is not possible to rely solely on bearings to bear the axial forces. The L10h calculated in this way will be very small. The total length of the rotor is the sum of the distances from the front and rear cover plates of the impeller to the guide vanes. Half of the clearance is taken to center the impeller flow channel. It cannot be adjusted by increasing the gap between the balance disc and the balance sleeve.
Hello, after the bearing is fixed, should the shaft remain stationary, or is there a clearance of 0.1~0.2 mm in back-to-back bearings?
During installation, the positioning surface of the outer ring of the bearing in the bearing holder is 0.1–0.2 mm larger than that of the shaft seat; when the bearing is secured using a round nut, the shaft moves backward by 0.1–0.2 mm. This amount represents the gap between the balance disk and the balance sleeve.
First, push all the shafts to the suction end; leave a gap of 10–20 turns between the outer ring of the bearing and the shaft shoulder, and then use round nuts to secure the entire shaft in place. Is this 10–20 gap filled in with a feeler gauge? Do back-to-back bearings have a clearance of 10 to 20 grades during operation? Why is there more air drawn in at the intake side than at the exhaust side after emerging halfway?
Push the rotor toward the drive end; this dimension can be measured with a depth gauge. Back-to-back bearings don’t have such a large clearance; usually, for back-to-back bearings, it’s preferable that the outer rings be able to slide relative to each other, which means they should be pre-tightened.
For back-to-back bearings with round nuts, a certain gap should be left between the bearing cover on this side and the outer ring of the bearing, usually around 0.05–0.1 mm.
Hello, my question still hasn’t been answered. The clearance of the balance disc is 10–20; the position of the balance disc relative to the shaft is relatively fixed. The inner ring of the bearing is fixed to the shaft, while the outer ring is fixed to the pump body. Thus, the only amount of movement possible is the axial play of the bearing. If this play isn’t that large, then how can the shaft move? How does the balance disc balance the axial force?
Is the entire shaft along with the bearing moving around inside the pump? Is the axial movement restricted by the balance disc and the bearing gland? I’m sorry; I tend to get fixated on things and ask detailed questions, so I apologize for the disturbance.
Do the balance sleeve and bearing cover define the axial movement range of the entire shaft? Is the bearing also shifting along with the bearing housing?