Low flow rate, semi-open impeller clearance
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It is a small semi-open impeller centrifugal pump with a flow rate of 3.5, a head of 42, and a motor power of 3.0; it has 2 poles and is designed for use with clean water at normal temperatures. What is an appropriate range for the gap between the semi-open impeller and the front wear-resistant plate? Those with experience, please reply
The last edit to this post was made by 3983596_FPPZ on 2018-12-16 at 09:16. 1.2mm is a bit too large; for this small pump I specified a clearance of 0.5mm, and during testing the head difference between the two pumps was as much as ten meters
Check the degree of matching between the curvature of the wear-resistant plate and that of the impeller!
The curved surfaces of both pumps were machined using a machining center, and the differences between them are negligible. The curvature of the impellers and wear-resistant plates was determined using CAD, with precision down to the micron level
In other words, you didn’t check it before assembling! Is the impeller precision-cast? What is the thickness of the rear cover? Are there any secondary blades or reinforcing ribs?
No, because it’s not possible to see whether the fit is good just by a quick glance; one has to use special lighting to check. The curved surfaces were all manufactured using a machining center, and I believe they are properly fitted together. The impeller was cast, while the flow channels were made using a machining center. The thickness of the rear cover plate is 5 mm, and there are relatively large auxiliary blades on the back side
This post was last edited by pump-fans on 2018-12-16 at 16:09; the value of 0.4 mm was used. The calculated value should be the impeller diameter divided by 1000, multiplied by 0.6 + 0.15 millimeters. Taking a 200 impeller as an example, the clearance is generally around 0.27 mm; of course, this depends on whether the pump is operating far from its rated point – the further away, the larger the clearance should be. Previously, I would leave 0.4 millimeters, and that didn’t affect the volumetric efficiency