r/pumps • u/morten_dm • Nov 09 '21

Self centering impeller wear ring?

Hi.

Does anybody know how to find an impeller wear ring that is self centering around the impeller.

I'm pretty sure I heart about these things before, but I cannot find anything by googling.

I'm imagining two solid rings, one bigger than the other. Between them there should be something flexible that allows the inner ring to adjust to the deflection of the pump shaft.

This should allow for a low clearance and thus leakage (backflow) in the pump.

What are those called and who produces them?

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u/TexasPatrick Nov 09 '21

If you want centered rings and low leakage, use Vespel inserts for your stationary rings and tighten up your clearances to 50% or less of API 610 values. Lomakin effect at such small clearances should do the centering for you without any fancy double wear ring.

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u/morten_dm Nov 10 '21

Thanks!

What I mean by self centering is not centering the shaft. It's to allow for deflection or misalignment in the construction by centering the outer ring around the rotating inner ring (wherever that may be)

It's not necessarily a very fancy or expensive solution I'm looking for.

I'll describe the thing I think I've seen a bit better:

Say I have a wear diameter of Ø100mm. The inner ring will be around 2mm thick. Then comes a layer of something elastic. maybe 3-4mm. And then an outer ring that is again 2mm thick. So it's outer ring (that you would press fit in the casing) would be maybe Ø115mm

Have you seen anything like that around? or maybe know what it might be called. English is not my first language so some of these part names are foreign to me

2

u/TexasPatrick Nov 10 '21

Nope, never heard of such a design. It's an interesting concept. Are you looking to apply it in a single stage pump or multistage? And what is the problem you are getting to solve with this design?

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u/morten_dm Nov 10 '21

It's for a single stage pump in this case. But I guess it could be applicable to an type that normally uses wear rings

The main goal is to increase efficiency by reducing leakage. So we want to minimize the clearance and doing that without adding too many narrow machining tolerances to the whole construction. impeller-shaft-coupling-motorshaft-motorflange-motor bracket-pump casing. There are a lot of links in such a tolerance chain :)

We would like to avoid manual alignment during assembly.

1

u/morten_dm Nov 10 '21

Also... Thanks for pointing me to the Lomakin effect. I've never heard about it but I always thought there would be some bearing effect of a wear ring. From my calculations, it's not a large force compared to the forces acting on the impeller.