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Multistage Impeller


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#1 betty

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Posted 09 January 2012 - 10:18 AM

As my info , the Multistage impeller for high flow and high pressure..

But how it will function ..

Could it be in Parallel?

Regards

#2 kkala

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Posted 09 January 2012 - 04:42 PM

Yes, there are multistage pumps with impellers in parallel (that is multiple shafts) for higher flow, as http://en.wikipedia....entrifugal_pump indicates in the para of multistage centrifugal pumps. But they must be rare, in comparison to multistage pumps with impellers in series. I have often seen the series option, but not understood to have seen the parallel. Pump handbook by Igor Karassik reports only impellers in series in Section 2.2, Centrifugal pump construction, classification and nomenclature (p. 2-32 of 1976 edition), an indication that this is the common case; even though impellers in parallel may be mentioned elsewhere.
Impellers in series increase total head, corresponding to pumps in series having same flow. As the liquid passes from each impeller, an additional head is added.
Impellers in parallel increase total flow, corresponding to pumps in parallel of same head each (see a.m. wikipedia ).
Assume two pumps in parallel, each delivering flow Q/2 against head H (head of the pump). Advantage may not so apparent, yet one pump of same speed would have bigger impeller (than the impeller of each pump)

Edited by kkala, 09 January 2012 - 05:42 PM.


#3 S.AHMAD

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Posted 09 January 2012 - 08:59 PM

1. Impellers in series will increase the discharge pressure, as mentioned by Fallah.
2. Impeller in parallel, for the same discharge pressure, will increase the volume flowrate (pump capacity)

#4 betty

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Posted 10 January 2012 - 03:33 AM

Dear Mr.
kkala &

S.AHMAD

The relation between pumps in series and parallel I know it very well..

But I heard that If we need high pressure with high flow then we have to use multi-implleres. ..

#5 kkala

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Posted 10 January 2012 - 06:25 AM

Impellers in series or parallel have some similarity to pumps in series or parallel correspondingly (how it will function..).
Required flow rate and head could give a more specific answer. As a preliminary choice, see "PumpSelectionCurve.pdf" attached to the post by S.AHMAD in http://www.cheresour...-or-centrifugal. Same diagram can be found in Perry, Section "Transport and storage of fluids", Pump selection, but in British units.

#6 S.AHMAD

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Posted 10 January 2012 - 07:31 PM

Betty
1. What you have heard about multi-impellers is right. We can have bigger volume and higher pressure by having more impellers in one single pump.
2. As mentioned by Kkala, two pump of single impeller in series gives similar characteristics to that of one pump with two impellers in series.
3. Take note that, I said similar but not necessarily the same.
4. The pump efficiency will be different.
5. It was also mentioned by Kkala that, one pump with two or more impeller in parallel is not normally used this is probably the efficiency is lower than that of single pump with bigger diameter.
6. We can get higher volume and pressure by choosing high diameter pump or higher speed. I believe that is more cost effective that multi-impellers pump.

#7 betty

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Posted 10 January 2012 - 11:32 PM

Mr.Kala and M.Ahmed

Thanks for such answers. I really appreciate such clarification..

Best Regards




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