2 replies to this topic

[Mohd Rasool]

Dear all,
I have come across a Multistage (4 Stages) Vertical Centrifugal Pump Characteristic Curve, from which I have to note Shutt off head. Im really confused whether this charactersitic curve is for a single stage rated impeller dia or it is for all the four stages.
If it is for a single stage, what would be the total shutt off head; What would be the approach for stages with different impeller diameters and how characteristic curves would appear in such cases?

[kkala]

The performance curve at hand must be for the pump as a whole, all four stages included. Multistage pumps are not rear in refineries or chemical industries, never seen performance curve of a single stage. Just observe the notes of the performance curve at hand. If nothing is written that it concerns a single impeller (quite improbable, if it does), you can safely assume that it is for the whole pump. Besides the label should clarify, for example, that the performance curve is for pump model XXXX, where XXXX will be described as four stage pump in vendor's pamphlet or catalogue.
To estimate the "composite" performance curve out of individual impellers' curves must be complex and beyond chemical engineering activities, as indicated in http://www.weiroilan...%20ANALYSIS.PDF.
We could merely suppose that total head for impellers in series would be the sum of individual heads, but there are several head losses (e.g. slippage) familiar to those manufacturing pumps.
You can also bring an image of the performance curve to the forum with clear info about pump model, RPM, etc.

Edited by kkala, 24 October 2011 - 09:38 AM.

[S.AHMAD]

1. The pump performance characteristic is normally established at the manufacturer workshop and the owner engineer can witness the test before delivery to the site.
2. Therefore, the pump curve should be for the 4-stage pump, unless otherwise stated by the manufacturer.
3. For your knowledge, if 4 identical pump installed in series (equivalent to 4-stage pump), the shut-off pressure would be 4 times the individual pump shut-off pressure.