Parallel condition - Centrifugal pump

[EngMecBra]

Hi everybody!

Here I have a pump that will operate in a parallel condition in its discharge, but I don't know how add their respective curves B-C and B-D, please see attached file. The pump will operate with flow 100 m3/h, but 25 m3/h in B-C and 75 m3/h in B-D.

Who can help me?

I've already done the calculation for suction and for A-B.

If you need any additional information please let me know!

Tks a lot!

 

[EngMecBra]

See attached XLS file with data and graphics (curves).

For information, each part has a control valve, i.e., a control valve in B-C and another control valve in B-D, if it'll be necessary change system curves to get parallel condition curve "B-C + B-D".

regards

 

[LittleInch]

These are both very flat lines. The only common point is B which plainly needs to have the same head for both legs. Therefore your control valve at D and B will need to control on flow and your pump will need to deliver more than 26m (prob around 30) at 100 m3/hr to give the valves something to control on.. B-D will then need to increase by about 10m. The lines are so flat that you can only really control by use of control valves.

what does the pump curve look like?

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Artisi]

How about showing us the pump curves.
Plus a search in Eng-Tips and the internet will turn up more info than you can handle regarding parallel pumping. A bit of self education does wonders for learning.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[Pumpsonly]

You did not mention how much flow you need to feed through each branch.

The 2 system curve are too flat and with different static head. You will not get any flow in B-C until the system curve for B-D is more than 26 meter.
You need to increase the losses in the B-D branch by throttling or add a RO.


1) Tabulate the pump QH curve at the discharge point A.
2) Tabulate the system curve losses between A-B.
3) Table 1- table 2 will give you the available head of the pump at point B.

To plot the over all system curve from A to C + D, you add the flow rates of the 2 curves at the same head.
It is not possible in you case.
Plot the curve from table 3 onto the curve sheet and the intersections will give you the flow rate through each branch.