7 replies to this topic

[Tween]

Hi,

 

Need some clarifications on Performance curves of pumps in parallel operation in pipeline.

 

Scenario : Totatl demand is 400 m3/hr.Ordered 3 pumps with individual capacity (2+1) of 200 m3/hr.But i think we cannot meet that total demand of 400 m3/hr if both the pumps are in parallel, correct me if i am wrong.Theoritically total flow will be less than the capacity of individual when both are running.What is the solution for this?

 

1) Is Variable frequency drive helps in this case? If yes how?

 

2) To meet any specific requirement to be asked from manufacturer?

 

Please reply.

 

 

Tween

[fallah]

Tween,

 

You should specify working point conditions (400 m3/hr and corresponding Head based on system curve) for pump vendor. They would select two identical pumps with BEP at 200 m3/hr and specified Head. These two pumps will provide 400 m3/hr at that head in parallel configuration. Obviously, if each pump would be worked individually, will provide a capacity higher than 200 m3/hr which should be considered in relevant motor sizing and NPSHR determination. As far as I know, VFD has nothing to do with flow adjustment in parallel pumps configuration.

[Tween]

Thanks Fallah,

 

What i understand from your reply is, if the pump work individually the BEP point is at higher flow rate than while running in parallel.

 

So i need to choose the BEP for 400 m3/hr with the required head in composite curve instead of choosing the indivdual  pump with BEP at 200 m3/hr.

 

My vendor provided curve for individual pump with BEP at 200 m3/hr.Is that ok or i need to ask for only composite curve with two pumps.

 

 

Please correct if my underatanding is worng.

[Chemitofreak]

Pumps in parallel  operation:

 

While calculating the pump hydraulics all you have to consider a flow of 200 m3/hr for individual pump lines and 400 m3/hr for common header.

 

The pump shall have a flowrate of 200 m3/hr and the head will be defined by the frictional losses in the individual piping (200 m3/hr) and common header (400 m3/hr).

[fallah]

 

 

What i understand from your reply is, if the pump work individually the BEP point is at higher flow rate than while running in parallel.

 

So i need to choose the BEP for 400 m3/hr with the required head in composite curve instead of choosing the indivdual  pump with BEP at 200 m3/hr.

 

My vendor provided curve for individual pump with BEP at 200 m3/hr.Is that ok or i need to ask for only composite curve with two pumps.

 

 

Please correct if my underatanding is worng.

 

Tween,

 

BEP for individual pump is to be at 200 m3/hr; then individual working point in higher flow rate isn't BEP.

 

When BEP of each pump would be at 200 m3/h, then composite curve has a BEP at 400 m3/hr

 

You can ask vendor to provide both individual (with BEP at 200 m3/hr) and composite curves of pumps...

[Tween]

Thanks Fallah ji

[breizh]

http://www.mcnallyin...-html/15-01.htm

 

Hi,

another resource to visualize what Fallah explained to you .

 

Breizh

[Tween]

Thank you Breizh