Sizing of balance tanks for water distribution systems

[Zhukowski]

Hi, how would you size the balance tank?

Here's a pump station delivering 40m head and 1000 l/s down a main line 45km long running mostly down hill with beaches off to outlets on both sides.

The pumps are variable speed. Does the system need a balance tank? What are the considerations in sizing a balancing tank?

 

[bimr]

A balance tank is probably not necessary.

[li]Are you sure about the flow rate? 1,000 l/s is a large flow.[/li]
[li]What is the elevation difference?[/li]
[li]What is the pipeline size?[/li]
[li]Is this seasonal?[/li]

 

[Zhukowski]

Yes, the flow will be big. We're taking water out of a river for irrigation and I've since convinced myself that I will be safer a balance tank. There's a rise just in front of the main pump station that will be the right spot for it.

From the pump station the pipe line diameter will initially be 710, then it will reduce in stages to DN630, DN 560, DN500... etc. after the take-off Tees. Demand will be seasonal for only 6-7 months of the year, the pipeline may be dry after that.

Any input in what are the considerations in sizing a balancing tank would be greatly appreciated.

 

[bimr]

If the system consists only of a pump station and pipeline, there is no reason for a balancing tank. The VFD's that you mentioned will be able to ramp flows up or down. Even without the VFD's, the balancing tank is not necessary.

 

[Zhukowski]

Thanks bimr, that's what I was thinking too. There are others here (non-engineers) that are convinced we need a balancing tank, is there any resourses or publication on this out there I can use to either justify the need for a balancing thank or not?

We will get the system modelled at a later stage, but I don't have access to those engineers right now and I need a cost estimate to get the project over the line.

 

[bimr]

You might try Pumping Station Design by Garr Jones.

You may wish to confirm the process requirements for the "balance tank". The term "balance tank" seems to be associated with UK practice.

Sense this is a seasonal application, there is no need for storage, there is no need to maintain a constant system pressure, and the pumping application is very large, any type of balancing tank would not be warranted.

 

[Zhukowski]

Thanks bimr for your input, I'll look into your ref.