Question - Hydraulics - Pump stations with VFD

[Tarek Farah]

Hello guys,

I have a doubt about water supply systems (in this case is a main system that will feed minor pipe networks for irrigation purposes, but it could be any water supply system):

If you have a system that is fed by a pump station with a variable frequency drive -VFD is it need to have flow control valves at the discharge points ( I mean the points of water taking) to avoid system unbalancing due to demands higher than the designed flow rate?

I'm asking it because the variable frequency drives are normally set up to adjust the motor speed in function of the pressure in the system (I think its about the pressure in the discharge points).

And then I’m in doubt if when it is adjusting the pressure to a "more or less" constant value for a discharge point, isn't it automatically controlling the maximum water flow rate? (in normal operating conditions)

I’d really appreciate to have your opinions about it.

Thanks,

[jtorero]

And then I’m in doubt if when it is adjusting the pressure to a "more or less" constant value for a discharge point, isn't it automatically controlling the maximum water flow rate?

Yes it is!!

Using a VFD it's like changing the impeller diameter, the pump's curve will move upwards or downwards.

Regards.