I am the systems integrator for a new water treatment plant project. It is a membrane filter system for drinking water. I am not doing the membrane filter control. The design calls for two raw water pumps with VFDs. There is also a raw water flow control valve and a flow meter for flow. I am used to constant speed pumps with a flow control valve and flow meter. Any idea why both are being used for this system?

Thanks,

Steve

 

Does sound a bit strange, is there any possibility of flow without the pumps running i,e, positive head from the supply point.
Its also possible the valve is used to throttle when the pump is running at minimum speed.
I would expect to see the valve at 100% normally with VFD control.

The engineering company must have the answer, ask them.

Roy