shalow flow measurement in a DN200 pipe

[gnr86]

Hi guys,

We 're dealing with a project where flow measurment in a DN200 round pipe is
needed. The pipe carries wastewater to industry's treatment plant.

The thing is that ocasionally the flow stops, and then starts with a shalow flow
for a certain period of time. This means that we need to measure flow at very shalow flows... <= 1 cm, or something like that.
We have been searching at some suppliers for a Area Velocity flowmeters with submerged sensors (inside and at the bottom of the pipe), but all these measure above
1" = 2.54 cm. So, a flow of 1" , which can't be measured with the above devices, for about 2 hours it could give a big inaccuracy in our measurement!
Does anybody have an idea if there's a sensor that could meet the prementioned requirement, or at the end another way to deal with this fact?

Thanks much!

 

[hacksaw]

there are several options to measuring such flows but not with your imposed constraints

 

[ScottyUK]

Flume chamber and level transmitter?

 

[roydm]

As Scotty said,
A Parshal flume or V notch weir

 

[wafer71]

I have used a propeller flow meter with good success in similar applications. Gravity feed 24" water line with varying liquid height in the pipe. Large bore pipe to allow water to flow freely.