Parshall Flume
Parshall Flume
(OP)
I'm working for a client with an existing 10' Parshall flume they use to measure the volume of their industrial effluent discharge. I pulled field measurements and had a survey of the bottom profile done.
The dimensions appear very close to what I find in my reference book, however, I was wondering how much tolerance is allowable for varius dimensions yet still allow the flume to provide accurate flow measurements?
For example, the throat width was exactly 10'-0" at the entrance, but was 9'-10.5" at the exit.
The dimensions appear very close to what I find in my reference book, however, I was wondering how much tolerance is allowable for varius dimensions yet still allow the flume to provide accurate flow measurements?
For example, the throat width was exactly 10'-0" at the entrance, but was 9'-10.5" at the exit.





RE: Parshall Flume
RE: Parshall Flume
Flumes that are correctly manufactured and installed, are intrinsically accurate. A particular throat geometry will consistently produce a given change in depth at a given flow rate. The real issue is not accuracy but resolution. Therefore if resolution is expressed as a percentage of flow rate, flumes will measure higher flows with greater resolution than lower flows. For a given flume and flow meter combination it is not at all difficult to resolve flows to within +/- 5 % of rate over the range of 10 - 100% of maximum capacity. If one is careful setting up and calibrating the depth sensor, it is possible to achieve resolutions better than +/- 2% of flow rate over the same range. Below ten percent of maximum flow resolution of flow rate drops off quickly due to the fact that flow through a flume is not a linear function of depth.
http://www.accuraflo.com/faq.htm#accuracy
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