The 60-inch Parshall Flume is a large flume, usually shipped in two pieces, that is primarily used to measure flows for water rights and watershed measurement as well as at sewage treatment plants.    

Applications

The 60-inch Parshall Flume is useful in a number of applications:

• Surface water
  • Streams
  • Rivers
• Water rights
  • Canals
• Wastewater treatment plants​

Configurations

Openchannelflow offers the 60-inch Parshall Flume in two different configurations:

• Plain
  • For field formed inlet / outlet transitions
• Wing Walls
  • Inlet / outlet wing walls for rectangular channels

The flume is too large to easily integrate into a flow metering manhole.

Flume Accuracy

For a properly installed 60-inch Parshall Flume, it is typical to expect accuracies of +/-5% (ASTM D1941).  Laboratory investigations have shown greater accuracy (+/-2%), but once dimensional tolerances, upstream conditions, and the installation itself are considered, +/-5% is more realistic to expect.

Should the flume ever experience submergence or shift out of position, corrections for both.

Flume Dimensions

ASTM D1941 requires that the dimensions of Parshall Flumes be within +/-2% of nominal for the flume to be accurate.    

Free-Flow Equation

For a Parshall Flume the general free-flow equation is:

For a 60-inch Parshall Flume:

Minimum Head (ft)	0.20	Minimum Head (m)	0.0610
Minimum Flow Rate (cfs)	1.555	Minimum Flow Rate (l/s)	44.04
Maximum Head (ft)	2.50	Maximum Head (m)	0.7620
Maximum Flow Rate (cfs)	80.53	Maximum Flow Rate (l/s)	2425
Equation (cfs, ft)	30*H1.587	Equation (l/s, m)	3732*H1.587

Discharge Table

The flow-vs-head table for the 60-inch Parshall Flume is available for download. 

The table provides:

• Plan view of the flume showing the point of measurement (H_a) 
• Discharge equations 
• Free flow accuracy
• Submergence transition (S_t)
• Source for the flow table 

Materials

Openchannelflow offers 60-inch Parshall Flume in four different materials:

• Fiberglass (FRP)
  • Lightweight and customizable
  • Two-piece construction
• Galvanized steel
  • Economical
  • One-piece construction available
• Stainless steel
  • Greatest resistance to abrasion and corrosion
  • One-piece construction available

Submergence Transition

Submergence in a flume occurs when the downstream conditions restrict the flow out of the flume.  

While negligible at first, as the submergence increases a point is reached where the actual flow rate and the indicated flow rates are sufficiently different that a correction has to be made. This point is termed the submergence transition (S_t).

The submergence transition (S_t) for the medium sized Parshall Flumes like the 60-inch is 70%.  At or above this point and the indicated discharge needs to be corrected to reflect the actual discharge.