Flumes

TRACOM offers seven type of flumes for open channel flow monitoring: Parshall, Palmer-Bowlus, H-Type, Trapezoidal, Cutthroat, RBC, and Montana. Each flume has its own advantages and disadvantages and it is recommended that before selecting a flume that the characteristics of each flume be considered.

Parshall

• Most widely used type of flume for permanent installations
• Standard design conforms to U.S. Department of the Interior, Bureau of Reclamation, Water Measurement Manual
• Available in throat widths of 1” to 180”
• Resistant to the effects of submergence
• 50% for 1” - 3” flumes
• 60% for 6” and 9” flumes
• 70% for 12” - 96” flumes
• 80% for 120” - 600” flumes
• Self-cleaning in most circumstances (not recommend for sanitary use in 1” and 2” sizes)
• Available in nested configurations
• Available with end adapters to connect to existing pipe
• Simple flow meter calibration
• Maximum flow rates from 85.3 GPM – 467,200 GPM with standard wall heighths
• Installation requires drop in conduit invert from inlet to outlet

Palmer-Bowlus

• 4”-108” sizes available (sized by throat width)
• Three primary styles:
• 4D+1” (permanent style with integral approach section)
  Point of measurement inside of the flume
• 2D+1” (short sectioned flume with only the trapezoidal ramp)
  Point of measurement upstream of the flume
• Insert style (2D+1” length but no end flanges and O.D. of flume is I.D. of pipe)
  Potential problems with accuracy due to reduced flume width
• Available with bulkheads to connect to existing pipe
• 4D+1” – inlet and outlet
• 2D+1” – outlet only
• Insert style – N/A
• No invert drop required
• Easily installed in manholes or round bottom channel
• Maximum flow rates from 55.2 GPM – 198,535 GPM
• Proprietary design varies from manufacturer to manufacturer
• Smaller useful range of flows
• Sedimentation at lower flow velocities
• Requires 25 straight run pipe diameters upstream

HS / H / HL-Type

• Standard design conforms to U.S. Department of Agriculture, Field Manual for Research in Agricultural Hydrology
• Available in a wide range of sizes from 0.4’ HS – 4.0’ HL
• Developed for agricultural runoff
• Approach section and inlet bulkhead available for connection to existing pipe
• Simple flow meter calibration
• Flat bottom for self-cleaning of small debris
• Wide range of flows
• Maximum flow rates from 36.0 GPM – 52,509.6 GPM
• Discharge must be unimpeded or spill freely from flume
• Cannot operate under submerged conditions
• Require 3-5 times the maximum head in straight channel upstream of the flume

Trapezoidal

• Initially designed to measure flows in irrigation channels
• Conforms to the normal shape of ditches (minimizing transition)
• Operates under higher degrees of submergence than Parshall flumes
• Straight through bottom permits the passage of debris
• Excellent usable head at low flow rates
• Maximum flow rates from 43.0 GPM – 663.8 GPM (Small to Extra Large 60 Degree V Trapezoidal)
• End adapters are available for Small, Large, and Extra Large 60 Degree V Trapezoidal flumes to connect to existing pipe

Cutthroat

• Similar to Parshall flumes except with flat bottom and no extended throat
• Developed for use in flat gradient channels
• Operates satisfactorily under both free and submerged flow conditions
• Sized by flume length and throat width
• Simpler construction than Parshall flumes
• Simple flow meter calibration
• Flat bottom for self-cleaning of small debris (1” and 2” throat widths not recommended for sanitary flows)
• Maximum flow rates from 52.6 GPM – 43,494 GPM
• Not available with standard end adapters to connect to existing pipe
• Most common uses include stream gauging and flow splitting

RBC

• Developed for use in small furrows and unlined canals
• Simple construction
• Scaled versions of the general flume
• Five throat widths (50mm, 75mm, 100mm, 150mm, 200mm)
• Ideal for very low flow rates
• Maximum flow rates from 22.98 GPM – 790.79 GPM
• Inlet and outlet wingwalls recommended for use in unlined canals
• Portable
• Caution should be used in flows with solids

Montana

• Design is a Parshall flume with the throat and discharge sections removed
• Uses the same discharge table as a similarly sized Parshall flume
• Standard design conforms to U.S. Department of the Interior, Bureau of Reclamation, Water Measurement Manual
• Available in throat widths of 1” to 180”
• Self-cleaning in most circumstances (not recommend for sanitary use in 1” and 2” sizes)
• Available in nested configurations
• Available with inlet end adapter to connect to existing pipe
• Simple flow meter calibration
• Maximum flow rates from 85.3 GPM – 467,200 GPM
• Cannot withstand any degree of submergence
• Not commonly used