Advantages and Disadvantages of Parshall Flume | Parshall Flume Construction and Applications

Advantages and Disadvantages of Parshall Flume | Parshall Flume Construction and Applications

What is Parshall Flume?| Advantages and Disadvantages of Parshall Flume | Parshall Flume Construction and Applications

What is Parshall Flume?

The Parshall flume is an open channel flow measuring device used to measure surface water and irrigation flows.

The Parshall flume is a permanently installed hydraulic structure. It is used to calculate the volumetric flow rate of industrial discharges, municipal sewage lines, and influent/effluent flows in wastewater treatment plants.

The Parshall flume increases flow by contracting both parallel sidewalls and dropping the floor at the flume throat.

The depth of water at a specific place upstream of the flume mouth can be translated to a rate of flow under free-flow conditions.

Some states require the use of Parshall flumes in certain instances by law.

Parshall Flumes are a type of flume with a short throat. The Parshall Flume, which was invented in the 1920s, has become the most investigated type of flume, leading to its widespread acceptance and use in a wide range of applications.

The Parshall Flume is used to monitor open channel flows in a variety of applications in North America, ranging from water rights / irrigation to surface waters (creeks / streams / rivers) to municipal sewage.

Parshall Flumes Construction

Parshall Flumes were initially constructed of wood, concrete, or, for smaller flumes, sheet metal. Today, fiberglass is the material of choice since it is strong, easy to customize, has consistent dimensional tolerances, and is corrosion resistant.

Wood is used infrequently, while concrete is only used on huge flumes. Galvanized sheet is utilized for water rights and irrigation applications.

However, there are worries about dimensional tolerances and fabricator application competence. Furthermore, rust can build fast when the galvanization is worn away.

Stainless steel is the material of choice for applications requiring abrasion resistance or resistance to harsh chemical elements.

Application of Parshall Flumes

Parshall Flumes are used to measure a wide range of uses, including:

  • Wastewater treatment plant flows
  • Surface water measurement
  • Irrigation runoff
  • Storm water runoff
  • Dam seepage monitoring
  • Industrial pre-treatment discharges
  • Spring discharge
  • Leachate monitoring
  • Mine dewatering

Advantages and Disadvantages of Parshall Flume

 Advantages of Parshall Flume

The advantages of the Parshall flume are:

  • It passes sediment and small trash easily.
  • It requires only a small head loss.
  • It allows accurate flow measurements even when partially submerged.
  • Widely used / recognized
  • Good submergence resistance (in larger sizes)
  • Good solids passage
  • Flat-bottomed inlet (easier calibration)

Disadvantages of Parshall Flume

A disadvantage of the Parshall flume is that it is not accurate at low flow rates. It is therefore not entirely satisfactory for measuring widely fluctuating flow rates.

Parshall flume FAQs

1. What is the purpose of a Parshall flume?

It is used to estimate the volumetric flow rate of industrial discharges, municipal sewage lines, and influent/effluent flows in wastewater treatment plants.

The Parshall flume increases flow by contracting both parallel sidewalls and dropping the floor at the flume throat.

2. How do you measure stormwater runoff?

Measurements are commonly used to determine the amount of surface flow entering a storm sewer system, which could then be used to determine the volume available for infiltration.

This information is useful in planning the location and design of detention ponds or other possible treatment facilities.

3. What is a standard Parshall flume installation?

A standard installation has a square inlet and a 0.4-to-0.6-meter opening. The flume is usually constructed of fiberglass reinforced plastic and is permanently installed.

4. How much does a Parshall flume cost?

Price varies with size; some smaller flumes cost a few thousand dollars while larger ones can go for over $100,000.

5. Is there a typical construction schedule involved with a Parshall flume installation?

A structural design is prepared before the flume is built. This includes accurate design information and specifications, as well as allowing for labor and material handling during the fabrication phase.

The concrete foundation must also be engineered and outlined in detail so that crane placement can be planned, and so that future work does not extend into the excavation or rebar placement areas.

6. What are some future considerations for Parshall flume construction?

A number of recent advances have been made, including the development of a fiberglass reinforced plastic flume that is corrosion-resistant and has a high fire rating.

The fiberglass flume is also vandal-resistant and more impervious to chemicals than the concrete version. In addition, some flumes have been tested for air release in laboratory settings.

7. What are the advantages of using fiberglass flumes?

Fiberglass flumes are lighter, easier to install and modify, and will not rust. It is also preferred for future applications requiring abrasion resistance or the ability to withstand harsh chemical elements.

8. What are some disadvantages of using Parshall flume?

The primary disadvantage involves low flow rate measurements. The flume is not accurate at low flow rates. It is therefore not entirely satisfactory for measuring widely fluctuating flow rates.

9. How precise is a Parshall flume?

Under laboratory circumstances, Parshall Flumes can be calibrated to within +/- 2%. However, practical considerations such as approach flow, installation, and dimensional tolerances result in +/-5 percent free-flow accuracies.

10.  What is the difference between Weir and flume?

The most significant distinction between a weir and a flume is that a weir generates a pond upstream of the weir, but a flume requires far less upstream depth.

This frequently precludes weirs from being utilized in flat canals, ditches, or canals with limited upstream head.

11. How does a flume measure flow?

A Parshall Flume is a permanent hydraulic device used to monitor water flow in an open channel or a conduit that is not full.

The flume increases flow by contracting the parallel sides and lowering the floor elevation of the throat.

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