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Venturi Flow Meters

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Venturi flow meters are based on the concept of the Venturi effect, which states that a reduction in fluid pressure occurs when a fluid flows through a constricted section of a pipe. The fluid’s velocity increases as it passes through the constriction, following the principle of the conservation of mechanical energy. The amount of energy accumulated by the increased velocity is balanced by a drop in pressure. A measurement of the change in pressure provides the flow rate of the fluid. Read More…

Venturi Flow Meters Venturi flow meters, or simply venturi meters, are devices used to measure the flow rate of a variety of fluids in many different applications. This type of flowmeter is commonly used in plumbing applications and applications involving flowing water, propane, and oil. However, venturi meters can be used to measure the flow rate of gaseous fluids as well.
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Leading Manufacturers

Monterey, CA  |  831-373-0200

Sierra manufacturers high performance mass flow meters and controllers for nearly any gas, liquid or steam. Customers choose Sierra when they need an accurate and repeatable flow measurement, short delivery lead times, expert flow advice and long term support. When it matters, choose Sierra. Visit www.sierrainstruments.com.

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Sierra Instruments $$$

Sturtevant, WI  |  262-886-2695

SIKA is a developer and manufacturer of flow control products and a wide variety of other measuring and monitoring systems. Our inventory includes flow sensors, flow meters, flow switches, and many more. We know that flow solutions aren't one-size-fits-all, which is why we provide consultation and flow management solutions that are individualized and customized to your requirements. When you choose SIKA, you will receive efficient, durable products and customer service tailored to your needs.

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SIKA USA $$$

Cranston, RI  |  877-737-3569

Primary Flow Signal offers a wide range of flow meters and measurement devices. Among this product offering are flow meters for pressurized line fluids (liquid, gas, steam); rectangular conduit meters; bidirectional flow meters; open channel flow meters and more.

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Primary Flow Signal, Inc. $$$

Huntersville, NC  |  800-325-1405

The flow meters that we are able to provide will withstand the tests of time in order to provide a long lasting value! We have locations in thirty five countries worldwide and we are dedicated to being wherever you need us to be! We have the knowledge and the capability to work with you closely in order to come up with the perfect product to suit your needs! Visit our website today to learn more about what we may do for you!

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Burkert Fluid Control Systems $$$

Acworth, GA  |  770-917-0940

Flow Network specializes in measurement and control of Flow, Pressure, Temperature, and Level. Local Stock and Technical Support along with competitive prices.

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Flow Network $$$
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Venturi Flow Meter

The pressure drop created by a Venturi flow meter is measured using a differential manometer pressure sensor. Calibration of the pressure drop is the flow rate of a fluid.

Bernoulli’s Principle

Bernoulli's Principle, or the Bernoulli effect, is one of the most important concepts regarding fluid dynamics and the relationship between fluid flow and fluid pressure. Fluid dynamics is the study of moving fluids, which is an essential aspect in regard to flow meters.

Swiss physicist Daniel Bernoulli developed the theory that if a fluid's speed increases, its static pressure and potential energy must decrease to compensate. This aspect of fluid theory relates to Venturi flow meters in that the constriction in the flow meter increases the velocity of a fluid. By doing so, the pressure in the fluid drops. The difference in the pressure outside and inside the constriction provides the necessary data to determine the flow rate.

Venturi Flow Meter Construction

Venturi flow meters have a simple design, with each component of the flow meter arranged systematically. The parts of a Venturi flow meter include a converging cone, cylindrical throat, and diverging cone.

Venturi Flow Meter Construction

Converging Cone

The converging cone has a conical shape to connect to the throat and is attached to the inlet pipe or upstream flow. Its area decreases as its length approaches the connection to the throat. The angle of convergence is 20° to 22°, which is limited to avoid vena contracta. The decrease in the area of the converging cone causes the velocity of the fluid to increase and the pressure to decrease.

Cylindrical Throat

The cylindrical throat in the middle of a venturi flow meter is a major part of its working mechanism. The diameter of the throat is 0.25 to 0.75 of the inlet pipe's diameter and is constant throughout its length. The throat's diameter is designed to increase fluid velocity and decrease fluid pressure, which is below vapor pressure resulting in cavitation.

Diverging Cone

The diverging cone is the third and final part of a Venturi flow meter attached to the outlet pipe. From the beginning to the end of its length, its diameter increases at an angle of 5° to 15°. The diverging cone's small angle avoids flow separation and prevents eddies that can result in a loss of flow energy.

Differential Manometers

Differential manometers measure the pressure between a Venturi flow meter's convergent cone and cylindrical throat. They are ideal for Venturi flow meters since they are a method for pressure comparison and not a pressure-measuring instrument. The two types of differential manometers are U tubes and inverted U tubes.

U Tube

U tube differential manometers have a glass tube bent into a U shape, with the ends of the U shape connected to two points on a Venturi flow meter. The U glass tubing is filled with a manometric fluid, mainly Mercury, with a specific gravity higher than the liquid in the pipe. In the case of Venturi flow meters, one limb of the manometer is connected to the convergent cone with the other limb connected to the throat. The level of manometric fluid will be lower in the convergent cone than in the throat.

Differential Manometer Attached to a Venturi Flow Meter

Inverted U Tube

An inverted U tube manometer follows the same principle as a U tube manometer except that it is attached above the Venturi flow meter and the horizontal pipe. It uses a lighter manometer liquid to prevent the liquid from entering the flow stream. As with a U tube manometer, the limbs of the tube are connected to the convergent cone and throat of the Venturi flow meter.

Benefits of a Venturi Flow Meter

Venturi flow meters are a versatile and adaptive solution for flow measurement that can fit any defined space and are a reliable method for billing or custody transfer. They can be oriented on any plane and accurately measure regardless of a fluid's directional flow.

Advantages of Venturi Flow Meters:

  • Simplicity of Design
  • Durability
  • Long Life of Usefulness
  • Exceptional Accuracy
  • Compact Shape
  • Cannot Clog
  • Very Little Maintenance
  • Easy Installation

Venturi Flow Meter Informational Video

 

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