Flow Measurement

What is a paddlewheel flow meter?

This type of flow meter would use a simple paddle wheel design to do the flow measurement. The paddle wheel would convert the mechanical action of the paddle rotating in the liquid flow into a user-readable rate of flow. It can be considered as a type of turbine flow meter, this device is similar to the insertion type turbine flow meter. The major difference from the turbine type meter is that instead of a turbine blade a paddle wheel is used and the paddlewheel would be perpendicular to the flow and it would rotate like a steamboat paddle wheel. We can use this type of flow meter to determine the velocity of substances and we could get the volumetric data with the help of this measurement.

How does a paddle wheel flow meter works?

The major parts of a paddlewheel flow meters are a paddle wheel sensor, pipe fitting, and display controller. The paddlewheel flow meter has a rotating impeller with embedded magnets. The rotor and blades of the paddlewheel flow meter are perpendicular to the flow. So when the magnets in the blade spin past the sensor, the paddlewheel meter would generate a frequency and voltage which will be proportional to the flow rate. If the flow is fast then the frequency and the voltage will be high. The LCD display in this flow meter would indicate the flow rate. The paddlewheel flow meter can measure the flow rate of a wide variety of liquids including acid, solvents, and corrosive fluids.

 The paddle flow meter are available in two mechanical class and they are

  • Tangential flow paddle wheel meter with a water wheel structure
  • Axis flow paddlewheel flow meter, with a windmill structure

How to install a paddle wheel flow meter?

There are two types of paddle wheel sensor insertion and inline sensors, the inline paddle wheel sensor is used for smaller pipes. It contains a rotor assembly with the magnet sealed inside and the main body. The paddle wheel meters are designed to be inserted in a pipe fitting it could be either inline or insertion style. These are available with wide range of fitting styles, connection methods. The paddle wheel meter would need minimum run of straight pipe before and after the sensor. The paddle wheel flow meter must be installed with at least 10 pipe diameter of straight pipeline upstream and 5 pipe diameter downstream from the sensor to get proper operation. If there are obstructions then longer upstream straight run can be done.   

How to select a paddle wheel flow meter?

  • It must be selected according to the fluid like water or chemical
  • Flow velocity
  • Response time
  • The paddle material must be suitable for the application
  • We must consider the operating voltage and the current consumption

What are the advantages of paddle wheel flow meter?

  • Repeatability
  • It can detect near zero flow rate
  • Compact in size
  • Low cost

The paddle wheel flow meter can be used for corrosive liquids which is non-granular or non-viscous. It can be used to detect the instantaneous flow and accumulated flow. It can be used to adjust the valve too. The paddle wheel shaft is perpendicular to the flow and due to this it sustains less axial from the flow so less friction. This device has smaller number of blades so less force is required to turn the wheel, so because of this it is highly accurate and sensitive.

What are the disadvantages of paddle wheel sensor?

  • It is sensitive to foreign objects
  • Periodic maintenance is required because of the rotation of the paddlewheel
  • Inaccuracy could happen if the pipe isn’t full or due to the presence of air
  • A straight run of pipe is needed before and after the flow meter

What are the applications of paddle wheel flow meter?

  • Food and beverage industry
  • Water treatment industry
  • Pharmaceutical industry
  • Chemical industry
  • Semi-conductor industry
  • Dyeing industry
  • PCB-wet process control
  • Oil and gas industries

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