Flow Measurement

What is a propeller flow meter and where is it used?

The propeller flow meters are widely used for irrigation water measurement, these flow meters can measure the flow with high accuracy and repeatability. The propeller flow meters can also be seen in many industrial applications. Mostly the propeller meters are installed in straight sections of pipelines. The propeller flow meter has rotating elements similar to the wheel in turbine meters. The rotation of the propeller is because of the fluid flow through the propeller and voltage pulses are generated when the propeller passes a magnetic or optical sensor. The frequency which is generated will be proportional to the flow rate of the fluid and the voltage that is generated will be according to the fluid flow rate. Mostly the propeller flow meters are used with water. The propeller flow meters are inline device that relates flow velocity and pipe cross-sectional area in order to measure the flow rate or volume.

How does a propeller flow meter work?

The propeller flow-meters rotating device is a propeller. This meter will be positioned in a flow stream so when the propeller or the blade rotates then it will be proportional to the flow. The propeller flow-meters have blades and they would rotate when the fluid flows through them. The rotation of the blades is interpreted by the totalizer and it would be mounted in the meter. This type of flow meter doesn’t need a power source for its operation. The propeller meter is of low cost and it only needs less maintenance.  

How to install a propeller flow meter?

The propeller meters can be installed in any position like vertical, horizontal, or at an angle. So we can install it according to our need but we must make sure the pipe must always be flowing full for proper measurement. The propeller meter must be installed at a certain meter from the valves, elbows, or other fittings that could disturb the flow. The propeller meters are installed in a way that the propeller is centered in the pipe with its centerline running on or parallel to the pipe axis. The propeller would be connected to the indicating head that can give the flow rate or volume.

All the propeller flow meters are calibrated for the full pipeline only, if less then the flow meter would over register the flow. Minimum line pressure is not required for an accurate measurement, only a full pipe is necessary. While installing the flow meter check the rate of the flow indicator. It should be stable to the point that it can be easily read. This type of flow meter can detect the flow speed so it will be affected by certain upstream disturbances and because of this, we must place the flow meter in the straight pipe run. This distance would be related to the pipe diameter. While installing the meter we must consider the upstream and downstream requirements and it could be in the manual.

What are the applications of propeller flow meters?

  

  • Multi-stage pump actuation and control
  • Irrigation system
  • Center pivot systems
  • Sprinkler irrigation system
  • Drip irrigation system
  • Water and wastewater management
  • Hot water and petroleum mixtures
  • Valve actuation and control
  • Process batching and chemical feed

Ashlin

post-graduate in Electronics & communication.

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