Explain about Turbine flow meter?


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Turbine flow meter

Principle:

Theturbine flowmeter is used for the measurement of liquid, gas and very low flow rates. It works on the basic principle of turbine.

Construction:

  • It consists of a multi-bladed rotor (turbine wheel) which is mounted at right angles to the axis of the flowing liquid, as shown in Fig.
  • The rotor is supported by ball or sleeve bearings on a shaft which is retained in the flowmeter housing by a shaft-support section. The rotor is free to rotate about its axis.

Working:

  • The flowing fluid impinges on the turbine blades (rotor), imparting a force to the blade surface which causes the rotation of the rotor.
  • The speed of rotor is directly proportional to the fluid velocity, and hence to volumetric flow rate when it is at a steady rotational speed.
  • The speed of rotation is monitored in most of the meters by a magnetic pickup coil, which is fitted to the outside of the meter housing.
  • The magnetic-pickup coil consists of a permanent magnet with coil windings which is mounted in close proximity to the rotor but internal to the fluid channel.
  • As each rotor blade passes the magnetic-pickup coil, it generate a voltage pulse which is a measure of the flow rate, and the total number of pulses give a measure of the total flow.
  • The electrical voltage pulses can be totalled; subtracted and manipulated by digital techniques so that a zero error characteristic of digital handling is provided from the pulse generator to the final read out.

The K factor (i e, the number of pulses generated per gallon of flow) is given as

K = (Tk x f) / Q

where,
K = pulses per volume unit, Tk =a time constant in min,
Q =a volumetric flow rate in gpm and f= frequency in Hz

Advantages:

  • No external power supply for Rotating vane and Woltman meters
  • Turbine flowmeters suitable for cryogenic liquids
  • Turbine flowmeters usable at extreme temperatures and pressures

Disadvantages:

  • Limited choice of materials
  • Only for low viscosities
  • Moving parts, wear
  • Sensitive to contamination
  • Axial flow totalizers are flow profile sensitive
  • Inlet and outlet sections required (not for rotating vane meters)
  • Affected by overloading and quick changes at high differential pressure, danger of over speeding
  • Vibration sensitive

Check out

>> Turbine Flow Meter Calibration Procedure


Turbine Flow Meter installation
Turbine Flow Meter Calibration Procedure