WHAT IS FLOW METER

FLOW MEASUREMENT 

Quantification of movement of  fluid can be defined as flow  

• Industrial flow measurements include measuring of flow rate of solids, liquids and gases

• There are two basic ways of measuring flow ; one on volumetric basis and the other on weight basis. Solid materials are measured in terms of either weight per unit time or mass per unit time.

• Very rarely solid quantity is measured in terms of volume. Liquids are measured either in volume rate or in weight rate. Gases are normally measured in volume rate

• Fluids are classified into two types, namely incompressible and compressible. Fluids in liquid phase are incompressible whereas fluids in gaseous phase are compressible

Units of fluids

• Solids - Normally expressed in weight rate like Tonnes/hour, Kg/minute etc.

• Liquids- Expressed both in weight rate and in volume rate. Tonnes/hour, Kg/minute, litres/hour, litres/minute, m3/hour etc.

• Gases - Expressed in volume rate at NTP or STP like Std m3/hour, Nm3/hour etc.

• Steam- Expressed in weight rate like Tonnes/hour, Kg/minutes etc. Steam density at different temperatures and pressures vary. Hence the measurement is converted into weight rate of water which is used to produce steam at the point of measurement. 

Measurement of flow

• Flowmeter is a device that measures the rate of flow or quantity of a moving fluid in an open or closed conduit. Flow measuring devices are generally classified into four groups.

•  Mechanical type flow meters. Fixed restriction variable head type flow meters using different sensors like orifice plate, venturi tube, flow nozzle, pitot tube, dall tube, quantity meters like positive displacement meters, mass flow meters,etc. fall under mechanical type flow meters.

•  Inferential type flow meters. Variable area flowmeters (Rotameters), turbine flow meter, target flowmeters, etc.

• Electrical type flow meters. Electromagnetic flow meter, Ultrasonic flow meter, Laser doppler Anemometers, etc. fall under electrical type flow meters.

• Other flow meters. Purge flow regulators, Flow meters for Solids flow measurement, Cross-correlation flow meter, vortex shedding flow meters, flow-switches,etc.

Classification of flow meter based on

•  Head type flow meter based on differential pressure measure measurement

-  Orifice plate

-  Venture  tube

-  Flow nozzle

-  Pitot tube 

•  Electromagnetic flowmeter

•  Rotameter (variable area meter )

•  Mechanical flow meter

      -   Positive displacement

      -   Turbine flow meter

•  Anemometer

      -  Cup type anemometer

      -  Hotwire anemometer

•  Ultrasonic flow meter

•  Vortex flowmeter

Necessity of flow measurement 

• Construction purpose

• To store the water for proper utilization

• To know the liquid volume and flow rate

• Laboratory purpose