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Flowmeter Presentation

Flowmeter Selection Guide

James Thompson

on 16 September 2012

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Transcript of Flowmeter Presentation

Selection Guide Flowmeter Head Dependent The orifice plate introduces an artificial pressure drop, using a differential pressure gauge it is possible to measure and calculate the flowrate. The size of the pressure drop is dependent on the diameter of the orifice.
Advantage: No moving parts, liquids & Gases
Disadvantage: Permenant pressure loss, Effected by density, viscosity & wear
Source: www.Wikipedia.com, Grip Manual Orifice Plate Like the orifice plate, the venturi works with the differential pressure drop. The Venturi restricts the flow of fluid causing a pressure drop. As the velocity of the fluid increases with the narrowing of the tube the pressure drops. The comparison of the two pressure measurements is used to calculate the flowrate.
Advantage: Efficient, Large diameters, liquids & gases
Disadvantage: Effected by density, viscocity & wear
Source: www.wikipedia.com, www.omega.com Venturi Tubes The flow nozzle is the exact same operation as the orifice plate, with a more robust construction. This make the nozzle more resistant to wear.
Rangeability: 5:1, <1%
Advantage: No moving Parts, Liquids & Gases, efficient
Disadvantage: Premenant Pressure Loss, Effected by wear, density & viscocity
Source: www.flowmeter.com, www.wikipedia.com Flow Nozzles The pitot tube is embedded in the pipe, with the leading edge of the pitot facing upstream of the flow. The pressure differential from the pipe pressure is used to calculate the flow rate.
Advantage: No pressure loss, Accurate Measurement
Disadvantage: Clean fluids only
Source: www.flowmeter.com Pitot Tubes & Annubars There are a number of positive displacement flow meters employed in industry. The most common being oval geared.. The basic operation is a set volume of fluid is pumped through the flow meter, with each revolution of the gear or piston the flowrate can be calculated.
Advantage: Density and viscose fluids, linear output
Disadvantage: Large pressure loss, clean fluid only, moving parts
Source: www.flowmeter.com, www.wikipedia.com Positive Displacment The rotameter is a angled glass with a rotating float mounted in the center. The glass tube is to see the level of the float. The float rises as the flow rate increases with the angled tube wall allowing a avriable amount pass through, this allows for a linear output.
Rangeability: 8:1, 2.5%
Advantage: linear ouptut, low cost
Disadvantage: moving parts, clean fluid only,density , vicosity & wear effected
Source: www.vega.com, www.wikipedia.com, www.flowmeter.com Variable Area Electronic Flow
Measurement Using Faradays law of Electromagnetic Induction a conductive
liquid moving through a mgnetic field will cause a potential diffevence
between the elctrodes. The velocity of the fluid is proportional
to the signal voltage generated.
Rangeability: 20:1 Turn Down or better, 1%
Advantage: Does not obstruct flow, can be used with clean,
sanitary, dirty, corrosive and abrasive liquids. Linear feed back.
Limited upstream and downstream insertion of probes, limited straight pipe run.
Disadvantage: Liquid must be conductive, wearing of electrodes.Almost any liquids
Source: www.abbaustralia.com.au, www.flowmeters.com Magnetic Flow Meter The turbine meter uses a bladed wheel, the flow of the liquid rotates the wheel . The rotation speed is directly proportional to the flow velocity.. A proximity sensor gives a pulse train output.
Rangeability: 10:1, 0.25%
Advantage: Rangeability, low maintenance, linear output
Disadvantage: Moving parts, density dependent, wear on parts
Source: Grips Manual, www.Wikipedia.com, www.omega.com Turbine Flow Meter The vortex meter uses a non-streamline bluff body within the flow of the fluid. Vortices form behind the bluff body ion an alternating pattern. This frequency is used to measure flowrate. The output is directly proportional to the Flow velocity.
Advantage: No moving parts, linear output,low cost
Disadvantage: Effected by vibration & viscosity
Source: www.wikipedia.com Vortex Flow Meter Ultrasonic sound waves are propagated through the fluid, the time of flight or Doppler effect can then be measured. The time of flight is measured between two transivers placed at an angle in the pipe, the differential time of flight between the downstream and upstream is measured, the faster the flow the larger the differential. The Doppler effect is measure when particulate matter is present in the fluid or slurry, the sound waves are reflected back to the source and the difference is measured to calculate the flow velocity.
Advantage: Non-intrusive, no pressure loss, bidirectional flow
Disadvantage: High cost, must be full pipe, no gas or bubbles, straight pipe install
Application: Can be install with no intrusion into the pipe, Ultrasonic Flow Meter Using Newtons Second Law ( F=ma),
a fluid is accelerated around a loop or C section
and the resulting twsiting of the section of pipe causes a vibration.
The frequency of the vibration is inversley proportional to the
density of fluid and directley proportional to the phase angle of the twist.
Rangeability: 100:1, 0.5%
Advantage: No moving parts, suitable for gas and liquid, Bidirectional flow
Disadvantage: High cost, must be full pipe, no bubbles, pressure loss
Application: Used for accurate, measurement of virtualy any fluid with a known density.
Source: www.abbaustralia.com.au, www.flowmeters.com Coriolis Flow Meter
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