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Panduan memilih tipe flow meter

After exploring how each flow meter works the way it does, learn more about which is the best fit for your needs and why. The price of the meter technology is one aspect to consider as well as installation and life cycle costs for the total ownership cost (includes factors such as footprint, flow conditioning, maintenance and calibration requirements).

1. Coriolis – $$$, total cost $$

Accuracy 0.05%

Advantages

  • Best measurement accuracy

  • Measures mass flow, liquid density and temperature

  • Flow profile insensitive

  • Unaffected by changes in temperature and pressure

  • Best rate of turndown

  • Suitable for gas, liquids, or slurry measurement

  • Able to measure high viscous fluids

  • Bi-directional

  • Low maintenance

  • Highly repeatable

  • Reliable

Disadvantages

  • Pressure drop might be higher (appropriate sizing mitigates)

  • Susceptible to severe system noise

  • Limited in large line sizes (>12″)

  • Low flow rates may result in lower measurement accuracy

Typical Applications

Custody transfer by mass and/or volume, precision batching, filling/dispensing, loading/unloading, continuous process control/monitoring, mass balance, density and/or concentration measurement, blending, utility metering, chemical injection, allocation, fuel consumption

2. Magnetic – $$, total cost $

Accuracy 0.15%

Advantages

  • Not constrained by Reynolds number or flow profiles

  • Immune to process variable changes such as temperature

  • High range of turndown

  • Negligible pressure loss with no obstructions

  • Able to handle large particles and chemicals

  • Not sensitive to variation in fluid velocity

  • Large line sizes

  • Variety of wetted path materials

  • Low power

  • Bi-directional

Disadvantages

  • Unable to measure gases and hydrocarbons

  • Typical minimum fluid conductance of 5 microsiemens (µS) required

  • Low conductivity versions available for fluid conductivities as low as 0.1 microsiemens (µS)

  • Electronics must be on same ground potential as the process

  • Use caution if installing near high voltage equipment to ensure proper meter isolation and process reference

  • Potential issues with electrode coating

Typical Applications

Conductive fluids in batching, filling/dispensing, continuous process control, utility metering, loading/unloading

3. Positive Displacement (PD) – $$, total cost $$

Accuracy 0.1%-2.0% depending on type

Advantages

  • Well understood and widely used technology

  • High turndown capacity

  • Suitable for high pressure applications

  • Relatively inexpensive and easy to install

Disadvantages

  • Frequent maintenance required

  • Potential for back flow from larger particle block

  • Inaccuracies

Typical Applications

Custody transfer by volume, batching, dispensing, allocation, chemical injection, fuel measurement, high pressure, hydraulic testing

4. Turbine – $, total cost $$

Accuracy 0.25%

Advantages

  • High accuracy and repeatability with clean fluids

  • High pressure and temperature tolerance

  • Fast response rate

Disadvantages

  • Two-phase flows may cause inaccuracies

  • Frequent maintenance required

  • Installation in small areas can be difficult

  • Wear out with non-lubricating fluids

  • Accuracy impacted by fluid characteristics (i.e. viscosity)

Typical Applications

Custody transfer by volume, batching, filling/dispensing, mass balance, blending, allocation, process control/monitoring

5. Ultrasonic – $$$, total cost $$$

Accuracy Wetted: 1% -2%, Non-invasive: 3% -10%

Advantages

  • Measures both liquids and gases

  • Reduced maintenance

  • No pressure drop

  • High turndown

  • Bi-directional

  • Large line sizes

Disadvantages

  • Partially filled pipes cause signal loss and lead to difficulty measuring

  • Transducer coatings can deflect beam and corrupt measurement

  • Process temperature can affect sound velocity and ultrasonic beam angle

  • Multiphase flow can cause error

Applications

Custody transfer by volume, precision batching, loading/unloading, continuous process control, mass balance, blending, utility metering, allocation

6. Vortex – $$, total cost $

Volumetric flow accuracy: 0.65% (liquid), 1.0% (gas)

Mass flow accuracy (temperature compensated): 2.0%

Advantages

  • 2-wire configuration means lower cost

  • 25%-40% reduced installation expense

  • Performs in extreme conditions

  • No field calibration required

  • Less leak potential, so fewer emissions

  • Wide flow range accuracy

  • No moving parts

Disadvantages

  • Not for low flow applications

  • Unsuitable for high viscosity fluids

  • Inaccurate in high vibration environments

Typical Applications

Steam, gas and liquid measurement in batching, filling/dispensing, continuous process control, utility metering

7. Differential Pressure (DP) flow – $, installed cost $$

Accuracy 1%

Advantages

  • Well understood and widely used technology

  • Established custody transfer and flow measurement standards

  • Wide variety of primary elements for multiple application suitability

  • Cost effective

  • Easy to calibrate in the field

Disadvantages

  • Consumes a large amount of available line pressure

  • Potentially difficult to install with flow conditioning straight pipe runs

  • Increased pumping and compression costs

  • Possible leak points due to traditional configuration

Typical Applications

Custody transfer by volume, batching, filling/dispensing, mass balance, blending, allocation, process control/monitoring, allocation

Reference

http://www.flowsolutionsblog.com/blog/comparing-flow-meter-technology-choosing-the-meter/

http://www.processindustryforum.com/article/choose-right-flow-meter-process-application

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