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| How to Select the Meter Model Correctly |
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It is very important to select right meter model in flowrate measurement. Many relative information point out that meter fault happened in application, two thirds is due to wrong selection meter model and installation. Right selection of meter model should be according to the conditions as follow:
¢ Parameters collection
(1) Composition, density, conductivity of the fluid to be measured
(2) Maximum, minimum, normal flowrate
(3) Max operating pressure
(4) Temperature range
¢ The fluid must be conductive and its conductivity
> 5μS/cm
¢ The full span must be conformed to the meter size.
Refer to table below: |
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¢ The actual maximum operating pressure must be less than rated pressure
¢ The maximum and minimum operating temperature should be conformed to the requirements
¢ Check up if there is negative pressure
You can select meter model according to the conditions above, if the meter size is not the same with the process pipe, the converging pipe or diverging pipe can be used.
¢ You should consider that the pressure loss will affect the process condition if converging pipe used.
¢ It is suggested that small size meter selection saves your cost as possible. |
| Figure of Relationship between Inside Diameter with Flowrate and Velocity |
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¢ When it is
used in tap water, economical velocity is 1.5-3 m/s,
can be properly increased to 3-4 m/s if measures for
crystallizable solution to prevent dirty deposit. When
used for slag, properly decrease the velocity to 1.0-2
m/s to prevent the liner and electrodes being worn,
over 7m/s is rare in application and over 10 m/s is
even uncommon.
¢ Figure of relationship between maximum cable distance for remote type and fluid conductivity. |
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The remote distance should be as short as possible to prevent the electric noise interference caused by the capacitance distribution in operation.
For example: conductivity of tap water is about 100μS/cm, the maximum distance of remote type is about 100 m, (the conductivity of acid, alkali, salt is slightly high, so their separated distance may be over 100 m, this value be determined by conductivity and cross section of cable core). |
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