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VA Master FAM540
METAL CONE VARIABLE AREA FLOWMETER | OI/FAM540-EN REV. E
… 7 Installation
… Operating conditions
Solids content in the measuring medium
Variable area flowmeters have only limited suitability for
measuring media containing solids.
Depending on the concentration, particle size and type of solid,
increased mechanical abrasion may occur, especially at the
critical measuring edge of the float.
In addition, solidified deposits on the float can change its weight
and shape.
These effects can lead to erroneous measurement results,
depending on the float type.
In general, the use of appropriate filters is recommended in such
applications.
For the flow measurement of measuring media containing
magnetic particles, we recommend the installation of a
magnetic separator upstream of the variable area flowmeter.
Float designs
Figure 16: Float designs
Float ‘S’:
Basic shape of float.
Low flow rates, minimal pressure losses, essentially independent
of viscosity; lower upstream pressure required for gas
measurement.
Float ‘N’:
Higher flow ranges, average pressure losses, well suited to
liquids with minimum viscosity; higher minimum upstream
pressure requirements for gas measurements.
Float ‘X’:
Highest flow rates, maximum pressure losses, well suited to
liquids with minimum viscosity; higher minimum upstream
pressure requirements for gas measurements.
Measuring range limits
1
Pressure loss (dP in mbar)
2
Diameter of the float weight (mm)
3
x 1000 l/h water
Figure 17: Flow rate depending on float shape and weight (example)
For measuring range limits depending on nominal size and float
type, refer to the measuring range tables.
Mounting
The following points must be observed during installation:
• The flow direction must correspond to the direction
indicated on the device (if labeled).
• The maximum torque must be complied with for all flange
screws
• The devices must be installed without mechanical tension
(torsion, bending)
• Install flange devices with plane parallel counterflanges
and use suited gaskets only.
• Only gaskets made from a material that is compatible
with the measuring medium and measuring medium
temperature may be used
• Gaskets must not extend into the flow area, since
possible turbulence could influence the accuracy of the
device
• The piping may not exert any inadmissible forces or
torques on the device
• Do not remove the sealing plugs in the cable glands until
you are ready to install the electrical cable
• Make sure the gaskets for the housing cover are seated
correctly. Carefully seal the cover. Tighten the cover
fittings
• Do not expose the transmitter to direct sunlight; where
necessary, provide appropriate sun protection.
