Q&A INTERVIEW
ON ‘FLOW METER
TECHNOLOGIES’
Q1) How has flow meter technology
advanced over the past 10-15 years?
A: In the past ten to fifteen years,
we’ve seen advances in the amount of
intelligence – that is to say diagnostic
capability and signal processing – in
flow meters. This increase in intelligence
enables functionality such as meter
diagnostics and remote meter verification.
Meter verification allows end users to
confirm that the meter is still performing
within its original specifications without
interrupting the process. This leads to less
downtime, more accuracy, and fewer trips
to the field
Q2) What are the major products
available in market today in terms of flow
meter?
A: The major technologies available for
process flow measurement are Coriolis,
differential pressure, magnetic, and
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vortex flow meters. We also see ultrasonic,
turbine, and positive displacement in
some applications.
Each of these technologies has its place
and each one has a specific set of benefits
– in some cases these benefits overlap,
which can make the choice between
technologies more subtle.
Q3) How does flow measurement
methods break down in terms of their
relevance and usefulness for different
applications?
A: In general, Coriolis flow meters measure
mass and density directly. These meters
have very high turn-down ratios.
The Emerson Elite Coriolis meters can
also detect two phase flow and maintain
highly accurate liquid flow measurement
so long as the gas phase is less than 10
– 12% of the volume. Coriolis is a often a
good fit for custody transfer and control
applications.
Differential Pressure (DP) is often a
lower cost flow measurement approach.
Traditionally the trouble with DP Flow
measurement was a requirement for
twelve pipe diameters of straight pipe,
although newer technologies have
reduced this to four.
Pressure drop depends on whether an
orifice plate or an Annubar is used. More
than 50% of flow measurements in the
process industry use differential pressure.
Magnetic flow meters measure volumetric
flow with no pressure drop. These meters
are ideal for conductive liquids and
slurries. Vortex flow meters are a good
choice for measuring liquids, gases steam.
They offer less turn-down than coriolis
meters, so the user should be careful
when sizing the meter, especially if the
application may have occasional low flow
rates.