Technology/IT ¦ IDM
Meierei Barmstedt processes raw milk and skimmed milk into cheese, butter, milk and milk concentrates at its plant in
Barmstedt, Germany.
cause the trucks are not full at the start of
the run, the tank still contains a considerable
amount of air. As the truck navigates
curves, accelerates and performs braking
maneuvers, the milk constantly swishes
around in the tank and mixes with the air.
This effect has an enormous disadvantage
for dairy operators.
If volume flow is used as the measurement
unit when the milk is retrieved from the
farm, it leads to an exaggerated measurement,
which in turn exaggerates the amount
of raw milk delivered to the dairy. This is because
the air has significantly increased the
volume. In practice, an increase of 10 percent,
or even 20 percent in extreme cases,
is not uncommon. This so-called “milk overrun”
has a negative impact on the finances.
Assuming the air is purged during the production
process, the dairy operator ends up
posting a loss when settling the raw materials
accounts. This also makes it difficult to
create accurate full cost pricing.
With this in mind, instead of volume
flow, many dairy companies use mass flow
to measure the amount of milk that is delivered
and processed during production.
Coriolis systems, such as the Promass family
of instruments from Endress+Hauser, have
proven their worth in such applications for
years now. Unfortunately, unwanted accounting
differences can still occur even
when Coriolis-based flowmeters are employed.
As with volume flow, one of the
reasons for this effect is air entrainment,
which influences mass flow measurements
as well. Although the effect is considerably
lower, it still exists and can lead to deviations.
When processing large quantities of
raw milk like Meierei Barmstedt, small percentage
errors add up to significant sums at
the end of the year.
Multifrequency technology
for reducing measurement
discrepancies
To eliminate discrepancies in the mass flow
measurements, Meierei Barmstedt relies on
the newest member of the Endress+Hauser
Promass family – the Promass Q, an instrument
that features the patented multifrequency
technology. The Promass Q was
designed to eliminate measurement errors
induced by gas entrainment down to a level
of nearly zero. The unique patented feature
of the sensor is that the Coriolis tube oscillates
within two superimposed resonance
frequencies instead of just one, a major
advantage over the conventional Coriolis
measurement principle. Measurement errors
caused by entrained gas can be virtually
eliminated. In simple terms, this has to
do with a physical effect in which the relationships
between the two stimulated resonance
frequencies equate to the relationship
of the measurement errors induced by
entrained gas in fluids. The oscillation of the
two superimposed resonance frequencies
means that both relationships – resonance
frequency and error – are known. The instrument
uses this information to determine
the value at which this error ratio, which is
tied to the entrained gas, is almost zero. It
then adjusts the oscillation frequency accordingly.
Elimination of the measurement error
caused by heavy gas entrainment has a considerable
impact on the incoming supply of
the raw milk. Compared to the processes
available to date, the Promass Q allows food
manufacturers to measure the quantity of
incoming raw milk more accurately than
with currently-available Coriolis mass flowmeters
and as a result, significantly optimize
the internal raw materials settlement even
further. Accounts settlement with the dairy
farmers is more accurate as well.
May/June 2021 ¦ international-dairy.com · 29
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