Proline Prowirl 73 F, W
2 Endress+Hauser
Function and system design
Measuring principle Vortex shedding flowmeters work on the principle of the Karman vortex street. When a fluid flows past a bluff
body vortices are alternately formed and shed and each generates a local low pressure point downstream of the
bluff body. The pressure fluctuations are detected by the sensor and converted to electrical pulses (digital sig-
nal). Within the operating limits of the device the frequency of vortices generated is directly proportional to the
volume flow.
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The K-factor is used as the proportional constant:
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Within the application limits of the device the K-factor (calibration factor) is dependant only on its mechanical
geometry and is independent of the fluid, velocity, viscosity and density. (gas, liquid or steam)
The primary measurement signal is digital (frequency signal) and a linear function of the flow. After
manufacture the K-factor is determined during a factory calibration and once derived is not subject to zero or
long term drift.
The device does not contain any moving parts and requires no maintenance.
The DSC (Differential Swit-
ched Capsitance) sensor
The measuring sensor for a vortex flowmeter has a major influence on the performance, robustness and
reliability of the whole measuring system.
The DSC sensor of the new Prowirl 73 incorporates the experience gained from an installed base of over
100.000 vortex measurement points with the benefits of an integrated temperature sensor (PT 1000).
To ensure that the DSC sensor meets the range of demands required in today’s applications it has been burst
tested to pressures in excess of 400 bar, vibrations in excess of 1g in all axes and temperature shocks of
150 K/s.
Prowirl 73 is capable of measuring low flow rates even with low density fluids and where pipe line vibrations
are present. The meter will maintain its wide turn down ratio even under conditions where vibrations of 1g
or more and frequencies up 500 Hz are experienced.
v
K-Factor =
pulses
unit volume [dm³]
Due to its internal mechanical balance the DSC sensor
reads only the pressure pulses caused by the vortices and is
immune to any influence from mechanical pipe line vibra-
tions.
Thanks to its mechanical design, the capacitive sensor is
also especially resistant to temperature shocks and water
hammer in steam lines.
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Sensor
Y-Axis
X-Axis
Z-Axis
Pt 1000
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