Turbine flow meter
Turbine flow meters are indirect volume meters , similar to the Woltmann impeller meter . Due to the short response time and high resolution, turbine flow meters are suitable for fast measurements, for example during filling processes .
Measuring principle
The measuring medium flows through the turbine flow meter in the axial direction, thereby causing the turbine wheel to rotate. Corresponding sensors in the turbine flow meters record the speed of the wheel, which is proportional to the mean flow velocity.
As an output signal, the sensors deliver an alternating voltage with a frequency (for example: pulses per liter) that is proportional to the current flow. After the voltage has been amplified and converted, square-wave pulses are available for evaluation.
Evaluation electronics
Various evaluation electronics for signal processing and display are available as accessories in conjunction with the measuring tubes. These include signal amplifiers and transmitters, alarm contacts, pulse dividers, flow and total displays with analog and digital outputs and dosing controls.
calibration
The K-factor (calibration factor) of the turbine flow meter expresses the exact pulse rate. To determine the K-factor, the sensors are calibrated and adjusted to the corresponding operating viscosities and customer specifications.
The following information is given in the calibration reports:
- Max. Measurement error related to the instantaneous value
- Max./min. Frequency with corresponding flow values
- K-factors at different flow rates within the measuring range
- Mean K-factor as average value for the entire measuring range
The signal conditioning instruments can be set on the basis of this information.
The following equation applies to the flow:
With
- = Flow rate in l / min
- = Frequency in Hz
- = K factor in pulses / l
Applications
The turbine flowmeters are accurate, reliable and robust devices for volume flow measurement of clean, low-viscosity liquids and are used in industries such as chemistry, petrochemistry, pharmaceuticals, food and beverage production.
For hydraulic applications that require high repeatability, high measurement accuracy and low pressure drop, special turbines are available that allow flow rates from 0.1 to 1500 L / min and pressures of up to 1000 bar and are compensated by means of built-in temperature sensors.
The so-called sanitary versions are special designs for the food, beverage and pharmaceutical industries. Due to the special construction, the system can be cleaned with chemical cleaning agents and also sterilized (CIP process) when installed. Connections according to DIN 11850 ( milk pipe and sterile screw connections ) or TRI-Clamp 245 (based on DIN 32676).
Special models in nominal sizes between DN 100 and DN 500 are available on the market for legal-for-trade billing transactions and these were specially designed for billing transactions.
advantages
- High definition output
- Large measuring span
- Accuracy 0.5% of the measured value
- Low operating costs
- Corrosion-resistant materials
- Can be used for hygienic applications
- Ex or intrinsically safe design also as flameproof enclosure
- Local display