High Precision Flowmeters for Test Benches.

We had already been developing and producing pumps for over 30 years when necessity made us inventive in the early 80s. To further optimize our pumps, their performance had to be tested and evaluated. However, we could not find a suitable flowmeter for our pump test bench on the market – which was due to our high demands on measuring accuracy. We needed precise measurement results over a wide measuring range.   

Without further ado we developed a flowmeter ourselves. We were able to use our experience in the manufacture of screw pumps. So we reversed the operating principle of the pumps and designed the positive displacement meter.

Flow measurement in industrial applications.
We soon realized that such a precision device could also be useful to our customers. So we added the KRAL flowmeter to our product range. Right from the start, we have concentrated and specialized on high precision flow measurement in industrial applications.

In real operation, the maximum permissible flow rate for which the systems are designed is not permanently operated. In addition, fluid pulsations often occur. The values vary and often lie outside the specified flow rate value. However, many flowmeters only achieve the guaranteed measuring accuracy for a very small viscosity and flow rate range. Therefore the entire measurement result is often wrong.

This is different with KRAL flowmeters. The high measuring accuracy of ± 0.1 % is maintained over a wide viscosity and flow rate range. This is particularly important in test benches, as the entire performance curve of the test object is traced. Furthermore different sizes can be measured on the same test bench. This requires a wide measuring range. KRAL flowmeters are also extremely robust and insensitive to system vibrations and pressure pulsations and show the actual flow rate even under such conditions.

Calibration.
Every KRAL flowmeter is tested and calibrated on our in-house test stand. KRAL standard is factory calibration. However, we also offer an accredited calibration according to ISO/IEC 17025. The measured values are traceable to the national standard. The measurement uncertainty from the national standard to the test object is specified.

All these characteristics predestine our flowmeters for use in test benches. Even the calibration and testing institute uses KRAL precision instruments for its own measuring tasks.

Reproducibility of ± 0.01 %.
Test benches test objects reproducibly for their properties and are an important tool for the development and testing of products. The object is tested thoroughly under strictly defined conditions. The measurement results obtained are an important basis. The tests must be reproducible – with all measured variables, processes and independent of the environment. The same starting and test conditions must be used for every test. Repeated tests must always produce the same result. KRAL flowmeters have a reproducibility of ± 0.01 %.

From practical experience.
Pumps and motors are tested in hydraulic test benches for their function and load capacity. The test runs simulate the extreme values of the application. Our flowmeters are integrated in the high-pressure circuit. While the test specimens only undergo these demanding tests during a test run, our flowmeters are exposed to these conditions every time. The particularly high load-bearings tests include emergency stop valve operation which creates extreme pressure pulsations.

Test benches for the aerospace industry test pumps and controllers of ten different engine fuel systems fully automatically.
Quote from our customer: "The low viscosity, the high pressure load, low flow rates and high measuring precision under high safety requirements (explosion protection) prevent the use of turbine and gearwheel meters. For this reason, KRAL screw meters were used for flow measurement. Thanks to the high-resolution frequency measurement, outstanding repeatability and linearization could be achieved across the entire flow range".

07.05.2020