They calibrate by direct volume comparison, the most accurate method possible (KROHNE mass flowmeters are calibrated by mass comparison with high precision scales).
Accuracy and reproducibility are important parts of a flowmeter's quality characteristics.
The renowned German accreditation authority PTB (Physikalisch Technische Bundesanstalt) relies on KROHNE flowmeters for its ‘transfer standards’.
In general, transfer standards ensure the accuracy of instrument manufacturers' calibration rigs.
To be able to carry the relevant transfer standard (accuracy: 0,02 % of measured value) on to other calibration rigs, PTB uses a mobile metering station consisting of a complete flow line with several electromagnetic flowmeters (from KROHNE) and fixed inlet/outlet sections.
Therefore, if calibration rigs of KROHNE’s competitors are PTB accredited, they rely on the accuracy and repeatability of KROHNE instruments.
KROHNE is using a worldwide network of high-end calibration facilities to ensure the absolute reliability of their flow meters.
The KROHNE site in Dordrecht, Netherlands, houses the world's largest and most accurate flow calibration rig in the world. Here, KROHNE calibrates electromagnetic and ultrasonic flowmeters.
At 44m high, the rig is capable of taking flowmeters of up to 3m in diameter, with almost half a million litres capacity, 430,000 litres per minute flow, 0,013% accuracy.
The flow rig has a capability of up to 10 point calibration for custody approval meters to the exacting standards of the world's oil and gas industry.
In Germany, France, England, the USA, Brazil, China and India, KROHNE also operates modern flow rigs that are accredited to the most demanding calibration standards.