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July 2006 Maintenance, Test & Measurement, Calibration

The method used to calibrate a flowmeter prior to shipment is key to its subsequent performance in the plant. Before Krohne ships any of its electromagnetic or ultrasonic meters to a customer, they are wet-calibrated by direct comparison of volumes. This is the most accurate method available.

Coriolis flowmeters are calibrated by comparing masses using high precision calibrated scales.

Accuracy and reproducibility are key quality attributes of a flowmeter. The PTB's (German national metrology institute) transfer standard relies on Krohne flowmeters. Transfer standards generally ensure the accuracy of calibration rigs from manufacturers of measuring instruments.

Krohne is PTB's transfer standard

The PTB uses a mobile measuring station with a measuring section consisting of several electromagnetic Krohne flowmeters and fixed inlet and outlet runs to validate other calibration rigs with respect to transfer standard reproducibility (0,02% of measured value). That is, when PTB calibrates calibration equipment from other manufacturers, the accuracy and reproducibility is based on Krohne flowmeters. Aside from PTB, other standards calibration authorities in Europe also rely on Krohne flowmeters for their transfer standards, including BEV in Austria.

Largest and most accurate calibration rigs in the world

Krohne has a global network of advanced calibration rigs that it uses to ensure the reliability of its flowmeters. The company operates the world's largest and most accurate calibration rig for electromagnetic and ultrasonic flowmeters in Dordrecht, the Netherlands. The height of 42 metres allows measuring instruments with a diameter of 3 metres and flow rates of up to 8000 litres per minute to be calibrated. The calibration tower has a capacity of one-half million litres of water. The calibration volume of the Altometer tower has an uncertainty of 0,011%. This fulfils the requirements of all custody transfer standards in the oil and gas industry.

Krohne operates additional calibration rigs accredited to the strictest calibration standards in Germany, France, Great Britain, the United States, Brazil, China and India. It is also able to calibrate flowmeters together with their inlet and outlet runs for particularly difficult and demanding applications. Detlef Jacobi, Krohne's technical director, points out: "It does not matter where our flowmeters are made; Krohne is always a leader when it comes to precise calibration."

For more information contact Kruben Bennie, Krohne, 011 315 2685, kruben@krohnesa.co.za, www.krohne.co.za

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Maintenance, Test & Measurement, Calibration

The benchmark for calibration

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