To achieve the Magmeters' high level of calibration accuracy, KROHNE relies on a calibration rig that is the world's largest and most accurate flow calibration rig. It is accurate up to 176,115 gal/min (40,000 m3/h) with measurement uncertainty less than 0.013%.Click here to enlarge imageThe accuracy and reliability of Krohne's magmeters is no accident. It is, at least in part, the product of painstaking calibration during and following the manufacturing process. Every magnetic-inductive and ultrasound flowmeter from the company has a calibration certificate. The company relies on a calibration rig that is not only the world's largest and most accurate flow calibration rig, it is accurate up to 40,000 m3/h with measurement uncertainty less than 0.013%. Nederlands Meetinstituut B.V. (NMI), the Dutch calibration authority, has certified that the volume serving as the testing standard for this large-scale calibration rig is accurate to within ±0.013% when calibrating volume-flowmeters in the range from 18 to 40,000 m3/h. This flow rate would be sufficient to fill a normal indoor swimming pool in less than one minute.
This test rig permits the precise calibration of flowmeters up to120" in diameter - big enough for a small goods vehicle to pass through. The stainless steel calibration tower is 42 metres high and has a water volume of some 400 m3. High-precision level switches at various heights mark a series of partial volumes; NMI precisely calibrated these partial volumes and total volume.
The test rig itself is certified by the Netherlands Calibration Organization (NCO) under EN 45001, ensuring that it conforms to both national and international standards. The computer automatically produces a calibration report documenting flow values and measurement errors for each calibration. Every flowmeter is wet-calibrated in a direct comparison with the volume calibrated by NMI. The calibration method is 10 times more precise than the flowmeter being tested. This guarantees that the specified error limits of these devices are achieved under reference conditions.
Recalibrating the meters on a regular basis is integral to helping to maintain accuracy. Krohne's MagCheck, a portable testing and verification device for Krohne electromagnetic flowmeters (EMF), enables plant personnel to verify accuracy of the magmeter's flowhead, converter and cables without removal from the pipeline or interruption of the process.
An ISO 9001-compliant portable device that uses available line power at the flow tube, MagCheck can be used with most Krohne flowmeter converters as either an automatic verification instrument or as a manual flow signal calibrator. MagCheck verifies flowmeter performance while creating an archived calibration record accurate within 1% of the original factory calibration. MagCheck is directly traceable to international standards.
Pete Williams of Sullivan Associates, a Krohne distributor, explained that the accuracy and reliability of MagCheck provides customers with a high confidence level.
"MagCheck creates a significant comfort factor," he said. "The calibration figures produced by MagCheck are certifiable and NIST-traceable [National Institute of Testing Standards]. Ultimately the device meets all government standards including the EPA.
Author's Note
Liesel Oliveira, was Krohne's product manager, based in Peabody, Massachusetts, USA, when she wrote this article. She has relocated to Florida as a technical sales representative.