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Title: Comparison Of Multipath Ultrasonic Meter Calibration Data From Two Liquid Hydrocarbon Facilities And One Water Facility
Author: Gregor J Brown Terry Cousins Bobbie Griffith Donald R Augenstein
Source: 2009 North Sea Flow Measurement Workshop
Year Published: 2009
Abstract: The comparison exercise presented here started as a bilateral inter-laboratory comparison of the Cameron calibration facility at the Caldon Ultrasonics Technology Centre in Pittsburgh with the oil flow facilities of TUV NEL Ltd in Scotland. The primary driver for the intercomparison was to provide results of proficiency testing in support of the laboratorys ISO 17025 accreditation. NEL was selected as the second laboratory for a number of reasons, including their ability to cover an overlapping flow and Reynolds number range, the low uncertainty of their facilities and their position holders of the UK national standards. Most importantly, NEL also has ISO 17025 accreditation for their facilities and regularly participates in international intercomparison exercises, thus ensuring a high level of confidence in the validity of the comparison. The facilities at NEL are based on gravimetric (weighing) systems, traceable to the UKs primary mass standards. The Cameron calibration laboratory uses a volumetric prover, which is in turn calibrated using a traceable volumetric tank. Good comparison results produced by these two different methods would therefore also demonstrate that the results obtained are independent of the calibration method used. When designing the transfer package to be used at the two laboratories it became clear, as with any intercomparison, that the meters should be as immune as possible to installation effects. Also as it was necessary to transport the package across the Atlantic, it would need to be compact and robust. To meet these requirements, and bearing in mind that the Cameron calibration facility is used primarily for calibration of ultrasonic meters, the decision was made use the Caldon 280Ci eight path ultrasonic in the package. The transfer package was assembled in the Cameron lab and included two 280Ci flowmeters, with an upstream straight run and a perforated plate (CPA) flow conditioner. The 8-path configuration of the Caldon 280Ci usually negates the need for a flow conditioner, but in this case the CPA plate was included in the package as additional insurance against installation effects, as the requirement was to reduce any possible meter related differences to an absolute minimum. The package was calibrated at the Cameron laboratory against the ball prover and then transferred by ship to NEL where the oil intercomparison tests were completed. The opportunity was then taken to also perform a water calibration at NEL, which would add a further data set, against another independent calibration system, and with a fluid having differing properties.