PETROBRAS TRANSPORTE S.A. - TRANSPETRO'S ULTRASONIC FLOW METER RECALIBRATION PROGRAM

摘要

In recent years, the use of ultrasonic flow meters has gained worldwide acceptance for natural gas custody transfer applications. TRANSPETRO has also increased significantly the use of this technology because of the important role it plays in reducing lost and unaccounted for (LUAF) gas. A plan of this equipment is essential to guarantee the proper operation and the specified accuracy of the meter runs as well as mandatory in order to comply with a national regulatory agency (ANP) ordinance, which requires ultrasonic meters to be recalibrated every 30 months. This interval can be extended if the agency approves a study submitted by the operator, presenting a reasonable historical metrological performance the meters. In 2009, the Measurement Technical Committee of the Pipeline Research Council International (PRCI) published a report recommending ultrasonic meters to be recalibrated based on time-in-service, but on periodic assessment of the diagnostic parameters provided by the equipment. The report states that if these diagnostic logs indicate performance change, the meter should be cleaned and the performance rechecked; the recalibration should be considered only if the performance change remains after the cleaning. Carrying out this procedure guarantees, according to the report, the calibration is within the uncertainty of the calibration facility for a period of at least six years. Although the several PRCI reports recommend some diagnostic parameters to be followed, their names, categories and limits vary from manufacturer to manufacturer. A narrow relationship with each manufacturer must be established in order to define the finest practices. The periodic basis of the diagnostic logs collection is also an important concern. The state-of-art on following the diagnostic parameters is to have them integrated to the SCADA system, random problems can be neglected if manual collection is performed from time to time. The objective of this paper is to present TRANSPETRO's ultrasonic flow meters recalibration program based on PRCI reports and manufacturers' recommendations, as well as show the company's strategy for the diagnostic parameters collection.