Typically, the fundamental objective of a performance test is to empirically determine the performance level of the supplied equipment when it is operated in accordance with the basis of guarantee at boundary conditions specified in the purchase contract. Numerous factors influence the accuracy of the test results. These factors can be broadly classified into operational factors and measurement uncertainty factors. Operational factors may impact the accuracy of the test results if/when the equipment is not operated in a manner consistent with the basis of guarantee and/or the design intent. Measurement uncertainty factors may impact the accuracy of the test results when taking into consideration the uncertainty of each measurement and the uncertainty in any assumptions inherent to the calculation process. As test inaccuracy ultimately translates to increased risk for all parties, it is in the interest of all concerned to design and execute the test program so as to achieve the best possible accuracy within any operational and budgetary constraints.
Traditional calculation of test uncertainty, per widely recognized industry standards, such as ASME PTC 19.1, tends towards a high degree of precision in estimating the readily quantifiable sensor uncertainty components of the overall test uncertainty scenario, and their propagation through the correction curves. The operational factors and the inaccuracy of corrections curves are typically not addressed in test uncertainty calculations, and can often be significant elements of the overall test inaccuracy. The influence of various factors, from both categories, are presented and discussed citing specific scenarios encountered and a quantification of uncertainty contributions where possible. The purpose is to help customers and conducting parties understand potential sources of test inaccuracy and make informed decisions regarding test preparation activities, test execution, and corrective measures that may influence the overall accuracy of the test program.