Risk analysis in conformity assessment of positive displacement flowmeter

Abstract

Volume measurement of manufactured liquids and liquid raw materials carried out by road tankers (RT) is usual and has economic relevance, justifying the need to ensure metrological reliability. It requires some actions, including choosing suitable standards. In this scenario and considering the practice for type evaluation of measuring instruments, the article proposes a case study, analyzing performance data from a positive displacement meter, a measurement principle widely used as a standard in RT verifications. Current criteria of legal metrology were used: for the 0.3 accuracy class, the maximum permissible error (MPE) is 0.2%. The meter was tested with three different fluids (with different viscosities), and measurement errors were contrasted with the MPE specification, being considered compliant in all situations. On the other hand, risk analysis tools for conformity assessment were incorporated (JCGM 106) based on the different consumer risks, the formulated decision rule, and the measurement uncertainty. Even though, when including the risk analysis, the flowmeter was considered non-compliant, showing the need for a better basis decision using measurement uncertainty in legal metrology actions.