An investigation of flow calibration standards, an inter-comparison and an accuracy test campaign

The aim of this work package is to confirm whether existing flow calibration standards meet the accuracy stipulated by technical standards and regulations when they are used with renewable gases. Current uncertainty targets for accuracy tests are 1/5 MPE for type testing and 1/3 MPE for field verification.

The properties and characteristics of renewable gases can differ significantly from those of natural gas and the effect of these gases on the performance and durability of gas meters is not well understood at the moment. There are likely to be additional contributions to the measurement uncertainty; therefore, the results performed with existing flow calibration flow standards may not be directly comparable with the results from meters operated in the field, when they are used with renewable gases or with mixtures containing natural gas.

Task 3.1 will investigate existing calibration flow standards and transfer standards with respect to their characteristics and their suitability to be used with renewable gases. It will also define the recommendations needed for flow calibration standards as well as the recommendations needed for calibration methods to reach a suitable level of performance.

Task 3.2 will work on the definition of an adequate transfer standard and will carry out an inter-comparison campaign in the most important flow rate range as determined in Task 1.2. The aim of this campaign is to obtain results that will demonstrate the equivalence of the test results and the improvements needed.

The practicality of the test procedure(s) developed in Task 2.1 will be investigated by calibrating domestic and commercial meters with hydrogen. A nozzle bench for domestic gas meters will be validated as this flow standard technology is wide spread for domestic gas meters and it delivers low uncertainties.