Domestic gas meters suitable for hydrogen

In order to ensure sufficient energy supplies and to reduce carbon dioxide emissions, the use of hydrogen, which would include injecting it into the natural gas grid, is becoming more and more important. The question that arises here is whether the meters widely used in private households are suitable for correctly measuring hydrogen-methane mixtures and pure hydrogen according to legal regulations.

To prepare for the transition to hydrogen in the public gas supply system, the Deutscher Verein des Gas und Wasserfaches (DVGW, the German Technical and Scientific Association for Gas and Water) is testing the injection of up to 20 % hydrogen (H₂) into suitable grids as part of a research project. Here, it is economically relevant whether the diaphragm gas meters currently in place can continue to be used. This is only possible if they remain within the maximum permissible errors, i.e., if they can measure with sufficient accuracy. The domestic gas pressure regulator valves connected upstream of the diaphragm gas meters also have to work reliably under changing flow rates and gas mixtures.

PTB has tested a total of six new diaphragm gas meters with two domestic gas pressure regulator valves (each from a different manufacturer) in various combinations as regards measurement errors and control accuracy at flow rates ranging from 40 l/h to 10 m³/h. As diaphragm gas meters are calibrated with air during the manufacturing process, the meters under test were also calibrated with air, nitrogen and pure methane, the main component of natural gas.

The results show that the maximum permissible errors of the diaphragm gas meters over the entire flow rate range of ± 1.5 % in the upper and ± 3 % in the lower range (as per EN 1359) are complied with when the meters are supplied either with pure hydrogen or with a 20 % or 30 % (mole fraction) blend of hydrogen in methane. No systematic differences were observed here. The meters can continue to be adjusted with air during the manufacturing process. The control characteristics of domestic gas pressure regulator valves are also independent of the gas type over the entire flow rate range. The results and experience gained will be taken into account in a follow-up project that will include similar tests being conducted on industrial meters that have been installed in the grid for at least one calibration interv