Influence of neodymium magnet field on fuel gas metering with diaphragm gas meters

The article deals with the problem of illegal fuel gas consumption among individual consumers in households, especially with regard to gas theft using neodymium magnets attached to diaphragm gas meters. First, the author presents a historical outline of the use of neodymium magnets for the purpose of illegal consumption of fuel gas. The current legal status regarding the requirements for gas meters resistance to tampering and the activities of the Oil and Gas Institute - National Research Institute (INiG - PIB) and Distribution System Operators aimed at eliminating the possibility of illegal gas consumption with the use of neodymium magnets were discussed. Currently possible methods of confirming gas theft using gas meters exposed to the magnetic field of neodymium magnets were presented. Next, the methods of performing at the INiG - PIB laboratory expert examinations of gas meters suspected to be used for illegal gas consumption after their removal from the distribution network were described, and the criteria for assessing these gas meters were given. Based on the expert examinations of gas meters carried out at the Laboratory of Flow Metrology INiG - PIB in the years 2006-2020, a summary of the share of gas meters tampered with the use of neodymium magnets and gas meters with an increased remanence level was presented in relation to performed in a given year expert examinations of gas meters suspected to be used for illegal gas consumption. The methods of counteracting the theft of fuel gas with diaphragm gas meters tampered with the use of neodymium magnets were shown. It has been proved that at present the EC type examination certificate (MID Directive) and the certificate of compliance with the requirements of EN 1359 or OIML R 137-1 & 2 specification do not confirm gas meters resistance to gas theft involving the use of a strong magnetic field. Requirements for new diaphragm gas meters in terms of their resistance to neodymium magnets were presented, and updated criteria for the evaluation of the test results of gas meters exposed to these magnets were given. Finally, a conclusion was proposed regarding the necessity to include provisions on the resistance of diaphragm gas meters to magnetic field in the relevant normative documents for gas meters in order to provide a systemic safeguard for the parties to fuel gas supply contracts.