Gas metering knowledge "Q&A"

1.Will the different mechanical structures of different gas meters (such as different gear sizes) cause inconsistent gas meter measurement counts?

No, the reason is: gas meters with different mechanical structures that have passed the inspection and are used within their range, their measurement results should meet the maximum allowable error requirements specified in the regulations.

2.Will the size of the gas transmission pipe affect the measurement error of the gas meter?

No, because the pipe diameter may cause a slight pressure change at the gas meter inlet. The diaphragm gas meter is a volumetric flow meter, and the pipe diameter will hardly affect the measurement error. All gas meters that have passed the inspection should meet the maximum allowable error requirements specified in the regulations.

3.Will the temperature and pressure compensation of the gas meter lead to an increase in gas consumption?

There is no such situation. The reason is: temperature and pressure compensation is to convert the volume of the gas meter under working conditions into the volume under standard conditions (20□C, 101.325kPa). The current national metrological verification procedures for gas meters do not involve temperature and pressure compensation. According to the first verification of household diaphragm gas meters installed in Chongqing by the Chongqing Metrology and Quality Inspection Institute, no household diaphragm gas meters equipped with temperature and pressure compensation devices have been found. Chongqing's gas is settled by volume under working conditions, and no corresponding components for temperature and pressure compensation have been found in Chongqing's household gas meters. There is no situation where temperature and pressure compensation leads to an increase in gas consumption.

4.Will the self-closing valve increase gas consumption?

No. Reason: The pipeline gas self-closing valve is a safety device installed on the gas inlet pipeline from the user's gas meter to the gas appliance. It has the function of automatically closing in case of overpressure, underpressure, and overcurrent. When there is a gas outage, abnormal gas supply pressure, or hose damage or detachment, the self-closing valve will automatically close to prevent gas leakage and safety accidents. Combined with the working principle and function of the self-closing valve, it does not consume gas itself, so it will not cause an increase in gas consumption.

5.Does the change in gas pressure affect the gas meter count?

The change in gas pressure has basically no effect on the gas meter count. Household diaphragm gas meters use the gas volume under working conditions for settlement, and the pressure does not affect the volume count; the gas pressure will affect the heat generated by the combustion of a unit volume of gas, but the effect is very small (negligible). Reason: According to the requirements of GB16410-2020 "Household Gas Cookers" 5.1.1 Rated gas supply pressure before the cooker, the rated gas supply pressure before the natural gas cooker is generally 2kPa (gauge pressure).

Gas meter measurement is related to the absolute pressure of natural gas. The calculation of the combustion heat per unit volume of gas also uses absolute pressure. Absolute pressure = Chongqing local average atmospheric pressure (98.3kPa) + gauge pressure. Because the gauge pressure accounts for a very small proportion of the absolute pressure, theoretically, the change in gas supply pressure has little effect on gas usage. At the same time, a test verification of the effect of pressure on the metering performance of the gas meter was carried out. The test results show that when the natural gas pressure changes from 1.5kPa to 3kPa, the fluctuation of the metering error of the gas meter is not large (the maximum change is only 0.40%, which is less than the maximum allowable error +1.5%). It can be seen that different gas input pressures have little effect on the metering performance of the gas meter.