Effect of common pressure regulating system on metering for special users

Multi-user common pressure regulating system is a process popularly used at the gas offtake terminal station. With increasing low flowrate users (e.g. small domestic gas users in towns) and intermittent gas users (e.g. CNG filling station), collectively referred to as special users, some users run up against significant metering errors. Through analysis and diagnosis, it is confirmed that such errors are resulted from the one-way metering function of the flowmeters and the inversion of local gas flow, while the latter depends on the flowrate variation frequency of high flowrate users within the common pressure regulating system. For these users, a separate pressure control valve or non-return/check value is added, which has enabled system to be normal by reducing the errors. In this paper, two typical cases are discussed to reveal the process how the common pressure regulating system leads to large metering error for special users, and it is pointed out that separate pressure control valve or non-return valve should be designed for special users, so as to avoid metering risks.