Characteristics of Natural Gas Flow Measurement and Its Requirements for Instruments

The characteristics of natural gas flow measurement and its requirements for instruments As a primary energy source, the proportion of natural gas in the world's primary energy structure has been increasing year by year. The amount involved in natural gas custody transfer measurement is huge, which has attracted widespread international attention. In order to ensure fair and reasonable trade measurement of natural gas production and utilization enterprises and safeguard the legitimate rights and interests of both sides of the trade, Europe was the first to formulate the 1776: 1998 'Basic Requirements for Natural Gas Measurement Systems'. On the basis of this standard, our country has also formulated corresponding standards&D 18603-2001 'Technical Requirements for Natural Gas Metering System'. The natural gas metering system has the following main characteristics and basic requirements. (!) Explosion-proof requirements The fluid is flammable and explosive, and the possible hazardous areas should be in compliance. 8 3836.1 for classification, in the hazardous area, any instrument and electrical equipment selection and installation should comply with the provisions of 68 3836. Requirements for uninterrupted gas supply In order to ensure continuous gas transmission, the gas supply cannot be interrupted due to maintenance of metering instruments, etc., the metering station and metering circuit should be provided with a bypass, and for important large flow users, it is recommended to use parallel double metering circuits. Bypass valves and upstream valves (or downstream valves) of parallel dual metering circuits should be shut-off valves with good closing performance, durability, and leak detection devices to avoid the diversity of non-metering conditions. All links need to be metered, the collection ring is 5:12; ^ pollution. The gas is mixed with liquid or even solid phase. The pressure of different gas wells varies greatly. The fluid pressure in the transportation link is also high, 5 7 distribution, 'at the end of the A household, the pressure may drop very low. Therefore, the flow measurement of different links should understand the fluid working conditions and specific conditions, and cannot be generalized. Different accuracy requirements require that natural gas measurement is a bulk energy measurement, and the greater the flow value, the greater the settlement amount involved. The price of the configured measuring instruments is related to the accuracy. The higher the accuracy, the higher the price. The measuring system with relatively small measurement values ​​generally cannot afford the much more expensive high-accuracy instruments. Therefore, only Reduce the requirements, but still meet the requirements of the relevant standards. Listed in Table 2.1 are the guidelines for the equipment and meters of different levels of natural gas metering systems. Table 2 and 2 are the accuracy requirements of supporting instruments of different levels of metering systems^.