In the commodity trading process can not be separated from an important parameter - the amount of goods, natural gas as a commodity for market transactions can not be separated from the amount of goods. Natural gas needs to be measured by the instrument to obtain the amount of gas, and then convert its value into currency. If you do not know the amount of natural gas, you cannot trade settlement. Therefore, it can be said that without accurate measurement of natural gas, transactions in the natural gas market can not be carried out normally. The live measurement of the natural gas market involves various aspects of the various sectors of the national economy and people’s lives. It is an important technical foundation of the national economy. The basic feature of measurement is measurement, but the tools for measurement are not general products but measurement instruments with unity, accuracy, and certain accuracy levels. In technical and legal management requirements, the measurement is higher than general measurement.
Metrological verification is the process of quantitative transmission according to the national metrological verification system. The value transfer is the unit value that is replicated by the measurement standard, passed to the next level measurement standard through measurement verification, and passed to the working measuring instrument step by step. The final purpose is to ensure that the measured value of the object is accurate and consistent. . After measurement instruments have been verified by the statutory metrology verification agencies in accordance with the national metrological verification system tables, they can be traced back to the national metrology benchmarks to ensure accurate and reliable metrological values.
All measurement instruments that are stipulated by the State's "Measurement Law" as compulsory inspections shall be subject to fixed-point and periodic verifications by the statutory measurement agencies designated by the measurement administrative department of the people's government at or above the county level or authorized metrological verification agencies, that is, the use of strong inspection and measurement instruments. The applicant shall submit the inspection to the designated statutory metrological verification agency or authorize the authorized metrological verification agency to carry out the verification.
China's natural gas measurement is usually expressed in terms of volume, and the legal unit is m3. Natural gas volume changes with the temperature and pressure of natural gas. In order to facilitate comparison, it is necessary to specify a certain state as a standard state.
The standard state of China's natural gas flow measurement is: the absolute pressure is 0.101325 MPa and the temperature is 293.15K. If there is no specific indication of natural gas flow under working conditions, it generally refers to the volumetric flow of natural gas under the above standard conditions. There are many methods of natural gas flow metering, and there are many available flow meters, which are roughly divided into the following three types according to the working principle:
1) Differential pressure flowmeter: In the current pipeline natural gas metering, more than 95% are still using standard orifice differential pressure flowmeters to indirectly measure the natural gas pressure, differential pressure and temperature through the standard orifice plate, according to experience The formula calculates the natural gas volume flow. The secondary instrument for measuring each indirect quantity requires a recording or totalization function, so the differential pressure flow metering system is also roughly divided into two categories: CW double bellows differential pressure, absolute pressure recorder (with glass rod thermometer ) And computer automatic metering system.
Since the standard orifice needs cleaning and verification every (2 to 3) months, the orifice plate is frequently loaded and unloaded from the pipeline pressure-receiving device. In order not to affect the gas supply, the pressure-taking device is preferably a high-grade orifice valve. Pipe section to maintain the roughness does not exceed the standard, it is best to carry out anti-corrosion treatment, because these parts once installed, as long as no damage is generally no longer disassembled.
2) Volumetric flowmeters: Gas waist flowmeters, also known as Roots flowmeters, are typically volumetric flowmeters that are used to continuously measure the total amount of gas flowing through a pipe (cumulative flow). The principle is that the rotor and the housing form a closed chamber, ie a measuring chamber. The rotor of the waist wheel flow meter is a pair of waist wheels that are mutually conjugate curves. Coaxially mounted with the lumbar wheel is the drive gear. When the fluid to be measured passes through the flow meter, a differential pressure is formed between the inlet and outlet and the waist wheel is rotated, and the waist wheel is mutually driven by the drive gear. For each revolution of the lumbar wheel, the fluid discharged is a fixed value, ie, the discharge amount is proportional to the number of rotations of the waist axle. Therefore, as long as the volume of the measurement chamber composed of the waist wheel and the flow meter housing and the number of rotations of the waist wheel are known, the volume flow rate of the gas can be calculated. Measure the speed of the waist wheel to obtain the flow rate per unit time, ie the average instantaneous flow rate. Volumetric flowmeter display value is generally the volume flow rate under working conditions, and the calculation is made by manual calculation when converting to standard conditions. The temperature and pressure values ​​adopt the long-term average or estimated value.
3) Speed-type flowmeter: It is a flowmeter that directly measures the flow rate of the full pipe flow in a closed pipe. Including turbine flowmeter, vortex flowmeter, precession vortex flowmeter, ultrasonic flowmeter and so on. Since the measured flow rate is under operating conditions, the last shown is the volumetric flow rate under operating conditions. Nowadays, intelligent precession vortex flowmeters that use computer to automatically compensate temperature and pressure are also appearing on the market.
4) Comparison of three commonly used flowmeters (see Table 1)
5) Flow measurement standards: There are many standards for natural gas flow measurement in the world. Such as the American standard AGANO3, Japanese standard JISM8010, French standard DIN1952, British standard IGE/GM/I, IGE/TD/9, the former Soviet Union standard 27-54 procedures and international standards ISO/R541, ISO5167 and so on. China's natural gas measurement standardization started late. In 1959, the former National Bureau of Weights and Measures recommended the former Soviet Union standard 27-54 as the provisional procedure for natural gas flow measurement in China. In 1965, the Sichuan Petroleum Administration formulated the “Regulations for the orifice metering device, verification, use, and management of natural gas flow (Draft)†in conjunction with natural gas metering characteristics as the basis for the flow measurement of natural gas.
In the late 1970s, China became an ISO Member State. In the 1970s, China's first standard GB2624-81 was formulated and passed. The former Ministry of Petroleum Industry formulated the industry standard SYL04-83 in combination with the measurement characteristics of natural gas. At present, the standards of most countries in the world gradually move closer to ISO 5167 "Measurement of Fluid Filled with Round Tubes with Orifice Plates". In recent years, China has formulated the GB/T2624-1993 standard, and the natural gas measurement standard has also been revised to SY/T6143-1996 "Standard orifice metering method for natural gas flow."
Some units in our country have not noticed the uniformity and legitimacy of the use of standards due to various reasons such as introduction and joint development. Mixed use of US standards and Chinese standards occurs, and mixed use of French standards and Chinese standards, etc., will cause many measurement disputes. Currently in China, the natural gas industry and enterprises should implement SY/T6143-1996 "standard orifice metering method for natural gas flow", otherwise it should be regarded as illegal.
Natural gas flow meter Hydrogen flow meter Methane flow meter Argon flow meter
Metrological verification is the process of quantitative transmission according to the national metrological verification system. The value transfer is the unit value that is replicated by the measurement standard, passed to the next level measurement standard through measurement verification, and passed to the working measuring instrument step by step. The final purpose is to ensure that the measured value of the object is accurate and consistent. . After measurement instruments have been verified by the statutory metrology verification agencies in accordance with the national metrological verification system tables, they can be traced back to the national metrology benchmarks to ensure accurate and reliable metrological values.
All measurement instruments that are stipulated by the State's "Measurement Law" as compulsory inspections shall be subject to fixed-point and periodic verifications by the statutory measurement agencies designated by the measurement administrative department of the people's government at or above the county level or authorized metrological verification agencies, that is, the use of strong inspection and measurement instruments. The applicant shall submit the inspection to the designated statutory metrological verification agency or authorize the authorized metrological verification agency to carry out the verification.
China's natural gas measurement is usually expressed in terms of volume, and the legal unit is m3. Natural gas volume changes with the temperature and pressure of natural gas. In order to facilitate comparison, it is necessary to specify a certain state as a standard state.
The standard state of China's natural gas flow measurement is: the absolute pressure is 0.101325 MPa and the temperature is 293.15K. If there is no specific indication of natural gas flow under working conditions, it generally refers to the volumetric flow of natural gas under the above standard conditions. There are many methods of natural gas flow metering, and there are many available flow meters, which are roughly divided into the following three types according to the working principle:
1) Differential pressure flowmeter: In the current pipeline natural gas metering, more than 95% are still using standard orifice differential pressure flowmeters to indirectly measure the natural gas pressure, differential pressure and temperature through the standard orifice plate, according to experience The formula calculates the natural gas volume flow. The secondary instrument for measuring each indirect quantity requires a recording or totalization function, so the differential pressure flow metering system is also roughly divided into two categories: CW double bellows differential pressure, absolute pressure recorder (with glass rod thermometer ) And computer automatic metering system.
Since the standard orifice needs cleaning and verification every (2 to 3) months, the orifice plate is frequently loaded and unloaded from the pipeline pressure-receiving device. In order not to affect the gas supply, the pressure-taking device is preferably a high-grade orifice valve. Pipe section to maintain the roughness does not exceed the standard, it is best to carry out anti-corrosion treatment, because these parts once installed, as long as no damage is generally no longer disassembled.
2) Volumetric flowmeters: Gas waist flowmeters, also known as Roots flowmeters, are typically volumetric flowmeters that are used to continuously measure the total amount of gas flowing through a pipe (cumulative flow). The principle is that the rotor and the housing form a closed chamber, ie a measuring chamber. The rotor of the waist wheel flow meter is a pair of waist wheels that are mutually conjugate curves. Coaxially mounted with the lumbar wheel is the drive gear. When the fluid to be measured passes through the flow meter, a differential pressure is formed between the inlet and outlet and the waist wheel is rotated, and the waist wheel is mutually driven by the drive gear. For each revolution of the lumbar wheel, the fluid discharged is a fixed value, ie, the discharge amount is proportional to the number of rotations of the waist axle. Therefore, as long as the volume of the measurement chamber composed of the waist wheel and the flow meter housing and the number of rotations of the waist wheel are known, the volume flow rate of the gas can be calculated. Measure the speed of the waist wheel to obtain the flow rate per unit time, ie the average instantaneous flow rate. Volumetric flowmeter display value is generally the volume flow rate under working conditions, and the calculation is made by manual calculation when converting to standard conditions. The temperature and pressure values ​​adopt the long-term average or estimated value.
3) Speed-type flowmeter: It is a flowmeter that directly measures the flow rate of the full pipe flow in a closed pipe. Including turbine flowmeter, vortex flowmeter, precession vortex flowmeter, ultrasonic flowmeter and so on. Since the measured flow rate is under operating conditions, the last shown is the volumetric flow rate under operating conditions. Nowadays, intelligent precession vortex flowmeters that use computer to automatically compensate temperature and pressure are also appearing on the market.
4) Comparison of three commonly used flowmeters (see Table 1)
5) Flow measurement standards: There are many standards for natural gas flow measurement in the world. Such as the American standard AGANO3, Japanese standard JISM8010, French standard DIN1952, British standard IGE/GM/I, IGE/TD/9, the former Soviet Union standard 27-54 procedures and international standards ISO/R541, ISO5167 and so on. China's natural gas measurement standardization started late. In 1959, the former National Bureau of Weights and Measures recommended the former Soviet Union standard 27-54 as the provisional procedure for natural gas flow measurement in China. In 1965, the Sichuan Petroleum Administration formulated the “Regulations for the orifice metering device, verification, use, and management of natural gas flow (Draft)†in conjunction with natural gas metering characteristics as the basis for the flow measurement of natural gas.
In the late 1970s, China became an ISO Member State. In the 1970s, China's first standard GB2624-81 was formulated and passed. The former Ministry of Petroleum Industry formulated the industry standard SYL04-83 in combination with the measurement characteristics of natural gas. At present, the standards of most countries in the world gradually move closer to ISO 5167 "Measurement of Fluid Filled with Round Tubes with Orifice Plates". In recent years, China has formulated the GB/T2624-1993 standard, and the natural gas measurement standard has also been revised to SY/T6143-1996 "Standard orifice metering method for natural gas flow."
Some units in our country have not noticed the uniformity and legitimacy of the use of standards due to various reasons such as introduction and joint development. Mixed use of US standards and Chinese standards occurs, and mixed use of French standards and Chinese standards, etc., will cause many measurement disputes. Currently in China, the natural gas industry and enterprises should implement SY/T6143-1996 "standard orifice metering method for natural gas flow", otherwise it should be regarded as illegal.
Natural gas flow meter Hydrogen flow meter Methane flow meter Argon flow meter
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