On-line Real Flow Verification of Gas Ultrasonic Flow Meter in Daqing Oilfield

Abstract: The online real-flow verification information of gas ultrasonic flowmeters in Daqing Oilfield is provided by excellent flowmeter and flowmeter manufacturers and quotation manufacturers. 1. Brief introduction of the verification device The mobile sonic nozzle gas flow standard device was introduced from the Colorado Engineering Experiment Station (CEESI) of the United States in 1988 by the National Crude Oil Mass Measurement Station. It is used for online real flow verification (test) of standard orifice flowmeters, gas Turbine flow. For more flowmeter manufacturers to select models and price quotations, you are welcome to inquire. The following is the details of the online real-flow verification article of the gas ultrasonic flowmeter in Daqing Oilfield. 1. Brief introduction of the verification device The mobile sonic nozzle gas flow standard device was introduced from the Colorado Engineering Experiment Station (CEESI) of the United States in 1988 by the National Crude Oil Mass Measurement Station. It is used for online real flow verification (test) of standard orifice flowmeters, gas Turbine flowmeter, gas ultrasonic flowmeter, etc. The standard device is a skid-mounted structure, consisting of a nozzle group (16 nozzles), a digital valve, a pressure transmitter, a temperature transmitter, a differential pressure transmitter, an online gas chromatograph and a data acquisition and processing system. It can process instantaneous quantity (standard volume flow or mass flow) signal and accumulated quantity (pulse) signal, which can be used for the verification of various types of natural gas flowmeters currently used in China. 2. Preparations before verification The gas ultrasonic flowmeter is equipped with secondary instruments such as pressure transmitter, temperature transmitter and flow computer. Before the flowmeter is verified, the transmitter must be verified according to the verification regulations, and the flow computer must be verified. The input and output channels are calibrated to minimize the system error brought by the secondary instrument. Start the online gas chromatography analyzer to analyze the natural gas components in the pipeline, and input the analysis results into the flow computer and the device data processing system. Check the configuration data of the flow computer to make it consistent with the on-site process conditions. 3. Selection of verification process To carry out on-line real-flow verification of the on-site flowmeter with the mobile sonic nozzle gas flow standard device, the device needs to be connected to the process flow of the metering station. Due to the various conditions of the metering station, the verification process should be selected according to the actual situation of the site. The first situation: Take Beijing Huayou Natural Gas Tongzhou Station as an example, this station is the last station of the Shaanxi-Beijing pipeline to Beijing. The incoming pressure is 4.0MPa, and the outgoing pressure is 1.4MPa. Since the maximum working pressure of the mobile sonic nozzle gas flow standard device is 2.0MPa, after the upstream gas passes through the flowmeter, first install a pressure regulating valve to adjust the pressure to about 2.0MPa, and then connect the sonic nozzle standard device. The second case: Take the Shijiazhuang Station of Hebei Natural Gas Company as an example, this station is a metering and distribution station that supplies gas to Shijiazhuang City. The incoming pressure is 1.7MPa and the outgoing pressure is 1.2MPa. Since the upstream air pressure is less than the maximum working pressure of the device, the verification device can be directly connected to the downstream of the flowmeter. The third situation: Take the third transmission and distribution plant of Beijing Gas Company as an example. This plant is the gate station of the urban pipe network in Beijing. The entry pressure is 1.5MPa, and the urban pipe network pressure is 1.1MPa. Due to the close distance between the station and the last upstream station, the ultrasonic flowmeter is affected by the pressure regulating valve of the upstream outlet, resulting in a large pulsating flow. The device needs to be connected to the upstream of the flowmeter during verification (the sonic nozzle plays the role of steady flow). 4. Selection of verification method When verifying the gas ultrasonic flowmeter, there are generally two methods to choose from. One is to verify only the flowmeter itself. During verification, the flowmeter signal, temperature signal, and pressure signal are directly connected to the data acquisition and control system of the device; the other is to verify the entire metering system. During verification, the analog signal is drawn from the output port of the flow computer and connected to the data acquisition and control system of the device. This method can include all factors such as installation conditions, working conditions, medium conditions, environmental conditions, signal transmission, calculation and conversion that may affect the flow measurement on site into the verification results, so as to discover and find out the problems in the metering system in time. , and eliminate the influence of a large number of uncertain factors through the correction of the flow meter coefficient, thereby improving the accuracy of flow measurement. 5. Processing of verification data The verification result of the gas ultrasonic flowmeter generally gives the MF coefficient of the flowmeter. For a flowmeter that can only input one flowmeter coefficient, use the weighted average method in the appendix of GB/T18604-2001 'Measurement of Natural Gas Flow with Gas Ultrasonic Flowmeter', and calculate the meter coefficient of the flowmeter according to the coefficient of each flow verification point. , place the new meter factor in the flow meter. For a flowmeter that can input multiple flowmeter instrument coefficients for segmental correction, the instrument coefficient of each flow verification point can be placed in the flowmeter. 6. Common problems and solutions in verification (1) Noise interference. During on-site inspection, the sonic nozzle and pressure regulating valve will generate noise. When the noise frequency is close to the operating frequency of the ultrasonic flowmeter,The ultrasonic flowmeter is not working properly. The solution is to set as many flow verification points as possible. After verification, the flow point coefficients with noise interference will be eliminated. In addition, the connecting pipeline between the sonic nozzle device and the ultrasonic flowmeter is lengthened to reduce the influence of noise on the ultrasonic flowmeter as much as possible, and this method has achieved good practical application results.

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