Knowledge of calibration equipment for the hottest

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Knowledge of verification equipment of industrial gas flow meters 1. Preface

in the past three years, the requirements for the verification of industrial gas flow meters have greatly increased. It is mainly reflected in the following three aspects:

1. The verification of high-pressure gas flowmeter with natural gas is not limited to turbine gas flowmeter, but also orifice plate, venturi and vortex baffle flowmeter

2. Low gas flow (less than 3.5 m3/h) verification of small flow meters, such as thermal mass flow meters, mass flow controllers, variable area instruments and detectors for medical and health equipment

3. Verification of gases other than air or natural gas and verification under different operating conditions (different pressures or different gases)

in view of these conditions, the Netherlands Institute of Metrology developed a new low flow detection device, and made the two existing verification devices automated. In addition, it is necessary to add high-voltage testing facilities in bergum, which has been included in the 1993 plan

Table 1 shows the existing facilities in the Netherlands for legal identification, verification and testing of industrial gas flow meters. The table provides the characteristics of these detection devices, such as flow, operating pressure and the type of gas used for detection. For the listed facilities, the partners of the Netherlands Metrology Institute will be responsible for legal identification and issuance of verification certificates. In addition to the facilities listed in Table 1, the number of detection devices in gas distribution companies and gas flowmeter manufacturers has also increased

II. High pressure detection device

there are several high pressure flow detection devices in the Netherlands. In terms of verification facilities or traceability, the detection devices of Groningen, bergum and Westerbork are very important. Natural gas can be used as the verification medium for the verification of these three devices under operating conditions

oningen's high voltage detection device

groningen's high voltage detection device is designed as a research device. Gasuni, the owner of the device, used the device to study gas flow meters, device effects, pressure reducers and other equipment. The detected device can be installed in several parts of the detection device to form the most suitable configuration. This device is rarely used for the normal verification of gas flow meters. However, it plays a very important role in the traceability of other high-voltage detection devices in the Netherlands

Table 1 test equipment used for legal identification, verification and detection of industrial gas flow meters or cooperation

device name device owner location flow gas type absolute pressure range are you ready? Enclosure (bar) low flow detection device NMI Dordrecht 2 ×~ 3.5 air, natural gas or cylinder gas 1 0.5m3 bell jar NMI Dordrecht 0.1 ~ 65 air or natural gas 1 1m3 bell jar NMI Dordrecht 0.4 ~ 160 air 1 3.5m3 bell jar NMI Dordrecht 0.4 ~ 400 air or natural gas 1 detection pipeline NMI Dordrecht 5 ~ 1000 air 1 high flow detection device NMI Dordrecht 40 ~ 12 × 103 air 1 internal detection pipeline Instromet silverde 8 ~ 10 × 103 air 1 external detection pipeline Instromet silverde 20 ~ 25 × Indication error is inevitable. 103 air 1 high pressure detection pipeline gasuni Groningen 45 ~ 36 × 103 natural gas 9 ~ 41 high pressure detection pipeline NMI bergum 45 ~ 132 × 103 natural gas 9 ~ 51 high pressure detection pipeline gasuni Westerbork 6000 ~ 2.4 × 106 natural gas 60 high pressure detection pipeline Instromet Utrecht 45 ~ 90 × 103 natural gas 9 standard volume pipe loop shell Pernis 5 ~ 200 ethylene 80

note: except for the flow of ethylene standard volume pipe loop, the other flows are under normal operating conditions (0oC, 1.01325bar)

the detection device located in Groningen, as shown in figure 1, is equipped with two sets of standard gas flow meters. One set consists of 10 parallel positive displacement (CVM) gas flow meters. Under conditions, the maximum flow of each flowmeter is 400m3/h. Like bergum transfer standard, this positive displacement flowmeter is only used to calibrate high standard flowmeter. Another set of standard gas flow meters is the working standard of the detection device used in Groningen's daily research. This set of flowmeter is composed of a positive displacement gas flowmeter with a maximum capacity of 400 m3/h and four turbine gas flowmeters with a maximum capacity of 650 m3/h, 1600 m3/h and two 4000 m3/h

due to the structure of the device, a set of 10 positive displacement flowmeter standards can be directly used to verify the working standards

in Groningen, these positive displacement flow meters always operate at an absolute pressure of 6 bar. The flowmeter tested can operate between 9 and 41 bar. When the test pressure exceeds 9 bar, the pressure shall be reduced to the range between the test flowmeter and the standard. Due to the pressure drop, the gas should be heated to the laboratory temperature. In view of the pressure drop and the gas temperature should be manually controlled, at this time, especially under low flow conditions, it is time-consuming to calibrate. If the pressure drops to the range between the test flowmeter and the standard, the compressibility of the gas plays a key role. To calculate the compression coefficient, either aga nx-19-mod algorithm or simplified gerg equation can be used. Since the compressibility depends on the composition of the gas, the gas chromatograph should be used to determine the mole fraction of the gas component. These parameters can be calculated from the composition of the gas, and they are the input parameters of the compressibility algorithm

rgum's high pressure detection device

bergum's high pressure detection device is designed to verify gas flow meters. As shown in Figure 2, the detection device is arranged in parallel with the gas supply station of a 668mw power plant. The operating pressure range of the device is 9 ~ 15 bar, and the pressure reaches 21 bar. The maximum flow rate is 8800m3/h, while the flow rate is 130000 when the pressure is between 21 and 51 bar. The unit indicates that the flow has been converted to normal conditions (0oC, 1.01325 bar)

Fig. 1 plan diagram of Groningen high pressure detection device. The 10 positive displacement flow meters on the left are high-pressure reference meters. The working standard on the right side of the figure is used to test the standard gas flow meters of

detection device, including four turbine gas flow meters with a maximum processing capacity of 4000 m3/h, one turbine gas flow meter with a processing capacity of 1000 m3/h and two CVM gas flow meters with a processing capacity of 400 m3/h and 1000 m3/h respectively

on bergum's device, both the standard gas flowmeter and the detected flowmeter operate under approximately the same pressure conditions. The advantage of this method is that in the verification process, there will be no other uncertainties caused by the gas compression coefficient algorithm. However, it also has disadvantages, that is, the standard gas flowmeter itself needs to be calibrated under several different pressure conditions. Bergum's standard gas flow meters are calibrated at pressures of 9 bar, 21 bar, 36 bar and 51 bar. The calibration coefficient between the calibration pressure of the standard is obtained by interpolating the error curve, in which the Reynolds number relationship curve corresponding to the calibration curve and the flow is drawn

the gas entering the detection device passes through two (safety) closed valves, a filter and a heater and then reaches the secondary pressure reducer. The test pressure is controlled by this pressure reducer. There are four parallel detection pipelines behind the pressure reducer. The length between flanges of three pipelines is, while the length between flanges of the other test pipeline is 11m. The diameter of these flow meters can be verified, and the range is 50 ~ 600 mm (ANSI or din flange)

the gas passes through one or several standard gas flow meters after passing through the detected flowmeter. After that, the pressure drops and the gas returns to the gas supply line of the power plant

gas flow meters from all over the world are calibrated on bergum's detection device. Vortex baffle flowmeter accounts for about 15% of the calibrated flowmeter, and the rest are orifice plate, venturi, nozzle, vortex flowmeter, plug-in flowmeter, ultrasonic flowmeter, etc. In recent years, the number of flow meters calibrated on the bergum test device has increased significantly (17% per year). This fully shows that the verification under operating conditions is of greater significance to the users of gas flow meters. In addition, the number of orifice plate, nozzle and Venturi verification has also increased significantly

in view of the large number of flow meters calibrated on this device, the standard gas flow meter must be checked frequently. A special detection instrument is installed on the newly configured detection device to detect the flowmeter with a flow rate of 25000 m3/h. In this way, the working standard can be checked continuously during the verification. Temporarily insert the transmission standard every week to check the working standard under high flow conditions

Figure 2 schematic plan of bergum high voltage detection device. The sonic nozzle used to control low flow is represented by SN. He is the high-pressure detection device of the heat exchanger


at the time of writing this article, Westerbork's detection device was the device with the highest flow in the world. The maximum amount of natural gas flowing through the unit is 2.4 at a pressure of about 60 bar × 104。 The device belongs to casunie, and part of the time is used for the research work carried out by casunie, while part of the time is used for the verification work carried out by the Netherlands Metrology Institute. The detection device is close to two large-diameter gas pipelines (1050 mm and 1200 mm) from Slochteren gas field to Ommen mixed transmission station. During calibration, the gas in these gas transmission lines flows through the bypass of the detection device (see Figure 3). The flow through the test device is controlled by bypass throttling. The gas first passes through 10 standard gas flow meters of the device. These standard flow meters are turbine gas flow meters with a maximum capacity of 4000 m3/h, so the maximum capacity under actual conditions is 40000 m3/h. This maximum gas flow can only be achieved in the cold season in the Netherlands when the gas consumption is quite large

the gas flows through one of the two test tubes after passing through the standard flowmeter. A detection line is used for gas flow meters up to 400 mm in diameter. The second line is usually used for flow meters with a diameter of 500 mm or greater. Two or three series flow meters can be calibrated on this device. Since the detection device is actually the bypass of the two main gas transmission lines, calibration can only be carried out when the line pressure is about 60 bar

the largest gas flowmeter ever calibrated in Westerbork is two 900 mm (36 in) venturis from the United States. In January, 1992, about 2.0 was adopted × These venturis were calibrated with a maximum gas flow of 106

Figure 3 schematic plan of Westerbork high pressure detection device

III. NMI low pressure calibration device

contrary to Westerbork's very high flow, the new low flow detection device located in Dordrecht is specifically used to calibrate the gas flowmeter with a maximum flow of 3 m3/h. The operating range of the low flow device is 2 ×~ 3 m3/h。 The instruments that can be calibrated are wet detection instrument, rotary piston flowmeter, mass flow controller, variable area flowmeter (rotameter), thermal mass flowmeter, soap film flowmeter, medical respiratory equipment detector and mercury sealed piston standard volume tube

the schematic device shown in Figure 4 includes four mercury sealed piston Standard volumetric tubes, which are used as standard flow meters; Four mass flow controllers, which produce a constant mass flow; There is also a flowmeter that has been tested. The nominal capacities of these standard volume tubes are 60 ml, 480 ml, 3500 ml and 13000 ml respectively. In essence, a mass flow controller includes a control valve, which forms a certain mass flow; A thermal mass flowmeter and a feedback system, which compares the actual mass flow with the preset mass flow and regulates the control valve. Use thermistor to measure the inlet and outlet of mercury sealed piston standard volume tube

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