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Technical analysis and summary of vortex flowmeter
Jan 17, 2020

Vortex flowmeter is often used for steam measurement. Steam is widely used as an important secondary energy. The accurate measurement of steam flow is closely related to the selection and installation of steam flowmeter. We select vortex flowmeter which is widely used in the market as the analysis object

Vortex flowmeter mainly consists of the following four parts: (1) vortex flow sensor; (2) pressure transmitter; (3) temperature platinum resistance; (4) flow totalizer. As a measuring instrument for trade settlement, the above four measuring instruments need to be properly selected, qualified by compulsory verification and installed correctly before trade settlement. The working principle of vortex flow sensor is Kaman vortex principle A vortex generator (choke) is set in the vortex generator. When there is air flow passing through, regular alternate vortices are generated from both sides of the downstream of the vortex generator. Within a certain range of Reynolds number (2 × 104 ~ 7 × 106), the frequency of the vortex is related to the geometric size of the vortex generator and the geometric size of the pipe, and the frequency of the vortex is proportional to the flow. This frequency can be detected by the probe

When general users choose to buy vortex flow sensors in the market, they need to buy vortex flow sensors with the mark of ○ ma. That is, vortex flow sensors produced by enterprises that have obtained the manufacturing license of measuring instruments of the people's Republic of Dubai of UAE. If the flowmeter is used for trade settlement, it is compulsory verification. Before use, it should be sent to the local measurement department for verification, and it can be installed and used only after passing the verification. Refer to j for verification Jg1029-2007 verification regulation of vortex flowmeter

Before purchasing vortex flowmeter, the first thing users should do is to select a suitable vortex flowmeter. It is very important to select a suitable vortex flowmeter. The diameter of vortex flowmeter is from DN15 to DN300. Because the larger the diameter of vortex flowmeter is, the smaller the instrument coefficient is, the lower the frequency resolution is, and the worse the accuracy is, the selection diameter should not be larger than DN300 generally. The measurement range of different caliber flowmeter is different. It should be based on oneself The actual use of vortex flowmeter should be reasonably configured. First, determine the approximate consumption of steam. Second, determine whether the steam in the pipeline is superheated steam or saturated steam. Finally, know the status of the steam in the pipeline, such as pressure and temperature, and reasonably configure the pressure transmitter and temperature platinum thermistor. Through the instrument manual, you can query the flow measurement range of different caliber instruments

Whether the vortex flowmeter is installed correctly or not directly affects its accurate measurement. When installing the instrument, the following points shall be paid attention to: 1. The installation shall meet the requirements of the instrument operation manual to ensure the length of the upstream and downstream straight pipe sections of the vortex flowmeter; 2. The inner diameter of the upstream and downstream piping shall be the same as the inner diameter of the sensor; 3. The piping shall be concentric with the sensor; 4. The sealing gasket shall not protrude into the pipe, and its inner diameter can be The inner diameter of the sensor is 1mm ~ 2mm larger than the inner diameter of the sensor. 5. The installation site of the sensor shall avoid the vibration source as much as possible, and the installation of pipeline support is an effective shock absorption method. 6. In the electrical installation, the shielded cable or low-noise cable shall be used to connect the sensor and the converter, and the distance shall not exceed the provisions of the operation manual. The wiring shall be far away from the strong power supply line, and shall be protected with a separate metal sleeve as much as possible Follow the principle of "one point grounding". The integral type and separate type shall be grounded at the sensor side, and the converter shell grounding point shall be "the same ground" with the sensor. This can effectively avoid the instrument damage caused by lightning stroke

The installation position of temperature platinum thermistor and pressure transmitter shall comply with the requirements of and 7.1.15 in jjg1029-2007 verification regulation of vortex flowmeter. The temperature measurement position shall be set at the downstream (2-5) d of flowmeter (D is the pipe diameter), and the pressure measurement position shall be at the downstream (2-7) D of flowmeter. The axis of pressure tapping hole shall be perpendicular to the axis of measuring pipe with the diameter of (4-12) mm. The installation of temperature platinum thermistor and pressure transmitter The installation method shall comply with the requirements of 4.2, 4.3 and 5.4 of gb50093-2002 code for construction and acceptance of automatic instrument engineering. When the pressure source parts and the temperature source parts are on the same pipe section, the pressure shall be installed on the upstream side of the temperature source parts

When measuring steam, the pressure tap shall be equipped with ring type or U-type condensing pipe. The installation height of the pressure transmitter for measuring low pressure shall be consistent with the height of the tap point. The following figure shows four installation methods of the pressure transmitter