Vortex flow sensor

1 Introduction 2 Vortex flow meter is based on Karman vortex street theory, using the natural vibration principle of fluids, using a piezoelectric crystal or differential capacitance as a detection component made of a speed flow meter.

Feige Ruisi vortex flow sensor has no moving parts, large measuring range, wide media adaptability, high measurement accuracy, long test cycle, long distance transmission signal, small pressure loss, simple structure, reliable operation, long service life , Easy installation and maintenance, and many other significant advantages. Can be widely used in petrochemical, metallurgical machinery, food, paper, and urban pipeline heating, water supply, gas and other industries of a variety of liquids, gases, steam and other single-phase fluid process measurement and energy management.

3 Features Edit

It adopts a new design of structure that resists mechanical shock, shock and dirt.

The use of the most advanced integrated circuits, high signal processing accuracy, high anti-interference, and high reliability.

Wide range models are available for superior low flow performance and widened flow range.

Capacitance type flowmeters can be used to provide excellent shock resistance and the highest measurement temperature can reach 400°C.

Submersible flowmeters are available, allowing long-term soaking in water.

Measuring principle

4 Editing

Vortex flowmeter is composed of vortex generators, detection probes and related electronic circuits designed in the flow field. When the liquid flows through the triangular columnar vortex generator, two sides of it become alternating alternate rows of vortices. This vortex is called Karman vortex street. These alternate vortices form a series of negative pressures for change. The pressure acts on the deep end of the test, and generates a series of alternating electrical signals. After the preamplifier converts, shapes, and magnifies the signal, it outputs a pulse frequency signal that is proportional to the vortex.

5 Vortex flow sensor how to make pressure compensation edit

[1] Selection of Pressure Compensation Pressure Transmitter: Due to the long saturated steam line and large pressure fluctuations, pressure compensation must be used. In consideration of the pressure, temperature, and density correspondence, only pressure compensation can be used in the measurement. Mingtong company's pipeline saturated steam pressure in the range of 0.3-0.7MPa, the pressure transmitter can choose 1MPa range.

1. When the measured medium contains more impurities, a filter should be installed in addition to the required length of the straight section upstream of the sensor. 2. The sensor should be installed on a pipe with mechanical vibration. When the vibration is unavoidable, a fixed support frame should be added to the straight pipe section at about 2DN before and after the sensor. 3. The sensor should be installed in a place with strong electromagnetic field interference, heat radiation, corrosive gas, small space, and inconvenient maintenance.

Vortex flow sensors are widely used in petroleum, chemical, metallurgical and other industrial sectors, and are also used in municipal engineering and environmental protection industries, as well as steam flow measurement and detection and control.

The vortex flow sensor is a new type of flow meter for measuring the flow of a closed pipe according to the Karmen vortex principle. Because of its good media adaptability, it can directly measure the volumetric flow rate of steam, air, gas, water, and liquid without temperature and pressure compensation. With temperature and pressure sensors, it can measure standard volume flow and mass flow, which is throttling. Ideal alternative to flowmeters.

6 Research and Discussion Editing

The experimental line consists of 8 standard sensor strings with a DN of 50-150mm and the parallel combination is compared with the large-diameter sensor (DN=80-300mm) tested. The test pipelines are arranged in a diagonal direction and arranged in parallel. The purpose is to save raw materials and reduce the cost. It also just meets the requirements of the straight sections of various aperture sensors (according to national standards ZBN12005-1989 or JJG643-1994). The length of the pipe section is greater than 50 DN; the length of the straight pipe section before being tested is greater than 20 DN; the resistance loss is reduced to a minimum value.

(2) The gas source is supplied by two 9-19 high-pressure centrifugal fans and one LG300×200-1 Roots blower. Two of the centrifuges of the same type achieve serial or parallel operation by controlling the electric valve according to the flow requirements to meet the requirements of different flow rates and different pressures.

(3) Standard sensor: The device uses eight standard sensors, all of which are stress vortex sensors. The advantage of this instrument is that it has no moving parts with high repeatability, and has strong overload and impact resistance. Stainless steel for the sensor body is resistant to wear and corrosion, and the sensor is highly stable. In addition, the meter factor of this kind of sensor is not affected by or very influenced by the physical property parameters of the measured medium. Therefore, when used as a standard sensor, it is only necessary to be consistent with the material to be measured.

At present, the standard of the gas vortex sensor in China is generally 0.5 to 1 level. From the level of accuracy, it cannot be used as a 0.5-level sensor, but the scope of this type of instrument is very wide. Generally about 10:1 to 15:1, and the repeatability is very good, both within 0.2%, or even higher, such as the use of compression range calibration in the fixed point is an effective way to improve accuracy. We have done a lot of experimental research. The results show that if the range is compressed to within 2:1 or 3:1, calibration at the fixed point can meet the requirements. Therefore, using this sensor standard, it is feasible to establish a gas flow device.
Precautions

[2] (1) Vortex flow sensor should pay attention to keep the probe clean in the application, when the technical indicators such as gain value/noise or signal to noise ratio/signal quality reflecting probe cleanliness approach or reach the limit value, vortex flow sensor The measurement results are inaccurate and affect the measurement results when the body and the straight pipe section are dirty. Therefore, the cleaning of gas vortex flow sensor probes, body and upstream and downstream straight pipe sections is an important task for maintenance.

(2) The vortex flow sensor and its secondary instrument used for custody transfer measurement shall be periodically verified in accordance with the requirements of relevant regulations. Vortex flow sensor verification is divided into offline verification and online calibration.

7 The basic structure of the device is edited

(1) Experimental pipeline. The device is composed of 8 standard sensor strings with a DN of 50-150mm, and the parallel combination is compared with the large-diameter sensor (DN=80-300mm) being tested. The test pipelines are arranged in a diagonal direction and arranged in parallel. The purpose is to save raw materials and reduce the cost. It also just meets the requirements of the straight sections of various aperture sensors (according to national standards ZBN12005-1989 or JJG643-1994). The length of the pipe section is greater than 50 DN; the length of the straight pipe section before being tested is greater than 20 DN; the resistance loss is reduced to a minimum value.

(2) The gas source is supplied by two 9-19 high-pressure centrifugal fans and one LG300×200-1 Roots blower. Two of the centrifuges of the same type achieve serial or parallel operation by controlling the electric valve according to the flow requirements to meet the requirements of different flow rates and different pressures.

(3) Standard sensor: The device uses eight standard sensors, all of which are stress vortex sensors. The advantage of this instrument is that it has no moving parts with high repeatability, and has strong overload and impact resistance. Stainless steel for the sensor body is resistant to wear and corrosion, and the sensor is highly stable. In addition, the meter factor of this kind of sensor is not affected by or very influenced by the physical property parameters of the measured medium. Therefore, when used as a standard sensor, it is only necessary to be consistent with the material to be measured.

At present, the standard of the gas vortex sensor in China is generally 0.5 to 1 level. From the level of accuracy, it cannot be used as a 0.5-level sensor, but the scope of this type of instrument is very wide. Generally about 10:1 to 15:1, and the repeatability is very good, both within 0.2%, or even higher, such as the use of compression range calibration in the fixed point is an effective way to improve accuracy. We have done a lot of experimental research. The results show that if the range is compressed to within 2:1 or 3:1, calibration at the fixed point can meet the requirements. Therefore, using this sensor standard, it is feasible to establish a gas flow device.

8 Lightning Research Editor

Frequently, companies have been installed with vortex flow sensors that have experienced lightning strikes that cause damage. Lightning is a common phenomenon in nature, so we have to find ways to eliminate its impact on flow sensors. First of all, let's find out what the impact of lightning on the sensor will be.
First, lightning strikes the sensor through the power supply.
Second, the lightning generated at the same time accompanied by a strong magnetic field instrumentation electronic components generate magnetic induction, instantaneously generate strong voltage and current, breakdown insulation burn sensor.
Third, lightning pulse waves invade a flow sensor through a wireless network and burn out a communication chip or sensor.
According to the on-site environment, lightning protection should not adopt a general lightning protection scheme. Common lightning protection schemes include:
1, external lightning protection. Including lightning rods, lightning protection strips, deflectors, grounding electrodes, etc.
2. Internal lightning protection. Install suitable lightning protectors at the front end of the equipment that needs to be protected to form a conditional equipotential body between the equipment and the circuit.
The two lightning protection schemes complement each other. The external lightning protection system protects the building body from lightning strikes, while the internal lightning protection is to prevent induction lightning and other forms of overvoltage from invading the device and causing damage.
If the flow sensor is damaged, it is best to check whether the lightning rod is installed first. If so, check whether the grounding resistance is qualified at the testing point; if the flow sensor is connected with the pipe flange, check whether the grounding screw of the internal amplification board is Connected, the shell can be used alone as a bottom line copper wire to connect to the pipe flange bolt, and then the cable into the line, the outside of the protective tube and the end of the connecting metal hose must be screwed into the hole into the hole; In addition, a surge protector can be added to the front end.
It is also necessary to explain that it is not time for the sensor to consider lightning protection measures and the work is over. Before the annual thunderstorm season, it is also necessary to regularly check the installed vortex flow sensor. If it is found that there is a great change in the value of the grounding resistance, the grounding system should be fully inspected, and if necessary, the grounding pile can be supplemented. If the conductor of each part of the lightning protection device is broken or rusted by more than 30% due to corrosion or other reasons, it must be replaced. In addition, check whether there is any subsidence of soil around the grounding device.
The lightning protection of the sensor is a system work. It cannot be omitted for a moment. Many of the damage caused by lightning to the flow sensor is permanent and unrecoverable, which directly affects the safe operation of production. This has a particularly significant effect on the manufacturers of continuous production.
Operating conditions

Flowmeters should be calibrated or real-time calibrated according to national standards or procedures prior to commissioning. Check various signal lines and the power cord is connected. First open the inlet bypass valve, slowly inflate the pipeline, and then slowly open the inlet stop valve (at least for 1min) to avoid the flowmeter over-high pressure difference or excessive flow rate, and slowly pressurize the pipeline to reach the operating pressure of the flowmeter. Check for gas leaks at all flange connections and at the pressure connector and the temperature sensor plug connector. Check the system wiring diagram provided by the manufacturer and check that all wiring is correct. The maximum flow rate of the flowmeter does not exceed 30m/s. Before the flowmeter is enabled, it is required to perform zero flow test. The site does not have the condition that zero flow test should be conducted under working conditions (zero flow test is to close the upstream and downstream valves of the ultrasonic flowmeter so that the gas flow rate through the flowmeter is zero , After the gas temperature in the pipeline is stable, read the zero flow rate reading. Record the gas flow rate of each channel for at least 30s, and the zero flow rate reading should be less than 12mm/s) [2] .