Anti corrosion and anti-interference high-temperature electromagnetic flowmeter

Anti corrosion and anti-interference high-temperature electromagnetic flowmeter consists of a primary device and a secondary device. According to the combination of the primary device and the secondary device, the flowmeter can be divided into split type and integrated type; Flow meters are mainly used to measure the volumetric flow rate of conductive liquids.

1、 Instrument Introduction:

High temperature electromagnetic flowmeter is specially designed for water metering and trade in water supply enterprises, with the ability to prevent water, corrosion, interference, and lightning strikes. The electromagnetic flowmeter is specially designed with a backlit wide temperature Chinese LCD display, which is fully functional, practical, intuitive, and easy to operate, reducing the inconvenience caused by the English menu of other electromagnetic flowmeters. In addition, we have designed a 4-6 multi electrode structure to further ensure measurement accuracy and eliminate the need for grounding rings at all times, reducing the size of the instrument and the trouble of installation and maintenance.

IIAnti corrosion and anti-interference high-temperature electromagnetic flowmeterWorking Principle:

The high-temperature electromagnetic flowmeter, based on Faraday's principle of electromagnetic induction, installs a pair of detection electrodes on the tube wall perpendicular to the axis and magnetic field lines of the measuring tube. When the conductive liquid moves along the axis of the measuring tube, it cuts the magnetic field lines and generates an induced potential. This induced potential is detected by the two detection electrodes, and its value is proportional to the flow rate. Its value is E=KBVD equation:

E - Induced potential;

K - coefficient related to magnetic field distribution and axial length;

B - Magnetic induction intensity;

V - average flow velocity of conductive liquid;

D - electrode spacing; (Measuring the inner diameter of the tube)

The sensor uses the induced potential E as a flow signal, which is transmitted to the converter. After amplification, transformation, filtering, and a series of digital processing, the instantaneous and cumulative flow rates are displayed on a backlit dot matrix LCD. The converter has 4-20mA output, alarm output and frequency output, and is equipped with communication interfaces such as RS-485, and supports HART and MODBUS protocols.

IIIAnti corrosion and anti-interference high-temperature electromagnetic flowmeterConstruction and purpose:

The high-temperature electromagnetic flowmeter consists of a primary device and a secondary device. According to the combination of the primary device and the secondary device, the flowmeter can be divided into split type and integrated type; Flow meters are mainly used to measure the volumetric flow rate of conductive liquids. While meeting on-site display requirements, it can also output 4-20mA current signals for recording, regulation, and control purposes. It has been widely used in industrial technology and management departments such as chemical, environmental protection, metallurgy, pharmaceuticals, papermaking, and water supply and drainage.

4、 Flow meter structure form:

1. Sensor:

The sensor mainly consists of a measuring conduit, measuring electrodes, excitation coils, iron cores, magnetic yokes, and a housing.

a、 Measurement catheter: composed of stainless steel catheter, lining, and connecting flange, it is a carrier for measuring the on-site working conditions of the measured liquid.

b、 Measurement electrode: a pair of electrodes installed on the inner wall of the measurement catheter, perpendicular to the axial flow direction, to generate signals for the measured liquid.

c、 Excitation coil: The upper and lower excitation coils that generate a magnetic field inside the measuring conduit.

d、 Iron core and magnetic yoke: Introduce the magnetic field generated by the excitation coil into the liquid and form a magnetic circuit.

e、 Shell: Instrument outer packaging.

2. Converter: It is an intelligent secondary meter that amplifies and processes flow signals. After being operated by a microcontroller, it can display flow and cumulative measurement, and output signals such as pulses and analog currents for measuring or controlling fluid flow.

3. Product assembly form: It is divided into two forms: integrated and split.

a、 Integrated: The sensor and converter are installed together.

b、 Split type: Sensors and converters are installed separately, forming a flow metering system through connecting cables.

c、 To meet the requirements of measuring different media, there are multiple choices for the lining and electrode materials of sensors.

5、 Advantages:

1. The instrument structure is simple, reliable, without moving parts, and has a long working life.

2. No flow blocking components, no pressure loss or fluid blockage.

3. No mechanical inertia, fast response, good stability, can be applied to automatic detection, adjustment, and program control systems.

4. The measurement accuracy is not affected by the type of measured medium and its physical parameters such as temperature, viscosity, density, pressure, etc.

5. Different combinations of PTFE or rubber lining materials and electrode materials such as Hc, Hb, 316L, Ti can adapt to the needs of different media.

6. There are various flow meter models available, including pipeline type and plug-in type.

7. Using EEPROM memory, the storage of measurement and operation data ensures safety and reliability.

8. It has two types: integrated and separated.

9. High definition LCD backlit display.

6、 Performance indicators:

1. Instrument accuracy: pipeline type 0.5 level, 1.0 level; Insertion type 2.5 level.

2. Measurement medium: various liquid and liquid-solid two-phase fluids with conductivity greater than 5 μ S/cm.

3. Flow velocity range: 0.2-8m/s.

4. Work pressure: 1.6MPa.

5. Environmental temperature: -40 ℃ to+50 ℃.

6. Medium temperature: PTFE lining ≤ 180 ℃; Rubber material lining ≤ 65 ℃.

7. Explosion proof mark: Exmibd Ⅱ BT4.

8. Explosion proof certificate number: GYB01349.

9. External magnetic interference: ≤ 400A/m.

10. Shell protection: Integrated type: IP65.

Detached type: Sensor IP68 (5 meters underwater, with rubber lining) Converter IP65.

11. Output signal: 4-20mA.DC, load resistance 0-750 Ω.

12. Communication output: RS485 or CAN bus.

13. Electrical connection: M20 × 1.5 internal thread, φ 10 cable hole.

14. Power supply voltage: 90-220V.AC, 24 ± 10% V.DC.

15. Maximum power consumption: ≤ 10VA.

7、 Selection of installation environment:

In order to ensure stable operation of the transmitter, the following requirements should be noted when selecting the installation environment:

1. Try to avoid ferromagnetic objects and specific equipment with strong electromagnetic fields (such as large motors, transformers, etc.) to prevent the magnetic field from affecting the working magnetic field and flow information of the sensor.

2. It should be installed in a dry and ventilated place as much as possible, and should not be installed in damp or water prone areas.

3. Avoid direct sunlight and rain as much as possible, and avoid environments with temperatures above 45 ℃ and relative humidity above 95.9%.

4. Choose a place that is easy to maintain and has convenient activities.

5. The flowmeter should be installed at the rear end of the water pump and must not be installed on the suction side; The valve should be installed on the downstream side of the flowmeter.

8、 Measurement performance requirements:

1. Accuracy level

The accuracy level and maximum allowable error of the flowmeter within the specified flow range shall comply with the provisions of Table 1. Flow meter error refers to the relative indication error.

Accuracy level and maximum allowable error accuracy level

Note: Priority should be given to using grades without parentheses

2. Citation error

For the error representation of flow meters used for instantaneous flow indication, reference error can also be used, and its maximum allowable error series should comply with the provisions of Table 1. The accuracy level is no longer given in the calibration results of the bid, but its maximum allowable error representation should be used, and FS should be marked after the maximum allowable error, such as ± 0.5% FS.

3. Error representation methods and selection principles

In the calibration of a flowmeter, the error representation method of the flowmeter should be given according to one of the accuracy level and reference error; For flow meters that use a combination of relative indication error and reference error to represent errors, a unified method should also be used to represent their errors during a single calibration.

4. Repeatability

The repeatability of the flowmeter shall not exceed one-third of the maximum allowable error value specified for the corresponding accuracy level.

9、 Introduction features:

1. The measurement accuracy is not affected by changes in fluid density, viscosity, temperature, pressure, and conductivity. The sensor's induced voltage signal is linearly related to the average flow rate, resulting in high measurement accuracy.

2. There is no obstruction in the measuring pipeline, so there is no additional pressure loss; There are no movable parts inside the measuring pipeline, so the sensor has an extremely long lifespan.

3. Due to the fact that the induced voltage signal is formed in the entire space filled with a magnetic field and is the average value on the surface of the pipeline, the sensor requires a shorter straight pipe section, with a length of 5 times the diameter of the pipeline.

4. The sensor part only has the inner lining and electrodes in contact with the measured liquid. As long as the electrode and inner lining materials are selected reasonably, they can be corrosion-resistant and wear-resistant.

5. The converter adopts microcontroller (MCU) and surface mount technology (SMT), which have reliable performance, high accuracy, low power consumption, stable zero point, and convenient parameter setting. Click on the Chinese display LCD to show cumulative flow, instantaneous flow, flow rate, flow percentage, etc.

6. A bidirectional measurement system that can measure both forward and reverse flow rates. Using special production processes and high-quality materials to ensure the stability of product performance over a long period of time.

10、 Classified by excitation method:

To generate a uniform and constant magnetic field, it is necessary to choose a suitable excitation method. According to the excitation current method, there are DC excitation, AC (power frequency or other frequencies) excitation, low-frequency rectangular wave excitation, and dual frequency rectangular wave excitation.

1. DC excitation

The direct current excitation method uses direct current or a magnet to generate a constant and uniform magnetic field. The biggest advantage of this DC excitation transmitter is that it is less affected by AC electromagnetic field interference, so the effect of self inductance in the liquid can be ignored. However, using a direct current magnetic field can easily polarize the electrolyte liquid passing through the measurement pipeline, that is, the electrolyte is electrolyzed in an electric field, producing positive and negative ions. Under the action of the electric field force, negative ions run towards the positive electrode and positive ions run towards the negative electrode, which will cause the positive and negative electrodes to be surrounded by ions of opposite polarity, seriously affecting the normal operation of the instrument. So, DC excitation is generally only used to measure non electrolyte liquids, such as liquid metal flow (mercury at room temperature and liquid steel, lithium, potassium at high temperature), etc.

2. Communication excitation

Most electromagnetic flow meters used in industry use AC excitation with a power frequency of 50Hz to generate an alternating magnetic field, avoiding polarization interference on the surface of the DC excitation electrode. However, using AC excitation can bring a series of electromagnetic interference problems (such as orthogonal interference, in-phase interference, zero drift, etc.). Nowadays, AC excitation is being replaced by low-frequency square wave excitation.

3. Low frequency square wave excitation

There are two types of low-frequency square wave excitation waveforms: binary (positive negative) and ternary (positive zero negative zero), with frequencies typically ranging from 1/2 to 1/32 of the power frequency. Low frequency square wave excitation can avoid orthogonal electromagnetic interference caused by AC magnetic fields, eliminate power frequency interference caused by distributed capacitance, suppress eddy currents caused by AC magnetic fields on pipe walls and inside fluids, and eliminate polarization phenomena caused by DC excitation.

11、 Range confirmation:

The flow rate of the medium measured by the general industrial electromagnetic flowmeter should be 2-4m/s. In special circumstances, the minimum flow rate should not be less than 0.2m/s, and the maximum flow rate should not be greater than 8m/s. If the medium contains solid particles, the commonly used flow rate should be less than 3m/s to prevent excessive friction between the lining and the electrode; For viscous fluids, the flow velocity can be chosen to be greater than 2m/s. A higher flow velocity helps to automatically eliminate the effect of viscous substances attached to the electrode, which is beneficial for improving measurement accuracy.

Under the condition that the range Q has been determined, the size of the flowmeter diameter D can be determined based on the range of flow velocity V mentioned above, and its value can be calculated by the following formula:

Q=πD2V/4

Q: Flow rate (㎡/h) D: Inner diameter of pipeline V: Flow rate (m/h)

The range Q of the electromagnetic flowmeter should be greater than the expected maximum flow value, while the normal flow value should be slightly greater than 50% of the flowmeter's full range scale.

12、 Installation precautions:

1. The sensor of the flowmeter should be installed vertically, and the fluid should flow from bottom to top to meet the mixing state of solid and liquid. The reason is that solid objects (such as sediment, small stone particles, etc.) in the medium are prone to precipitation. In addition, if there are fish and weeds in the pipeline, the movement of fish in the pipeline will cause the output of the flowmeter to oscillate back and forth; The back and forth swing of weeds hanging near the electrode can also cause instability in the output of the flowmeter. Install a metal filter at the upstream inlet of the flowmeter to block fish and weeds from entering the measuring tube.

2. Improper setting and operation of the pipeline to prevent negative pressure may cause negative pressure to be generated inside the sensor. When the valves upstream and downstream of the flowmeter are closed simultaneously, if the temperature of the fluid is higher than the air temperature, it will shrink after cooling, which poses a risk of forming negative pressure inside the pipe. Negative pressure causes the lining to peel off from the metal conduit, resulting in electrode leakage.

3. Add a negative pressure prevention valve near the flowmeter, open the valve to connect to atmospheric pressure to prevent negative pressure from being generated inside the sensor. When a vertical pipeline is connected downstream of the flowmeter, if the upstream valve of the flow sensor is used to close or adjust the flow rate, negative pressure will be formed inside the measuring tube of the sensor. To prevent negative pressure, it is necessary to add back pressure or use downstream valves to regulate and close the flow rate.

4. Adequate maintenance space is often required for large-diameter flow meters to be installed in instrument wells for the convenience of pipeline installation, wiring, inspection, and maintenance. For the convenience of observation, wiring, and maintenance, instrument installation should be at a certain height from the ground for easy cleaning and installation.

13、 Main technical data:

1. Technical data of the whole machine and sensors

2. Converter technology data

3. Selection of lining

4. Selection of imported protective flanges and grounding flanges (or grounding rings)

5. Selection of electrodes

14、 Correct selection:

The selection of instruments is a very important task in instrument applications. Relevant data shows that 2/3 of instrument failures in practical applications are caused by incorrect selection or installation of instruments. Please pay special attention.

1. Collect data:

The composition of the fluid being tested;

Zui high traffic, Zui low traffic;

The highest work pressure;

Zui high temperature, Zui low temperature;

2. Range confirmation:

The flow rate of the measured medium in general industrial flow meters should be between 2-4m/s. In special cases, the minimum flow rate should not be less than 0.2m/s, and the maximum flow rate should not be greater than 8m/s. If the medium contains solid particles, the commonly used flow rate should be less than 3m/s to prevent excessive friction between the lining and the electrode; For viscous fluids, the flow velocity can be chosen to be greater than 2m/s. A higher flow velocity helps to automatically eliminate the effect of viscous substances attached to the electrode, which is beneficial for improving measurement accuracy.

Under the condition that the range Q has been determined, the size of the flowmeter diameter D can be determined based on the range of flow velocity V mentioned above, and its value can be calculated by the following formula:

Q=πD2V/4

Q: Flow rate (㎡/h) D: Inner diameter of pipeline V: Flow rate (m/h)

The electromagnetic range Q should be greater than the expected maximum flow rate value, while the normal flow rate value should be slightly greater than 50 times the full scale of the flowmeter.

3. Reference flow range:

15、 Selection Table:

16、 Ordering Notice:

1. Product: If there are model standards, please call directly to inquire about prices and learn more details!

2. If there are no product model specifications, please send the operating requirements, design drawings, and technical specifications to our company.

3. Product ordering requires parameters such as diameter (DN), nominal pressure (Mpa), temperature (℃), flow range (m3/h), medium name (such as water), connection method (clamp type, threaded type, flange type, clamping type, split type, insertion type, etc.).

4. Quotation confirmation: Our company provides a quotation list and technical standard specifications to the customer for confirmation. After both parties confirm the technical aspects, the contract will be drafted.

5. Quality requirements, quality standards, and conditions for suppliers to be responsible for quality: in accordance with relevant national quality standards.

After-sales service

1. From the date of contract signing, our company provides free maintenance and upkeep services for the products provided, and promises lifelong repair services;

2. Jiangsu Desen Instrument Co., Ltd. will regularly communicate with customers to understand the usage of the product and solve any problems that arise during their use, providing free services;

3. During the warranty period, if there is any man-made damage, our company is responsible for repairing it and collecting the repair costs incurred;

4. If there are quality problems or dissatisfaction with the product, users can choose to return or exchange it unconditionally. The company does not charge any handling fees. If there are quality problems, the company will bear the round-trip shipping costs.