Intelligent high-precision electromagnetic flowmeter

Intelligent high-precision electromagnetic flowmeter, in addition to measuring the flow rate of general conductive liquids, can also measure the volumetric flow rate of liquid-solid two-phase flow, high viscosity liquid flow, and salt, strong acid, and strong alkali 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.

1、 Instrument Introduction:

High precision electromagnetic flowmeter is an induction instrument for measuring the volume flow rate of conductive medium inside a tube. It adopts embedded technology of single-chip microcomputer to achieve digital excitation, and adopts CAN fieldbus on the electromagnetic flowmeter. It can achieve an accuracy of 0.2%, with high precision and a flow measurement range of up to 150:1. Can be used to measure the volumetric flow rate of conductive fluids in closed pipelines.

IIIntelligent high-precision electromagnetic flowmeterWorking Principle:

The high-precision electromagnetic flowmeter is based on Faraday's principle of electromagnetic induction. A pair of detection electrodes are installed on the pipe wall perpendicular to the axis of the measuring tube and the magnetic field lines. 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 the 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.

3、 Main components:

A high-precision electromagnetic flowmeter consists of a sensor and a converter. The sensor is installed on the measuring pipeline, and the converter can be combined with the sensor to form an integrated electromagnetic flowmeter. The converter is installed within 30 meters or 100 meters of the sensor and connected by a shielded cable to form a separate electromagnetic flowmeter. The main components of an electromagnetic flowmeter sensor are: measuring tube, electrode, excitation coil, iron core, and magnetic yoke housing.

4、 Application scope:

High precision electromagnetic flowmeter can not only measure the flow rate of general conductive liquids, but also measure the volumetric flow rate of liquid-solid two-phase flow, high viscosity liquid flow, and salt, strong acid, and strong alkali 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.

5Intelligent high-precision electromagnetic flowmeterAdvantages:

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、 Structural 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:

Is it an intelligent secondary meter that amplifies and processes traffic signals?? After calculation by the microcontroller, it can display flow rate, cumulative measurement, and output signals such as pulses and analog currents for measuring or controlling fluid flow rate.

3. Product assembly form:

It is divided into two forms: one-piece and split type.

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.

8、 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.

9、 Production installation requirements and usage:

1. Requirements for external environment:

a、 Flow meters should be avoided from being installed in places with large temperature changes or high temperature radiation from equipment. If installation is necessary, insulation and ventilation measures must be taken.

b、 The flowmeter needs to be installed indoors. If it must be installed outdoors, it should be protected from rainwater, waterlogging, and direct sunlight. Moisture and sun protection measures must be taken.

c、 Flow meters should be avoided from being installed in environments containing corrosive gases, and ventilation measures must be taken when installation is necessary.

d、 For installation, maintenance, upkeep, and convenience, there needs to be ample installation space around the flowmeter.

e、 The installation site of the flowmeter should avoid strong magnetic fields and vibration sources. If the pipeline vibration is large, there should be fixed pipe supports on both sides of the flowmeter.

2. Requirements for process pipes

The flowmeter has certain requirements for the upstream and downstream process pipes of the installation point, otherwise it will affect the measurement accuracy.

a、 The inner diameter of the upstream and downstream process pipes should be the same as that of the sensor, and should meet the requirement of 0.98DN ≤ D ≤ 1.05DN (where DN is the inner diameter of the sensor and D is the inner diameter of the process pipe)

b、 The process pipe and sensor must be concentric, and the coaxial deviation should not exceed 0.05DN

3. Requirements for bypass pipes

In order to facilitate the maintenance of flow meters, a bypass pipe must be installed. In addition, for heavily polluted fluids and flow meters that require cleaning and cannot be stopped, a bypass pipe must be installed.

10、 Installation precautions:

1. When transporting and lifting sensors, the sling should be placed at the neck position next to the flanges at both ends of the sensor. Do not insert the pipe support into the measuring or pipe for lifting to avoid damaging the lining.

2. Before installation, carefully wipe the electrode surface inside the sensor with alcohol cotton to remove any oily contaminants caused by hand touch or other reasons.

3. The inner diameter of the sealing gasket during installation should be equal to the inner diameter of the measuring tube lining.

4. It is necessary to ensure that the junction box is dry, otherwise the instrument may produce measurement errors.

11、 Preparation before operation:

1. Before officially putting into operation after installing the wiring, the installation and wiring should be checked again for correctness. (For split body types)

2. Open the valve before the bed dries up and close the valve after the sensor, allowing the sensor to be filled with the measured medium.

3. After the preparation work is completed, first open the upstream valve of the sensor, then slowly open the downstream valve, and observe that the instantaneous flow display of the converter should change towards the large direction, indicating that the direction of the signal line is correct. Otherwise, swap the wiring positions of signal lines A and B. (For split body types)

4. Open the front and rear valves of the sensor, drain the liquid for a few minutes, and release the gas inside the pipe.

5. Close the downstream valve of the sensor and then close the upstream valve to fill the sensor with the measured medium. Then make matching adjustments. Please refer to the converter manual for the zero adjustment and instrument coefficient setting of the sensor and converter.

12、 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

13、 How to choose correctly:

Selection 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:

① Composition of the tested fluid

② Zui high traffic, Zui low traffic

③ The highest work pressure

④ Zui high temperature, Zui low temperature

2. 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-scale scale.

3. Reference flow range:

14、 Selection Table:

15、 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.