Discharge flowmeter

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Basic Overview of Sewage Flow Meter

Electromagnetic flowmeter, abbreviated as EMF, is a new type of flow measurement instrument that rapidly developed with the development of electronic technology in the 1950s and 1960s. It is an instrument made according to Faraday's law of electromagnetic induction, used to measure the volumetric flow rate of conductive liquids. Due to its unique advantages, it has been widely used for flow measurement of various conductive liquids in industrial engineering, such as corrosive media such as acids, alkalis, salts, etc; Various flammable and explosive media; The measurement of various slurry flow rates in wastewater treatment, chemical, food, pharmaceutical and other industries has formed a unique application field.

Principle of sewage flowmeter

The working principle of electromagnetic flowmeter is based on Faraday's law of electromagnetic induction. The conductive medium inside the measuring tube is equivalent to a conductive metal rod in Faraday's test, and the two electromagnetic coils at the upper and lower ends generate a constant magnetic field. When a conductive medium flows through, an induced voltage is generated. The induced voltage generated by measuring the two electrodes inside the pipeline.

Structurally, it consists of two parts: an electromagnetic flow sensor and a converter. Sensors are installed on industrial process pipelines, and their function is to linearly transform the volume flow rate value of the liquid flowing into the pipeline into an induced potential signal, and send this signal to the converter through a transmission line. The converter is installed not too far from the sensor, which amplifies the flow signal sent by the sensor and converts it into a standard electrical signal output proportional to the flow signal for display, accumulation, and adjustment control.

The basic principle of electromagnetic flowmeter

1. Measurement principle

According to Faraday's law of electromagnetic induction, when a conductor moves in a magnetic field and cuts magnetic field lines, an induced electric potential e is generated at both ends of the conductor, and its direction is determined by the right-hand rule. Its magnitude is proportional to the magnetic induction intensity B of the magnetic field, the length L of the conductor in the magnetic field, and the velocity u of the conductor. If B, L, and u are perpendicular to each other, then

e＝Blu

Similarly, in a uniform magnetic field with a magnetic induction intensity of B, a non-magnetic pipeline with an inner diameter of D is placed perpendicular to the direction of the magnetic field. As can be seen from the above equation, the volumetric flow rate qv is linearly related to the induced electromotive force e and the inner diameter D of the measuring tube, and inversely proportional to the magnetic induction intensity B of the magnetic field, regardless of other physical parameters. This is the measurement principle of an electromagnetic flowmeter

It should be noted that in order for the equation to strictly hold, the measurement conditions must satisfy the following assumptions:

① Magnetic field is a uniformly distributed constant magnetic field;

② The axisymmetric distribution of flow velocity of the measured fluid;

③ The tested liquid is non-magnetic;

④ The conductivity of the tested liquid is uniform and isotropic.

Principle diagram

1- Magnetic pole; 2- Electrode; 3- Pipeline

Product features of sewage flowmeter

1. There are no internal flow barriers, with almost no pressure loss or fluid blockage.

2. No mechanical inertia, fast response, wide flow measurement range (flow velocity 0.3~12m/s), good stability, can be used for automatic detection, adjustment, and program control systems.

3. The measurement of liquid conductivity greater than 5u S/cm is not affected by changes in fluid density, viscosity, temperature, pressure, and conductivity. The sensor induced voltage signal is linearly related to the average velocity, and the measurement accuracy is high.

4. Accuracy levels: 0.2, 0.5, 1.0, 1.5. Meet the needs of different users.

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

6. Divided into conventional type (pressure less than 4.0MPa) and high-pressure type (pressure greater than 4.0MPa).

7. The plug-in electromagnetic flowmeter system is divided into simple installation type and online installation type.

8. Using EEPPOM memory, the storage of measurement and operation data is secure and reliable.

9. Adopting internationally advanced microcontroller (MCU) and surface mount technology (SMT), it has reliable performance, high accuracy, low power consumption, zero point stability, Chinese menu, and convenient parameter setting.

10. Equipped with 4-20mA, frequency and pulse output, alarm level output, RS485 communication interface, Hart and ModBus protocols.

11. High definition LCD backlight displays instantaneous flow, cumulative flow (∑+, ∑ -, ∑ D), flow rate, flow percentage, flow status (excitation, flow, air traffic control), etc.

12. 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.

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

14. Protection level: Integrated structure IP65, split structure IP68.

15. Explosion proof grade: Exd Ⅱ BT4.Main technical data of sewage flowmeter

1. Nominal diameter: DN6-2200mm

2. Nominal pressure: 0.6, 1.0, 1.6, 2.5, 4.0 MPa (high pressure can be processed according to user requirements)

3. Accuracy: ± 0.2% ± 0.5% (indication error)

4. Measurement range (flow rate): 0-1m/s to 0-10m/s

5. Medium temperature: Split type -10 ℃~+80 ℃ (PTFE and F46 lining -40 ℃~+180 ℃) Integrated type -10 ℃~+80 ℃

6. Environmental temperature: -25 ℃~+60 ℃

7. Environmental humidity: 5-100% RH (relative humidity)

8. Dielectric conductivity: greater than 20 μ S/cm

9. Installation: integrated type, split type

10. Shell protection level: Sensor IP65, IP68 optional (IP65: dust tight, anti spray type, allowing the faucet to spray water from any direction on the instrument; IP68: Dust tight, submersible type, capable of long-term operation in water) Converter IP65

11. Electrode structure: Three electrode structure, electrode structure

12. Tested medium * * * high temperature: chloroprene rubber lining * * * high 80 ℃, polyurethane lining * * high 80 ℃, polytetrafluoroethylene lining * * high 180 ℃, high temperature resistant rubber lining * * high 120 ℃

13. Sensor output signal: 0-0.2mVp-p to 0-2mVp-p

14. Electrode materials: stainless steel OCrl8Nil2Mo2Ti, Hastelloy B, C, titanium Ti, tantalum (Ta), stainless steel coated tungsten carbide, special

15. Explosion proof signs: Exm Ⅱ T4, Exmd Ⅱ BT4

Selection of lining materials for sewage flow meters

The lining material should be selected based on the corrosiveness, wear resistance, and temperature of the tested medium

Selection of electrodes for sewage flowmeter

The material of the electrode should be selected based on the corrosiveness of the fluid being tested. Please refer to the relevant manual. For special fluids, a corrosiveness test should be conducted

Type spectrum of sewage flowmeter

Installation of sewage flowmeter

1. It should be installed at the lower and vertically upward positions of the horizontal pipeline, avoiding installation at the highest points and vertically downward positions of the pipeline;

2. Should be installed at the rising point of the pipeline;

3. When installing an open discharge pipeline, it should be installed at the lower part of the pipeline;

4. If the pipeline drop exceeds 5m, install an exhaust valve downstream of the sensor;

5. Control valves and shut-off valves should be installed downstream of the sensor, rather than upstream of the sensor;

6. Sensors cannot be installed at the inlet and outlet of the pump, they should be installed at the outlet of the pump;

7. The method of installing liquid flow meters in the measuring well;

Figure 7 Remarks: 1. Inlet 2. Overflow pipe 3 Inlet grille 4. Cleaning hole 5. Flow meter 6. Short pipe 7. Outlet 8. Discharge valve

How to choose the installation node correctly:

Choosing the correct installation point and installing the flow meter correctly are both very important steps. If there is a mistake in the installation process, it can affect the measurement accuracy in mild cases, the service life of the flow meter in severe cases, and even damage the flow meter.

Special attention should be paid when selecting the installation location:

The axis of the non measuring electrode must be approximately horizontal;

The measuring pipeline must be completely filled with liquid;

There should be at least a 5 × D (D is the inner diameter of the flowmeter) straight pipe section in the front * * *, and at least a 3 × D (D is the inner diameter of the flowmeter) straight pipe section in the rear * * *;

The flow direction of the fluid is consistent with the arrow direction of the flowmeter;

Vacuum inside the pipeline can damage the lining of the flowmeter, so special attention should be paid;

There should be no strong electromagnetic field near the flowmeter;

There should be ample space nearby for installation and maintenance;

If there is vibration in the measuring pipeline, there should be fixed supports on both sides of the flowmeter. When measuring mixed liquids of different media, the distance between the mixing point and the flowmeter should be at least 30 × D (D flowmeter inner diameter). To facilitate future cleaning and maintenance of the flowmeter, a bypass pipeline should be installed;

Jiangsu Huayun Instrument Co., Ltd. is a key complete unit of measurement and control engineering in China, a domestic instrument manufacturer with extensive application achievements and cases in the industry. Its products are known for their high quality and are renowned throughout the country. The brand has a high degree of trust among customers in the industry. Our main products include flow meters (steam flow meters, electromagnetic flow meters, vortex flow meters, turbine flow meters, etc.), pressure transmitters, level gauges, and other related series. The company has a large number of professional talents and efficient service teams who have been engaged in the research and development, manufacturing, and sales of instruments and meters for a long time. The quality of our products is always our goal. Welcome customers to consult and choosePurchase!