Application and Maintenance of Insertion Magnetic Flow Meters

Insertion magnetic flow meters are instruments designed to measure conductive liquids based on Faraday's electromagnetic induction law. These instruments are widely used in the petroleum and chemical industries to measure the volumetric flow of non-corrosive conductive liquids (such as water supply and drainage) in closed pipelines due to their simple structure, lightweight, ease of installation, and minimal maintenance.

Working Principle and Characteristics of Insertion Magnetic Flow Meters

1. Measurement Principle
   The insertion magnetic flow meter works based on Faraday’s electromagnetic induction law to measure conductive liquids. The flow meter's measuring tube is housed in an insulated casing, which contains coils, an iron core, and a magnetic yoke. Electrodes are installed on the ends of the casing. The excitation coil, powered by a bidirectional square pulse, generates a magnetic field with a magnetic flux density BBB. When the fluid, with a certain conductivity, flows through the measuring tube at an average velocity VVV, it cuts through the magnetic lines of force, inducing an electromotive force (EMF) EEE. This EMF is proportional to the product of the magnetic flux density BBB and the average flow velocity V:
   E∝K⋅B⋅V
   where K is a constant related to the instrument's structure.
   The EMF E(flow signal) is detected by the electrodes and sent to the transmitter via cables.

2. Structural Features
   The insertion electromagnetic flow meter consists of two main parts: the sensor and the transmitter. The sensor and transmitter can be configured as either a split or integrated type.

3. Applicable Range
   The measurement range of the insertion electromagnetic flow meter is the same as that of general electromagnetic flow meters.

Main Technical Features and Applications of Insertion Magnetic Flow Meters

1. High Accuracy
   The measurement results are unaffected by changes in flow velocity distribution, fluid pressure, viscosity, temperature, density, or conductivity.

2. Wide Range of Nominal Diameters
   Suitable for use on metal pipelines with nominal diameters from DN15 to DN2200.

3. Wide Measurement Range
   The flow meter offers a wide range, up to 100:1.

4. Corrosion and Wear Resistance
   The sensor part only has internal linings and electrodes in contact with the measured fluid. By selecting appropriate materials for the electrodes and linings, corrosion and wear resistance can be ensured.

5. High-Performance Transmitter
   The transmitter uses a 16-bit high-performance microprocessor and features a 128×64 LCD display with Chinese characters. Parameters can be easily set, and programming is reliable.

6. Low Straight Pipe Requirements
   The straight pipe requirements are minimal, with only 5D before and 3D after the meter (D is the nominal diameter of the pipeline).

Installation of Insertion Magnetic Flow Meters

1. Installation of Split-type Transmitters
   Split-type transmitters should be installed as close to the sensor as possible, either on a wall or a column. For outdoor installations, they should be placed inside a protective enclosure to prevent direct sunlight or rain exposure.

2. Installation of Sensors (or Integrated Type)
   The sensor (or integrated type) should be installed by making a hole in the pipeline and welding a mounting seat (or pipe fitting), then fixing the sensor (or integrated type) to the mounting seat (or pipe fitting).

   Technical Requirements for Pipeline Installation:

1. Choose a location with minimal vibration, and avoid direct sunlight.

2. To ensure the sensor is always filled with fluid, it can be installed at the lowest point of a U-shaped pipeline.

3. If installed vertically or inclined, the fluid should flow from bottom to top.

4. The pipeline must be completely filled with the fluid.

5. The sensor can be installed horizontally or vertically, as long as the geometric line passing through the two electrodes is perpendicular to the pipeline axis.

6. To minimize the effect of air bubbles on the measurement, the instrument can be installed away from the highest point of the pipeline.

7. The installation position should be convenient for wiring, operation, and reading of the instrument.

Insertion magnetic flow meters are easy to install, widely used, have excellent measurement performance, and are convenient for retrofitting older systems. They are widely used for measuring the fluctuating flow of various water-based media (such as fresh water, circulating water, and wastewater), playing an effective role in balance and metering of system fluid usage. Therefore, understanding the working principle, structure, characteristics, and solutions will help us use and maintain these instruments more effectively.