Partially Full Pipe Electromagnetic Flow Meter Working Principle:
The Partially Filled Pipe Electromagnetic Flow Meter is an automated device for measuring open channel flow. It comprises an electromagnetic flow sensor, an ultrasonic level sensor, and an intelligent converter.
The electromagnetic flow sensor operates based on Faraday’s law of electromagnetic induction.
When conductive fluid flows through the sensor, it cuts magnetic field lines. Generate an induced electromotive force (EMF) proportional to flow velocity. A pair of signal electrodes mounted on the sensor’s side wall—perpendicular to both the conductive fluid axis and magnetic field lines—detects this EMF and transmits it to the flow converter. The signal is converted into a digital signal, enabling flow velocity measurement. An internal high-frequency, small-dead-zone ultrasonic level sensor continuously monitors changes in the internal liquid level of the pipeline.
What are the different types of electromagnetic flow meters?
Electromagnetic flow meters are designed based on Faraday’s principle. They measure the volume and instantaneous flow rate of conductive liquids with conductivity. Their specialized inner linings accommodate flow measurement in various corrosive media. They also measure solid-liquid two-phase suspensions like mineral slurries and mud. They are now widely applied across industries, including chemical, petroleum, papermaking, metallurgy, light textiles, environmental protection, and food processing. So, what specific types of electromagnetic flow meters exist:
1. General-purpose electromagnetic flow meters:
Split-type medium-to-large diameter flange connections are commonly used in metallurgy, petrochemicals, papermaking, printing and dyeing, textiles, water supply, and wastewater treatment industries. In pharmaceuticals, biotechnology, and fine chemicals, miniature and small-diameter instruments are common. Integral clamp-on or threaded connection electromagnetic flow meters are suitable for a wide range of applications.
2. Explosion-proof Electromagnetic Flowmeters:
Explosion-proof electromagnetic flowmeters are deployed in flammable atmospheres. Due to the high excitation current energy in most models, they are typically designed as flameproof, sand-filled, cast-resin, or gas-tight types. However, some modern flow meters feature significantly reduced excitation power. Enabling intrinsically safe (formerly known as spark-proof) designs. Under suitable conditions, the flow sensor and converter sections can be integrated into a single unit. Allow full installation within hazardous zones.
3. Sanitary Electromagnetic Flowmeters:
Industries such as dairy, food processing, pharmaceuticals, and biochemistry require periodic steam sterilization. Sensors must be easily disassembled for cleaning with pipeline connections utilizing quick-release sanitary fittings. Materials in contact with liquids must be non-toxic and harmless. Sanitary electromagnetic flowmeters were developed specifically to meet these requirements.
4. Submersible Electromagnetic Flow Meter
Designed for installation in underground manholes, it withstands temporary submersion equivalent to IP68 enclosure protection. Models meeting the IP68 protection rating are capable of sustained submersion.
5. Partially Filled Pipe Electromagnetic Flow Meter
Measures flow in municipal stormwater, wastewater, sewage discharge, and irrigation pipelines.
What are the disadvantages of electromagnetic flow meters?
- Cannot measure liquids with very low conductivity, such as petroleum products;
- Cannot measure gases, steam, or liquids containing large bubbles;
- Cannot be used at high temperatures.
- Which liquid cannot be measured by the magnetic flow meter?
Which liquid cannot be measured by the magnetic flow meter?
Liquids containing large amounts of gas:
When liquids contain significant gas content, insufficient back pressure or improper installation of the electromagnetic flow sensor may prevent the measuring tube from being fully filled with liquid. This can impair the normal operation of the electromagnetic flow meter, resulting in inaccurate measurement outcomes.
Non-conductive or poorly conductive liquids:
The operating principle of electromagnetic flow meters requires the measured media to have a certain level of conductivity. Typically, the medium’s conductivity must exceed 10μS/cm for effective measurement. For non-conductive or poorly conductive liquid media. such as deionized water, ultrapure water, or certain organic solvents. Electromagnetic flow meters may be unable to perform effective measurements.
Additionally, while electromagnetic flow meters can measure some corrosive liquids, certain highly corrosive or physically/chemically unique media may require flow meters with corresponding corrosion resistance and high-temperature tolerance. However, excessively corrosive or high-temperature media may exceed the flow meter’s measurement range, rendering effective measurement impossible.
