The working principle of the electromagnetic flowmeter is based on Faraday's electromagnetic induction law. When a conductor moves in a magnetic field, an induced electromotive force is generated at both ends of the conductor perpendicular to the direction of the magnetic field and the direction of motion. The magnitude of the electromotive force is proportional to the speed of movement of the conductor and the magnitude of the magnetic induction of the magnetic field.
The electromagnetic flowmeter consists of two parts: an electromagnetic flow converter and an electromagnetic flow sensor. The separate type also requires a dedicated double-shielded cable to connect the converter and the sensor. The electromagnetic flowmeter is divided into two types: integral type and separated type. Can be used in specified explosion-proof places. The sensor is available in 7 different material electrodes and 4 different material linings.
The sensor of the split type electromagnetic flowmeter should be installed vertically, and the fluid flows from bottom to top to satisfy the mixed state of the solid and liquid. The reason is that solid matter (sand, pebbles, etc.) in the medium is prone to precipitation. In addition, there are fish and weeds in the pipeline. The swimming of the fish in the pipeline will cause the flowmeter output to swing back and forth; the back and forth swing of the weeds hanging near the electrode will also cause the output of the flowmeter to be unstable. A metal strainer is placed at the upstream inlet of the flow meter to block fish and weeds from entering the measuring tube.
The split type electromagnetic flowmeter prevents improper operation of the pipeline setting of the negative pressure, which will cause a negative pressure in the sensor. When closing the upstream and downstream valves of the flowmeter, if the temperature of the fluid is higher than the temperature. Shrinkage after cooling, there is a danger of creating a negative pressure in the pressure inside the tube. Negative pressure causes the liner to peel off from the metal conduit, causing electrode leakage.
A negative pressure prevention valve is added in the vicinity of the split electromagnetic flowmeter, and the valve is opened to the atmospheric pressure to prevent a negative pressure from being generated in the sensor. When a vertical pipe is connected downstream of the split type electromagnetic flowmeter, if the upstream valve of the flow sensor is used to close or adjust the flow rate, a negative pressure will be formed in the sensor measuring tube. To prevent negative pressure, add back pressure or use a downstream valve to regulate and shut off the flow.
Proper electromagnetic flowmeters have appropriate maintenance space. Large-diameter flowmeters are often installed in instrumentation wells. For the convenience of pipeline installation, wiring, inspection and maintenance, proper space is required. For the convenience of observation, wiring and maintenance, the instrument should be installed at a certain height from the ground to facilitate cleaning and installation.
Installation and use of split-pipeline electromagnetic flowmeters should pay attention to the requirements of the external environment
a. The flowmeter should be installed in a place where the temperature changes greatly or is subject to high temperature radiation from the equipment. If it must be installed, it must be insulated and ventilated.
b. The flowmeter Zui is installed indoors. If it must be installed outdoors, it should be protected from rain and water, and the water should be flooded and exposed to the sun. It must be protected against moisture and sun.
c. The flowmeter should be avoided in an environment containing corrosive gases. Ventilation measures must be taken when installing.
d. For installation, maintenance and maintenance, there is ample installation space around the flowmeter.
e. The flowmeter installation field should avoid strong magnetic field and strong vibration source. If the pipeline vibration is large, there should be fixed pipeline support on both sides of the flowmeter.
