Electromagnetic flowmeter to measure the effect of coal water slurry

　　Application of electromagnetic flowmeter in water-coal slurry However, the reinforced polytetrafluoroethylene developed in recent years has been widely used. It has excellent wear resistance, extrusion resistance and corrosion resistance, and has good adhesion to the measuring tube, and the lining will not peel or fall off. The induced potential signal generated by the liquid flow is very weak and is greatly affected by various interference factors. The role of the converter is to amplify the induced potential signal and convert it into a unified standard signal and suppress the main interference signal.

　　Introduction to the effect of electromagnetic flowmeter measuring water-coal slurry: When the streamline distribution does not meet the set conditions, measurement errors will occur. Therefore, there must be a straight pipe section of about 5~10D in front of the electromagnetic flowmeter to eliminate the impact of various local resistances on the symmetry of the streamline distribution. Due to the special physical properties of water-coal slurry, its measurement is very difficult. It contains more than 60% fine coal solid particles, plus auxiliary additives. Under pressure conditions, its dynamic viscosity reaches 800~1500mPa.s. The extrusion of the medium on the lining and the scouring environment on the electricity require the adhesion performance of the lining of the electromagnetic flowmeter sensor and the measuring conduit, as well as the noise resistance and anti-leakage performance of the electricity. In addition, water-coal slurry is a non-Newtonian fluid, and the designed pipeline flow rate is very low, about 1.0m/s, and it is corrosive.

　　Years of comparative experience in the operation of coal chemical plants have proven that the use of electromagnetic flowmeters to measure the flow of water-coal slurry is currently the only reliable method. The installation location of the electromagnetic flowmeter should be far away from interference from magnetic sources. The signal of the electromagnetic flowmeter is relatively weak, only a few millivolts at full scale, and only a few microvolts when the flow rate is very small. Any slight interference from the outside world will affect the measurement accuracy. Therefore, the housing, shielding wire, and measuring conduit of the flowmeter must be grounded. The grounding point should be set separately and never connected to the motor or the upper and lower pipes.

　　Function of the electromagnetic flowmeter magnetic circuit system: The electromagnetic flowmeter is mainly composed of a magnetic circuit system, a measuring conduit, a conductor, a housing, a lining and a converter. The function of the magnetic circuit system is to generate a uniform DC or AC magnetic field. Electromagnetic flowmeters generally use an alternating magnetic field, and the function of the measuring conduit is to allow the conductive liquid to pass through. The measuring conduit must be made of non-magnetic, low magnetic permeability, low thermal conductivity and mechanically strong materials. Non-magnetic stainless steel, fiberglass, high-strength plastic, aluminum, etc. can be used.

　　The function of the resistor is to induce an induced potential signal proportional to the measured flow rate. The resistor is generally made of non-magnetic stainless steel and is required to be flush with the lining so that the fluid can pass through without obstruction. It should be installed in the horizontal axis direction of the pipeline to prevent sediment from accumulating on it and affecting the measurement accuracy. In the case of water-coal slurry, the scouring of the resistor by the compressed coal slurry will produce signal noise. Usually, manufacturers with technical experience will use low-noise resistors to reduce the scouring noise. The outer shell is made of ferromagnetic material, which is the outer cover of the excitation coil and isolates the interference of the external magnetic field. There is a complete insulated lining on the inner side of the measuring conduit and the flange sealing surface. It is in direct contact with the measured liquid. Its function is to prevent the induced potential from being short-circuited by the measuring conduit wall and can adapt to the corrosion resistance and wear resistance of the measuring conduit.