METHOD OF VERIFICATION OF ELECTROMAGNETIC FLOWMETER OF LIQUID METALS Russian patent published in 2015 - IPC G01F25/00 

FIELD: instrumentation.

SUBSTANCE: electromagnetic flowmeter for liquid metals has a pipe with electrodes, a low-frequency magnetic field inductor and an electronic converter. The flowmeter has no insulating coating of the duct, and electrodes are welded to the outer side of the pipe. The offered method is as follows. The preliminary, i.e. pre-pouring preparation of the liquid metal flowmeter is performed for verification on a water flow-meter stand. The preliminary preparation consists in that an electric insulating lining with electrodes which protects the induced electric field in the measured medium from the shunting action of the metal wall of the duct is inserted into the duct. The lining can be made of rubber. Besides, the input of the electronic converter is connected to the electrodes installed on the duct lining, but not to the flowmeter electrodes welded to the external wall of the pipe. The flowmeter is verified at the water flowmeter bench using the same method as for a standard industrial flowmeter. On the metering section of the pipe of the water flowmeter bench the flowmeter to be verified is installed with the lining inserted into it. Through the flowmeter duct the rated flow of tap water is passed at the room temperature. By results of the flowmeter verification at the water flowmeter bench the flowmeter conversion coefficient is determined by the formula K=α/Q (1), where α - reading of the electronic converter, Q - volumetric flow rate of tap water. After tests of a flowmeter on the water flowmeter bench the post-pouring preparation of the flowmeter is performed. From the flowmeter the lining is withdrawn, the input of the electronic converter is connected to the electrodes welded to the external surface of the flowmeter pipe, and in the electronic converter by software means the conversion coefficient is corrected by means of adding of correction which take into account the difference of conditions of water and liquid metal verification of the flowmeter. The flowmeter conversion coefficient for liquid metal K_m is calculated by the formula K_m=K(1-k_D)(1-k_M) (2). The correction factor k_D takes into account the change of diameter of the channel caused by adding of electric insulating lining, and the correction factor k_M takes into account the shunting action of the conducting channel wall at measurement of liquid metal. The correction factor k_D is calculated by the formula of , where D_F - diameter of the channel with the lining, D₁ - diameter of the channel without lining at the working temperature of liquid metal. The correction factor k_M is calculated by the formula , where D₂ - outer diameter of the pipe at the working temperature, σ and σ_t - conductivity of liquid metal and material of the pipe at the working temperature (2).

EFFECT: improvement of accuracy of measurement of liquid metal flow rate in pipes with large diameter.

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