RU2599766C2 - Electromagnetic flow meter - Google Patents

Abstract

FIELD: instrument making.

SUBSTANCE: invention relates to heat and flow measurement, and enables to measure flow rates of electrically conducting fluid and heat carrier in pressure pipelines, mainly in apartments or other personal or service premises. In electromagnetic flow meter, comprising a housing, a measuring pipe, outer surface of which there is a magnetic system consisting of two magnetic field excitation coils with cores, arranged in tubular magnetic core, in cross section of measuring pipe at two opposite holes, in which there are two electrodes, in housing at equal distance relative to tubular magnetic conductor there is tubular screen made of ferromagnetic material; tubular screen can be multilayered.

EFFECT: elimination or minimisation of possibility of interference in metrological parameters of flow meter through effect of magnetic field.

1 cl, 2 dwg, 1 tbl

Description

The invention relates to the field of instrumentation, in particular to heat and flow meters, and allows you to measure the flow rate of electrically conductive fluid and coolant in pressure pipelines, mainly in apartments or other other personal or office rooms.

Known electromagnetic flow transducer comprising a pipe, a magnetic system and electrodes recessed into the wall of the pipe; in order to reduce zero drift, the electrodes are surrounded by magnetic screens, SU 606103, publ. 05/05/1978.

This device does not provide the required measurement accuracy, since magnetic screens do not sufficiently reduce the magnetic induction in the area of the electrodes and, accordingly, zero drift.

Greater accuracy of measurements is provided by an electromagnetic flow transducer, comprising a housing, a terminal box, a ceramic measuring tube with flanges at its ends, on the outer surface of which is a magnetic system consisting of two magnetic field excitation coils, two counter-holes are made in diameter in the cross section of the measuring tube in diameter in which two electrodes are installed, while the electric wires from the field coils and electrodes are brought out into the terminal box, RU 2349880 C2, publ. 03/20/2009.

The ceramic pipe used in this device is a non-conductive and chemically resistant element, however, its mechanical strength is very small due to the fragility of the ceramic, which often leads to damage and failure of the device; in addition, it should be noted that during operation, deposits are deposited on the inner surface of the ceramic pipe in the form of salts contained in the flowing liquid; as a result of this, the flow cross section of the measuring tube is reduced and thereby the measurement error is created.

A known electromagnetic flowmeter comprising a housing, a terminal box, a measuring pipe with flanges at its ends, on the outer surface of which is a magnetic system consisting of two magnetic field excitation coils with magnetic cores, two counter-holes are made in diameter in the cross section of the measuring pipe in diameter, of which two electrodes are installed, while the electric wires from the excitation coils and electrodes are brought out into the terminal box; the measuring tube is made of two layers, the outer and inner, the outer layer is made of non-magnetic material, and the inner layer is of a chemically resistant non-conductive polymer material, RU 107859 U1, publ. 08/27/2011.

This technical solution provides an increase in the strength of the measuring tube and the durability of the device as a whole, as well as a decrease in measurement error during operation of the device.

However, the disadvantage of this flow meter is the dependence of its readings on the flow of fluid in the measuring tube, and therefore it is necessary to use additional elements to stabilize the flow of fluid after passing curved sections of the pipeline, which are flow perturbators. To equalize (eliminate turbulence) of the flow, a straight section of the pipeline of the required length must be in front of the flowmeter. This limits the possibility of using this device or even makes it impossible to use it in a limited space or in the case of pipelines with many flow perturbators.

Known electromagnetic flow meter containing a housing, a measuring tube, on the outer surface of which is placed a magnetic system consisting of two magnetic field excitation coils with cores placed in a tubular magnetic circuit, in the cross section of the measuring tube in diameter there are two counter holes in which two electrodes are installed , RU 2504736 C1, publ. 01/20/2014.

This technical solution is made as a prototype of the present invention.

The disadvantage of the prototype is the lack of protection against unauthorized interference in the metrological parameters of the flow meter through extraneous magnetic exposure. As you know, the installation of a permanent magnet on the body of the flowmeter is the most affordable and most common type of intervention.

The objective of the present invention is to eliminate or minimize the possibility of interference with the metrological parameters of the flow meter by exposure to a magnetic field.

According to the invention, in an electromagnetic flow meter comprising a housing, a measuring tube, on the outer surface of which a magnetic system is placed, consisting of two magnetic field excitation coils with cores placed in a tubular magnetic circuit, two counter-holes are made in diameter in the cross section of the measuring tube in diameter, in which are installed two electrodes, in the case equidistant relative to the tubular magnetic circuit, a tubular screen made of ferromagnetic material is strengthened; the tubular screen can be multilayer.

The invention is illustrated by drawings, which depict:

in FIG. 1 is a longitudinal section of a device;

in FIG. 2 is a section AA in FIG. one.

The electromagnetic flow meter comprises a housing 1 made of plastic, and a measuring tube 2, on the outer surface of which is placed a magnetic system consisting of two coils 3, 4 of magnetic field excitation. Coils 3, 4 have cores 5, 6, respectively. The magnetic system is housed in a tubular magnetic circuit 7. In the cross section of the measuring tube 2, two opposing holes are made in diameter, in which two electrodes 8 and 9 are installed. In the housing 1, a tubular screen 10 made of a ferromagnetic material is reinforced relative to the tubular magnetic circuit 7, in particular "Black" steel, 1 mm thick. The tubular screen 10 may be multilayer. The air gap between the outer surface of the magnetic circuit 7 and the inner surface of the screen 10 is at least 3 mm. The width of the screen 10 should be 20-50% more than the width of the magnetic circuit 7.

The device operates as follows.

The principle of operation of the device is based on the phenomenon of induction of electromotive force (EMF) in a conductor moving in a magnetic field created by coils, which is a measured liquid electrically conductive medium, in particular water. The electromagnetic flowmeter has an external power supply.

The device is mounted in a pipeline (not shown) and is in this case its section. Water flowing through the pipeline also flows through the measuring tube 2 of the flow meter. EMF induced in the water moving in the measuring tube 2 is proportional to the speed and, accordingly, the volumetric flow rate of water. EMF is perceived by electrodes 8, 9 and enters the electronic unit for converting and processing signals (not shown in the drawings).

In the event of an unauthorized attempt to interfere with the flowmeter by installing a permanent magnet, the tubular screen 10 shields the field created by the permanent magnet and virtually eliminates its effect on the metrological parameters of the electromagnetic flowmeter.

In a specific example, the claimed electromagnetic flowmeter was tested, the nominal diameter of the passage is 15 mm.

The external constant magnetic field source is two D37 × 5A disk permanent magnets from Nd-Fe-B alloy and a black steel disk with a diameter of 37 mm and a thickness of 2 mm. The total magnetic induction was ≥300 mT.

The test results are shown in table 1.

Thus, the tests (in comparison with the prototype) confirmed the achievement of the technical result, which consists in preventing the effects of external interference using a constant magnetic field on the metrological parameters of the electromagnetic flow meter.

Claims (2)

1. An electromagnetic flow meter comprising a housing 1, a measuring tube 2, on the outer surface of which is placed a magnetic system consisting of two coils 3, 4 of magnetic field excitation with cores 5, 6, placed in a tubular magnetic circuit 7, in the cross section of the measuring tube in diameter two counter-holes are made, in which two electrodes 8, 9 are installed, characterized in that a tubular screen 10 made of a ferromagnetic material is fixed in the housing 1 equidistantly relative to the tubular magnetic circuit 7. 2. The electromagnetic flow meter according to claim 1, characterized in that the tubular screen is multilayer.

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