JPH05312609A - Electromagnetic flow meter - Google Patents

Abstract

(57) [Abstract] [Purpose] It is smoothly inserted into the measurement pipe, has no disconnection of the flow rate signal, does not adhere to liquid metal, etc., has excellent maintainability, and improves reliability. [Structure] An electrode 13 is provided in the first guide tube 11, a second guide tube 12 is concentrically inserted in the first guide tube 11, and a magnet portion 15 is provided in the second guide tube 12. Has been inserted. The electrode 13 is connected to the first terminal box 17 by the lead wire 14, and the magnet portion 15 is connected to the second terminal box 19 by the guide cable 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic flow meter for measuring the flow rate of liquid metal sodium coolant used in a fast breeder reactor, for example.

[0002]

2. Description of the Related Art One of the most important cooling instrumentation systems, not limited to fast breeder reactors, is a system for measuring the flow rate of the coolant. Among the flow rate measurements, the flow meter of the main cooling system is also particularly important because it is also used as a safety protection system.

Conventionally, as a system for measuring the flow rate of the main cooling system, there is a permanent magnet type electromagnetic flow meter having a shape of enclosing a pipe. The larger the pipe diameter, the larger the weight and size. For example, in a 20B class permanent magnet type electromagnetic flowmeter for piping, the weight is 5 tons and the size is 3 m x 2 m x 2
It becomes large with m. Also, if it becomes a demonstration reactor, the pipe diameter will be 30B.
As described above, the weight and size are further increased.

In order to solve these increases in size, a small electromagnetic flowmeter that is inserted into a pipe to measure the flow rate is used.
This small electromagnetic flowmeter uses an eddy current type flowmeter that uses a change in the magnetic field strength across the detection coil due to the eddy current generated in the coolant by applying a high frequency to the coil, and a signal generated in the electrode directly immersed in the coolant. There is a direct immersion type electromagnetic flow meter that detects

[0005]

However, the above-mentioned conventional electromagnetic flowmeter has the following problems.

That is, since the permanent magnet type electromagnetic flowmeter enclosing the pipe is heavy and dimensional, it is difficult to handle and economically higher than other small flowmeters.

Further, the eddy current type flow meter is excellent in maintainability because it is inserted into the guide tube, but a power source for supplying an exciting current to the coil, a complicated signal processing circuit for processing the signal of the detection coil, etc. Is required, which is inferior to other electromagnetic flow meters in terms of reliability.

Further, in the direct immersion type electromagnetic flowmeter, since the electrode is directly attached to the electromagnetic flowmeter, it comes into direct contact with the coolant, and the flowmeter body forms a coolant boundary. Then, there is a problem that the maintainability of the flow meter is impaired by the adhesion of the coolant.

A coil type (eddy current type) flow meter uses a coil instead of a permanent magnet to generate a magnetic field as shown in FIG. The coil type (eddy current type) flowmeters that have been manufactured so far flow an alternating current of several hundreds of hertz into an exciting coil, and detect the magnetic field generated by the exciting coil to know the flow rate.

Therefore, a complicated signal processing circuit is required to process the signal from the detection coil into a flow rate signal, which is as simple as measuring the electromotive force generated in the electrode like a permanent magnet type flow meter. However, there is a problem that the reliability is lower than that of other methods.

The present invention has been made in order to solve each of the problems described above, and is smoothly inserted into a measurement pipe, has no disconnection of a flow signal, does not adhere to liquid metal, etc., and has excellent maintainability and reliability. It is intended to provide a high insertion type electromagnetic flow meter.

[0012]

SUMMARY OF THE INVENTION The present invention is an electromagnetic flowmeter for measuring the flow rate of a liquid metal, wherein a first guide tube having an electrode attached to the inner surface thereof and a second guide tube inserted into the first guide tube are provided. And a magnet portion inserted into the second guide tube.

[0013]

In the electromagnetic flowmeter having the above structure, the electrode is separated from the magnet part and attached to the inside of the first guide tube. Therefore, the electrode does not move together with the magnet, so that the reliability is remarkably improved. .. Moreover, since the magnet portion is inserted into the second guide tube, the magnet portion and the signal line of the electrode can be smoothly inserted without interference. Further, the magnet portion does not become a boundary of liquid metal (coolant) and is excellent in maintainability.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of an electromagnetic flowmeter according to the present invention will be described with reference to FIG. FIG. 1 shows a configuration of an embodiment of the present invention. In the figure, reference numeral 1 is an electromagnetic flow meter according to the present embodiment, reference numeral 2 is a pipe through which a coolant is passed, and 3 is a coolant.

The electromagnetic flowmeter 1 separates the coolant 3 and the magnet portion 15, and has a first guide tube 11 having an electrode 13 and a second guide portion 11 in which the magnet portion 15 is passed inside the first guide tube 11. The guide tube 12 and the magnet portion 15 are provided in the second guide tube 12. The first guide pipe 11 and the second guide pipe 12 are fixed to the pipe 2 by welding, and form a coolant boundary.

A guide cable 16 is connected to the magnet portion 15 so that the magnet portion 15 can freely move in the second guide tube 12. However, the magnetic field created by the magnet unit 15 and the electrode 13 must be fixed in position.

Therefore, the length of the guide cable 16 is fixed, and it is firmly fixed to the first and second guide pipes 11 and 12 by the flange 18 fixed to the guide cable 16, and the guide cable 16 is fixed to the second guide pipe 16. It is connected to the terminal box 19 of. The electrode 13 is attached to the first guide tube 11 by welding, and is connected to the first terminal box 17 by the lead wire 14.

The lead wire 14 passes between the first guide tube 11 and the second guide tube 12, and the magnet portion 15 moves inside the second guide tube 12. Therefore, the magnet portion 15 can be smoothly inserted without touching the lead wire 14, and since the lead wire 14 is protected by the first guide tube 11 and the second guide tube 12, disconnection etc. There is no failure and the signal from electrode 13 is more reliable.

If a permanent magnet is used as the magnet of the magnet portion 15, the magnet portion 15 is merely a permanent magnet, and the guide cable 16
Also serves only as a guide, and the structure is simple. If an electromagnet having a coil wound around the magnet of the magnet unit 15 is used, the guide cable 16 becomes a high temperature MI cable through which an exciting current of the coil flows.

Generally, in the case of a fast breeder reactor, since the coolant 3 is liquid metal sodium, the temperature rises from 200 ° C to 500 ° C, the cable is covered with stainless steel, and the insulating material is MgO.
It is necessary to use an MI cable using In this case, the exciting current is supplied from the external power supply device to the second terminal box 19 on the flange 18.

The principle of the permanent magnet type electromagnetic flowmeter is the same as that of a conventional permanent magnet type electromagnetic flowmeter in which a magnet is installed outside the pipe to measure the flow rate, and it is orthogonal to the magnetic field according to "Fleming's right-hand rule". Since an electromotive force proportional to the flow rate is generated in the direction of flow, the flow rate can be measured by measuring the electromotive force. This signal output is obtained by the following equation. E = K · B · l · v where K: correction coefficient, B: magnetic field strength, 1; pipe diameter, v;
Flow rate of sodium However, the pipe diameter 1 is the diameter of the guide pipe shown in FIG. 2 in the case of the insertion type. The relationship between the magnetic flux lines and the magnet shape is shown in FIG.

According to the above embodiment, however, the guide tube has a concentric double structure, and the electrode and its lead wire are passed between the two guide tubes to facilitate the insertion of the magnet portion, and the electrode It is possible to avoid a decrease in reliability in flow rate measurement due to disconnection or the like. Further, the flowmeter main body does not serve as a boundary of liquid metal, and a flowmeter with good maintainability can be obtained, which can contribute to improvement in safety of the fast breeder reactor plant.

[0023]

According to the present invention, it is possible to obtain a flowmeter which is smoothly inserted into a measurement pipe and has no flow signal disconnection or liquid metal adhesion and which is excellent in maintainability. Therefore, by obtaining the flow rate signal with improved reliability, it is possible to contribute to the improvement of the safety of the fast breeder reactor plant.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of an electromagnetic flowmeter according to the present invention.

FIG. 2 is a vertical cross-sectional view showing the tip of the electromagnetic flow meter in FIG.

FIG. 3 is a schematic diagram showing the relationship between a cross section taken along the line AA in FIG. 2 and magnetic force lines.

FIG. 4 is a conceptual diagram showing a conventional coil type flow meter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electromagnetic flowmeter, 2 ... Piping, 3 ... Coolant, 11 ... First guide tube, 12 ... Second guide tube, 13 ... Electrode, 14 ... Lead wire, 15
… Magnet part, 16… Guide cable, 17… First terminal box, 18
… Flange, 19… Second terminal box.

Claims (1)

[Claims] 1. An electromagnetic flowmeter for measuring the flow rate of liquid metal, comprising: a first guide tube having an electrode on its inner surface; a second guide tube inserted into the first guide tube; Two
And a magnet part inserted in the guide tube of the electromagnetic flowmeter.