JPH04289419A - Electromagnetic flowmeter - Google Patents

Abstract

PURPOSE:To obtain an electromagnetic flowmeter which can obtain large electromotive force and can measure even a small flow rate. CONSTITUTION:An electromagnetic flowmeter is submerged into the flow of fluid having conductivity, and the flow rate in this region is detected. The thickness of a fluid pipe 1 wherein the fluid flows is thinly formed. Magnets 2 and magnetic substances 3 are alternately arranged at the outer surface of the fluid pipe 1. The large electromotive force is obtained, and the flow rate can be measured even if the flow rate of the fluid is small.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic flowmeter for detecting the flow rate of a conductive fluid, and more particularly to a miniaturized electromagnetic flowmeter that is immersed in a fluid flow and detects the flow rate in that region. .

0002

[Prior Art] There are various types of flow rate detectors, but they utilize Fleming's right-hand rule, which states that when an electric conductor moves in a magnetic field, an electromotive force is generated in that conductor. There are electromagnetic flowmeters that measure fluids that are This electromagnetic flowmeter is used, for example, to detect the flow rate of liquid sodium in a plant such as a fast breeder reactor that uses liquid sodium as a coolant.

FIG. 3 shows an example of how an electromagnetic flowmeter is used to measure the flow rate in a large-diameter pipe in a plant such as a fast breeder reactor. A small electromagnetic flowmeter c is immersed in this flowmeter c.
is measuring the flow rate of sodium. Fig. 4 shows an example of the use of an electromagnetic flowmeter in the core d of a nuclear power plant such as a fast breeder reactor. A flowmeter c is installed to measure the sodium distribution at the outlet of the fuel assembly e in the core d. In this case, the key point is how to handle the signal extraction cable from the small electromagnetic flowmeter.

[0004] It can also be used in industrial fields other than those mentioned above to measure the flow rate of a conductive fluid with no polarization effect at the electrode. This polarization effect means that when electrolysis is performed using direct current, the anions in the solution are attracted to the anode and the cations are attracted to the cathode, so the concentrations of both the anode and the anode become higher near the anode and cathode, respectively, resulting in a kind of It is a concentration battery that generates an electromotive force in the opposite direction to the voltage applied from the outside. The electromotive force caused by this polarization interferes when measuring flow rate with an electromagnetic flowmeter.

The conventional small electromagnetic flowmeter c is shown in FIG. 5(A), (
As shown in B), attach a magnet i to a flow tube h according to the purpose of use.
, an MI cable (mineral insulated wire) with electrode j and thermocouple k attached, and the measurement points of magnet i, electrode j and thermocouple k are cylindrical to prevent direct contact with fluid. A case l is provided.

In the above configuration, the opposing magnets i,
A magnetic field is generated within the flow tube h by i. This flow tube h
When a conductive liquid such as sodium flows inside the tube, an electromotive force is generated in a direction perpendicular to the direction of the magnetic field. This electromotive force is taken out by electrodes j and j placed opposite each other to measure the velocity of the fluid. The product of this speed and the cross-sectional area of the flow tube h, which is the measuring section, is the flow rate. Since the generated electromotive force changes the specific resistance of the fluid and the strength of the magnetic field depending on the temperature change of the fluid, a thermocouple k is used to simultaneously measure the temperature change of the fluid.

[0007]

However, in conventional small electromagnetic flowmeters, when the flow rate of the fluid to be measured is small, the electromotive force generated is proportionally small. In order to measure even small flow rates, it is necessary to increase the strength of the magnetic field. Further, even if the flow rate is the same, the larger the electromotive force is, the easier the signal processing is.

[0008] Conventionally, the flow tube h suited to the purpose of use has been manufactured by cutting a single piece, so that the wall thickness of the part where the electrode j is attached cannot be made very thin. If this wall thickness is thick, the resistance value between the opposing electrodes j, j will be small, the generated electromotive force will flow through this resistance, and the voltage value of the electromotive force will be reduced. Another problem is that there are many cables for taking out electrical signals to the outside: two for electrode j and one for thermocouple k.

The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to provide an electromagnetic flowmeter that can obtain a large electromotive force and can measure even a small fluid flow rate. [Structure of the invention]

0010

[Means for Solving the Problems] In order to solve the above-mentioned problems, the electromagnetic flowmeter according to the present invention is an electromagnetic flowmeter that is immersed in a flow of conductive fluid and detects the flow rate in that area. In the flowmeter, the flow tube through which the fluid flows is formed to have a thin wall structure, and magnets and magnetic bodies are alternately arranged around the outer periphery of the flow tube.

[0011]

[Function] In the electromagnetic flowmeter of the present invention, the flow tube is formed into a thin-walled structure, and magnets and magnetic bodies are arranged alternately around the outer periphery of the flow tube, so the strength of the magnetic field can be increased. A large electromotive force can be obtained.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the electromagnetic flowmeter according to the present invention will be described below with reference to the accompanying drawings.

FIGS. 1A and 1B show an embodiment of an electromagnetic flowmeter according to the present invention. In this embodiment, the wall thickness of the cylindrical flow tube 1 is reduced to form a thin-walled tube structure, and a magnet 2 and a magnetic body 3 each having a shape in which the cylinder is divided into four, for example, are placed on the outer circumferential side of the flow tube 1 in the circumferential direction. They are arranged alternately. The mutual arrangement of the magnet 2 and the magnetic body 3 increases the strength of the magnetic field,
The aim is to increase the electromotive force. In addition, an electrode with a thermocouple (M
I cable (3 cores) 4 and electrode (MI cable 1 core) 5
is connected to one MI cable (four cores) 8 in a space 7 formed between the magnet 2 and the piping connection part 6 to facilitate signal extraction to the outside. Therefore, in this embodiment, by changing the shape of only the pipe connection part 6 of the flow pipe 1,
The configuration is tailored to suit the purpose of use.

FIGS. 2(A) and 2(B) show an electrode with a thermocouple (M
I cable) 4 configuration, and the thermocouple electrode 4 is MI
The cable has three cores, one electrode 4a and one thermocouple 4b.
Two core wires are arranged in the sheath 4c so as to be insulated by an insulator 4d.

The electrode 5 placed opposite to the thermocouple-equipped electrode 4 is a one-core MI cable, and one four-core MI cable is installed in the space 7 provided between the magnet 2 and the piping connection part 6. M of
It is connected to the I cable 8 and treated to maintain insulation and confidentiality. Electrode 4 and electrode 5 with thermocouple
The tip is electrically connected to the flow tube 1 and is mechanically firmly attached.

On the other hand, an electromagnetic flowmeter in which magnets 2 and magnetic bodies 3 are arranged alternately in the circumferential direction on the outer circumferential side of the flow tube 1 is housed in a cylindrical case 9. This case 9 has magnets 2,
Magnetic material 3 and thermocouple electrode 4, electrode 5 and MI cable 8
The inside has an airtight seal structure to prevent external fluid from coming into direct contact with the connecting part. The flow pipe 1 and the piping connection part 6 are assembled for the same purpose as the case 9 so as to maintain airtightness. Moreover, the assembly of the piping connection part 6 and the MI cable 8 is the same.

Both ends of the magnet 2 and the magnetic body 3 are fixed with a presser fitting 10 so that the magnet 2 and the magnetic body 3 do not shift. The rotation stopper 11 prevents rotation of the magnetic body 3 so that the direction of magnetic flux and the relative positional relationship with the electrode 5 do not deviate.

According to this embodiment, the strength of the magnetic field can be increased by forming the flow tube 1 into a thin-walled tube structure and by arranging the magnets 2 and magnetic bodies 3 alternately in the circumferential direction. This makes it possible to obtain a large electromotive force and allows measurement even with a small fluid flow rate.

Furthermore, since the space 7 is formed between the magnet 2 and the piping connection part 6, the thermocouple electrode 4 and the electrode 5 can be connected to the MI cable 8 within this space 7.
In addition to being able to take out external signals with a single MI cable 8, it becomes difficult for heat to be transferred to the magnet 2 when welding the case 9 and the piping connection 6, or when welding the piping connection 6 and external piping. The deterioration caused by the temperature described in No. 2 can be prevented. and,
Since the external signal can be taken out with one MI cable 8, handling of the cable becomes easy.

Note that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made. For example, in the above embodiment, the magnets 2 and the magnetic bodies 3 are formed into a shape divided into four parts in the circumferential direction, but any shape other than this may be used as long as the magnets 2 and the magnetic bodies 3 are arranged alternately. Further, in the above embodiment, a thermocouple is attached only to the electrode 4, but a thermocouple may also be attached to the electrode 5. This improves the accuracy of measuring fluid temperature changes.

[0021]

[Effects of the Invention] As explained above, according to the electromagnetic flowmeter according to the present invention, the flow tube through which the fluid flows is formed into a thin-walled structure, and magnets and magnetic bodies are alternately arranged around the outer periphery of the flow tube. Therefore, a large electromotive force can be obtained, and even if the flow rate of the fluid is small, the flow rate can be measured.

[Brief explanation of the drawing]

[Fig. 1] (A) is a partial vertical sectional view showing an embodiment of an electromagnetic flowmeter according to the present invention, and (B) is a B--B in Fig. 1 (A).
B-line sectional view.

FIGS. 2A and 2B are a partial vertical cross-sectional view and a cross-sectional view showing an electrode with a thermocouple included in the electromagnetic flowmeter of the present invention.

FIG. 3 is an explanatory diagram showing an example of how an electromagnetic flowmeter is used in a plant such as a fast breeder reactor.

FIG. 4 is an explanatory diagram showing an example of use in which an electromagnetic flowmeter is installed above the core of a nuclear reactor.

[Fig. 5] (A) is a cross-sectional view showing a conventional electromagnetic flowmeter;
B) is a sectional view taken along the line BB in FIG. 5(A).

[Explanation of symbols]

1 Flow pipe 2. Magnet 3 Magnetic material 4 Electrode with thermocouple 5 Electrode 6 Piping connection 7 Space 8 MI cable

Claims (1)

[Claims] Claim 1: In an electromagnetic flowmeter that is immersed in a flow of a conductive fluid and detects the flow rate in that area, a flow tube through which the fluid flows is formed to have a thin wall structure, and the outer periphery of the flow tube is An electromagnetic flowmeter characterized by alternately arranging magnets and magnetic materials.