JPH04198816A - Electromagnetic flow meter - Google Patents

Abstract

PURPOSE:To obtain an electromagnetic flow meter which has a simple structure and sufficient strength and can hold practically sufficient measurement accuracy by making the lining of the flow meter shorter than a measuring tube and arranging the lining at a prescribed location including the area where a magnetic flux for flow rate measurement passes through. CONSTITUTION:A magnetic field generator 1 is provided near the outside of a measuring tube 2 and a lining 3 is arranged on the internal surface of the tube 2 where an electromotive force is generated by the interaction between the magnetic field from the generator 1 and a fluid to be measured. The lining 3 is shorter than the tube 2 and the end section of the tube 2 which is directly brought into contact with the fluid to be measured forms an earthing section. In addition, an electrode for detecting the electromotive force is arranged through the tube 2 and lining 3. A spring 7 is put between the lining 3 and an electrode clamp 8 and, since the spring 7 always presses the electrode 6 against the lining 3, the fluid to be measured is sealed and the lining 3 is fixed. Therefore, the electrode 6 does not make any electrical short circuit through the tube 2 and the measurement accuracy does not receive any practically adverse influence.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) This invention relates to an electromagnetic flowmeter in which a measuring tube is provided with a lining.

(Prior art) In the conventional electromagnetic flowmeter, as shown in Fig. 3, the measuring tube 2
A lining 3 is provided on the entire inner surface of the lining 3 and the measuring tube 2 is fixed to prevent the fluid to be measured from entering between the lining 3 and the measuring tube 2.

The purpose of providing the lining 3 on the entire inner surface of the measuring tube 2 is to electrically insulate the measuring tube 2 and the fluid to be measured, and to prevent the electromotive force detection electrodes from shorting together through the measuring tube. be.

Another purpose of the lining is to protect the measuring tube 2 from chemical and mechanical attack by the fluid to be measured.

(Problems to be Solved by the Invention) Covering the entire inner surface of the measuring tube with a lining requires a large amount of expensive lining material, is difficult to manufacture, and has a complicated structure.

If the lining and the measuring tube are fixed together, a problem arises in that a vacuum is created between the two or that gas generated from the fluid to be measured enters between them. In addition, to prevent the lining from peeling off, it is necessary to take measures such as inserting a wire mesh or perforated pipe into the lining, or suspending the lining with an anchor structure.

This invention was made in view of the above circumstances, and its purpose is to have a simple structure, but with sufficient strength for practical use against chemical and mechanical attacks of the fluid to be measured. An object of the present invention is to provide an electromagnetic flowmeter with high measurement accuracy.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, an electromagnetic flowmeter according to the present invention includes a measuring tube and a measuring tube made of an electrically conductive material, and a measuring tube that is guided to the fluid to be measured. a liner that has an electrode for detecting the electromotive force generated by the flow rate, and an outer surface that is in contact with the inner surface of the measurement tube, is shorter than the length of the measurement tube, and is arranged at a predetermined position that includes a region through which a magnetic flux for flow rate measurement passes. Be prepared.

The liner may be fixed to the inner surface of the measurement tube.

Additionally, the liner may include a feeler.

(Function) With the above configuration, in the electromagnetic flowmeter according to the present invention, the lining is applied not to the entire inner surface of the measuring tube but only to a portion where a magnetic flux (magnetic field) for flow measurement is generated by a coil or the like. will be applied.

This lining insulates the electrode and the measuring tube to an extent that poses no practical problem. Furthermore, at least one end surface of the lining is open, allowing the fluid to be measured to flow between the lining and the measuring tube, and a complicated structure for fixing the lining to the measuring tube is not required. A part of the inner surface of the measuring tube is not provided with a lining, and the measuring tube is in direct contact with the fluid to be measured. Therefore, if the measuring tube is set to the ground voltage, there is no need to separately provide a ground ring or the like.

By fixing the lining to the inner surface of the measurement tube, the movement and peel strength of the lining are strengthened. Further, if a feeler is included in the liner, the liner itself can be hardened and its strength can be increased.

(Example) If the use of an electromagnetic flowmeter is limited to measuring the flow rate of tap water, etc., if the measuring tube is made of stainless steel, etc., it will be chemically and mechanically improved without using a lining. In many cases, an electromagnetic flowmeter can be obtained that is fully satisfactory.

Therefore, in the present invention, by limiting the use of the electromagnetic flowmeter, a conductive tube is used as the measurement tube, and an insulating lining is provided only in a predetermined area including the vicinity of the electrode.

Hereinafter, an electromagnetic flowmeter according to an embodiment of the present invention will be described with reference to FIG.

The measurement tube 2 is made of an electrically conductive, ζ non-magnetic, and relatively corrosion-resistant material, such as stainless steel such as 5US304.5US316, and the measurement tube 2 is grounded. A magnetic field generating device 1 that generates a magnetic field within the measuring tube 2 is arranged near the outside of the measuring tube 2 .

A lining 3 is disposed on the inner surface of the α-shaped tube 2 at a portion where an electromotive force is generated according to Faraday's law of electromagnetic induction due to the interaction between the magnetic field from the magnetic field generator 1 and the fluid to be measured. This lining 3 is shorter than the length of the measuring tube 2, and the end of the measuring tube 2 is in direct contact with the fluid to be measured and serves as an earth grounding section. The lining 3 is not fixed to the inner surface of the measuring tube 2, but its end is open, allowing the fluid to be measured to flow between the lining 3 and the measuring tube 2. However, since the pressures applied to the inner and outer surfaces of the lining are approximately equal, the lining 3 does not move due to the difference in pressure applied to the lining. Further, the end of the lining 3 has a model shape so as to be less affected by the flow of the fluid to be measured. , the measuring tube 2 is welded 4 to the upstream or downstream vibrator 5.
or via flanges 4a, 5a.

An electrode 6 is arranged to penetrate the measurement tube 2 and the lining to detect the electromotive force. A metal fitting 8 for tightening the electrode is attached to the leg portion of the electrode 6, and a spring 7 is disposed between the line 3 and the metal fitting 8 for tightening the electrode. The electrode 6 constantly presses against the lining 3 by the force of the spring 7, sealing the fluid to be measured and fixing the position of the lining 3.

According to the configuration shown in FIG. 1, the lining 3 is arranged in a portion where an electromotive force is generated based on Faraday's law of electromagnetic induction (a portion through which a magnetic flux for measurement passes). Therefore, the plurality of electrodes 6 are not electrically short-circuited via the measurement tube 2, and there is no effect on measurement accuracy in practice. Furthermore, since the measuring tube 2 is grounded and in direct contact with the fluid to be measured, there is no need to use a separate grounding ring or the like.

Conventionally, the lining and the measuring tube are fixed together, but in this embodiment, the fluid to be measured can flow between the measuring tube 2 and the lining 3, simplifying the structure of the electromagnetic flowmeter.

In addition, since the measuring tube 2 is mainly made of metal, it is strong even if the measuring tube 2 is thin, and can be used for direct welding with the mating pipe 5, spot welding of parts of the magnetic field generator 1 to the measuring tube 2, and for sealing the waterproof case. Welding to the measuring tube 2 is easy, and manufacturing costs can be reduced.

2A and 2B show the structure of an electromagnetic flowmeter according to a second embodiment of the present invention.

In FIG. 2A, only the central part of the conductive measuring tube 2 is provided with a lining 3. An insulating electrode holder is placed in the electrode mounting portion of the measuring tube 2 at a seat 9. The measuring tube 2, the lining 3, and the electrode holder pass through the seat 9, and the electrode 6 is placed therein.

The electrode 6 has a conical head with a flared tip. Electrode 6
A metal fitting 8 is attached to the leg of the electrode for tightening the electrode.
The electrode is tightened using a spring 7 between the metal fitting 8 and the electrode holder seat 9.
is located. Due to the action of spring 7, electrode 6
The head of the electrode 6 is always pressed against the lining 3 to ensure airtightness between the electrode 6 and the lining 3.

The end of the liner 3 is held by a reinforcing body 10 fixed to the measuring tube 2 by spot welding 11.

Also in FIG. 2B, the lining 3 is applied only to the central part of the conductive measuring tube 2. The flared part of the liner 3 constitutes the electrode seat 9. An electrode 6 is placed through the measuring tube 2 and the lining 3.

The electrode 6 includes a flat plate 6b having a convex portion. A metal fitting 8 is attached near the electrode 6 for tightening the electrode. A spring 7 is arranged between the metal fitting 8 and the flat plate 6b to tighten the electrode. Due to the action of the spring 7, the flat plate 6b is constantly pressed against the flared portion of the lining 3, and the electrode 6 and the lining 3 are
Airtightness between the parts is ensured.

In these configurations, since the measuring tube 2 is lined in the vicinity of the electrode 6, the flow rate can be measured accurately. In addition, practically sufficient corrosion resistance can be obtained by directly contacting the measurement tube 2 with the fluid to be measured or by limiting the type of fluid to be measured. Furthermore, lining 3
Since the ends of the lining 3 are reinforced by the reinforcing body 10, the lining 3 does not move or wobble even when the flow velocity of the fluid to be measured is high.

In the case of FIG. 2 as well, the lining 3 is not fixed to the inner surface of the measuring tube 2, and the fluid to be measured can flow between the lining 3 and the measuring tube 2. Instead of the reinforcing body 11, the lining 3 may be fixed by a method such as fitting a metal ring inside the lining 3.

It is desirable that the length of the lining is neither unnecessarily long nor so short as to cause errors in measurements. Therefore, we conducted an experiment regarding the length of the lining.

According to experiments and computer simulations, it varies slightly depending on the shape of the coil (saddle shape, pole piece, etc.), the angle between the line connecting the end of the coil and the center of the measuring tube, and the line connecting the electrode, but within the practical range. In this case, it is desirable that the position of the electrode be aligned with the center of the lining, and that the length of the lining be approximately 0.4 to 2 times the diameter of the measuring tube, particularly 0.7 to 1.3 times. It has been found that it is preferable that the

Furthermore, in relation to the excitation part 1, as shown in FIG. 1, it was confirmed that it is effective even when the length is shorter than the length of the excitation part 1 (the length of the region where the magnetic field exists).

In the embodiments of FIGS. 1, 2A, and 2B, it is also possible to mix a feeler into the lining 3 in order to harden the lining 3 and increase its strength. For example, when using a tetrafluoride resin as the lining 3, a hard lining can be obtained by mixing short glass fibers into the powder of the tetrafluoride resin and shaping the powder into the shape of the lining. can. ``This invention is not limited to the above embodiments. For example, in the above embodiment, tap water was shown as the fluid to be measured, but if the measuring tube is made of stainless steel, the flow rate of not only tap water but also sewage and various types of chemicals can be measured. Further, the type of fluid to be measured is arbitrarily determined depending on the relationship between the measurement tube 2 and the fluid to be measured. Further, the lining is not limited to tetrafluoride resin, and for example, other resins can also be used.

In the above embodiment, both ends of the lining 3 are open (a structure that allows the fluid to be measured to pass between the measurement tube and the lining), but only one end may be open.

Further, a part of the outer circumference of the lining 3 may be fixed to the inner circumference of the measuring tube 2.

Note that it is also possible to use a pipe made of electrically insulating resin as a measuring tube without lining. but,
In this structure, the earth ring must be connected,
In addition, it has disadvantages such as being weak in strength and difficult to connect with other pipes, making it impractical. On the other hand, in the above embodiment, since the measuring tube is made of metal, there is no need for an earth ring, the strength is strong, and connection with other pipes is easy.

[Effects of the Invention] In the present invention, since the lining is applied to the vicinity of the electrode, the flow rate can be measured relatively accurately.

Since only a portion of the measurement tube is lined, the measurement tube comes into direct contact with the fluid to be measured, but by limiting the type of fluid to be measured, it is possible to obtain sufficient corrosion resistance for practical use. I can do it. Moreover, by opening at least one end of the lining, the process of fixing the lining to the measuring tube becomes unnecessary. Furthermore, since the pressure of the fluid to be measured is applied almost equally to the outer surface of the lining, the lining does not move or wobble.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of an electromagnetic flowmeter according to an embodiment of the present invention, FIGS. 2A and 2B are sectional views showing the structure of an electromagnetic flowmeter according to another embodiment of the invention, and FIG. FIG. 3 is a sectional view showing an example of the structure of a conventional electromagnetic flowmeter. DESCRIPTION OF SYMBOLS 1... Magnetic field generator, 2... Measuring tube, 3... Lining, 4... Welding point, 6... Electrode. Applicant's agent Patent attorney Takehiko Suzue

Claims (3)

[Claims] (1) A measurement tube made of an electrically conductive material, an electrically insulating lining disposed within the measurement tube, and an electrode that is in contact with the fluid to be measured and detects the electromotive force induced in the fluid to be measured. , the lining is shorter than the length of the measurement tube, is placed at a predetermined position including a region through which magnetic flux for flow rate measurement passes, and has an outer surface of the lining and an inner surface of the measurement tube. At least one end surface is open so that the fluid to be measured can flow in between the electrodes, and the electrode has a structure that seals the fluid to be measured so that the fluid to be measured does not leak to the outside. An electromagnetic flow meter. (2) The electromagnetic flowmeter according to claim 1, wherein the liner is fixed to the inner surface of the measuring tube. (3) The electromagnetic flowmeter according to claim 1, wherein the liner includes a feeler.