JPH09126843A - Electromagnetic flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the electrical connection between an electromagnetic flowmeter and a pipeline from becoming uncertain when the flowmeter is attached to or detached from the pipeline so as to stabilize the measurement accuracy of the flowmeter by electrically connecting the lug sections of a liquid-wetted ring with lug and a frame ring to a case with electrical connecting members. SOLUTION: Since the lug sections 9b of a liquid-wetted ring 9a integrally formed with the sections 9b are directly electrically connected to a case 7 with electrical connecting terminals 12b, the potential at a fluid to be measured can be sent to a measurement electrode as a reference potential. In addition, even when the electrical connection between the ring 9a and a frame ring 11 becomes uncertain, the potential at the fluid can be sent surely to the measurement electrode and the measurement accuracy of an electromagnetic flowmeter can be stabilized. Moreover, since an electrical conducting path exists to the case 7 through the rings 9a and 11 in addition to a direct passage to the case 7 from the ring 9a, the certainty of sending the potential at the fluid to the measurement fluid can be improved further.

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 detecting the flow rate of a fluid to be measured based on the law of electromagnetic induction.

[0002]

2. Description of the Related Art FIG. 1 is a block diagram showing the principle of measurement of an electromagnetic flow meter. In the figure, 1 is a measuring tube whose inside is formed with Teflon or the like, 2 is a fluid to be measured flowing in the measuring tube 1, 3 is a core provided on the outer circumference of the measuring tube 1, 4
Is an exciting coil wound around the core 3, 5 is a measuring electrode provided at a position facing a part of the measuring tube 1 and intersecting the magnetic field, and 6 is noise from the electromotive force detected by the measuring electrode 5. It is a converter that removes the above and converts it into a signal according to the flow rate of the fluid 2 to be measured.

FIG. 2 is a schematic view of an electromagnetic flowmeter. In the figure, 7 is a case that covers the core 3, the exciting coil 4 and the measuring electrode 5 and around, 8 is a flange, 9 is tantalum and platinum. , Titanium and Hastelloy B, C, etc. are liquid contact rings provided at one end of the measuring tube 1 so as to come into contact with the fluid to be measured 2, and the liquid contact ring is electrically connected to the case 7. The potential of the fluid 2 to be measured is sent to the measurement electrode 5 as a reference potential.

FIG. 4 is a block diagram showing the details of the connecting portion of a conventional electromagnetic flowmeter. In the figure, 10 is a gasket for preventing leakage of the fluid 2 to be measured between the liquid contact rings 9.
Is a frame ring made of a slightly inexpensive corrosion resistant material such as stainless steel and provided on the outer periphery of the gasket 10 and in contact with the liquid contact ring 9. Reference numerals 12a and 12b denote electrical connection pins and electrical connection terminals that electrically connect the frame ring 11 and the case 7, and are measured via the liquid contact ring 9 and the frame ring 11 with the potential of the fluid to be measured 2 as a reference potential. It is to be sent to the electrode 5. Further, 13 is a spot welding portion for connecting the liquid contact ring 9 and the frame ring 11.

Next, the operation will be described. First, the measurement principle of the electromagnetic flow meter will be described. As shown in FIG. 1, when the fluid to be measured 2 moves in the magnetic field, an electromotive force is generated according to Faraday's law of electromagnetic induction. If the magnetic field is perpendicular to the measuring tube 1 and the conductivity of the fluid 2 to be measured is not too low, the voltage can be measured between the pair of measuring electrodes 5 provided on the inner surface. This voltage is proportional to the strength of the magnetic field, the average flow velocity of the fluid to be measured 2, and the distance between the measuring electrodes 5. By this principle, the flow velocity and flow rate of the fluid to be measured 2 can be measured. further,
The converter 6 removes noise and the like from the electromotive force detected by the measuring electrode 5 and converts the electromotive force into a signal corresponding to the flow rate of the fluid to be measured 2.

FIG. 2 shows a flange type electromagnetic flow meter of the wafer type and the flange type, in which the core 3, the exciting coil 4 and the measuring electrode 5 are surrounded by a case 7, and a measuring tube. The inside of 1 is lined with Teflon or the like to prevent corrosion by the fluid to be measured 2.

Further, as shown in FIG. 4, an earth ring composed of a liquid contact ring 9 and a frame ring 11 is provided at one end of the measuring tube 1, and this earth ring is based on the potential of the fluid 2 to be measured. The potential is sent to the measurement electrode 5 via the liquid contact ring 9 and the frame ring 11, and the reason for providing this earth ring is that if there is no earth ring, a floating potential will be generated in the fluid 2 to be measured, Is not constant, and the potential obtained at the measuring electrode 5 fluctuates.
As a result, in the case of an electromagnetic flow meter, which constantly measures the flow rate and integrates the flow rate to obtain the total amount, the above situation should be avoided in order to ensure the reliability of the measured value.

In these earth rings, the liquid contact ring 9 that is in direct contact with the fluid 2 to be measured and whose degree of corrosion is large is made of expensive materials such as tantalum, platinum, titanium, and Hastelloy B and C, which have extremely high corrosion resistance. In addition, the frame ring 11 having a small degree of corrosion was made of a material such as stainless steel which is corrosion resistant and slightly inexpensive. Then, the liquid contact ring 9 and the frame ring 11 are configured to be spot-welded to enhance electrical conduction, and the gasket 10 seals the joint portion to satisfy both corrosion resistance and manufacturing cost.

[0009]

Since the conventional electromagnetic flowmeter is constructed as described above, when the gasket 10 is displaced when attaching the end of the electromagnetic flowmeter to the pipe,
The fluid to be measured 2 may enter the joint portion between the liquid contact ring 9 and the frame ring 11, the spot welding at the joint portion may separate, and once the corrosive fluid to be measured enters the gap, this There was a problem that the joint was expanded and several spot joints were peeled off at a stretch, the electrical continuity became uncertain, and the measurement accuracy deteriorated. Further, when the pipe is removed from the electromagnetic flow meter, the gasket 10 sticks to the pipe, and as a result, the inner circumference of the frame ring 11 is pulled and peeled off at the joint between the liquid contact ring 9 and the frame ring 11. Even if this occurs, the peeling cannot be noticed from the outside, and if the electromagnetic flowmeter is reattached to the pipe without noticing the peeling, the electrical continuity becomes uncertain and the measurement accuracy becomes the same. However, there was a problem that Further, when the electrical continuity becomes uncertain as described above, there is a problem that the piping line must be stopped and the electromagnetic flow meter must be removed and repaired, which requires a lot of labor. . On the other hand, it is also possible to construct the ring not with such a two-body structure of stainless steel and platinum, but with a food-resistant material consisting of only platinum. In order to adopt such a configuration,
This corrosion resistant material must have a constant plate thickness, which is problematic in terms of cost.

The present invention has been made in order to solve the above problems, and an electromagnetic flow rate capable of stabilizing measurement accuracy without uncertain electrical continuity due to attachment and detachment to a pipe. The purpose is to obtain a total.

[0011]

SUMMARY OF THE INVENTION An electromagnetic flowmeter according to the present invention is made of a corrosion-resistant material, and has at least one end of a pipe line with an ear-contacting liquid contact ring for contacting a fluid to be measured and a frame contacting with the ear-contacting liquid contact ring. A ring is provided, and the ears of the liquid contact ring with ears and the frame ring are electrically connected to the case by an electrical connecting member.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. Hereinafter, an embodiment of the present invention will be described. FIG. 1 is a block diagram showing the measurement principle of an electromagnetic flow meter,
In the figure, 1 is a measuring pipe (pipe) whose inside is formed by lining with Teflon or the like, 2 is a fluid to be measured flowing in the measuring pipe 1, 3 is a core provided on the outer periphery of the measuring pipe 1, 4 is its core An exciting coil wound around 3, a measuring electrode 5 provided at a position facing a part of the measuring tube 1 and intersecting the magnetic field, and 6 removing noise and the like from the electromotive force detected by the measuring electrode 5. , A converter for converting into a signal according to the flow rate of the fluid to be measured 2.

FIG. 2 is a schematic view of an electromagnetic flow meter. In the figure, 7 is a case that covers the core 3, the exciting coil 4 and the measuring electrode 5, the flange 8 and the tantalum and platinum. , Titanium and Hastelloy B, C, etc. are liquid contact rings provided at one end of the measuring tube 1 so as to come into contact with the fluid to be measured 2, and the liquid contact ring is electrically connected to the case 7. The potential of the fluid 2 to be measured is sent to the measurement electrode 5 as a reference potential.

FIG. 3 is a block diagram showing the details of the connecting portion of the electromagnetic flowmeter according to the first embodiment of the present invention. In the figure, 9a is a wetted ring with ears, and this wetted ring with ears is shown. 9a is integrally formed with the ear 9b. Reference numeral 10 is a gasket for preventing the fluid to be measured 2 from leaking between the wetted rings 9a with ears, and 11 is made of a slightly inexpensive corrosion-resistant material such as stainless steel so as to contact the outer circumference of the gasket 10 and the wetted rings 9a with ears. It is a frame ring provided in. 12a and 12b are frame rings 11
And an electrical connection terminal (electrical connection member) for electrically connecting the case 7 to the case 7. The electrical connection terminal 12b is the ear portion 9 of the bent ear-contacting liquid contact ring 9a.
b is also electrically connected to the case 7, and the potential of the fluid to be measured 2 is used as a reference potential, from the liquid contact ring 9a with ears directly to the measurement electrode 5, or via the liquid contact ring 9a with ears and the frame ring 11. It is sent to the measurement electrode 5.

Next, the operation will be described. First, the measurement principle of the electromagnetic flow meter will be described. As shown in FIG. 1, when the fluid to be measured 2 moves in the magnetic field, an electromotive force is generated according to Faraday's law of electromagnetic induction. If the magnetic field is perpendicular to the measuring tube 1 and the conductivity of the fluid 2 to be measured is not too low, the voltage can be measured between the pair of measuring electrodes 5 provided on the inner surface. This voltage is proportional to the strength of the magnetic field, the average flow velocity of the fluid to be measured 2, and the distance between the measuring electrodes 5. By this principle, the flow velocity and flow rate of the fluid to be measured 2 can be measured. further,
The converter 6 removes noise and the like from the electromotive force detected by the measuring electrode 5 and converts the electromotive force into a signal corresponding to the flow rate of the fluid to be measured 2.

FIG. 2 shows a flange type electromagnetic flowmeter of a wafer type and a flange type, in which the core 3, the exciting coil 4 and the measuring electrode 5 are surrounded by a case 7 and a measuring tube. The inside of 1 is lined with Teflon or the like to prevent corrosion by the fluid to be measured 2.

Further, as shown in FIG. 3, at one end of the measuring tube 1, a liquid contact ring 9a with an ear and a frame ring 11 are provided.
A grounding ring made of is used as the grounding ring. The grounding ring is used as a reference potential and the liquid contact ring 9a with ears is directly connected to the measurement electrode 5, or the liquid contact ring 9a with ears and the frame ring 11 are provided. The reason why this earth ring is provided is that if there is no earth ring, a floating potential will be generated in the fluid to be measured 2 and the electric potential will not be constant, so This is because the potential fluctuates and the measured value lacks reliability.

In these earth rings, the ear-contacting liquid contact ring 9a, which is in direct contact with the fluid to be measured 2 and has a large degree of corrosion, includes tantalum, platinum, titanium, and Hastelloy B, C, etc., which are extremely corrosion resistant and expensive. Frame ring 11 made of material and having a low degree of corrosion
Is made of a material such as stainless steel, which has corrosion resistance and is relatively inexpensive. The joint portion is hermetically sealed by the gasket 10 so as to satisfy both the corrosion resistance and the manufacturing cost.

As described above, conventionally, when the electromagnetic flowmeter is attached and detached from the pipe, the spot welding between the liquid contact ring 9 and the frame ring 11 is peeled off, resulting in uncertain electrical continuity. However, in this embodiment, the ears 9b of the integrally formed wetted ring 9a with ears are electrically connected to the case 7 directly by the electrical connection terminals 12b, and the potential of the fluid 2 to be measured is used as a reference potential for measurement. It can be sent to the electrode 5, and the potential of the fluid 2 to be measured can be reliably sent to the measurement electrode 5 even if the electrical contact between the liquid contact ring with ear 9a and the frame ring 11 becomes uncertain. It is possible to stabilize the measurement accuracy. In addition to the above-described electrical conduction path from the liquid contact ring 9a with ears directly to the case 7, the liquid contact ring 9a with ears and the frame ring 1 are provided.
Since there is an electric conduction path to the case 7 via 1, the electric potential of the fluid 2 to be measured can be reliably sent to the measurement electrode 5. In the above embodiment, the measuring tube 1
Although the ground ring is provided only at one end of the above, the ground ring may be provided at both ends of the measuring tube 1.

[0020]

As described above, according to the present invention, at least one end of the conduit made of a corrosion-resistant material is provided with the ear-contacting liquid contact ring that comes into contact with the fluid to be measured, and the ear-contacting liquid contact ring has an ear portion. Since it is configured to be electrically connected to the case by an electrical connection member, the ears of the integrally formed wetted ring with ears are electrically connected to the case directly by the electrical connection terminals, and the potential of the fluid to be measured is changed. An electromagnetic flowmeter that can be reliably sent to the measurement electrode as a reference potential and that can stabilize measurement accuracy without uncertainties in electrical continuity due to installation and removal from piping is effective. is there. Also, since it is possible to secure the grounding reliability of the liquid contact ring provided between the pipe and the electromagnetic flow meter, which is difficult to find from the outside, for a long period of time, there is a long-term span from installation to regular maintenance. In the meantime, there is an effect that the reliability of the electromagnetic flow meter for constantly measuring the flow rate and integrating the flow rate to obtain the total flow rate can be improved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a measurement principle of an electromagnetic flow meter.

FIG. 2 is a configuration diagram showing an outline of an electromagnetic flow meter.

FIG. 3 is a configuration diagram showing details of a connecting portion of the electromagnetic flow meter according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram showing details of a connection portion of a conventional electromagnetic flow meter.

[Explanation of symbols]

 1 Measurement Pipe (Pipe) 2 Fluid to be Measured 4 Excitation Coil 5 Measurement Electrode 9a Wetted Ring with Ear 12b Electric Connection Terminal (Electric Connection Member)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Kato 2-12-19 Shibuya, Shibuya-ku, Tokyo Inside Yamatake Honeywell Co., Ltd. (72) Inventor Tokki Hirano 2-12-19 Shibuya, Shibuya-ku, Tokyo Yamatake Honeywell Co., Ltd.

Claims (1)

[Claims] 1. A pipe through which a fluid to be measured flows, an exciting coil which is provided on the outer periphery of the pipe so as to face each other and generates a magnetic field orthogonal to the longitudinal direction of the pipe, and a part of the pipe. A measurement electrode that is provided at a position facing each other and that intersects with the magnetic field and that detects an electromotive force according to the flow rate of the fluid to be measured; a case that covers the exciting coil and the periphery of the measurement electrode; and a corrosion-resistant material. Of at least one end of the conduit, a liquid contact ring with an ear provided so as to contact the fluid to be measured, a frame ring provided so as to contact the liquid contact ring with an ear, and the liquid contact ring with an ear An electromagnetic flow meter, comprising: an electrical connection member that electrically connects the ear portion and the frame ring to the case, and sends the fluid to be measured as a reference potential to the measurement electrode.