JPH047934B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electromagnetic flowmeter equipped with a ceramic measuring tube.

[Conventional technology]

An electromagnetic flowmeter measures the flow rate by converting the flow rate of a conductive fluid passing through a measuring tube into an electrical signal using Faraday's electromagnetic induction phenomenon, and there are no moving parts during measurement. Not only does it have advantages such as no pressure loss during measurement, but it is also capable of measuring the flow rate of corrosive fluids, slurry solids, etc., which are difficult to measure with other measuring devices. widely used.

The measuring tubes of this type of electromagnetic flowmeter have traditionally been metal tubes lined with synthetic resin such as Teflon, but in recent years ceramic measuring tubes with various features have become widely used. It's here. Conventionally, this type of ceramic measuring tube and metal case are generally fixed by shrink fitting. For example, FIG. 5 is a cross-sectional view of an electromagnetic flowmeter disclosed in Japanese Patent Publication No. 58-501552, etc.
A ceramic measurement tube 1 having flanges 1a at both ends is connected to pipes 2 and 3 via a non-conductive gasket 4, and a pair of excitation coils is attached to the outer periphery of the measurement tube 1. 5 is fixed. And, on the flange 1a of the measuring tube 1,
A metal case 6 is fixed by shrink fitting.
A pair of electrodes 7 are inserted and fixed into electrode holes in the outer wall of the measuring tube 1 with their axes perpendicular to the direction of the magnetic field of the excitation coil 5 and the direction of fluid flow.

With this configuration, when the excitation coil 5 is excited and the conductive fluid flows through the inner hole of the measuring tube 1, an electromotive force proportional to the average flow rate is generated between the electrodes 7. The flow rate can be obtained by measuring the .

Moreover, the one whose sectional view is shown in FIG. 6 is an electromagnetic flowmeter disclosed in, for example, Japanese Utility Model Application Publication No. 59-28219, in which the inner hole of the metal measuring tube 8 having flanges 8a at both ends is A ceramic pipe 9 is shrink-fitted, and pipes 2 and 3 are connected to the measuring tube 8 via a gasket 4. In the measuring tube 8,
An excitation coil 5 and an electrode 7 similar to those shown in FIG.
A metal case 6 is fixed to the flange 8a of the measurement tube 8 by shrink fitting. The operation is the same as shown in FIG.

[Problems to be Solved by the Invention] However, among such conventional electromagnetic flowmeters, the one shown in FIG. Since the high heat for shrink fitting is transmitted to the excitation coil 5, etc., there is a problem that the material must be heat resistant. There was a problem in that since the tube 1 could not be replaced, the entire meter had to be replaced.

In addition, in the case shown in FIG. 6, the gasket 4, which is the sealing surface when joining the pipes 2 and 3, is in contact with the end surface of the metal flange 8a, so even if ceramic is used, it is better to use ceramic in terms of corrosion resistance. There was a problem that the superiority of the system could not be demonstrated.

[Means for solving problems]

In order to solve these problems, in the present invention, a metal ring is shrink-fitted to the outer periphery of both open ends of a ceramic measuring tube, and a metal case is removably fitted to the outer periphery of this ring via an O-ring. .

[Effect]

With this configuration, the excitation coil is attached to the ceramic measurement tube after the metal ring is shrink-fitted, and the metal case is fitted with an O-ring interposed between the ring and the electromagnetic flowmeter. Once completed, connect the piping via the gasket. As a result, the gasket contacts the ceramic surface and the measuring tube can be removed from the metal case for replacement or the like.

〔Example〕

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of the electromagnetic flowmeter according to the present invention. A pair of excitation coils 13 formed in a substantially saddle shape are fixed to the section. In addition, a pair of electrode holes 12b provided in the wall of the measurement tube 12 are provided with a pair of electrodes 14 whose axes are orthogonal to the direction of the magnetic field of the excitation coil 13 and the direction of the flow path within the measurement tube 12. It is inserted and fixed fluid-tightly in contact with the fluid. A metal ring 15 is fitted and fixed to the outer periphery of the flanges 12a, which are both open ends of the measurement tube 12, by shrink fitting. 16 is a metal case integrally formed with a cylindrical portion 16a and an exchanger support portion 16b, and is connected to the measuring tube 12 by fitting the inner circumferential surface of the cylindrical portion 16a with the outer circumferential surface of the flange 12a. The flange 1
An O-ring 17 is fitted into the annular groove provided on the fitting surface 2a to prevent rainwater from entering from the outside. Furthermore, on both opening end surfaces of the measuring tube 12,
Piping (not shown) is connected via a seal gasket. Further, the exchanger support portion of the case 16 supports a converter, a terminal box, and the like.

With the above configuration, when the excitation coil 13 is excited and the conductive fluid flows through the inner hole of the measuring tube 12, a flow occurs between the electrodes 7 provided perpendicularly to the magnetic field direction and the flow path direction. Since an electromotive force is generated that is proportional to the average flow velocity of the fluid, the flow rate can be measured by introducing this to a converter and converting it.

In such electromagnetic flowmeters, the case is fitted onto a metal ring that has been shrink-fitted into a ceramic measuring tube and then kept at room temperature, so that excitation coils, etc. are already attached when this fitting is done. Since the temperature does not rise even if the material is heated, there is no need to consider heat resistance when selecting the material.
In addition, in case of replacement or maintenance of the measuring tube, use case 1.
6 can be easily disassembled by moving it in the axial direction.

Since the metal ring 15 is easy to process unlike ceramic, a screw hole is provided in the metal ring 15 as shown in FIG. By screwing into this screw hole, the case 16 can be detachably and firmly fixed to the metal ring 15.

In addition, as shown in FIG. 3, which is a cross-sectional view of the vicinity of the metal ring, when the metal ring 15 is shrink-fitted to the flange 12a of the measuring tube 12, if the flange 12a is provided with a stepped portion 12c, the positioning becomes easy and reliable. become.

Furthermore, FIG. 4 is a longitudinal cross-sectional view of an electromagnetic flowmeter showing another embodiment of the present invention corresponding to FIG. A metal ring 15A having a larger diameter than that shown in FIG. 1 is shrink-fitted to the open end portions on both sides thereof. The rest of the configuration is the same as that shown in FIG. The effect is the first
Same as shown in the figure.

[Effects of the Invention] As is clear from the above description, in an electromagnetic flowmeter according to the present invention, a metal ring is shrink-fitted to the outer periphery of the opening at both ends of a ceramic measuring tube, and an O-ring is fitted to the outer periphery of the ring. By attaching the metal case removably, the excitation coil, electrodes, etc. can be attached to the measurement tube at room temperature after shrink-fitting the metal ring, and the excitation coil etc. will not rise in temperature. When selecting these materials, there is no need to consider heat resistance, etc., and the range of material selection is expanded.
In addition, since the mating partner of the metal case is a metal ring, it is easy to process O-ring grooves, etc., unlike in the case of ceramics, reducing processing costs compared to processing ceramics, and improving the characteristics of ceramics. able to demonstrate. Furthermore, since the case and the measuring tube are not shrink-fitted and can be easily attached and detached, the measuring tube can be replaced and maintained, resulting in cost savings compared to conventional systems in which the entire meter has to be replaced. Furthermore, since the seal gasket for piping connection comes into contact with the ceramic, corrosion resistance is improved and the superiority of the ceramic can be demonstrated.

[Brief explanation of drawings]

1 to 4 show an embodiment of an electromagnetic flowmeter according to the present invention, FIG. 1 is a longitudinal sectional view thereof, and FIGS. 2 and 3 are metal rings showing other embodiments of the present invention, respectively. A nearby sectional view, FIG. 4 is a longitudinal sectional view showing another embodiment of the present invention corresponding to FIG. 1, and FIGS. 5 and 6 are longitudinal sectional views of a conventional electromagnetic flowmeter, respectively. . 11...Electromagnetic flowmeter, 12...Measuring tube, 12a
...Flange, 15...Metal ring, 16...Case, 17...O ring.

Claims (1)

[Claims] 1. An electromagnetic flowmeter characterized in that a metal ring is shrink-fitted to the outer periphery of both open ends of a ceramic measuring tube, and a metal case is removably fitted to the outer periphery of this ring via an O-ring.