JPS61283824A - Electromagnetic flowmeter - Google Patents

Abstract

PURPOSE:To avoid a stress concentration due to an external force and improve the durability of a measuring pipe by welding the inner wall surface of an annular flange plate and the outer wall surface of a metallic conduit to each other with a gentle gradient and forming a groove with the same gradient in the opposite side outer wall surface. CONSTITUTION:The inner wall surface of an annular flange plate 2 and the outer wall surface of a metallic conduit 3 are welded to each other by overlay welding such that a weld overlay forms a gentle gradient starting from the outer wall surface of the metallic conduit 3. A groove 20 with a tapered face 20a that continues with almost the same inclination and a smoothly curved surface 20b is formed in the opposite side outer wall surface of the metallic conduit 3. The inclination of the overlay at a weld 8 and the inclination alphaof the tapered face 20a are set, for example, to 10 deg.-30 deg.. Thus, a stress concentration due to an external force, such as a load on the piping side or the like, is efficiently dispersed along the tapered face 20a and the curved surface 20b and the maximum stress value is decreased. Therefore, the durability of a measuring pipe 1 and a measuring accuracy can be increased to improve reliability.

Description

[Detailed Description of the Invention] - [Industrial Application Field] The present invention is an improvement of an electromagnetic flowmeter comprising a measuring tube formed by welding and fixing annular flange plates to the outer periphery of both open ends of a metal conduit. Regarding.

[Conventional technology]

In general, an electromagnetic flowmeter uses Faraday's electromagnetic induction phenomenon to convert the flow rate of a conductive fluid to be measured passing through a measuring tube into an electrical signal, and measures the flow rate. 5 Such electromagnetic flowmeters have no moving parts during measurement.

Also, there is no pressure loss during measurement.

Furthermore, it has the advantage of being able to measure the flow rate of mixed fluids containing corrosive fluids, slurries, solids, etc. that are difficult to measure using other measurement methods, and is widely used in various fields.

By the way, this type of electromagnetic flowmeter had a configuration as shown schematically by a path 354. To briefly explain this, the symbol l in the figure is shown in FIG. 4(a).

As is clear from the figure, the measuring tube 1 is made up of a metal conduit 3 formed by welding and fixing annular flange plates 2, 2 for supporting the case fitted to the outer periphery of both open ends. A pair of excitation coils are wound around the outer periphery of the tube 1 in a substantially saddle shape to apply a magnetic field in a direction perpendicular to the flow direction of the fluid to be measured in the measurement tube 1, sandwiching the excitation coil from above and below. 4.4, cores 5, 5, etc. are arranged.

Further, an insulating lining (not shown) made of Teflon or the like is formed on the inner wall surface of the measuring tube 1, and
A cylindrical case 6 is fitted and fixed to the outer circumference of the flange plate 2.2 via an O-ring or the like.

Furthermore, in the above-mentioned measurement tube l, a pair of electrodes 7 (one of which is not shown) is provided in a direction perpendicular to the flow direction of the fluid to be measured and the direction of the magnetic field generated by the excitation coil 4.4, as is well known. (2) are disposed facing each other, and are configured to extract the electromotive force generated in the conductive fluid to be measured. In addition, 8.9 in Figure 4(a)
In this case, the annular flange plate 2.2 is fitted to the stepped portions 3a, 3a formed on the outer periphery of both opening ends of the metal conduit 3, and the inner hole is bent and the outside is joined and fixed. This is a welded part that has been overlaid.

As is well known, an electromagnetic flowmeter having such a configuration is capable of passing the fluid to be measured through the flanges 10a, 10a formed at the ends of the left and right piping 10, respectively. By tightening and fixing with screws 11 and 12, etc., it is inserted and fixed in the middle of a fluid piping, and the flow rate of the fluid to be measured is measured.

[Problem that the invention seeks to solve]

However, in the conventional electromagnetic flowmeter having the above-mentioned configuration, the measurement tube l formed by welding the annular flange plates 2 to both open ends of the metal conduit 3 does not allow the fluid piping to
, to, a considerable amount of external force was applied to the flange plate 2.2 from the outside in the axial direction, and internal pressure from the fluid to be measured flowing inside the measuring tube l was also applied.

The stress caused by these external forces is then applied to the metal conduit 3. Flange plate 2. It concentrates on a part of the measuring tube 1 consisting of welded parts 8, 9, etc., and as a result, the measuring tube 1 is locally fatigued and deformed plastically, which causes problems in terms of reliability of measurement accuracy, etc. Therefore, it is desired that some kind of countermeasure be taken to solve such problems.

[Means for solving problems]

In order to meet such demands, an electromagnetic flowmeter according to the present invention is a measuring tube in which an annular flange plate is fitted to the outer periphery of each opening end of a metal conduit and is welded and fixed to the outer periphery of each opening end of the metal conduit.
The inner wall surface of the annular flange plate and the outer wall surface of the metal conduit are welded by a build-up that rises at a gentle slope from the outer wall surface of the metal conduit, and from the rising part, the outer wall surface of the metal conduit opposite to the flange plate is welded. Further, a groove portion is formed which has a continuous tapered surface with substantially the same slope as the build-up of the welded portion and is folded back with a smooth curved surface.

[Effect]

According to the present invention, stress concentration due to external force is avoided by the presence of the groove formed on the outer wall surface of the metal conduit in the axially inner part of the conduit than the rising part of the welded part with the flange plate.
This enables appropriate stress distribution.

〔Example〕

Hereinafter, the present invention will be explained in detail using embodiments shown in the drawings.

Figures 1 and 2 show an embodiment of the electromagnetic flowmeter according to the present invention, and in these figures, parts that are the same as or correspond to those in Figure 3, etc. described above are designated by the same numbers. Therefore, the explanation will be omitted.

Now, according to the present invention, in the measuring tube l in which the annular flange plate 2.2 is fitted onto the outer periphery of each open end of the metal conduit 3 and fixed by welding, the inner wall surface of the flange plate 2.2 and the outer wall surface of the metal conduit 3 are welded by a build-up that rises at a gentle slope from the outer wall surface of the metal conduit 3, and from the rising portion P to the outer wall surface of the metal conduit 3 on the opposite side from the flange plate 2, The groove 20 is characterized in that it has a continuous tapered surface 20a with substantially the same slope as the build-up of the welded portion 8, and is folded back with a smooth curved surface 20b.

The reason for adopting such a configuration is as follows. That is, in the measuring tube l of the electromagnetic flowmeter mentioned above, the stress value due to external force on each part has conventionally been determined according to JIS
Due to the structure of the pressure vessel according to the standards, it was only possible to confirm the approximate value at the flange part, but the present inventors adopted the finite element method (FEM), which has been attracting attention in recent years, to calculate the above-mentioned value. The stress values at each part of the measuring tube 1 were calculated and determined. From the calculation results, the stress in the axial direction (z-axis direction) of the measuring tube l with respect to the metal conduit 3 in the conventional structure is as shown in FIGS. 4(a) and (b). It was confirmed that a sudden stress concentration (see the arrow in FIG. 5) occurred at the position P of the build-up of the weld portion 8 that fixed the outer wall surface and the inner surface of the flange plate 2. In order to reduce the maximum stress value σ zwax in this case, it is necessary to increase the axial length L of the welded portion 8 and its build-up height t, as well as the wall thickness of the metal conduit 3. All of these methods are unfavorable from the viewpoint of material cost, and may also lead to problems such as an increase in the size of the entire measuring tube. Note that the broken line in FIG. 5 shows an enlarged view of the displacement state caused by the application of concentrated stress in the conventional example.

Therefore, as a result of various studies and experiments based on the above-mentioned calculation results using the finite element method, the inventors of the present invention have determined that the rising part P of the weld is built up as shown in FIGS. 1 and 2. By positioning the welded portion 8 between the welded portion 8 and the tapered surface 20a of the groove portion 20 formed continuously on the slope thereof, stress concentration due to external forces such as loads from the piping side can be avoided, and this groove portion 20 inner surface 20a of
, 20b, and it was confirmed that an appropriate stress distribution distribution (indicated by arrows in FIG. 2) could be obtained. Of course, by such stress dispersion, the maximum stress value σ zmax can be reduced without increasing the build-up size of the welded part 8 or the thickness size of the conduit 3 as described above, and the overall measurement tube l It is also possible to achieve smaller size and lighter weight. The build-up inclination angle of the welded portion 8 and the inclination angle θ of the tapered surface 20a of the groove portion 20 may be, for example, 10 to 300 (particularly around 15°).

Note that the present invention is not limited to the structure of the embodiment described above, and the shape, structure, etc. of each part may be modified and changed as appropriate. For example, it will be clear that the groove portion 20 that characterizes the present invention may be formed in advance on the outer wall surface of the metal conduit 3, or may be formed after welding.

〔Effect of the invention〕

As explained above, according to the electromagnetic flowmeter according to the present invention, the inner wall surface of the annular flange plate constituting the measuring tube and the outer wall surface of the metal conduit are formed such that they rise with a gentle slope from the outer wall surface of the metal conduit. In addition to welding by overlaying,
A groove portion is formed on the outer wall surface of the metal conduit on the side opposite to the flange plate from the rising portion, the groove portion having a continuous tapered surface with substantially the same slope as the build-up of the welded portion and folded back with a smooth curved surface. Therefore, despite the simple configuration, the presence of a groove formed on the outer wall of the metal conduit on the inner side of the axial direction of the conduit than the rising part of the welded part with the flange plate avoids stress concentration due to external forces and maintains appropriate stress. Dispersion is possible, which not only improves the durability of the measuring tube and the reliability of measurement accuracy, but also allows the measuring tube to be made smaller and lighter, resulting in cost reduction and various excellent effects such as barreling. be.

[Brief explanation of drawings]

Fig. 1 is an enlarged sectional view of the main part of a measuring tube showing one embodiment of the electromagnetic flowmeter according to the present invention, Fig. 2 is an explanatory diagram of its operation, and Fig. 3 is a sectional view of the main part showing the schematic configuration of the electromagnetic flowmeter. Figure 4 (a
) and (b) are a side sectional view and a stress characteristic diagram in the axial direction for explaining the problems with the conventional example, and FIG. 5 is a diagram showing the displacement state of the measuring tube analyzed by the finite element method. 111@-・Measuring tube, 2・Fist・annular flange plate, 3
...Metal conduit, 6.Dispute/case. 8.9...Welded part, 10-...Fluid piping, 10a
Fist, fist, flange, 11φ fist, through bolt, 20.
...Groove portion, 20a...Φ tapered surface, 20b---
Curved surface, rising part of P-/kistφ welding part.

Claims (1)

[Claims] In an electromagnetic flowmeter equipped with a measurement tube in which an annular flange plate is fitted onto the outer periphery of each opening end of a metal conduit and then welded and fixed, the inner wall surface of the annular flange plate and the outer wall surface of the metal conduit is welded with a build-up that rises with a gentle slope from the outer wall surface of the metal conduit, and from the rising part on the outer wall surface of the metal conduit opposite to the flange plate, there is approximately the same build-up of the welded part. An electromagnetic flowmeter characterized in that a groove portion is formed that has a continuous tapered surface with the same slope and is folded back with a smooth curved surface.