JPH04535B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an improvement in 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. .

[Conventional technology]

In general, an electromagnetic flowmeter uses Faraday's electromagnetic induction development 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. This kind of electromagnetic flowmeter has no moving parts during measurement.
Also, there is no pressure loss due to measurement.
Furthermore, corrosive fluids that are difficult to measure using other measurement methods,
It has the advantage of being able to measure the flow rate of mixed fluids containing slurry, solids, etc., and is widely used in various fields.

By the way, this type of electromagnetic flowmeter had a configuration as schematically shown in FIG. To briefly explain this, as is clear from Fig. 4a, the reference numeral 1 in the figure is in a state in which annular flange plates 2, 2 for supporting the case are fitted around the outer periphery of both opening ends. A measurement tube 1 is made of a metal conduit 3 which is welded and fixed in place.The outer circumference of the measurement tube 1 is sandwiched from above and below, and has a diameter that corresponds to the flow direction of the fluid to be measured in the measurement tube 1. A pair of excitation coils 4, 4 and cores 5, 5, etc., wound in a substantially saddle shape, which apply a magnetic field in orthogonal directions, 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 an O-ring or the like is provided on the outer periphery of the flange plates 2, 2 on the outside of the measuring tube 1. A cylindrical case 6 is fitted and fixed therebetween. Furthermore, in the above-mentioned measurement tube 1, a pair of electrodes 7 are provided in the direction perpendicular to the flow direction of the fluid to be measured and the direction of the magnetic field generated by the excitation coils 4, 4, as is well known.
(one not shown) are disposed to face each other, and are configured to extract the electromotive force generated in the conductive fluid to be measured. Note that 8 and 9 in FIG. 4a indicate the inner holes of the metal conduit 3 with the annular flange plates 2 and 2 fitted to the stepped portions 3a and 3a formed on the outer periphery of both open ends of the metal conduit 3. Inner side,
This is a welded part that is built up so that the outside is joined and fixed.

An electromagnetic flowmeter with such a configuration is
As is well known, by tightening and fixing the flanges 10a, 10a formed at the ends of the left and right piping 10, 10, respectively, with through bolts 11 and nuts 12, the fluid can be measured. It is installed and fixed in the middle of piping and measures the flow rate of the fluid to be measured.

[Problem that the invention seeks to solve]

However, in the conventional electromagnetic flowmeter having the above-mentioned configuration, the measuring tube 1 is formed by welding the annular flange plate 2 to both open ends of the metal conduit 3. A considerable amount of external force was applied to the flange plates 2, 2 from the outside in the axial direction, and internal pressure from the fluid to be measured flowing inside the measuring tube 1 was also applied.
The stress caused by these external forces is then applied to the metal conduit 3,
The force is concentrated on a part of the measuring tube 1 consisting of the flange plate 2 and the welded parts 8, 9, etc., and as a result, the measuring tube 1 is locally fatigued and deformed plastically, which deteriorates the reliability of measurement accuracy, etc. It is desired that some kind of countermeasure be taken to solve this problem.

[Means for solving problems]

In order to meet such demands, the electromagnetic flowmeter according to the present invention has a measuring tube in which an annular flange plate is fitted onto the outer periphery of each opening end of a metal conduit and is fixed by welding. The inner wall surface of the 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 to the outer wall surface of the metal conduit opposite to the flange plate. , 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, due to 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, stress concentration due to external force is avoided and appropriate stress distribution is achieved. It is possible.

〔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, the annular flange plate 2,
In the measuring tube 1, the inner wall surfaces of the flange plates 2, 2 and the outer wall surface of the metal conduit 3 are connected to the outside of the metal conduit 3. Welding is performed by a build-up that rises from the wall surface with a gentle slope, and from the rising part P, a weld that is approximately the same as the build-up of the welding part 8 is applied to the outer wall surface of the metal conduit 3 on the opposite side from the flange plate 2. Continuous tapered surface 2 with a slope
It is characterized by forming a groove portion 20 which has a curved surface 20a and is folded back with a smooth curved surface 20b.

The reason for adopting such a configuration is as follows. In other words, in the measurement tube 1 of the electromagnetic flowmeter described above, the stress value due to external force on each part could conventionally be confirmed only as an approximate value at the flange part due to the structure of the pressure vessel according to the JIS standard. However, the present inventors adopted the finite element method (FEM), which has been attracting attention in recent years, to calculate and obtain the stress values at each part of the measurement tube 1 described above. From the calculation results, the stress in the axial direction (z-axis direction) of the measuring tube 1 with respect to the metal conduit 3 in the conventional structure is determined by the stress on the outer wall surface of the metal conduit 3 and the flange, as shown in Fig. 4a and b. Rising part P of the build-up of the welding part 8 that fixes the inner surface of the plate 2
It was confirmed that a sudden stress concentration (see arrow in FIG. 5) occurred at the position. In order to reduce the maximum stress value σzmax in this case, it is necessary to increase the axial length L of the welded part 8 and its build-up height t, as well as the wall thickness h of the metal conduit 3. This is not preferable in terms of material cost, and also causes problems such as increasing the size of the measuring tube 1 as a whole. In addition, the broken line in FIG. 5 illustrates the displacement state due to 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 have determined that the welding part rising part P is as shown in FIGS. 1 and 2. , a welded part 8 with built-up overlay and a groove part 2 formed continuously on the slope of the welded part 8
By positioning it between the tapered surface 20a of 0,
In addition to avoiding stress concentration due to external forces such as loads from the piping side, the inner surface 20 of this groove 20
It was confirmed that stress could be efficiently dispersed along lines a and 20b and that an appropriate stress distribution (indicated by arrows in FIG. 2) could be obtained. Of course, due to such stress dispersion, the overlay dimension of the welded part 8 and the thickness dimension of the conduit 3 as described above are not increased.
The maximum stress value σzmax can be reduced, and the measurement tube 1 as a whole can be made smaller and lighter. Note that 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 are, for example, 10 to 30° (especially around 15°).
It is sufficient to do so.

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 or 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 rise up with a gentle slope from the outer wall surface of the metal conduit. In addition to welding with a build-up of this kind, the outer wall surface of the metal conduit opposite to the flange plate from the rising part has a continuous tapered surface with approximately the same slope as the build-up of the welding part and is smooth. Despite the simple structure, the groove formed on the outer wall of the metal conduit on the inner side in the axial direction of the conduit than the rising part of the welded part with the flange plate is formed. Due to its presence, it is possible to avoid stress concentration due to external forces and to distribute stress appropriately, thereby improving the durability of the measuring tube and the reliability of measurement accuracy, as well as making the measuring tube smaller and lighter. There are various excellent effects such as cost reduction.

[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. Figures 4a and 4b are side sectional views and stress characteristic diagrams in the axial direction for explaining problems with the conventional example, and Figure 5 is a diagram showing the displacement state of the measuring tube analyzed by the finite element method. It is. 1... Measuring tube, 2... Annular flange plate, 3...
...Metal conduit, 6...Case, 8, 9...Welded part,
10...Fluid piping, 10a...Flange part, 11
...Through bolt, 20...Groove portion, 20a...Tapered surface, 20b...Curved surface, P...Welding portion rising portion.

Claims (1)

[Claims] 1. 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 by a build-up that rises at a gentle slope from the outer wall surface of the metal conduit, and the build-up of the welded part is welded from the rising part to the outer wall surface of the metal conduit on the opposite side from the flange plate. 1. An electromagnetic flowmeter characterized in that a groove portion is formed which has a continuous tapered surface with substantially the same slope as the curved surface and is folded back with a smooth curved surface.