Centering device and flow meter unit

Abstract

To provide a centering device capable of suppressing deterioration of measurement accuracy by suppressing deviation between a center axis of an inflow / outflow port of a flowmeter and a center axis of a flow passage of a pipe connected to the flowmeter.SOLUTION: A centering device 5 includes a plate-like plate part 51 with an opening 52 which is formed to penetrate in a first direction being a thickness direction and in which a cylindrical part for making a fluid pass is fitted inside. A concave portion 53 recessed toward a center of the opening 52 is formed at the outer edge of the plate part 51, and a convex 54 is formed at a bottom surface 53a of the concave portion 53.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a centering device and a flow meter unit. [Background technology]

[0002] 2. Description of the Related Art There is a flow meter that is formed with an inlet for allowing a fluid to flow into the interior and an outlet for allowing the fluid to flow out from the interior, and that measures the flow rate of a fluid passing through the interior.

[0003] Pipes are connected to the inlet and outlet. If the central axis of the inlet is misaligned with the central axis of the flow path of the connected pipe, or if the central axis of the outlet is misaligned with the central axis of the flow path of the connected pipe, the flow of the fluid will be turbulent at the connection, causing drift inside the flow meter and reducing measurement accuracy.

[0004] Therefore, Patent Document 1 discloses an example in which a jig (centering device) is used in which multiple clamps that surround and support the pipes and flow meters from the outside are fixed to a single reference beam in order to prevent the central axis from shifting. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Utility Model Application Publication No. 5-40825 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the tolerance for precision in the external dimensions and shape of pipes is large and varies from product to product. Therefore, in pipes and flow meters that are supported by clamps from the outside, variations in the external dimensions and shape can cause misalignment of the central axes, resulting in reduced measurement accuracy.

[0007] The present invention aims to provide a centering device that can reduce the misalignment between the central axis of the inlet and outlet of a flow meter and the central axis of the flow path of a pipe connected to the flow meter, thereby reducing the decrease in measurement accuracy. [Means for solving the problem]

[0008] The centering device of the present invention comprises a plate-like plate portion that is formed to penetrate along a first direction, which is the thickness direction, and has an opening formed inside into which a cylindrical portion that allows fluid to pass through is fitted, and a recess that is recessed toward the center of the opening is formed on the outer edge of the plate portion, and a convex portion is formed on the bottom surface of the recess. [Effects of the Invention]

[0009] According to the present invention, it is possible to obtain a centering device that can reduce the misalignment between the central axis of the flow meter's inlet and outlet and the central axis of the flow path of the piping connected to the flow meter, thereby reducing the decrease in measurement accuracy. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of a flowmeter unit according to a first embodiment. [Figure 2] 2 is an exploded perspective view of the flowmeter unit shown in FIG. 1, as viewed from the outlet side of the flowmeter. FIG. [Figure 3] FIG. 1 is a perspective view of a centering device according to a first embodiment. [Figure 4] FIG. 10 is a view of the recessed portion of the centering device as viewed in the first direction, illustrating a case where the outer diameter of the through-bolt is smaller than the specified dimension due to an error. [Figure 5] 10 is a view of the recessed portion of the centering device as viewed in a first direction, illustrating a case where the outer diameter of the through-bolt is larger than the specified dimension due to an error. FIG. [Figure 6] FIG. 10 is a diagram showing a first modified example of a convex portion, and is a partially enlarged perspective view showing an enlarged concave portion. [Figure 7] FIG. 10 is a diagram showing a second modified example of the convex portion, and is a partially enlarged perspective view showing an enlarged concave portion. [Figure 8] FIG. 10 is a diagram showing a third modified example of the convex portion, and is a partially enlarged perspective view showing an enlarged concave portion. [Figure 9] FIG. 10 is a diagram showing a fourth modified example of the convex portion, and is a partially enlarged perspective view showing an enlarged concave portion. [Figure 10] FIG. 10 is a diagram showing a fifth modified example of a convex portion, and is a partially enlarged perspective view showing an enlarged concave portion. DETAILED DESCRIPTION OF THE INVENTION

[0011] A centering device and a flow meter unit according to an embodiment of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the embodiment described below.

[0012] [Embodiment 1] 1 is a perspective view of a flowmeter unit according to embodiment 1. The flowmeter unit 1 includes a flowmeter 2, a primary piping unit 3, a secondary piping unit 4, a centering device 5, and a through bolt 6.

[0013] FIG. 2 is an exploded perspective view of the flowmeter unit shown in FIG. 1, viewed from the outlet side of the flowmeter. The flowmeter 2 measures the flow rate of a fluid passing through it. The flowmeter 2 is a so-called wafer-type flowmeter 2. In a wafer-type flowmeter 2, the flowmeter 2 itself does not have a flange for connecting to a pipe, and the flowmeter 2 is connected to the pipe by being sandwiched between a flange that the pipe has. The flowmeter 2 is, for example, an electromagnetic flowmeter, but is not limited to this. A housing 21 of the flowmeter 2 is formed with cylindrical portions 24 that protrude in opposite directions. The inside of the cylindrical portion 24 forms a flow path for allowing fluid to flow in and out of the inside of the flowmeter 2. The end of the flow path forms an inlet / outlet 22 at the end face of the cylindrical portion 24, allowing fluid to flow in and out of the inside of the flowmeter 2.

[0014] The inlet / outlet port 22 formed in one of the two cylindrical portions 24 serves as the inlet 22a. The outlet / outlet port 22 formed in the other cylindrical portion 24 serves as the outlet 22b. Note that in Figure 2, the end face of one of the cylindrical portions 24 is not visible, and the inlet 22a is indicated by a dashed line.

[0015] The inlet 22a and the outlet 22b are in communication with the interior of the housing 21. The inlet 22a is an opening for allowing the fluid to flow into the interior of the housing 21. The outlet 22b is an opening for allowing the fluid to flow out from the interior of the housing 21.

[0016] The flow path of the cylindrical portion 24 has a circular cross section, and the flow inlet / outlet 22 also has a circular shape. The central axes of the flow paths of the two cylindrical portions 24 coincide with each other. The direction in which this central axis extends is defined as a first direction, and is illustrated by arrow X in Figure 2 and other figures. The central axis of the outer surface of the cylindrical portion 24 coincides with the central axis of the flow path formed in the cylindrical portion 24.

[0017] The primary side piping unit 3 includes a primary side piping 31 and a primary side flange 32. The primary side piping 31 has a cylindrical shape, and its inside forms a flow path 31a through which a fluid passes. The primary side piping 31 is a pipe connected to the inlet 22a of the flow meter 2. Therefore, the fluid flowing through the flow path 31a of the primary side piping 31 flows into the inside of the flow meter 2 through the inlet 22a.

[0018] The primary side flange 32 is provided at one end of the primary side piping 31. The primary side flange 32 is a plate-shaped member. The primary side flange 32 abuts against the end surface of the cylindrical portion 24 where the inlet 22 a is formed. The primary side flange 32 is formed with a plurality of through holes 32 a extending parallel to the first direction while abutting against the end surface of the cylindrical portion 24. A through bolt 6 is passed through the through holes 32 a. The distance between the central axis of the through holes 32 a and the central axis of the flow path 31 a of the primary side piping 31 is equal among the plurality of through holes 32 a formed in the primary side flange 32.

[0019] The secondary-side piping unit 4 includes a secondary-side piping 41 and a secondary-side flange 42. The secondary-side piping 41 has a cylindrical shape, and its inside forms a flow path 41a through which a fluid passes. The secondary-side piping 41 is a piping connected to the outlet 22b of the flow meter 2. Therefore, the fluid flowing through the flow path 41a of the secondary-side piping 41 is a fluid that has flowed out of the flow meter 2 through the outlet 22b.

[0020] The secondary side flange 42 is provided at one end of the secondary side piping 41. The secondary side flange 42 is a plate-shaped member. The secondary side flange 42 abuts against the end surface of the cylindrical portion 24 on which the outlet 22b is formed. The secondary side flange 42 has a plurality of through holes 42a formed therein, which extend parallel to the first direction while abutting against the end surface of the cylindrical portion 24. A through bolt 6 is passed through the through holes 42a. The distance between the central axis of the through holes 42a and the central axis of the flow path 41a of the secondary side piping 41 is equal among the plurality of through holes 42a formed in the secondary side flange 42.

[0021] The through hole 32a formed in the primary flange 32 and the through hole 42a formed in the secondary flange 42 are positioned so that their central axes coincide with each other when the primary flange 32 and the secondary flange 42 are in contact with the end face of the cylindrical portion 24. This makes it possible to pass one through bolt 6 through both the through hole 32a and the through hole 42a.

[0022] With the through bolt 6 passed through the through holes 32a and 42a, a nut can be screwed onto the through bolt 6 to fasten the primary side flange 32 and the secondary side flange 42 together, allowing the primary side flange 32 and the secondary side flange 42 to be tightly attached to the end face of the cylindrical portion 24 of the flow meter 2.

[0023] 3 is a perspective view of the centering device. The centering device 5 includes a plate portion 51 formed in a plate shape. The plate portion 51 is formed of, for example, but not limited to, resin. An opening 52 is formed in the plate portion 51. The opening 52 is formed to penetrate the plate portion 51 in the thickness direction.

[0024] 1 and 2, the centering device 5 has the cylindrical portion 24 of the flowmeter 2 fitted inside the opening 52. In the following description, the state in which the cylindrical portion 24 of the flowmeter 2 is fitted inside the opening 52 may be referred to as the state in which the centering device 5 is assembled to the flowmeter 2.

[0025] When the centering device 5 is assembled to the flowmeter 2, the central axis of the flow path of the cylindrical portion 24 coincides with the central axis of the opening 52. As shown in FIGS. 1 and 2 , when the centering device 5 is assembled to the flowmeter 2, the thickness direction of the plate portion 51 coincides with the first direction indicated by the arrow X. In the following description, when the term "first direction" is used with respect to the centering device 5, it means the first direction when the centering device 5 is assembled to the flowmeter 2.

[0026] A plurality of recesses 53 are formed on the outer edge of the plate portion 51, recessing toward the center of the opening 52. When the centering device 5 is assembled to the flowmeter 2, the recesses 53 are formed in the shape of grooves extending along the first direction.

[0027] The bottom surface 53a of the recess 53 has an arc shape when viewed along the first direction. A plurality of protrusions 54 are formed on the bottom surface 53a of the recess 53. The protrusions 54 extend along the first direction. The plurality of protrusions 54 are aligned along the circumferential direction of the arc-shaped bottom surface 53a. This can also be said as the plurality of protrusions 54 being aligned along the circumferential direction of the opening 52. In the example shown in FIG. 4, three protrusions 54 are aligned.

[0028] The centering device 5 is provided between the flowmeter 2 and the primary-side flange 32 and between the flowmeter 2 and the secondary-side flange 42. When the centering device 5 is assembled to the flowmeter 2 and the primary-side flange 32 and the secondary-side flange 42 are abutted against the end faces of the cylindrical portion 24 of the flowmeter 2, the recess 53 is formed so that the central axis of the bottom surface 53a, which is an arcuate surface, coincides with the central axes of the through-hole 32a and the through-hole 42a.

[0029] The flowmeter unit 1 is assembled as follows. First, the centering device 5 is attached to the flowmeter 2. Next, with the primary side flange 32 and the secondary side flange 42 abutting against the end face of the cylindrical portion 24 of the flowmeter 2, a through-bolt 6 is passed through the through-hole 32 a, the through-hole 42 a, and the inside of the recess 53. Next, nuts are tightened onto both ends of the through-bolt 6, thereby fastening the primary side flange 32 and the secondary side flange 42 together and assembling the flowmeter unit 1. This brings the primary side flange 32 and the secondary side flange 42 into tight contact with the end face of the cylindrical portion 24 of the flowmeter 2.

[0030] Here, in order to prevent a decrease in the accuracy of the flow rate measurement by the flowmeter 2, it is necessary to prevent the occurrence of drift in the fluid inside the flowmeter 2. Drift is likely to occur when steps occur in the flow path at the connection between the primary piping unit 3 and the flowmeter 2, or at the connection between the secondary piping unit 4 and the flowmeter 2.

[0031] The step in the flow path occurs when the central axis of the flow path 31a of the primary side piping unit 3 is misaligned with the central axis of the flow path on the flow meter 2 side including the inlet 22a, or when the central axis of the flow path 41a of the secondary side piping unit 4 is misaligned with the central axis of the flow path on the flow meter 2 side including the outlet 22b.

[0032] The outer diameter of the through bolt 6, the inner diameter of the through hole 32a formed in the primary flange 32, the inner diameter of the through hole 32b formed in the secondary flange 42, the distance between the central axis of the through hole 32a and the central axis of the flow path 31a, and the distance between the central axis of the through hole 42a and the central axis of the flow path 41a have allowable errors set for each standard to which the components comply. In the following description, the allowable errors set for each standard to the outer diameter of the through bolt 6, the inner diameter of the through hole 32a formed in the primary flange 32, the inner diameter of the through hole 32b formed in the secondary flange 42, the distance between the central axis of the through hole 32a and the central axis of the flow path 31a, and the distance between the central axis of the through hole 42a and the central axis of the flow path 41a will be simply referred to as the "allowable error of each component."

[0033] Even if the through bolt 6, the primary flange 32, and the secondary flange 42 are designed and manufactured so that their respective central axes coincide, the central axis of the flow path 31a of the primary piping unit 3 may be misaligned from the central axis of the flow path on the flowmeter 2 side, including the inlet 22a, or the central axis of the flow path 41a of the secondary piping unit 4 may be misaligned from the central axis of the flow path on the flowmeter 2 side, including the outlet 22b, by the tolerance of each part mentioned above.

[0034] The centering device 5 prevents the central axis of the flow path 31a of the primary side piping unit 3 from misaligning with the central axis of the flow meter 2 side including the inlet 22a, and prevents the central axis of the flow path 41a of the secondary side piping unit 4 from misaligning with the central axis of the flow meter 2 side including the outlet 22b.

[0035] For example, the centering device 5 is designed so that when the through bolt 6, the through hole 32a, and the through hole 42a are all formed to the specified dimensions, the position through which the outer surface of the through bolt 6 passes is between the bottom surface 53a of the recess 53 and the top of the protrusion 54.

[0036] 4 is a view of the recessed portion of the centering device viewed in the first direction, illustrating a case where the outer diameter of the through-bolt 6 is smaller than the specified dimension due to an error. When the outer diameter of the through-bolt 6 is smaller than the specified dimension, the protrusion 54 formed on the bottom surface 53a of the recessed portion 53 of the centering device 5 positions the through-bolt 6 at a position away from the bottom surface 53a.

[0037] This allows the position of the central axis of a through bolt 6 having an outer diameter smaller than the specified dimension to be aligned with the position of the central axis of a through bolt 6 formed to the specified dimension.

[0038] 5 is a view of the recessed portion of the centering device viewed in the first direction, illustrating a case where the outer diameter of the through-bolt 6 is larger than the specified dimension due to an error. If the outer diameter of the through-bolt 6 is larger than the specified dimension, when the through-bolt 6 is passed through the through-holes 32a and 42a or when a nut is tightened onto the through-bolt 6, the protrusion 54 formed on the bottom surface 53a of the recess 53 of the centering device 5 is scraped off by the outer surface of the through-bolt 6. By scraping off the protrusion 54, the through-bolt 6 is positioned closer to the bottom surface 53a.

[0039] This allows the position of the central axis of a through bolt having an outer diameter larger than the specified dimensions to be aligned with the position of the central axis of through bolt 6 when through bolt 6 formed to the specified dimensions is used.

[0040] As described above, the central axes can be aligned even when a through-bolt 6 smaller than the specified size is used, or even when a through-bolt 6 larger than the specified size is used. This allows the primary flange 32 and secondary flange 42, which are fastened together by the through-bolt 6, to be positioned more accurately.

[0041] This prevents misalignment between the central axis of the flow path 31a of the primary-side piping unit 3 and the central axis of the flow meter 2 side including the inlet 22a, and prevents misalignment between the central axis of the flow path 41a of the secondary-side piping unit 4 and the central axis of the flow meter 2 side including the outlet 22b, thereby preventing drift in the flow meter 2. By preventing drift in the flow meter 2, it is possible to prevent a decrease in the measurement accuracy of the flow meter 2.

[0042] Here, the outer diameter of through-bolt 6 has been described as an example, but even if the inner diameter of through-holes 32a, 42a differs from the specified diameter, through-bolt 6 can be positioned closer to the position it would be if through-holes 32a, 42a were formed with the specified dimensions by supporting through-bolt 6 with protrusion 54 or by grinding down protrusion 54. Furthermore, even if the distance between the central axis of through-hole 32a and the central axis of flow path 31a or the distance between the central axis of through-hole 42a and the central axis of flow path 41a differs from the specified diameter, through-bolt 6 can be positioned closer to the position it would be if through-holes 32a, 42a were formed in the specified position by supporting through-bolt 6 with protrusion 54 or by grinding down protrusion 54.

[0043] Furthermore, the tolerances of the above-mentioned components are generally smaller than the tolerances of the outer diameters of the primary-side pipe 31 and the secondary-side pipe 41. Therefore, compared to suppressing deviation of the central axis using a jig in which multiple clamps that surround and support the primary-side pipe 31 and the secondary-side pipe 41 from the outside are fixed to a single beam that serves as a reference, using the centering device 5 makes it possible to suppress deviation of the central axis with greater precision.

[0044] In the flowmeter unit 1, the maximum expected deviation between the central axis of the flow path 31a of the primary side piping unit 3 and the central axis of the flowmeter 2 side including the inlet 22a, and the maximum expected deviation between the central axis of the flow path 41a of the secondary side piping unit 4 and the central axis of the flowmeter 2 side including the outlet 22b are calculated by adding up the allowable errors of each of the above-mentioned components.

[0045] The tolerances vary depending on the standards to which each component complies, such as ASME Class 150, ASME Class 300, EN PN 10, EN PN 16, EN PN 40, JIS F12, JIS 10K, and JIS 20K.

[0046] According to the tolerances set forth in these standards, the maximum deviation of the central axis is 1.2 mm to 1.8 mm, so it is preferable that the height of the convex portion 54 from the bottom surface 53a be 1.8 mm or less.

[0047] Of the three protrusions 54, the protrusion 54 formed between two of the protrusions 54 may be formed so that its height is lower than the height of the protrusions 54 formed on both sides. In this case, the protrusions 54 formed on both sides position the through bolt 6 in the circumferential direction of the bottom surface 53a, and the protrusions 54 formed between the two protrusions 54 are ground down as necessary when positioning the through bolt 6 in the radial direction of the bottom surface 53a. The example of forming the protrusions 54 with low height is not limited to the above example. For example, the number of protrusions 54 is not limited to three, but may be four or more. Furthermore, the number of protrusions 54 with low height is not limited to one, but multiple protrusions 54 may have low heights. Furthermore, when five or more protrusions 54 are provided, the protrusions 54 closer to the center may be formed so that their heights are lower. In other words, it is sufficient that a protrusion 54 with a lower height than at least two protrusions 54 is formed between the two protrusions 54. Furthermore, a plurality of low protrusions 54 may be formed between two protrusions 54, and the heights of the low protrusions may be the same or different.

[0048] 6 is a diagram showing a first modified example of the protrusion, and is a partially enlarged perspective view of the recess portion. As shown in FIG. 6, one protrusion 54 may be formed on the bottom surface 53a of the recess 53.

[0049] 7 is a diagram showing a second modified example of the protrusion, and is a partially enlarged perspective view of the recess portion. As shown in Fig. 7, five protrusions 54 may be formed on the bottom surface 53a of the recess 53. The number of protrusions is not limited to five, and may be four, or six or more.

[0050] 8 is a partially enlarged perspective view showing a third modified example of the protrusion, in which the recess portion is enlarged. As shown in FIG. 8, a single protrusion 54 may be formed on bottom surface 53a of recess 53 so as to extend in the circumferential direction of bottom surface 53a.

[0051] 9 is a diagram showing a fourth modified example of the protrusion, and is a partially enlarged perspective view of the recess portion. As shown in Fig. 9, a plurality of protrusions 54 extending in the circumferential direction of bottom surface 53a may be formed on bottom surface 53a of recess 53.

[0052] Fig. 10 is a diagram showing a fifth modified example of the protrusion, and is a partially enlarged perspective view of the recess portion. As shown in Fig. 10, a plurality of protrusions 54 may be formed on a bottom surface 53a of the recess 53, arranged in the circumferential direction of the bottom surface 53a and in the first direction. The shape of the protrusions 54 may be, for example, a cone shape, a cube shape, or a rectangular parallelepiped shape.

[0053] <Summary of effects> The centering device 5 has a plate-like plate portion 51 that is formed to penetrate along a first direction, which is the thickness direction, and has an opening 52 formed therein into which a tubular portion 24 that allows fluid to pass through is fitted, and a recess 53 that is recessed toward the center of the opening 52 is formed on the outer edge of the plate portion 51, and a protrusion 54 is formed on the bottom surface 53a of the recess 53.

[0054] By scraping off the convex portion 54 in accordance with errors in the inner diameter of the through holes 32a, 42a formed in the flanges 32, 42 that abut the end face of the tubular portion 24, errors in the outer diameter of the through bolt 6, errors in the distance between the central axis of the through hole 32a and the central axis of the flow path 31a, and errors in the distance between the central axis of the through hole 42a and the central axis of the flow path 41a, it is possible to reduce the misalignment between the central axis of the inlet / outlet 22 of the flow meter and the central axis of the flow path of the piping connected to the flow meter 2, and to prevent a decrease in the measurement accuracy of the flow meter.

[0055] The protrusions 54 may extend parallel to the first direction, which prevents the protrusions 54 from fitting into the valleys of the threads formed on the outer surface of the through-bolt 6, and allows the through-bolt 6 to be stably supported by the protrusions 54.

[0056] A plurality of protrusions 54 may be formed and lined up in the circumferential direction of bottom surface 53a of recess 53. By forming a plurality of protrusions 54, through bolt 6 supported by protrusions 54 is less likely to shift in the circumferential direction of bottom surface 53a. In addition, the ease with which protrusions 54 are worn can be adjusted by changing the number of protrusions 54 formed.

[0057] Three protrusions 54 are formed, and the height of the protrusion 54 formed between two of the protrusions 54 may be lower than the height of the protrusions 54 formed on both sides. As a result, the through-bolt 6 is positioned in the circumferential direction of the bottom surface 53a by the protrusions 54 formed on both sides, and when positioning the through-bolt 6 in the radial direction of the bottom surface 53a, the protrusions 54 formed in between are cut off as necessary.

[0058] Protrusion 54 may extend parallel to the circumferential direction of bottom surface 53a of recess 53. Even protrusion 54 extending parallel to the circumferential direction of bottom surface 53a can support through-bolt 6 and can be trimmed as necessary.

[0059] A plurality of protrusions 54 may be formed and aligned in the first direction. The ease with which the protrusions 54 are scraped can be adjusted by adjusting the number of protrusions 54 formed.

[0060] A plurality of protrusions 54 may be formed and lined up in the first direction and in the circumferential direction of the bottom surface of recess 53. By forming a plurality of protrusions 54 and lined up in the first direction and in the circumferential direction of the bottom surface of recess 53, the ease of scraping of protrusions 54 can be adjusted more widely by changing the number of protrusions 54 and their positions.

[0061] The height of the protrusion 54 from the bottom surface 53a of the recess 53 may be 1.8 mm or less. If the protrusion 54 is too high, the resistance when passing the through bolt 6 increases, which may reduce work efficiency or make it impossible to pass the through bolt 6. Considering the standards to which the flowmeter 2 complies, setting the height of the protrusion 54 to 1.8 mm or less can prevent the resistance when passing the through bolt 6 from becoming too great.

[0062] The flowmeter unit 1 includes a flowmeter 2 having a cylindrical portion 24 formed to protrude in opposite directions from a housing 21, with an end face of the cylindrical portion 24 having an inlet / outlet 22 for allowing fluid to flow in and out of the housing 21, and measuring the flow rate of a fluid passing through the interior of the housing 21, and a centering device 5 having a plate-like plate portion 51 formed to penetrate along a first direction which is the thickness direction and having an opening 52 into which the cylindrical portion 24 fits, with a recess 53 formed on the outer edge of the plate portion 51 recessed toward the center of the opening 52, and a protrusion 54 formed on a bottom surface 53a of the recess 53. The flowmeter unit 1 may further include a pair of flanges 32, 42 abutting against the end faces of the cylindrical portion 24 and having through holes 32a, 42a formed therein and penetrating along the first direction, and a through-bolt 6 passed through the through holes 32a, 42a and the recess 53 to fasten the pair of flanges 32, 42.

[0063] The convex portion 54 is worn down depending on the error in the inner diameter of the through holes 32a, 42a formed in the flanges 32, 42 that abut the end face of the cylindrical portion 24 and the outer diameter of the through bolt 6, thereby reducing the misalignment between the central axis of the flow meter's inlet / outlet 22 and the central axis of the flow path of the piping connected to the flow meter 2, and preventing a decrease in the measurement accuracy of the flow meter.

[0064] 〔others〕 Some examples of combinations of the disclosed technical features are set out below.

[0065] (1) A centering device comprising a plate-like plate portion having an opening formed through it in a first direction, which is the thickness direction, and into which a cylindrical portion for passing a fluid fits, and a recess formed on the outer edge of the plate portion that is recessed toward the center of the opening, and a protrusion formed on the bottom surface of the recess.

[0066] (2) The centering device according to (1) above, wherein the protrusion extends parallel to the first direction.

[0067] (3) The centering device according to (2) above, wherein the convex portions are formed in a plurality of rows aligned in the circumferential direction of the bottom surface of the concave portion.

[0068] (4) The centering device according to (3) above, wherein the plurality of protrusions includes a protrusion formed at a height lower than the protrusions formed adjacent to it.

[0069] (5) A centering device as described in (4) above, in which three convex portions are formed, and the height of the convex portion formed between two of the convex portions is lower than the height of the convex portions formed on both sides.

[0070] (6) The centering device according to (1) above, wherein the protrusion extends parallel to the circumferential direction of the bottom surface of the recess.

[0071] (7) The centering device according to (6) above, wherein the protrusions are formed in a plurality of rows aligned in the first direction.

[0072] (8) The centering device according to (1) above, wherein the protrusions are formed in a plurality of rows aligned in the first direction and in the circumferential direction of the bottom surface of the recess.

[0073] (9) The centering device according to any one of (1) to (8), wherein the height of the protrusion from the bottom surface of the recess is 1.8 mm or less.

[0074] (10) A flowmeter unit comprising: a flowmeter having cylindrical portions protruding in opposite directions from a housing, with inlets and outlets formed on end faces of the cylindrical portions for allowing fluid to flow in and out of the housing, for measuring the flow rate of fluid passing through the interior of the housing; and a centering device having a plate-like plate portion formed to penetrate along a first direction, which is the thickness direction, and having an opening into which the cylindrical portion fits, with a recess formed on the outer edge of the plate portion that is recessed toward the center of the opening, and a protrusion formed on the bottom surface of the recess.

[0075] (11) A flow meter unit as described in (10) above, further comprising a pair of flanges abutting the end surfaces of the cylindrical portion and having through holes formed therethrough along the first direction, and through bolts passing through the through holes and the recesses to fasten the pair of flanges. [Explanation of symbols]

[0076] 1 Flow meter unit 2 flow meter 21. Cabinet 22 Inlet / Outlet 22a Inlet 22b Outlet 24 Cylindrical part 3 Primary side piping unit 31 Primary side piping 31a Flow path 32 Primary flange 32a through hole 4 Secondary piping unit 41 Secondary piping 41a Flow path 42 Secondary flange 42a through hole 5. Centering Device 51 Board part 52 Aperture 53 Recess 53a bottom 54 Convex part 6 through bolts

Claims

1. a plate-like plate portion having an opening formed therethrough along a first direction which is a thickness direction and into which a cylindrical portion through which a fluid passes is fitted, a recess formed on the outer edge of the plate portion and recessed toward the center of the opening; A centering device in which a protrusion is formed on the bottom surface of the recess.

2. The centering device according to claim 1 , wherein the protrusion extends parallel to the first direction.

3. The centering device according to claim 2 , wherein the plurality of protrusions are arranged in a circumferential direction on the bottom surface of the recess.

4. The centering device according to claim 3 , wherein the plurality of protrusions include a protrusion formed at a height lower than an adjacent protrusion.

5. The centering device according to claim 4, wherein three of the protrusions are formed, and the height of the protrusion formed between two of the protrusions is lower than the height of the protrusions formed on both sides.

6. The centering device according to claim 1 , wherein the protrusion extends parallel to the circumferential direction of the bottom surface of the recess.

7. The centering device according to claim 6 , wherein the protrusions are formed in a plurality of rows aligned in the first direction.

8. The centering device according to claim 1 , wherein the protrusions are arranged in the first direction and in the circumferential direction of the bottom surface of the recess.

9. 9. The centering device according to claim 1, wherein the height of the protrusion from the bottom surface of the recess is 1.8 mm or less.

10. a flow meter including cylindrical portions projecting in opposite directions from a housing, end faces of the cylindrical portions being formed with inlet / outlet ports for allowing fluid to flow in and out of the housing, the flow meter measuring the flow rate of fluid passing through the interior of the housing; a centering device having a plate-like plate portion formed to penetrate along a first direction which is a thickness direction and having an opening into which the cylindrical portion fits, the plate portion having a recess formed on the outer edge thereof that is recessed toward the center of the opening, and the recess having a protrusion formed on the bottom surface thereof.

11. a pair of flanges abutting against the end surfaces of the cylindrical portion and each having a through hole extending along the first direction; The flow meter unit according to claim 10 , further comprising a through-bolt that is passed through the through-hole and the recess to fasten the pair of flanges together.

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