Orifice plate flowmeter and application method thereof

Abstract

The invention relates to the technical field of flow meters, and provides an orifice plate flow meter and an application method thereof.The orifice plate flow meter comprises a rear end pipe, an orifice plate and a front end pipe, the rear end pipe comprises a rear pipe body, a positioning ring and an inner turned edge, and the positioning ring is fixedly arranged in the rear pipe body; the inner curled edge is arranged in the rear pipe body, and one end of the inner curled edge and one end of the rear pipe body are integrally formed and continuously arranged; the hole plate is fixed between the positioning ring and the inner turned edge in an abutting mode. The front end pipe and the rear pipe body are coaxially arranged, and one end of the front end pipe is welded and fixed to the outer side of the inner curled edge. According to the orifice plate flow meter, the rear end pipe comprises the rear pipe body, the positioning ring and the inner turned edge, the orifice plate and the rear end pipe can be fixed firstly, then the rear pipe body and the front end pipe are connected, the orifice plate flow meter can be assembled conveniently, the mounting precision of the orifice plate can be guaranteed, and therefore the detection precision of the orifice plate flow meter is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of flowmeters, in particular to an orifice flowmeter and an application method thereof. Background Art

[0002] The orifice flowmeter is a differential pressure flow measuring instrument based on the throttling principle. It uses the fact that when the fluid flows through the throttling device (orifice plate) in the pipeline, the flow beam will form a local contraction at the orifice plate, thereby increasing the flow velocity and reducing the static pressure, and generating a certain pressure difference before and after the orifice plate. By measuring this pressure difference and combining it with the known geometric parameters of the pipeline and orifice plate and the physical properties of the fluid, the flow rate of the fluid can be calculated.

[0003] Orifice flowmeters have advantages such as simple structure, wide adaptability, and high standardization. They are widely used in fields such as petrochemicals, electric power, metallurgy, and heating. For example, patent publication CN112113623B discloses a welded orifice flowmeter with an annular chamber pressure measurement. This meter features an orifice plate positioned between a front clamping ring and a rear clamping ring, with pressure-taking tubes located on either side of the orifice plate. These two pressure-taking tubes, in conjunction with a pressure-differential measuring device, measure the pressure differential across the orifice plate, thereby detecting the flow rate of the medium within the measuring tube.

[0004] In the above technical solution, in order to fix the orifice plate, the front clamping ring and the rear clamping ring need to be welded and fixed, and the welding positions of the front clamping ring and the rear clamping ring should avoid the position of the orifice plate; however, this technical solution also requires the provision of a front ring chamber, a rear ring chamber and a groove that serves as a connection, which not only makes the processing of the front clamping ring, the rear clamping ring and the orifice plate relatively difficult, but also makes it difficult to ensure the processing accuracy of the front clamping ring, the rear clamping ring and the orifice plate, which is not conducive to improving the detection accuracy of the orifice flowmeter. Summary of the Invention

[0005] In view of this, the present invention proposes an orifice flowmeter and an application method thereof, which can not only reduce the processing difficulty of the rear-end pipe and the front-end pipe, but also improve the installation accuracy of the orifice plate, thereby ensuring the detection accuracy of the orifice flowmeter.

[0006] The technical solution of the present invention is implemented as follows: on the one hand, the present invention provides an orifice flowmeter, including a rear end tube, an orifice plate and a front end tube, wherein the rear end tube includes a rear tube body, a positioning ring and an inner curl, and the positioning ring is fixedly arranged in the rear tube body; the inner curl is arranged in the rear tube body, and one end of the inner curl is integrally formed with one end of the rear tube body and is continuously arranged; the orifice plate is abutted and fixed between the positioning ring and the inner curl; the front end tube is coaxially arranged with the rear tube body, and one end of the front end tube is welded and fixed on the outer side of the inner curl.

[0007] On the basis of the above technical solution, preferably, the cross section of the inner curled edge is spiral, and the inner curled edge abuts against the inner wall of the rear tube body.

[0008] More preferably, the inner curl and the rear tube body are combined to form a winding cavity; a plurality of connecting grooves are provided at one end of the inner curl away from the rear tube body, and the winding cavity is connected to the interior of the rear tube body through the connecting grooves.

[0009] More preferably, the rear end tube also includes a plurality of abutting portions, and the plurality of abutting portions correspond one-to-one to the plurality of connecting grooves. One end of the abutting portion is integrally formed in the connecting groove and is continuously arranged with the inner curling edge, and the abutting portion abuts against the orifice plate.

[0010] More preferably, a limiting groove is provided on the orifice plate, and the side surface of the supporting portion is engaged with the limiting groove.

[0011] More preferably, the limiting groove includes an arc surface and an inclined surface, the inclined surface and the arc surface are both inner walls of the limiting groove, and both abut against the supporting portion; the inclined surface is located on the side of the arc surface away from the rear tube body, the inclined surface is tangent to the arc surface, the minimum distance between the inclined surface and the positioning ring is a, the minimum distance between the arc surface and the positioning ring is b, a<b.

[0012] Further preferably, the front end tube includes a front tube body and an arc-shaped closing, one end of the arc-shaped closing is integrally formed at the end of the front tube body and is continuously arranged therewith, and the other end of the arc-shaped closing abuts against the abutting portion; the peripheral side of the arc-shaped closing abuts against the inner curling edge, and the two are enclosed to form a V-shaped welding groove, and the rear end tube and the front end tube are fixedly connected by the welding material in the welding groove.

[0013] On the basis of the above technical solution, preferably, a positioning structure is provided between the orifice plate and the positioning ring.

[0014] On the basis of the above technical solution, preferably, two pressure-taking tubes are further included, and the two pressure-taking tubes are respectively passed through and fixed on the rear end tube and the front end tube.

[0015] In the second aspect, the present invention provides an application method of an orifice flowmeter, comprising the following steps: S1, connecting one end of the rear end tube away from the orifice plate and one end of the front end tube away from the orifice plate and setting them in the pipeline to be measured; S2, connecting the two pressure taking tubes to the pressure differential measuring device; S3, conducting the pipeline to be measured, allowing the medium in the pipeline to be measured to pass through the orifice plate, and calculating the flow rate of the medium in the pipeline to be measured through the pressure differential measuring device; S4, cutting off the pipeline to be measured, emptying the medium in the pipeline to be measured, and disassembling the pressure differential measuring device, and spraying clean gas or protective oil onto the orifice plate through the two pressure taking tubes.

[0016] The orifice flowmeter and its application method of the present invention have the following beneficial effects compared with the prior art:

[0017] (1) By setting the rear end tube to include a rear tube body, a positioning ring and an inner curling edge, the orifice plate and the rear end tube can be fixed first, and then the rear end tube and the front end tube can be connected. This not only facilitates the assembly of the orifice flowmeter, but also ensures the installation accuracy of the orifice plate, thereby improving the detection accuracy of the orifice flowmeter.

[0018] (2) By setting the inner curling edge in a spiral shape, when the inner curling edge is welded to the front end tube, the thermal deformation of the inner curling edge can be used to enhance the fixation of the orifice plate. By setting the abutting portion and the limiting groove, the orifice plate can be prevented from rotating or shaking during use, thereby ensuring the fixation stability and fixation firmness of the orifice plate.

[0019] (3) By opening a connecting groove, the winding cavity can be connected to the interior of the rear tube body, thereby avoiding the problem of inaccurate detection caused by the presence of bubbles in the winding cavity.

[0020] (4) By configuring the front end tube to include a front tube body and an arc-shaped closing, the arc-shaped closing and the inner curling edge can be combined to form a V-shaped welding groove, thereby improving the welding convenience and welding quality of the front end tube and the rear end tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 It is a cross-sectional view of the orifice flowmeter of the present invention.

[0023] Figure 2 for Figure 1 Enlarged view of point A in the middle.

[0024] Figure 3 It is a three-dimensional view of the supporting portion of the orifice flowmeter of the present invention.

[0025] Figure 4 It is a cross-sectional view of the inner curling edge of the orifice flowmeter of the present invention.

[0026] Figure 5 It is a three-dimensional view of the inner curling edge of the orifice flowmeter of the present invention.

[0027] Figure 6 It is a three-dimensional view of the rear tube body of the orifice flowmeter of the present invention.

[0028] Figure 7 It is a three-dimensional diagram of the orifice plate in the orifice flowmeter of the present invention.

[0029] Figure 8 It is a cross-sectional view of the limiting groove in the orifice flowmeter of the present invention.

[0030] Figure 9 It is a stereoscopic view of the positioning ring in the orifice flowmeter of the present invention.

[0031] Figure 10 It is a stereoscopic view of the rear end tube in the orifice flowmeter of the present invention.

[0032] Figure 11 It is a three-dimensional diagram of the front end tube in the orifice flowmeter of the present invention.

[0033] Figure 12 It is a three-dimensional diagram of the orifice flowmeter of the present invention.

[0034] Among them: 1. Rear end tube; 11. Rear tube body; 12. Positioning ring; 13. Inner curling edge; 14. Abutment portion; 101. Winding cavity; 102. Connecting groove; 2. Orifice plate; 201. Limiting groove; 2011. Arc surface; 2012. Inclined surface; 202. Positioning structure; 3. Front end tube; 31. Front tube body; 32. Arc-shaped closing; 301. Welding groove; 4. Pressure taking tube. DETAILED DESCRIPTION

[0035] The following will be combined with the specific embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] like Figure 1 and Figure 12As shown, the orifice flowmeter of the present invention comprises a rear-end tube 1, an orifice plate 2, a front-end tube 3, and two pressure-taking tubes 4. The rear-end tube 1 and the front-end tube 3 are circular tubular structures of the same specifications, coaxially arranged and sealed in communication, forming a sealed tubular structure. Both the end of the rear-end tube 1 remote from the front-end tube 3 and the end of the front-end tube 3 remote from the rear-end tube 1 are provided with flanges for connection to the pipeline to be measured.

[0037] The orifice plate 2 is a circular plate-like structure, sealed and fixed within the rear end tube 1. Two pressure-taking tubes 4 are respectively fixed to the rear end tube 1 and the front end tube 3. When the medium in the pipeline to be measured enters the front end tube 3, the medium flow will form a local contraction at the center hole of the orifice plate 2, thereby increasing the flow rate of the medium and reducing the static pressure. The medium flow generates a certain pressure difference before and after the orifice plate 2. This pressure difference has a certain functional relationship with the flow rate of the fluid. After the two pressure-taking tubes 4 are connected to the pressure difference detection equipment, the pressure difference can be measured, and then the flow rate of the fluid can be calculated based on this pressure difference. Among them, the pressure difference detection equipment is existing technology, such as a differential pressure transmitter.

[0038] The rear end pipe 1 and the front end pipe 3 provide a sufficiently long passage for the medium flow, so that the flow of the medium in the pipeline to be measured is sufficiently stable and the throttling effect of the orifice plate 2 is guaranteed.

[0039] like Figure 4 and Figure 5 As shown, the rear end tube 1 includes a rear tube body 11, a positioning ring 12 and an inner curling edge 13. The positioning ring 12 is a circular plate structure with an inner diameter larger than the inner diameter of the orifice plate 2. The positioning ring 12 is fixedly arranged in the rear tube body 11, and the side surface of the positioning ring 12 is perpendicular to the axis of the rear tube body 11.

[0040] After the orifice plate 2 is placed in the rear tube body 11, the end of the rear tube body 11 is curled using a curling machine so that the end of the rear tube body 11 is bent inward, forming an inner curling edge 13 located in the rear tube body 11. The inner curling edge 13 supports the orifice plate 2, thereby supporting and fixing the orifice plate 2 between the positioning ring 12 and the inner curling edge 13.

[0041] By adopting the above method, the orifice plate 2 and the rear end tube 1 can be fixed before the front end tube 3 and the rear end tube 1 are welded and fixed, thereby ensuring the installation accuracy of the orifice plate 2.

[0042] One end of the inner curl 13 is integrally formed with one end of the rear tube body 11 and is continuously arranged. The inner curl 13 can be quickly processed by curling the rear tube body 11. Compared with the existing technology, the structure of the rear end tube 1 is simpler and can be processed quickly, which also helps to improve the processing efficiency of the orifice flowmeter.

[0043] The connection between the orifice plate 2 and the rear end pipe 1 is not fixed by traditional welding. The orifice plate 2 can be disassembled, replaced or recycled by bending or cutting the inner curling edge 13, thereby improving the maintenance convenience and recycling performance of the orifice flowmeter.

[0044] After the orifice plate 2 is fixed in the rear end tube 1, the front end tube 3 is made coaxial with the rear tube body 11, and one end of the front end tube 3 is welded and fixed to the outer side of the inner curling edge 13, so that the front end tube 3 and the rear end tube 1 can be connected and fixed.

[0045] The cross section of the inner curling edge 13 is spiral-shaped. Figure 4 As shown, the inner curl 13 abuts the inner wall of the rear tube body 11, thereby enhancing the structural strength of the inner curl 13 and ensuring the secure fixation of the orifice plate 2. The figure only shows 3 / 4 of the inner curl 13, and the end of the inner curl 13 abuts the inner wall of the rear tube body 11 to ensure the structural strength of the inner curl 13. In actual production, the number of turns of the inner curl 13 can be appropriately increased to avoid problems such as the inner curl 13 sinking during assembly.

[0046] Since the welding position of the front end tube 3 and the rear tube body 11 is not on the position of the orifice plate 2, the welding operation will not affect the orifice plate 2 and can also facilitate flaw detection of the weld to ensure the assembly quality of the orifice flowmeter.

[0047] At the same time, when the front end tube 3 and the rear tube body 11 are welded, the inner curl 13 will be thermally deformed after being heated, causing the inner curl 13 to expand outward, thereby further improving the firmness of the inner curl 13 against the orifice plate 2.

[0048] like Figure 5 As shown, the inner curl 13 and the rear tube body 11 enclose a winding cavity 101. When the inner curl 13 is processed, a gap may appear between a portion of the inner curl 13 and the rear tube body 11. During the use of the orifice flowmeter, the medium in the rear tube body 11 does not quickly fill the winding cavity 101, resulting in a certain amount of gas in the winding cavity 101. This gas will intermittently flow into the winding cavity 101 in the form of bubbles, affecting the detection accuracy of the orifice flowmeter.

[0049] In order to solve the above problem, a plurality of connecting grooves 102 are provided at one end of the inner curling edge 13 away from the rear tube body 11, and the winding cavity 101 is connected to the interior of the rear tube body 11 through the connecting grooves 102. When the rear end tube 1 and the front end tube 3 are connected to the pipeline to be measured and the medium to be measured flows through the orifice flowmeter, the medium can quickly fill the winding cavity 101, thereby avoiding the presence of bubbles that affect the detection accuracy of the orifice flowmeter.

[0050] In order to improve the efficiency of filling the winding chamber 101 with the medium, that is, to improve the efficiency of exhausting the gas inside the winding chamber 101 , at least one connecting groove 102 should be located on the top of the inner curling edge 13 .

[0051] like Figure 2 As shown, the rear end tube 1 further includes a plurality of abutting portions 14, and the plurality of abutting portions 14 correspond one to one with the plurality of communicating grooves 102. One end of the abutting portion 14 is integrally formed in the communicating groove 102 and is continuously provided with the inner curling edge 13, and the abutting portion 14 abuts against the orifice plate 2; Figure 6 As shown, the supporting portion 14 is made by grooving and bending the inner curling edge 13, and the bending direction of the supporting portion 14 is opposite to the bending direction of the inner curling edge 13 away from the end of the rear tube body 11. The cooperation between the supporting portion 14 and the inner curling edge 13 can further increase the range of the orifice plate 2 being supported, thereby helping to improve the firmness of the fixation of the orifice plate 2.

[0052] At the same time, the supporting portion 14 can also partially block the communicating groove 102, reducing the impact of the medium on the inner wall of the winding cavity 101 when the medium first flows into the winding cavity 101, thereby protecting the orifice flowmeter and the pipeline to be measured.

[0053] The pressure-taking tube 4 on the front tube 3 can also be fixed through the rear tube body 11, with the pressure-taking tube 4 aligned with the winding chamber 101. During use, the inner curling edge 13 can wrap and protect the end of the pressure-taking tube 4. The gap between the supporting portion 14 and the inner curling edge 13 not only forms a filter structure to prevent impurities from entering the pressure-taking tube 4, but also ensures the stability of fluid pressure changes.

[0054] like Figure 2 and Figure 7 As shown, the orifice plate 2 is provided with a limiting groove 201, and the side surface of the abutting portion 14 engages with the limiting groove 201, thereby preventing the orifice plate 2 from rotating during use and ensuring the detection accuracy of the orifice flowmeter. There are also multiple limiting grooves 201, and the multiple limiting grooves 201 correspond one-to-one with the multiple abutting portions 14.

[0055] Similarly, if Figure 9 As shown, a positioning structure 202 is provided on the positioning ring 12, and a corresponding positioning structure 202 is provided on the orifice plate 2. The two positioning structures 202 can be grooves and protrusions that are connected to each other. When the inner curling edge 13 is processed, the positioning structure 202 can be used to prevent the orifice plate 2 and the positioning ring 12 from rotating relative to each other, thereby ensuring the installation accuracy of the orifice plate 2 and smoothly completing the subsequent assembly work.

[0056] The limiting groove 201 includes an arc surface 2011 and an inclined surface 2012. The arc surface 2011 is an arc-shaped surface, and the inclined surface 2012 is a plane. The inclined surface 2012 is inclined with respect to the side surface of the orifice plate 2. Figure 2 As shown, the inclined surface 2012 and the arc surface 2011 are both inner walls of the limiting groove 201, and the inclined surface 2012 and the arc surface 2011 are in contact with the supporting portion 14; Figure 8 As shown, the inclined surface 2012 is located on the side of the arc surface 2011 away from the rear tube body 11, and the inclined surface 2012 is tangent to the arc surface 2011. Assuming that the minimum distance between the inclined surface 2012 and the positioning ring 12 is a, and the minimum distance between the arc surface 2011 and the positioning ring 12 is b, then a<b.

[0057] When installing the orifice plate 2, it is first necessary to groove the end of the rear tube body 11, then curl the end of the rear tube body 11 for a distance, then use a tool to bend the abutment portion 14 in the direction opposite to the bending direction of the inner curling edge 13, and finally continue to curl the end of the rear tube body 11 to form a Figure 2-Figure 6 The rear end tube 1 is shown.

[0058] During the above processing, Figure 8 As shown, the end of the supporting portion 14 first extends from the top of the arc surface 2011 into the limiting groove 201. Guided by the arc surface 2011, the supporting portion 14 forms a curved structure. When the rear tube body 11 continues to be curled, the end of the supporting portion 14 first moves to the inclined surface 2012 and then moves out of the limiting groove 201.

[0059] The arc surface 2011 and the inclined surface 2012 do not hinder the movement of the end of the supporting portion 14, and the arc surface 2011 and the inclined surface 2012 can adapt to supporting portions 14 of different lengths to avoid affecting the assembly of the orifice flowmeter. Of course, the end of the supporting portion 14 after processing is preferably extended out of the limiting groove 201.

[0060] Compared with the rectangular groove body, this limit groove 201 can adapt to the excessively long supporting portion 14, avoiding the excessively long supporting portion 14 from being unable to extend out of the limit groove 201. Compared with the arc-shaped groove body, this limit groove 201 can increase the radial span of the supporting portion 14 in the limit groove 201 along the orifice plate 2, thereby improving the connection reliability between the limit groove 201 and the orifice plate 2.

[0061] like Figure 2 、 Figure 4 and Figure 11 As shown, the front end tube 3 includes a front tube body 31 and an arc-shaped closing 32. The arc-shaped closing 32 can be obtained by shrinking the end of the front tube body 31, so that one end of the arc-shaped closing 32 is integrally formed at the end of the front tube body 31 and is continuously arranged therewith.

[0062] like Figure 2As shown, the arc-shaped closing end 32 is in contact with the abutting portion 14 at one end away from the front tube body 31 , thereby squeezing and fixing the abutting portion 14 and improving the fixing strength between the abutting portion 14 and the orifice plate 2 .

[0063] like Figure 2 and Figure 4 As shown, the arcuate side wall of the arc-shaped closing 32 partially abuts against the arcuate side wall of the inner curling edge 13 , which can effectively improve the connection sealing and connection stability between the front end tube 3 and the rear end tube 1 .

[0064] like Figure 4 and Figure 12 As shown, a V-shaped welding groove 301 is formed between the arc-shaped closing 32 and the inner curling edge 13. The rear end tube 1 and the front end tube 3 are fixedly connected by the welding material in the welding groove 301. The V-shaped welding groove 301 can improve the welding convenience of the rear end tube 1 and the front end tube 3, allowing the molten welding material to quickly fill the welding groove 301, thereby helping to improve the welding efficiency and welding quality of the rear end tube 1 and the front end tube 3.

[0065] like Figure 1 As shown, the inner diameter of the arc-shaped closing 32 gradually decreases from right to left, and the inner wall thereof is smooth and continuous, which can guide the medium well to maintain the flow stability of the medium.

[0066] The orifice flowmeter and its application method of the present invention are used as follows:

[0067] S1, respectively install the flange of the rear end pipe 1 away from the orifice plate 2 and the flange of the front end pipe 3 away from the orifice plate 2 in the pipeline to be tested, so that the rear end pipe 1 and the front end pipe 3 are sealed and connected to the pipeline to be tested.

[0068] S2, connecting the two pressure-taking pipes 4 to the differential pressure measuring device so that the two detection ends of the differential pressure measuring device are connected to the interior of the rear end pipe 1 and the interior of the front end pipe 3 respectively.

[0069] In step S3, the pipeline to be tested is opened, and the medium in the pipeline to be tested enters the front-end pipe 3 and the rear-end pipe 1, and flows through the orifice plate 2. At this time, the orifice plate 2 locally contracts the medium flow, thereby forming a pressure difference between the positions of the medium on both sides of the orifice plate 2. The flow rate of the medium in the pipeline to be tested can be calculated by measuring the pressure difference with the pressure difference measuring equipment and the functional relationship between the pressure difference and the flow rate.

[0070] S4, when the medium in the pipeline to be tested stops being transported, some medium residue or stains may remain on the surface of the orifice plate 2. If not cleaned in time, the surface of the orifice plate 2 may rust, solid impurities may adhere to the surface of the orifice plate 2, and the detection accuracy of the orifice plate 2 may be affected. Therefore, after the pipeline to be tested is cut off, the medium in the pipeline to be tested is first drained, and then the pressure difference measuring device connected to the two pressure pipes 4 is disassembled. Finally, clean air or protective oil is sprayed onto the orifice plate 2 through the two pressure pipes 4 to flush and protect the orifice plate 2, thereby extending the service life of the orifice plate 2.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. Orifice flow meter, characterized by: It comprises a rear end tube (1), a perforated plate (2) and a front end tube (3), wherein: The rear end tube (1) comprises a rear tube body (11), a positioning ring (12) and an inner curling edge (13), wherein the positioning ring (12) is fixedly arranged in the rear tube body (11); the inner curling edge (13) is arranged in the rear tube body (11), and one end of the inner curling edge (13) is integrally formed with one end of the rear tube body (11) and is continuously arranged; The orifice plate (2) is fixed between the positioning ring (12) and the inner curling edge (13); The front end tube (3) is coaxially arranged with the rear tube body (11), and one end of the front end tube (3) is welded and fixed to the outer side of the inner curling edge (13).

2. The orifice flowmeter according to claim 1, wherein: The cross section of the inner curling edge (13) is spiral-shaped, and the inner curling edge (13) abuts against the inner wall of the rear tube body (11).

3. The orifice flowmeter according to claim 2, wherein: The inner curling edge (13) and the rear tube body (11) enclose and form a winding cavity (101); A plurality of communication grooves (102) are provided at one end of the inner curling edge (13) away from the rear tube body (11), and the winding cavity (101) is connected to the interior of the rear tube body (11) through the communication grooves (102).

4. The orifice flowmeter according to claim 3, wherein: The rear end tube (1) further comprises a plurality of abutting portions (14), the plurality of abutting portions (14) corresponding one to one with the plurality of communicating grooves (102), one end of the abutting portion (14) being integrally formed in the communicating groove (102) and being continuously arranged with the inner curling edge (13), and the abutting portion (14) abuts against the orifice plate (2).

5. The orifice flowmeter according to claim 4, wherein: A limiting groove (201) is provided on the orifice plate (2), and the side surface of the supporting portion (14) is engaged with the limiting groove (201).

6. The orifice flowmeter according to claim 5, wherein: The limiting groove (201) comprises a curved surface (2011) and an inclined surface (2012); the inclined surface (2012) and the curved surface (2011) are both inner walls of the limiting groove (201) and are in contact with the abutting portion (14); The inclined surface (2012) is located on a side of the arc surface (2011) away from the rear tube body (11), the inclined surface (2012) is tangent to the arc surface (2011), the minimum distance between the inclined surface (2012) and the positioning ring (12) is a, and the minimum distance between the arc surface (2011) and the positioning ring (12) is b, where a<b.

7. The orifice flowmeter according to claim 6, wherein: The front end tube (3) comprises a front tube body (31) and an arc-shaped closing end (32), one end of the arc-shaped closing end (32) is integrally formed at the end of the front tube body (31) and is continuously arranged therewith, and the other end of the arc-shaped closing end (32) abuts against the abutting portion (14); The circumferential side of the arc-shaped closing opening (32) abuts against the inner curling edge (13), and the two enclose a V-shaped welding groove (301), and the rear end tube (1) and the front end tube (3) are fixedly connected via the welding material in the welding groove (301).

8. The orifice flowmeter according to claim 1, wherein: A positioning structure (202) is provided between the orifice plate (2) and the positioning ring (12).

9. The orifice flowmeter according to claim 1, wherein: It also includes two pressure-taking tubes (4), which are respectively passed through and fixed on the rear end tube (1) and the front end tube (3).

10. The application method of the orifice flowmeter according to claim 9, characterized in that: The following steps are involved: S1, connecting one end of the rear end tube (1) away from the orifice plate (2) and one end of the front end tube (3) away from the orifice plate (2) and placing them in the pipeline to be tested; S2, connecting the two pressure-taking pipes (4) to a pressure differential measuring device; S3, conducting the pipeline to be tested, allowing the medium in the pipeline to be tested to pass through the orifice plate (2), and calculating the flow rate of the medium in the pipeline to be tested by the pressure difference measuring device; S4, cutting off the pipeline to be tested, draining the medium in the pipeline to be tested, disassembling the pressure difference measuring device, and spraying clean air or protective oil onto the orifice plate (2) through the two pressure taking pipes (4).

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