Integrally-formed elbow flow meter sensor and welding-free machining method thereof

Abstract

The invention relates to an integrally formed elbow flowmeter sensor and a processing method, and the sensor is integrally and synchronously processed and formed by a single thick-wall seamless steel pipe and comprises a 90-degree elbow section and straight pipe sections (15-55mm) at two ends. The outer surface of the bent pipe section is machined into a 4-20-edge polyhedral structure, and the outer diameter of the straight pipe section is matched with that of a standard pipeline. During manufacturing, an elbow blank with a straight pipe section is firstly prepared, then the inner surface and the outer surface are synchronously and finely machined through a machining center, and part of outer ridge faces serve as positioning and curvature measuring references. And the machining precision reaches IT6 level. According to tests, the qualified rate of finished products is increased to 98%, the pressure bearing capacity is improved by 40%, the installation efficiency is improved by 50%, and the technical problems that in a traditional technology, welding deformation exists, the size is enlarged, and precision is limited and installation is not convenient due to the fact that an integrally-formed straight pipe section does not exist are solved.

Description

Technical Field

[0001] This invention relates to the field of fluid measurement technology, specifically to a one-piece molded curved tube flowmeter sensor and its weldless precision machining method. It is particularly suitable for precise measurement of high-pressure fluids in fields such as petrochemicals and nuclear power. Background Technology

[0002] 1. Rough machining process (push-forming / stamping / welding): This process results in low dimensional accuracy and high surface roughness, which limits the accuracy of the flow meter (usually ≥1.5 grade) and causes insufficient pressure resistance.

[0003] 2. Precision machining processes (such as the expired application number CN03137147.7, and the authorization announcement number...).

[0004] The patent CN1293368C is the most representative, but its obvious drawbacks are:

[0005] - The two semi-circular rings need to be welded into a whole ring and then cut. The welding deformation is uncontrollable, which reduces the processing accuracy.

[0006] - Weld defects lead to a finished product qualification rate of less than 85%, and high-pressure media can easily corrode the micro-cracks at the stop.

[0007] - Larger circular rings (diameter increased by more than 4 times) need to be processed first, increasing equipment costs by 30%-50%;

[0008] - Traditional processing methods take 8-12 hours per piece, while this invention can shorten the processing time to 3-5 hours per piece;

[0009] - The sensor body is limited to a 90° structure, which cannot be integrated into a straight pipe section. During installation, an additional straight pipe section needs to be connected, which reduces the product's accuracy and reliability and increases the risk of leakage. Summary of the Invention

[0010] I. Purpose of the Invention

[0011] This invention addresses three major technical challenges in precision machining: welding deformation, size enlargement, and the lack of integrally formed straight pipe sections, enabling the manufacturing of integrated sensors with high precision, high reliability, and low cost.

[0012] II. Technical Solution (I) Sensor Structure (Combined with) Figure 1-3 )

[0013] 1. Matrix: It is integrally formed from a single piece of thick-walled seamless steel pipe, including a 90° bend section and straight pipe sections at both ends (length 15-55mm);

[0014] 2. Inner surface: The inner cross-section of the sensor is circular, and the diameter is consistent with the inner diameter of the standard pipe (tolerance grade IT6);

[0015] 3. Outer surface:

[0016] The outer surface of the -90° bend section is a multi-faceted structure or a combination of multi-faceted and arc-shaped surfaces, with 4, 8, 12, 16 or 20 facets.

[0017] - The outer diameter of the straight pipe section is consistent with the outer diameter of the standard pipe (tolerance ±0.1mm);

[0018] 4. Pressure tapping hole: located on the 45° axial plane, with the same diameter on the inner and outer sides, ranging from 2 to 12 mm;

[0019] 5. End bevel: V-shaped bevel, blunt edge 1-2mm, single-sided angle 30°±2°.

[0020] (II) Production Method (Combined with) Figure 1-3 )

[0021] 1. Blank preparation:

[0022] - Thick-walled seamless steel pipes are selected and formed into 90° elbow blanks with straight pipe sections by stamping / pushing. The straight pipe section is 20-60mm long, the wall thickness meets the processing allowance requirements, and the bending diameter ratio is ≥1.5.

[0023] 2. Precision machining:

[0024] - Import 3D graphics into CAD / CAM software and generate milling paths, dynamically adjust milling parameters, and simultaneously machine inner and outer surfaces on CNC;

[0025] - The inner surface is machined to be circular, with a diameter matching that of standard pipes;

[0026] - The outer surface is machined into a multi-faceted surface or a combination of multi-faceted and curved surfaces. Facets A, B, C, and D serve as the curvature measurement reference and clamping reference.

[0027] 3. Curvature measurement: The radius of curvature is measured online using the bow height and chord length method or the equal chord geometry method through the generatrix of the prism face; 4. The radius of curvature and the roundness of the inner hole are key characteristic parameters of the bend flowmeter;

[0028] 5. Beveling: V-shaped bevels are machined at both ends;

[0029] 6. Pressure tapping hole machining: Drill pressure tapping holes at a 45° angle.

[0030] III. Beneficial Effects

[0031] 1. Elimination of welding defects: Integral molding eliminates welding, increasing the finished product qualification rate to 98% and improving pressure resistance by 40%. Verified by a third-party testing agency, no deformation was observed when the pressure resistance reached 42MPa.

[0032] 2. Improved accuracy: No welding deformation affects the dimensional accuracy to IT6 level, and the flow meter accuracy can reach 0.5 level;

[0033] 3. Cost reduction: Avoiding large-scale processing reduces equipment costs by 35%;

[0034] 4. Installation optimization: Integrating straight pipe sections reduces the impact of subsequent straight pipe connections on the flow meter sensor in the bend, improving installation efficiency by 50%;

[0035] 5. Convenient measurement: The multi-faceted design enables rapid positioning and high-precision curvature measurement. Attached Figure Description

[0036] Figure 1 : Structural diagram of a thick-walled elbow blank (DN200 as an example);

[0037] Figure 2 : Finished sensor structure diagram (DN200 as an example);

[0038] Figure 3 : Finished sensor image (DN200 as an example). Detailed Implementation

[0039] Taking the DN200 sensor as an example:

[0040] 1. Seamless steel pipe is selected, material No. 20, tensile strength ≥410MPa, elongation ≥24%, outer diameter Φ245mm, wall thickness 25mm, stamped elbow blank (R=340mm), straight pipe section length 37mm;

[0041] 2. Clamped on a five-axis machining center, milling speed 800-1200 r / min, feed rate 0.1-0.3 mm / r;

[0042] 3. The inner surface is machined to Φ205±0.0145mm (IT6 grade);

[0043] 4. The outer surface is machined with a 12-faceted assembly, with a facet width of approximately 60mm. The outer diameter of the straight pipe section is machined to...

[0044] 5. Both ends are machined with a 30°±2° bevel, with a blunt edge of 1.5mm;

[0045] 6. Drill an 8mm pressure tapping hole at a 45° angle.

[0046] 7. The radius of curvature is measured by the bow height and chord length method or the equal chord geometry method through the generatrix of the facet, with an error of <0.05mm.

Claims

1. A bend-pipe flow meter sensor, characterized in that: It includes a 90° bend pipe section integrally formed from a single piece of thick-walled seamless steel pipe and straight pipe sections at both ends. The length of the straight pipe section is 15-55mm. The inner cross-section of the bend pipe section is circular and its diameter is consistent with the inner diameter of the standard pipe. The outer surface of the bend pipe section is a multi-faceted structure or a combination of multi-faceted and arc-shaped surfaces, with 4, 8, 12, 16 or 20 facets. The outer diameter of the straight pipe section is consistent with the outer diameter of the standard pipe.

2. The sensor according to claim 1, characterized in that: The multifaceted composite structure includes measurement reference surfaces (A, B) and clamping reference surfaces (C, D), which are located on the inner and outer (A, B) and upper and lower (C, D) sides of the bend section, respectively.

3. The sensor according to claim 1, characterized in that: The sensor has V-shaped bevels at both ends, with a bevel thickness of 1-2mm and a single-sided bevel angle of 30°±2°.

4. The sensor according to claim 1, characterized in that: An inner pressure tapping hole and an outer pressure tapping hole are provided on the axial plane in the 45° direction of the 90° bend section. The diameter of the pressure tapping hole is 2-12mm, and its inner edge intersects with the inner surface of the sensor.

5. The sensor according to claim 1, characterized in that: The bending-to-diameter ratio (the ratio of the radius of curvature R to the inner diameter D) is ≥1.

5.

6. A method for manufacturing a bent-tube flowmeter sensor as described in any one of claims 1-5, characterized in that... Includes the following steps: (a) Select thick-walled seamless steel pipes and form 90° elbow blanks with straight pipe sections by stamping or push forming process, with the straight pipe section length being 20-60mm; (b) Simultaneously finish machine the inner and outer surfaces of the elbow blank on a machining center: - The inner surface is machined to a circular cross-section that matches the inner diameter of a standard pipe; - Inner surface roughness Ra≤3.2μm; - The outer surface is machined into a multi-faceted composite structure; (c) Machining V-shaped bevels at both ends of the sensor; (d) Drill pressure tapping holes on the inside and outside of the 90° bend at a 45° angle.

7. The method according to claim 6, characterized in that: In step (b), the radius of curvature is measured online using the processed outer edge generatrix, employing the bow height and chord length method or the isochoric geometry method.

8. The method according to claim 6, characterized in that: The number of facets in the multifaceted combination is selected as 4, 8, 12, 16 or 20 depending on the machining allowance.

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