The manufacturing process of large diameter elbow is commonly organized as followings:

1. Blanking
The plate can be selected according to the wall thickness of the elbow, the plate thickness t=2mm. According to the technical requirements of the elbow, there are several welding seams to cut, usually 90. The elbow can allow 3 to 4 welding seams, so the elbow can be cut into 3 to 4 sections. In order to ensure the smoothness of the welding seam, the edges of each section (weld seam) are cut according to the plane unfolding curve.

2. Rolling
After blanking, roll bending is performed, and the radius of rolling curvature is 1/2 of the diameter of the elbow, and single curvature rolling is selected for each section. Single curvature r=5OOmm. When rolling, the straight edge should be used as the benchmark to avoid rolling.

3. Welding to form a closed ring shell
The roll-bent shell plate is welded section by section to form a closed annular shell, and a water injection port and a drain port are welded on the closed annular shell. (Pressure test pump) applies internal pressure to the closed casing, and the drain port is used for pressure relief and pressure regulation. Under the effect of internal pressure, the shell is plastically deformed and gradually tends to the ideal shape
4. Ring-shell bulging process
When bulging, the internal pressure load is applied to the annular shell according to a certain pressure curve, and after each certain pressure is applied, the pressure is maintained for a period of time, and then the radial displacement data is tested. The radial displacement in the test is obtained by measuring the relative displacement of each point and the reference point. When the pressure reaches 0.705MPa, the compression is stopped, and the shape and size of the annular shell are close to the ideal state after maintaining the pressure for a period of time.

5. Cut into sections
After the ring shell is press-formed, the welds are ground to ensure that the curved surface of the elbow is lubricated, and then the elbow is cut into sections according to the required camber of the elbow. Such as 30. , 60. , 75. , 90. After segmenting, each segment is connected with the corresponding flange to produce large stainless steel elbows with different cambers.

6. Analysis of the test results of the ring-shell bulging test
Regarding this test annular shell, the initial yield pressure P ) of the annular shell has been calculated according to the above formula. 523MPa, the cracking pressure of the ring shell is 1.44MPa, and the forming pressure in the test is 0.705MPa, which is about 35% higher than the initial yield pressure. During bulging, with the continuous increase of internal pressure, the radial displacement of the shell to the outside continues to increase, and the toroidal shell polyhedron continues to approach the annular shell. When the internal pressure reaches 0.705MPa, the size of the ring is close to the theoretical value. The size of the ring after bulging is obtained by measuring the external size of the ring. The diameter of the outer ring and the axial section diameter of the ring after forming are respectively measured. The measured maximum diameter and minimum diameter of the outer ring of the annular shell are 3006 ram and 2997 mm, respectively, and the measured maximum and minimum diameters of the section are 1003 mm and 1000 mm, respectively. It can be seen from the measured data that after the multi-faceted ring shell is expanded by hydraulic pressure, it is basically close to the ring, and the size meets the design requirements.

Large diameter pipe fittings are mass-produced in Longtiaidi all seasons. Because Longtaidi is the designated and qualified supplier of pipe fittings for domestic large energy groups, such as CNPC CNOOC,SINOPEC,SINOCHEM,CHINA COAL CHINALCO. Long-term tech cooperation with domestic research institutes has established and will promote our research and development on new products and advanced technology continuously. Now Longtaidi is the leading level professional industry home and broad.

Our main products are bimetal clad pipes, bimetal clad pipe fittings(elbows, tees, reducers,forged fittings) and bimetal clad flanges; Steel pipes, pipe fittings(elbows, tees, reducers,forged fittings) and flanges.

We especially focus on the production of high-pressure wall sickness pipe fittings, bimetal clad pipe fittings, anti-sulfer and anti-hydrogen pipe fittings, X-steel large diameter pipe fittings, gas collecting pipe fittings and other products.

The available range of pipe fitting is DN≤3200mm, S≤150mm, and PN≤42Mpa. Available materials are SS, AS,CS and bimetal clad, nickel base alloy and inconel alloy.

The available range of bimetal pipe is DN≤1000mm, S≤60mm. The lined materials can be stainless steel, duplex steel, nickel base alloy, cooper alloy, aluminum, titanium etc.

pipe fittig elbow
pipe elbow

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