large diameter elbows:
Butt welded steel elbow
LSAW welded elbow
Size:406mm to 2000mm
Seamless welded steel elbow
Size:406mm to 1200mm
Precautions for the use of large diameter elbows:
1. When the large-diameter elbow is bent, the outer wall of the inner layer of the inner layer is subjected to tensile stress and thinned under the action of external force M, and the inner side is under compressive stress. The effect is thickened, and the combined forces N1 and N2 change the cross section of the tube. Based on this factor, the main cause of the deterioration of the bend quality is RX and SX. Therefore, in GBJ235-82, the RX value and the amount of external thinning under various pressure levels are clearly defined, in order to control RX. With the value of SX, thus ensuring quality.
2. When the large-diameter elbow is made, the elbow is pulled by the outer side of the material, and the position of the inner pressed neutral shaft is different from the elbow method. In the top-bend type (compression and bending), the neutral axis is about 1/3 from the outer wall. the neutral shaft is at 2/3 of the outer wall when working in a turning (back bend). Therefore, the thin-walled pipe is curved, and it is advantageous to use the spin bending method.
3. The accuracy of bending of large diameter pipe is also one of the factors affecting the quality of pipe bending. When manufacturing the bending tires, in addition to the specification of the dimensional requirements, the user is also required to select the corresponding bending tire according to the bending diameter.