The bend is bent by a complete set of bending equipment, which is divided into two processes: cold bending and hot pushing. No matter what kind of equipment and pipes, most of them use elbows.

Analysis of the main causes of the decrease in the quality of the bend pipe and the methods for attention:
When the 1. is pure bending, the outer arm wall of the neutral layer is thinned by tensile stress &1 under the action of M external force distance, and the inner compression stress. The joint force N1 and N2 make the cross section of the pipe change. On the basis of this factor, the main reasons for the decrease of bend pipe quality are RX and SX. Therefore, in the GBJ235—82, the RX value and the lateral thinning amount under various pressure grades are clearly stipulated. The purpose is to control the value of RX and SX to ensure quality.
As has been said in the front of the 2., the outside of the material is pulled when the bend is bent, and the position of the inner compression neutral shaft is different from the bend method. The neutral axis is 2/3 from the outer wall. Therefore, thin-walled pipe bending, the use of rotary bending method is beneficial.
3. the accuracy of bending tire is also one of the factors affecting the quality of bend pipe. In the manufacture of bending tire, in addition to the specification and size requirements to control in a certain tolerance range, but also require users to use according to the bending pipe diameter to select the corresponding bending tire.
4. bending property and surface corrosion of pipe itself may also affect the quality of bend pipe. During site construction, the operator should also understand the material, processing performance and surface corrosion of the pipeline.

Material of ASME B16.9 Bend

Dimensions of ANSI B16.9 bend

Dimension:	ANSI B16.9, MSS-SP-43 Type A, MSS-SP-43 Type B, JIS B2312, JIS B2313
	Radius Available 3D Bend 5D Bend 6D Bend 8D Bend 10D Bend 20D Bend Customized radius