2. Welding and analysis welding test shall be conducted by cylinder, material A105. Its main purpose is to test, verify and determine the valve body raw materials, welding wire diameter, welding flux brand, optimize the welding groove structure and welding parameters, predict and control the temperature change, deformation and welding residual stress during welding, and provide reference for the production design of all welded pneumatic ball valve. The welding test system consists of current and voltage measurement system, displacement and deformation measurement system and temperature measurement system.
1) The temperature shall be determined at the side during welding. According to the temperature measurement results (as shown in Figure 1), when welding pneumatic ball valves, the control interlayer temperature shall not exceed the safe use temperature of the seat sealing ring by 150 ℃, which will not affect the valve sealing performance. Fig. 1 Temperature Change Curve at 25mm from the Weld Center
2) Determination of welding deformation. Cylinders with inner diameter of 600mm and thickness of about 50mm shall be welded. There is no binding at both ends of the cylinder during welding. After welding, the measured cylinder deformation is about 2.5mm in axial direction and 1.5mm in radial direction. During the design of all welded pneumatic ball valve, the influence of welding deformation on the sealing performance of the pneumatic ball valve shall be considered, and the fit clearance between the valve seat and the valve body shall be properly adjusted. Different auxiliary methods such as air cooling and vibration can be used during welding to improve the deformation of workpiece during welding. In general, vibration welding has less deformation, followed by air cooling.
3) Determination of welding residual stress. After welding, the welding residual stress shall be measured by the through hole method. The distribution curve of welding residual stress is shown in Figure 2.

The non-metallic contraction joint meets the requirements for the economy of pipe system establishment and the reliability of safe operation, brings great convenience to the construction, operation and maintenance of pipe system establishment, and makes the domestic pipe system establishment process close to or catch up with the development of prosperous countries. The functional design of non-metallic contraction joints in each component part is as follows
1. The corners of non-metallic contraction joints form a rectangular cross section by large arc transition, and the stress degree of corner section will be relatively reduced, eliminating the dead angle of deformation and the overall average deformation of the product during online operation, thus greatly reducing the risk of damage caused by regional high stress and extending the service life of non-metallic contraction joints.
2. The non-metallic shrink joint reduces the thrust of the low pipeline system under the condition of not losing stability as a whole and adhering to the fundamental working stiffness, which improves the thermal compensation ability of the non-metallic shrink joint and reduces the cost of flexible parts in pipeline establishment.
3. Due to the compliance change of geometric shape, non-metallic contraction joints can work reliably in a benign force system under the action of external tensile stress, compressive stress and alternating stress, avoiding some stress risk areas. When working in the atmosphere containing H2SO, CO and H2 smoke, stress corrosion cracking (SEE) and corrosion fatigue cracking (CFF) are effectively improved Under the premise of not affecting the service life, the allowable number of thermal cycles of non-metallic shrink joints is improved.
4. When the non-metallic contraction joint is welded on the corrugated pipe, the weld can be far away from the arc tangent point. When the length of one side of the rectangle is less than 2M, the weld can be missed by one. The misalignment of the weld seam is greatly reduced. The error of corrugated pipe section shape and corrugated envelope length at any position of the product is very small. The corrugated forming and stretch bending forming are full of sophistication; It is consistent with the theoretical criterion of good maximum fatigue life of bellows.
5. The arc steel plate at the corner of the non-metallic contraction joint is welded and reinforced. The interface is made of channel steel, which strengthens the structural rigidity of the non-metallic contraction joint. The overall product line is fluent and the appearance is bright.