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.

Most potential safety hazards of natural gas users come from rubber hoses. Once the rubber hose is used for a long time or bitten by animals, it will lead to aging, cracking, bubbles or damage, laying hidden dangers for accidents.
On December 8, the publicity activity for safe gas use in winter jointly hosted by Changsha Municipal Commission of Housing and Urban Rural Development and Changsha Municipal Bureau of Gas and Heat Management was launched in Hunan Martyrs Park, Wuyi Business District, Dongtang Business District, Huangxing South Road Commercial Pedestrian Street and other places.
Zhao Zhiyong, director of Changsha Gas and Heat Administration Bureau, said that the service life of the pneumatic butterfly valve connecting the stove can reach 10 years, which can prevent rats from biting, scattering and accidents. The service life of the rubber hose is only one and a half years, and it is easy to be bitten by animals. However, at least 900000 of Changsha's more than 1.1 million natural gas users and 400000 liquefied gas users are still using the rubber hose, It is suggested that the 900000 users spend 50-80 yuan to use Ping An 304 stainless steel pneumatic butterfly valve.