Butt Welded Fitting has the following precautions during installation:
1、 Preparation before welding
Pipe inspection
Firstly, carefully inspect the quality of butt welded fitting. Check its surface for defects such as cracks and sand holes. For example, if there are small cracks in the pipe fittings, the cracks may expand under pressure during welding and use, leading to serious problems such as leakage.
Check if the specifications and models of the pipe fittings match the design requirements. Ensure the accuracy of parameters such as pipe diameter and wall thickness, as different specifications of fittings are used in different pipeline systems, and incorrect specifications may affect the fluid transport capacity and safety of the entire system.
Pipeline cleaning
Before installation, the welding ends of the pipeline and the welding parts of the fittings must be thoroughly cleaned. To remove impurities such as rust, oil stains, and oxide scales. Tools such as wire brushes and sandpaper can be used for polishing, followed by wiping with organic solvents such as acetone to ensure the cleanliness of the welding surface. Because these impurities can enter the weld seam during the welding process, affecting the welding quality and reducing the strength and corrosion resistance of the weld seam.
Welding equipment inspection
Check if the welding equipment is working properly. Including the stability of the welding power source, whether the adjustment range of welding current and voltage meets the requirements, etc. For automatic welding equipment, it is also necessary to check the accuracy of the welding track to ensure that the pipe fittings and pipelines can be accurately docked and welded according to the predetermined path.
2、 Precautions for welding process
Welding process selection
Select the appropriate welding process based on the material of the pipe fittings and the requirements for the use of the pipeline system. For carbon steel Butt Welded Fitting, manual arc welding, gas shielded welding, etc. are commonly used welding methods. For stainless steel fittings, in order to avoid weld oxidation, it may be more inclined to use processes such as argon arc welding.
Control welding parameters such as welding current, voltage, and welding speed. Excessive welding current may cause overheating of the weld seam, resulting in defects such as undercutting and burning through; If the welding speed is too fast, it may cause problems such as incomplete weld seam and incomplete penetration.
Welding operation
When welding, it is necessary to ensure that the axis of the pipe fittings and pipelines are aligned, and the deviation cannot exceed the specified range. Otherwise, it will cause welding stress concentration and affect the quality of the weld seam.
During the welding process, attention should be paid to the welding sequence, generally using symmetrical welding and other methods to reduce welding deformation. For example, for large diameter pipe fittings, two people can weld them symmetrically from both sides at the same time, which can balance the welding stress and avoid the pipe fittings from being unable to be installed properly due to welding deformation.
3、 Inspection and acceptance after welding
Appearance inspection
After welding is completed, the first step is to conduct a visual inspection. Check whether the shape of the weld seam is regular, and whether there are defects such as porosity, slag inclusion, and lack of fusion on the surface of the weld seam. The excess height of the weld seam should meet the design requirements. Excessive excess height can cause stress concentration, while insufficient excess height may affect the strength of the weld seam.
Non destructive testing
Perform non-destructive testing based on the pressure rating and usage requirements of the pipeline system. If radiographic testing, ultrasonic testing and other methods are used to inspect whether there are defects inside the weld seam. For some important pipeline systems, non-destructive testing is a crucial step in ensuring welding quality and safe system operation.
Pressure test
Finally, after the installation of the pipe fittings is completed, a pressure test should be conducted. Conduct a pressure test at a certain multiple of the design pressure (such as 1.5 times) to check for leaks in the pipeline system, including the welded parts of the fittings. Only after passing the pressure test can it be officially put into use.
