Analysis of PE pipe hot-melt welding problem
A certain pipe network engineering installation uses PE pipe hot-melt welding. The diameter of the main water supply pipe is greater than 63mm and the wall thickness is greater than 5mm. In the process of welding such pipe components, the maximum water pressure of the pipe network is within 60m. The precision of welding can be ignored. However, in actual work, due to the high water pressure required by the mountainous terrain, some defects will occur if the welding technology is not enough, it is difficult to improve the work level and quality, and cannot meet the work requirements.
1) Defects in the formation of welded joints.
Under normal circumstances, the defects in the welding joint forming are mainly due to deviations in the geometry and structure of the crimping, which cannot meet the relevant requirements.
First, if there are stains or foreign objects on the welding end face, it will cause deviations in the thickness of the welding wall on both sides. In the case of uneven heating, the periphery of the welding port will appear asymmetry, and the size cannot meet the relevant regulations. For example: Defects such as cuts and gaps appear.
Second, if the end face of the welding port is relatively wet during welding, the port welding is not strong enough; or there is water vapor, it will cause welding quality problems and leak channels.
Third, if the degree of ellipse of the welded pipe does not meet the relevant regulations, the reliability of the counterpart work cannot be guaranteed, and the problem of wrong edges will occur.
Fourth, if there is a deviation in the fixture stroke, or during melting, the butt temperature and pressure are lower, and the welding time is shorter, which will cause the quality of the welding joint to decrease. If the speed of the fixture is fast, or the temperature and pressure are too high, the height of the welding port is too high or too wide, artificially causing the cross-section of the water to become smaller, and the design flow rate is reduced.
2) The problem of micro-defects.
Microscopic defects are quality problems in the welding joint during welding work, such as cracks, cracks, and poor penetration.
First, if the quality of the hot melt used by the construction technicians is poor, or there is a deviation in the flow rate, the quality of the pipe joint will be reduced. For example, when the flow rate deviation is greater than about 0.6g/10min, it will cause a welded joint. Quality defect issues. If the melting temperature is low, or the welding environment is poor, problems such as cracks and cracks in the welding joint will also occur.
Second, in actual construction, the end faces of the pipeline are not parallel, or the end faces are not fully welded by heater plates, etc., resulting in poor weld penetration.
3) The problem of microscopic defects.
In actual welding work, because the heating temperature is too high or the heating time is too long, the pipe material will be oxidized and damaged. In severe cases, carbonization problems will occur, and then material deterioration problems will occur. For welding defects, various problems are interrelated. If the operating technicians lack technical ability and sense of responsibility, and cannot carry out related work according to equipment performance and welding requirements, the quality of the welding project will gradually decrease.
