Urban underground waterway construction, domestic drinking water and wastewater discharge, and South-to-North Water Transfer Project all need pipelines, which shows that pipelines are also an indispensable part of life. Do you know anything about pipeline welding and installation?
No matter what pipeline installation, although there are differences, they are all similar. The following will focus on this issue.
Foreign pipeline welding construction has experienced the development of manual welding and automatic welding. Manual welding mainly includes cellulose covered electrode downward welding and low hydrogen covered electrode downward welding. In the automatic welding of pipelines, there is a pipeline flash butt welding machine developed by the former Soviet Union, which accumulated tens of thousands of kilometers of large-diameter pipelines during the former Soviet Union. Its remarkable characteristics are high efficiency and strong adaptability to the environment. Bellows manufacturers also found that the automatic welding system of CRC multi-head gas shielded pipeline developed by CRC Company in the United States consists of three parts: pipe end beveling machine, internal butt welding machine and internal welding machine combination system, and external welding machine. Up to now, the cumulative length of welded pipelines in the world has exceeded 34,000 kilometers. Bellows manufacturers visited France, the former Soviet Union and other countries, and found that they also studied and applied similar automatic welding technology inside and outside pipelines, which has become the mainstream of automatic welding technology for large-diameter pipelines in the world today.
The girth welding technology of steel pipeline in China has undergone several major changes. As an old enterprise, bellows manufacturers all know that in the 1970s, traditional welding methods were adopted and low hydrogen covered electrode manual arc welding overhead welding technology was adopted. In 1980s, manual arc welding downward welding technology was popularized, and cellulose covered electrode and low hydrogen covered electrode downward welding were adopted. In 1990s, self-shielded flux-cored wire semi-automatic welding technology was applied. Today, bellows manufacturers began to fully promote all-position automatic welding technology.
Manual arc welding includes the application of cellulose covered electrode and low hydrogen covered electrode. According to the bellows manufacturer, in the past, the overhead welding process of manual arc welding was mainly used in pipeline construction in China, which was characterized by large gap between nozzle assemblies, arc stopping operation during welding, large thickness of each welding layer and low welding efficiency. Bellows manufacturers also learned that manual arc welding downward welding is a welding technology imported from abroad in the 1980s, which is characterized by small nozzle assembly gap, large current, multi-layer and fast welding, suitable for assembly line operation and high welding efficiency. Due to the thin thickness of each welding layer, the toughness of the ring welding joint can be improved by heat treatment of the front welding layer by the rear welding layer. Manual arc welding method is flexible, simple and adaptable. The organic combination of downward welding and upward welding and the good adaptability of cellulose covered electrode to root welding are still irreplaceable by automatic welding method in many occasions.
Bellows manufacturers further learned that the semi-automatic welding technology of self-shielded flux-cored wire was applied to pipeline construction in 1990s, mainly for filling and covering. It is characterized by high deposition efficiency, good all-position forming, strong environmental adaptability and easy mastery by welders. It is an important welding process method for pipeline construction at present.
With the increase of strength grade, pipe diameter and wall thickness of steel pipes for pipeline construction, automatic welding technology is gradually applied to pipeline construction. Bellows manufacturers know that automatic pipeline welding technology has the advantages of high welding efficiency, low labor intensity and little influence of human factors in the welding process, and has great potential in the construction of large-diameter thick-walled pipelines. According to the market observation of corrugated pipe manufacturers, it is found that the automatic welding technology of pipelines in China is in its infancy, the problem of automatic welding of roots has not been solved, and the supporting facilities such as pipe end groove forming machine are not yet mature, which limits the large-scale application of automatic welding technology. At present, automatic root welding mainly adopts ST mode.