Regarding welding methods for pressure pipelines
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Why are pressure pipelines nowadays welded with TIG welding as the base layer followed by MIG welding, with direct MIG welding being used only rarely? Can’t we use direct manual arc welding? Can single-sided welding not guarantee double-sided formation? What is the basis for this?
The use of TIG welding is primarily to ensure that the welds inside the pipes remain clean, with no slag formation, and this is especially necessary for pipes carrying flammable or explosive substances.
Currently, for the utility pipeline GB1, the actual welding method used is manual arc welding. If it is not allowed, can specific reasons be found? Thank you
This shall be governed by the terms of the contract; if there are provisions in the contract that refer to certain standards, it is still the contract that takes precedence. For example, when welding oxygen pipelines, my requirement is that there must be no weld slag or other particulate impurities inside, which is why TIG welding is necessary. Before TIG welding became widespread, welding had to be done directly; after welding, the area was subjected to repeated tapping and vibration, along with cleaning using a strong airflow at high speed. However, there may still be safety risks during use. Now that TIG welding is widely used, cost issues may still exist during its implementation; therefore, it is necessary to clarify these matters in the contract to define responsibilities. If it is a later engineering change, it can be negotiated separately. This is the entry point that both parties need to find. Everything is subject to the terms of the contract; in case of issues, engineering changes can be made. Nor can they each stick to their own version, resulting in harm for both sides. It's best to handle things flexibly.