由于长途运输的困难,炼油化工装置中许多大型容器和设备(在我国直径超过φ3800毫米的容器和设备)都是在制造厂预制成片,再到施工现场进行整体组对焊接的。这些容器和设备成形后,要求在器壁上划线以确定(焊接)其上的配件的准确位置,划线工作将直接影响容器和设备的制造及使用质量。 Due to the difficulties of long-distance transport, many large vessels and equipment in refining and petrochemical installations (containers and equipment over 3800 mm in diameter in our country) are prefabricated in the manufacturing plant and welded to the construction site as a whole. After these containers and equipment are formed, it is required that the walls of the equipment be marked to determine the exact location of the fittings on them, which will have a direct impact on the quality of manufacture and use of the containers and equipment.