First, the quality of pipe cut shall meet the following requirements:

(1) the surface of the incision shall be smooth and free from cracks, double skin, burr, concave convex, shrinkage, slag, oxide, iron filings, etc;

(2) the inclination deviation of the end face of the incision shall not be greater than 1% of the outer diameter of the pipe and shall not exceed 3 mm;

(3) for groove processing requirements, the groove processing form shall be carried out according to the provisions of the welding scheme.

Second, the pipeline components should be selected according to the quantity, specification and material specified in the single line diagram, and the system number of the pipeline should be indicated according to the single line diagram and the sequence number of each component according to the prefabrication sequence.

Third, the selection of free pipe section and closed pipe section should be reasonable. The closed section must be processed according to the measured size on site. After prefabrication, the internal cleanliness should be checked, the pipe orifice should be closed and stacked reasonably in order.

Fourth, the butt weld position of polyurethane insulation steel pipe should meet the following requirements:

(1) the distance between the pipe position and the bending starting point of the elbow shall not be less than the outer diameter of the pipe or not less than 100 mm;

(2) the distance between two butt welds of the pipe shall not be greater than 5mm

(3) the position of the pipe part of the support and hanger shall not coincide with the butt weld of the pipe, and the distance between the weld and the edge of the support and hanger shall not be less than 50 mm;

(4) the pipe interface shall avoid the opening position of water drainage, vent and instrument pipe, and the distance from the opening edge shall not be less than 50 mm, and shall not be less than the hole diameter.