What preparations should be made before welding pipeline flanges?

(1) The flange contact surface shall be smooth, and annular shallow grooves are allowed, but there shall be no spots, sand holes and the amplitude injected into the grooves, and the contact between the two flange surfaces shall be even and tight.

(2) The center line of the flange plane shall be perpendicular to the center line of the pipeline, and the deviation shall not be greater than1-2.5mm. ..

(3) The allowable error of the distance position of the flange screw hole (measured in a straight line) is 0.5-65438 0.0 mm. ..

④ The allowable displacement error between the center line of flange hole and the center line of pipeline is 1-2mm.

(5) The allowable deviation of two flange planes is 0.2-0.3mm. ..

⑥ When welding flanges and pipes, pay attention to welding stress and deformation (especially stainless steel).

It is necessary to ensure the verticality between the flange and the pipeline, and to avoid the large deviation of parallelism between the two flanges during bolt connection, which will lead to the leakage of the gasket due to lax clamping.