When welding steel pipe, the nozzle should be prepared as follows:
(1) Clear the interface at the floating rust, dirt and grease.
(2) Steel pipe with steam welding or mechanical cutting, the cross-section should ensure that the straight to ensure that the pipe is completed concentricity, cutting in the welding before the removal of burrs or attachments.
(3) When the three holes in the pipeline to open the hole, should be carried out in the mouth, the tube should be removed clean residue, saddle-shaped opening height should not be less than 1 /
(4) In order to ensure that the pipe wall during the welding process can be fully welded, the nozzle should be made groove, groove form can be selected according to the thickness of the wall.
(5) The wall thickness of less than 3.5 below the pipeline is not open groove, the gap is 1 to 2, wall thickness greater than 3.5mm pipe must be open groove, groove angle is generally 30 ° ~ 35 ° blunt edge of 1 ~ 2, the gap is 1 ~ 3 
(6) Groove forming can be used gas cutting (artificial groove) or groove machine processing, processing after the groove should remove the slag and iron oxide, and steel filework, until the exposed metallic luster.
(7) Different wall thickness of the pipe butt welding, the thickness of the two pipe walls shall not exceed 10% of the smaller wall thickness, up to no more than 3mm (referring to the difference between the two wall thickness), or deal with the thickness of the tube for processing.
(8) In the welding, the distance between the two adjacent pipe joints shall not be less than 200mm, the minimum should not be less than the nominal diameter of the pipeline.