Notes for pipeline welding

In brief, pipe, welding material (baking, heat preservation), welding joint treatment (cleaning, type of break), welding precautions (current, voltage, influence of gas welding wind, rain and snow weather)

Pipe welding and inspection

(1) The welder according to the welding work instruction welding;

(2) The welder must hold a certificate on the post, not exceed the time limit for welding;

(3) Before welding should be the groove surface and groove edge within the scope of not less than 20mm dirt clean;

(4) Welding materials according to the requirements of the welding instructions baking, insulation, distribution;

(5) Welding arc should be carried out in the groove, strictly prohibited in the pipe wall arc;

6 NG process pipeline using electrode arc welding, CNG process pipeline using argon arc welding method, the previous layer is not finished welding the next layer, in welding should ensure the quality of arc starting and arc closing, arc closing should be filled with arc pit, layer indirect head should stagger each other;

7 in addition to the welding process has special requirements, each bead should be a joint welding. If for some reason is forced to interrupt, should take anti-crack measures. Rewelding must be checked to confirm that there are no cracks before continuing welding;

8 after welding each weld, should be easy to observe the edge of the weld with a marker to make welder mark steel number, and fill in the "welding record";

(9) in the following environment should stop welding (without protective measures)a, electrode arc welding, the wind speed is equal to or greater than 8m/s; B. During gas shielded welding, the wind speed is equal to or greater than 2m/s; C. relative humidity is greater than 90%;D. rainy days.

The surface quality of the attended welded joint shall meet the following requirements:

A. There shall be no cracks, no fusion, air holes, slag inclusion and splash;

B. No edging on welding seams.

C, weld surface shall not be lower than the pipe surface, weld residual height delta h should meet the following requirements:

(1)百% radiographic detection of welding joint, its delta h≤1+0.1b1, and not greater than 2mm;

(2) other welded joints, △h≤1+0.2b1, and no more than 3mm;

(3) the height of the fillet weld is not less than the thickness of thin pieces;