Long Distance Pipeline Welding Scheme

I. Personnel Requirements

1, Welders engaged in the welding of this project shall be trained and qualified according to the corresponding welding methods before starting construction. At the same time should have a certain practical experience and technical level.

2, Non-destructive testing of welds must be performed by professionals who have been professionally trained and qualified

II. Welding Equipment

1, The beveling group was paired with an internal mouthpiece.

2, The welding machine for welding is the all-position welding machine provided by WINCOO.

III. Weld Groove and Pipe Mouth Group

1, Pipe groove processing and size

a, The bevel of the straight pipe section has been machined by the steel pipe factory in the process of steel pipe manufacturing, and the pipe should be protected during transportation and installation, so as not to damage the bevel;

b, Before pipe assembly, use special pipe cleaning tools to remove all debris in the pipe. Before assembly, clean the oil and rust within 100mm at both ends of the pipe mouth with tools such as grinder and wire brush, and check whether there are indentation, cracks and other defects at the pipe mouth. If found, notify the supervisor in time and repair according to requirements, and the pipe that does not meet the requirements shall not be assembled.

2, For the less undulating zone, the pipe group adopts the internal matching machine and the pipe hanging machine; When the slope is large, the bend pipe connection and the dead mouth, the external mouthpiece is used. Assembly shall not be forced when matching. When using the inner matching machine, withdraw the matching machine after the root layer welding, and move the matching machine, the pipe should maintain balance. When using the external mouthpiece, remove it after 50% of the root welding is completed, and the completed root welding should be divided into 8 sections according to the circumference and distributed evenly.

3, The straight weld or spiral weld of the two pipe mouths must be staggered by more than 100mm on the circumference.

4, At both ends of all welded pipe sections, install temporary pipe caps with waterproof function at the pipe mouths before work every day.

IV. Welding Process

1, Welding method: downward manual arc welding

2, Welding material: E6010 Φ3.2 Φ3.2

a, Welding material drying :70~80×1h

b, Special personnel should be responsible for keeping, distributing and recycling welding materials.

c, The welding material warehouse should be kept dry, and the relative humidity should not be greater than 60%.

d, If the electrode is damp or not used up on the same day, the electrode should be recycled, stored and re-dried before use, but the number of re-drying should not exceed two times.

3. Welding process parameters

4, Welding general requirements

a, In rainy days and when the relative humidity of the air is greater than 90%, welding shall not be performed; When the wind speed is greater than 8m/s, the wind shelter must be put up during welding. If the wind speed cannot be guaranteed by taking measures, the welding should be stopped.

b, The arc starting of welding must be carried out in the groove, and the arc starting on the pipe wall is prohibited.

c, The ground wire of the welding machine should be firmly connected to prevent the arc between the ground wire and the pipe from burning the surface of the pipe.

d, After the root pass is welded, the hot pass should be welded as soon as possible, and the welding interval between the root pass and the hot pass should not exceed 5min.

e, When replacing the electrode with two layers of each phase, the joint should not overlap and should be staggered by 20~30mm.

f, All position downward welding should follow the principle of thin layer and variable pass, and the slag and splash must be removed between layers, and the next layer can be welded only after the appearance inspection is qualified.

V. Weld Quality Inspection

1, Appearance inspection: the weld surface shall not have cracks, non-fusion, porosity and slag inclusion and other defects; The depth of the biting edge shall not be greater than 0.5mm, and the cumulative length of the biting edge on both sides shall not be greater than 50mm in any length 300mm weld; The residual height of the weld should be 0.5~1.6mm, individual parts should not exceed 3mm, and the length should not exceed 50mm.

2, Non-destructive inspection: 100% ultrasonic inspection of all butt welds, the implementation of SY4065-93 standard, grade I qualified; 10% radiographic reinspection of all butt welds, SY-4056-93 standard, Class II qualified.

VI. Defect Repair

1, The welding defects shall be removed by Angle polishing machine, and the original welding process shall be implemented in the repair welding process.

2, The length of all repaired welds shall be greater than 50mm.

3, The number of defects repaired in the same part shall not exceed two times, when more than two times, there must be a process and technical measures for repair, and approved by the chief technical officer of the construction project.

VII. Construction Safety

1, Welders should keep welder gloves and feet dry to prevent electric shock.

2, Prevent being hurt by pipes and falling into deep ditches;

3, The welding machine should be placed on a high place to prevent rain soaking;

4, After finishing work every day, you should take good care of your belongings and welder to prevent loss;

5, Take good care of the fire source to prevent it from igniting surrounding trees, crops and other items.