The inner and outer surfaces of large-diameter spiral submerged arc welded steel pipes should be bright and free of residual acid and oxide scale. The surface should be free of defects such as cracks, inclusions, scarring, delamination, concave welds, and incomplete welding. Surface defects should be removed by grinding, the grinding area should have a smooth transition with the base material, and it should be ensured that the wall thickness after grinding is not less than the minimum wall thickness specified in 3.0.6. If the depth of the defect exceeds the minimum wall thickness mentioned above, welding repair can be carried out with the consent of the purchaser. The welding materials and welding processes used for welding repairs must also comply with the provisions of 4.0.2. After welding repair, the weld area should be filmed and reviewed according to the requirements of 4.0.9.
The internal and external weld beads of large-diameter welded steel pipes should be flush with the surface of the welded steel pipe or evenly convex. The weld reinforcement should meet the following requirements:
1. The outer side is not greater than 50% of the wall thickness, but the maximum Z is 3mm; take the smaller value.
2. The inner side is not greater than 25% of the wall thickness, but the maximum Z is 3mm, whichever is smaller.
3. The surface of the inner and outer weld beads should be smooth without any unevenness. The weld seam and the base metal should have a smooth transition, and no concave phenomenon is allowed.
4. According to various equipment, pipelines, structural parts, and usage environments, the contained medium and pressure level requirements are different, and the welding technology requirements are different.
1) Welding technical purposes and requirements:
1. Master the definition, classification, advantages, and disadvantages of welding.
2. Master the safety technical measures to prevent electric shock and prevent fire, explosion, poisoning, radiation, and special environment welding.
3. Understand the importance of safe welding production and welding labor protection measures.
4. Understand the development and application of welding technology at home and abroad.
2) Contents of welding technology
1) Welding method: A) Protected state; B) Unprotected state; C) Vacuum state; D) Water state, etc.;
2) Welding equipment: A) arc welding machine; B) resistance welding machine; C) spot welding machine; D) black welding machine; E) explosion welding machine; F) bimetal composite diffusion (metallurgy) welding machine, etc.;
3) Welding control: A) Automatic welding control; B) Computer welding control; C) Profile welding control, etc.
Post time: Dec-21-2023