What to do if the material surface is mechanically damaged during the manufacturing of pressure vessels?

Thread Content

What are the requirements for the material surface during the manufacturing of pressure vessels? What should be done if the surface of the material is mechanically damaged? Surface requirements for materials used in pressure vessels: HG/T 20584-2020, \"Technical Specifications for the Manufacturing of Steel Chemical Vessels\", stipulates that the surface quality of steel plates used for pressure-bearing components as well as those used after the vessels are manufactured must meet the following requirements: (1) The surface of the steel plates may have local defects such as scratches, rolling marks, pitting, and roughness resulting from the removal of oxide scale, provided that the depth of these defects does not exceed half of the negative deviation from the specified thickness; furthermore, the thickness of the steel plate at these defective areas must not be less than its allowable minimum thickness. (2) Defects with a depth exceeding those specified in Paragraph 1, as well as any tearing, bubbles, cracks, scars, folds, embedded scale, inclusions, weld marks, cratering, spatter, etc., shall be removed by grinding. The area to be cleaned and polished should not exceed 30% of the steel plate’s surface area. The pits resulting from polishing should blend smoothly with the base material, with a slope of no more than 1:3. (3) After grinding, if the remaining thickness is not less than its allowable minimum thickness, and the grinding depth is not more than 5% of the nominal thickness or 2 mm (whichever is smaller), welding repair is not required. If the grinding depth is deep, but the remaining thickness still meets the above requirements, it should be resolved through consultation with the designer. What to do if the surface of the material is mechanically damaged? 1. HG/T 20584-2020 \"Technical Specifications for the Manufacturing of Steel Chemical Containers\" stipulates that defects beyond those mentioned in paragraphs (1) to (3) above shall be repaired by welding, but the area and depth that can be repaired must comply with the following requirements: (1) For carbon steel and C-Mn steel, the area of any single repair shall not exceed 200 cm2, while the total repair area shall not exceed 600 cm2, or 3% of the side area of the steel plate that has been ground (whichever is smaller) ； (2) Low-alloy high-strength steel and Cr-Mo steel: The area of a single repair shall not exceed 100 cm2, the total area shall be less than or equal to 300 cm2, or 2% of the area of the side of the steel plate that has been ground (whichever is smaller) ； (3) The depth permitted for welding repair should not exceed 1/5 of the plate thickness ； (4) When the delamination length at the edge of the steel plate is not greater than 25 mm, repair or removal may be omitted ； Striations with a length greater than 25 mm and a depth greater than 1.5 mm should be polished away. When the grinding depth is no more than 3 mm, welding repair is not required; otherwise, it should be repaired by welding before use. In the same plane, layers with a spacing not exceeding 5% of the plate thickness shall be considered as a continuous layer length. 2. The sections on manufacturing, inspection, and acceptance in GB/T 150-2011 \"Pressure Vessels\" stipulate that: (1) Mechanical damage to the material surface should be avoided during manufacturing. Sharp scars, as well as local defects such as scratches and grooves on the corrosion-resistant surface of stainless steel containers, should be polished, with a maximum polishing slope of 1:3. The grinding depth shall not exceed 5% of the steel thickness δs at that location, nor more than 2 mm; otherwise, repair welding shall be performed. (2) For the formed parts, surfacing parts, and metal lining layers of composite steel plates, the grinding depth shall not exceed 30% of the thickness of the coating (or surfacing layer, lining), nor more than 1 mm; otherwise, repair welding shall be carried out. When mechanical damage occurs on the material surface during the manufacturing process, one can refer to the requirements outlined in the aforementioned specifications to address it.