If the wall thickness of stainless steel pipe fittings differs by 3 millimeters and the manufacturer has created an internal bevel, what should be done if defects are detected during inspection?
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Workers have reported that if the inner groove is not polished smoothly, issues such as undercutting, voids, and areas that fail to fuse can occur, resulting in rejected samples. Does any expert have a solution?
It is ground by the manufacturer themselves; if an internal groove is not created, steps will appear after welding, and the inspection via X-rays will result in failure to meet the standards.
We are an EPC company and handle the procurement ourselves.
Use a straight pipe to extend the elbow, and then machine the straight pipe to have an equal wall thickness
150 pipe, elbow wall thickness 4mm； There is still a 3 mm difference with the pipe; is the wall thickness of your pipe only 2 mm? If that’s the case, then why purchase elbows with such a thick wall? Generally, the thickness of pipe fittings is equal to that of the pipe itself. If thickening is required, according to the appendix of GB/T12459, it can at most reach 1.25 times the wall thickness.
No welding inspection issues will arise as long as the elbow and the inner diameter of the pipe are the same. The inner groove can be ground, but the designed wall thickness must be maintained.
Just return it directly and choose another one; what solution is there to think about?
This post was last edited by niat8888 on 2022-3-15 08:34. The problems that arise from this RT are mainly caused by excessive excess height of the internal welds, misalignment of the inner walls, uneven thickness of the inner walls, as well as improper ellipticity of the pipe fittings and angle of the internal bevels. When a sharp angle is formed between the weld and the bevel groove, it will result in a dark shadow of a groove appearing on the film. Causes and countermeasures: 1. For fitting components, standards and practices are such that the outer diameter serves as the reference; when the material thickness increases, the inclination angle of the inner bevel is determined by the standard ratio of 1:3, meaning the inner bevel angle A is 18°. Countermeasure: When the nominal inner diameter (outer diameter – 2 * nominal wall thickness) is kept consistent, it is necessary to ensure that the inner bevel angle A of the fitting components is as small as possible. For example, 14° is required. 2. The inner diameter tolerances of all fittings are too loose. Countermeasures: Require control of the inner diameter tolerance, require control of the inner diameter ellipticity tolerance, and require control of the T2 thickening tolerance. 3. During welding alignment, all the parts were aligned as if they were machined parts, without any additional bevel trimming. Solution: During alignment, the pipe fitter adjusts the inner diameter accordingly based on the dimensions of the pipes and fittings. This is a necessary process. Otherwise, why should plumbers be paid the same as welders? 4. The welding technique is not up to standard. Solution: Try to use TIG welding for the root pass, and control the remaining height on the inner wall.
There are definitely manufacturers that can produce qualified products, unless you set the purchase price too low.