Welding of pipes with different wall thicknesses
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Can pipes with different wall thicknesses be welded? For a DN200 pipe where one section is 207 and the other is 211, will it meet the requirements after welding? This post was last edited by chping80 on 2008-12-11 10:02.]
The inner end of the pipe should be chamfered; refer to GB50236 for details. However, the chamfered pipe must not have any burrs or grooves resulting from the machining process, otherwise it will not pass the non-destructive testing, as false dark marks indicating unmelted areas will appear
Welding is possible; our factory has one example of this. Due to the use of different standards, the outer diameter of the pipes varies, and it’s not clear exactly how welding should be carried out.
Solution: 1. If the wall thicknesses differ by not much, polish the inner wall slightly before welding. 2. If the wall thicknesses differ significantly, fabricate flanges for each section of the pipe separately, and connect them together using flanges after welding
For pipes with thicker walls, it’s sufficient to chamfer them; and since you mentioned that the inner diameters are the same, this will not affect flaw detection
It's sufficient to ensure consistent inner diameters. Round off inconsistent inner diameters.
Take a look at the **standards for pipe welding**; generally, variations in the outer diameter of pipes mainly affect the effective wall thickness after welding. Whether it is an internal crack or an external crack, the process requires a smooth transition. However, if its effective wall thickness after welding does not meet the system’s requirements, it cannot be used even if welding is possible.
Alignment can be achieved through transition welds, but the key is that the wall thickness after the transition must not be lower than the designed wall thickness of the pipeline; otherwise, a transition pipe needs to be fabricated to achieve alignment. This is very crucial!
Are there any standards in this regard?
For welding pipes (or welded components) with varying wall thicknesses, refer to the following standard: GB50236-98 \"Code for Construction and Acceptance of Welding Works for Field Equipment and Industrial Pipelines\"； SH3501 \"Code for Construction and Acceptance of Pipelines for Highly Toxic and Flammable Media in Petrochemical Industries\" ； CJJ28-2004 \"Code for Construction and Acceptance of Urban Heating Pipeline Networks\" ； DL/T869-2004 \"Code for Welding Techniques in Thermal Power Plants\".
For welding pipes (or welded components) with varying wall thicknesses, refer to the following standard: GB50236-98 \"Code for Construction and Acceptance of Welding Works for Field Equipment and Industrial Pipelines\"； SH3501 \"Code for Construction and Acceptance of Pipelines for Highly Toxic and Flammable Media in Petrochemical Industries\" ； CJJ28-2004 \"Code for Construction and Acceptance of Urban Heating Pipeline Networks\" ； DL/T869-2004 \"Code for Welding Techniques in Thermal Power Plants\".