Thickness issue of the straight flange edge section
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The thickness of the straight edge section of the equipment connection flange, which should be 16 mm for pressures of 250–6.3 MPa, has now been made to 6 mm. How can this flange be used? Can it be surfaced to 16, or can the straightness issue be resolved by butting it directly against the pipe fitting? I seek advice from those who are more knowledgeable. This post was last edited by xbxmys on 2009-4-5 at 18:17.]
How could this happen? Straight edge section 16, while the adapter is only 6? A lot of trimming is needed, at least 30. It would be best to see if it’s possible to put it on a lathe and machine it again.
This is a high-pressure flange; it’s best not to use it, but it can be downgraded for use in other sections. If your operating pressure is higher than 6. 3MPa is one level lower, for example 2. Below 5 MPa, the method of removing the straight edge section and performing butt welding with the pipeline can be used. The quality of this weld must be strictly ensured.
If it’s WN, the flange is unusable, as the thickness of the straight edges of the flange needs to match that of the pipe. A 16mm 273 pipe should correspond to an XS size; a 6mm pipe obviously won’t work, and even on a lathe, the thickness can only be reduced further. So it’s basically scrapped. The reasons are as follows: 1. For pipes with a diameter of Φ273, when the pressure exceeds 4.0 Mpa, it is basically impossible to use materials with a wall thickness of around 6 mm (Sch20). Under normal circumstances, the difference in thickness between the two occurs when the flange is larger and the pipe is smaller; flanges are usually machined, and it is rare to see edge trimming done on butt pipes. (Unless it is a thick-walled pipe under high pressure) 2. Use it at a lower grade – where can you find a matching flange? :lol
It is recommended to scrap it and return the standard parts to the flange manufacturer for remanufacturing; there will be no loss in doing so. If modifications are made, it will become a non-standard flange. A flange with a diameter of 250 is a key pressure-bearing component, and there is no need to take risks using it on containers!
The thickness of the straight edge section of the flange is 6 mm; I’m not sure what standard the original poster used as a reference. In other words, it determines whether the outer diameter of 273 is to be guaranteed or the inner diameter. If the inner diameter is to be guaranteed, it means that the strength of the flange is still sufficient; in this case, you can machine off the straight sections and weld the pipe directly to the tapered section of the flange. In this case, the axial force acting on the flange will act directly on the weld; although the stress effect is somewhat reduced, it is still acceptable. Otherwise, it is scrapped.
Those of WN can be taken to a lathe to be turned into SO format and kept for future use
The straight edge section can be thinned after surfacing, and it can then be used; this is equivalent to widening the weld groove. It has little impact on the stress experienced by the flange, but the straight edge section cannot be removed and welded directly to the pipe, as that area will be subjected to the forces and moments transmitted by the flange. Generally, the material used for surfacing is of better quality than the base material, which can cause some internal stresses; however, by carrying out proper inspections and heat treatment, there should be no major problems.
Changing 16mm to 6mm – it definitely can’t be used anymore; it should be scrapped. Perhaps it could be used elsewhere in a low-pressure application
Thank you all for your advice. It has been scrapped. I’m not sure how to mark this post as resolved; please ask the moderator for help