What to do if the desired diameter is not available for the corresponding pressure rating in standard HG/T47021?
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This post was last edited by 311yj on 2023-4-24 at 18:57. What to do if there is no desired diameter for the corresponding pressure grade in standard HG/T47021? For example, if my equipment requires a type A flat welding flange with a DN700 size and a design pressure of over 1 MPa, then there is no other choice but to use a flange with a pressure rating of 1.6 MPa; however, flanges with a 1.6 MPa rating are available only in DN650 sizes, not in DN700 sizes. What should I do? Is it by using a DN700 flange at 1.0 MPa, increasing the effective thickness of the flange, and using SW6 software to verify that it meets the requirements? Should we still choose the HG/T47023 1.6MPa long-neck butt weld flange? However, for the 1.6MPa DN700 long-neck butt-welded flange, the minimum thickness of the butt joint cylinder section is required to be 10 mm, while the thickness of the equipment cylinder itself is only 6 mm. Should a 10-mm short section be added and joined to this 6-mm thick cylinder?
If the desired diameter is not available for the corresponding pressure class under standard HG/T47021, the following solutions can be considered: 1. Design a custom flange and use software for calculations. It should be noted, however, that the design of non-standard flanges must meet relevant standards and safety requirements, and they must be able to withstand factors such as the operating pressure and temperature of the equipment. 2. Select a long-neck butt-welded flange according to HG/T47023 with a pressure rating of 1.6 MPa, choosing a value slightly lower than the design pressure; however, attention should be paid to the thickness of the cylinder. If the thickness of the equipment shell is only 6 mm, using a 10-mm stub to join it to the shell may pose a risk of insufficient joint strength. At this point, it is necessary to redesign the thickness of the cylinder or adopt other feasible solutions. Regardless of the approach chosen, thorough calculations and experimental verification are required to ensure the safe and stable operation of the equipment. It is also necessary to comply with relevant standards and regulations to ensure that the equipment meets safety requirements. .
A long-neck butt weld flange can be used, and then the edges can be trimmed； A non-standard flange can also be made.
The answer on the 2nd floor is quite comprehensive. In fact, it can be summed up in one sentence: those standards that exist can be used directly, while for those that don’t exist, one has to design something non-standard