Issues related to the calculation of RJ flanges for non-standard equipment
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This post was last edited by guoshu258 on 2024-2-2 at 11:48. Input conditions: design pressure of 15 MPa, design temperature of 50°C. It is a valve that is connected via flanges; the dimensions of the seals and fasteners have been determined and cannot be adjusted. The flange size is a standard WN300(B)-160RJS=24 flange in accordance with HG/T20592-2009; the gasket used is an octagonal gasket of type 300-160, as specified in HG/T20612-2009. The material of the cylinder is 20III (NB/T 47008), with a corrosion allowance of 2 mm. If the pressure and temperature values for the flange exceed the specified limits, calculations are required. Are the values entered below correct? Flange outer diameter Do: 585 Flange inner diameter Di: 281 (after deducting the corrosion allowance) Effective flange thickness: 76 (Should the corrosion allowance for the seal groove also be deducted?) Cone neck height h: 87.6 (or 79?) ) Effective thickness at the larger end of the neck, g1: 59.5; effective thickness at the smaller end of the neck, g0: 18 (should this be the smaller value between the thickness of the cylinder and that of the flange end?). Inner diameter at the point where the gasket makes contact with the sealing surface, D1: 359 (for elliptical gaskets, is this the diameter at the contact surface?) ) Outer diameter D2 at the contact point between the gasket and the sealing surface: 401 (Is this the contact area for elliptical gaskets?) ) Contact surface width w: 21 (is it at the widest or narrowest point?) Is the elliptical pad the contact surface? ) Other questions: Non-standard flanges are designed and calculated in accordance with GB/T150.3 – is it necessary to follow the corresponding provisions of GB150.3 as well? 1. When the standard flange dimensions do not meet the LA/Le value criteria specified in Article 7.5.2.1 of GB/T150.3, is it necessary to adjust the standard flange dimensions? For M39 bolts, refer to HG/T 20583 – clause 4.5.8; the minimum value for LA is 52, while in this diagram it is 502. According to figure e of clause 7.4.4 in GB/T150.3, when the taper angle is greater than 1:3, the length of the straight section must be 1.5δ0 or more; the value of 18 mm in this diagram does not meet this requirement. Is it necessary to increase this length to 30 mm? 3. According to Article C.6.3 of GB/T150.3, the material for octagonal gaskets should be of grade III or IV forged material, with a hardness that is 30HBW to 40HBW lower than that of the material used for the ring groove components. The material with the lowest hardness listed in Table C.8 is carbon steel per NB/T 47008; after heat treatment of the flanges, the hardness difference cannot reach 30HBW. Can steel of grade 10 (GB/T699) as specified in HG/T20612 be used instead?
1. If the standard flange dimensions do not meet the LA/Le values specified in Article 7.5.2.1 of GB/T150.3, the flange dimensions need to be adjusted to satisfy the required specifications. 2. For cases where the cone angle slope in Figure e of GB/T150.3 7.4.4 is greater than 1:3, the length of the straight section indeed needs to be greater than or equal to 1.5δ0; if 18 mm does not meet this requirement in this figure, it needs to be increased to at least 30 mm. 3. The material for the octagonal gasket must be of grade III or IV forgings, with a hardness 30HBW~40HBW lower than that of the ring groove component material. If, after heat treatment of the flange, the hardness difference of carbon steel does not meet the requirement of 30, it is possible to consider using a material with lower hardness. Steel No. 10 specified in HG/T20612 (Q235 steel per GB/T699) is a conventional material choice that can be used if it meets the hardness requirements and other performance specifications. .
Thank you for the answer. Could you please check again whether the size values in the image are correct? As for other issues, the main point is whether, in the case of non-standard calculations, it is necessary to strictly adhere to the provisions of GB150; moreover, GB150 states that \"selection can be made according to Table 7-3\", and \"forgings of grade III or IV are recommended\". Because at the current size, the flange calculation passes. It feels a bit reluctant to change a fully standard-sized flange to a non-standard one.
This post was last edited by plt on 2024-2-2 09:27. Why not design custom flanges? Additionally, HG20612 is a standard for pipe flanges, not for containers. There is a type of heat treatment called heat treatment for restoring the mechanical properties of materials.
There is no No. 10 steel in the forged material; it’s NB47008
This post was last edited by wanlirn on 2024-2-2 at 11:38. I don’t understand it – you can just use the standard flange you selected
The pressure and temperature values are out of range; it cannot be used directly
So this is the dilemma: the material hardness requirements specified in GB150 cannot be met, and the materials mentioned in HG/T20612 are not referenced in GB150. The equipment itself requires post-weld heat treatment, but no performance-restoring heat treatment is needed. If it is necessary to create a gap, heat treatment to improve the mechanical properties of the materials can be used to harden the sealing surface, but this significantly increases manufacturing costs, making it uneconomical.
This post was last edited by plt on 2024-2-2 at 15:16. OP, have you mixed things up? This is not a container flange but a container nozzle flange; you can simply choose the HG/T20592 pipe flange. Even for containers, HG/T20592 can be directly selected; refer to Chapter 4 of the six standards HG/T20583-2020 issued by the Ministry of Chemical Industry. This standard meets GB150 by default. Additionally, Appendix C of GB150 is an informational appendix, not a regulatory one.
There’s no confusion here; it is used on the container body, and even at the pipe outlet, 20III belongs to the 1C4 material category. According to the pressure-temperature ratings in page P32 of HG/T20592, a pressure of 14.4 MPa is the maximum allowable at 50°C, which does not meet the required design pressure of 15 MPa.
I checked a few main dimensions; it seems to be a standard flange? For non-standard flanges: First, the standards are only recommendations; the SW6 calculations are meant to serve as a guide only, not as mandatory requirements. Of course, as long as the installation is proper, it’s fine (refer to the flange standards – such an installation is acceptable). Second, it’s better to use a standard of 150. Third, I recommend following HG20612; a standard lower than that of the flanges will suffice. As for the requirement of 30-40, I’m not sure where it comes from; I think specialized standards like those for flanges are more professional