How is the size of the connection pipe selected for a pressure vessel based on the flange?
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When designing pressure vessels, the flange model is usually specified, and the pipes are selected through calculations based on that flange. However, I’m not quite sure how to determine the exact dimensions of the pipes Should it be based on the inner diameter of the flange or the thickness of the flange neck?
The takeover size is specified by the process, not calculated by the equipment; it is given in DN form, and there’s no need to consider inner or outer diameters
Based on the flange model used for pairing pressure vessels, simply select the appropriate pipe flange; they are all standard components, so there is no need to design them or determine their inner and outer diameters.
The pipe flange standards specify the outer diameter of the pipes that fit with each nominal diameter of flange (some are divided into Series A and B; it is advisable to check with the relevant professionals to see if there are any specific requirements). You should determine the outer diameter of the pipe to be connected to the flange based on its nominal diameter, and calculate the required wall thickness for that pipe. The inner diameter of the flange can generally be set to match the inner diameter of the pipe. If the upstream discipline specifies the wall thickness or wall thickness class for the corresponding pipeline, the fittings on your equipment can have a wall thickness that is the same as or similar to that of the corresponding pipeline. It is then necessary to check whether such wall thickness is sufficient; generally, we choose a wall thickness for the equipment fittings that is close to that of the pipeline fittings, though this is not mandatory.
Aren’t the nozzles connected to the flanges on the equipment the result of design calculations?
I want to know how to choose the size of the pipe fitting to be connected to this flange on the equipment, based on the flange specified in the process specifications
Do you mean the outer diameter of the pipe fitting? Or wall thickness? The outer diameter of steel pipes is standard; the wall thickness needs to be determined based on factors such as internal pressure, reinforcement required for openings, and external loads. I suggest using the wall thickness of the connected pipelines as a reference to ensure that the flow rate at the opening is similar to that in the pipeline – though this factor can also be ignored.
I am very grateful for your patient answers. Do you think my approach is correct? During the design process, specifications for flanges are provided; we determine the outer diameter of the pipe fitting based on the outer diameter of the flange, and then calculate the wall thickness of the pipe fitting as well as the wall thickness of the flange to ensure sufficient strength. Another scenario is when the process specifies flanges with matching flanges; generally, the thickness of these matching flanges is given, and we then choose the thickness and outer diameter of the pipe fittings based on that thickness of the matching flanges, that is, their inner diameter. I’m not sure if my understanding is correct – thank you.
Yes, if the process specifications specify the wall thickness for the flanged connections, you can use that thickness to check whether the reinforcement on the equipment’s connections is sufficient; if it is, you can choose the same wall thickness.
Thank you very much for your patient answers.