Questions about HG20615 flanges? ? ? ? ?

79 is the dimension of the large end N of the flange neck; the data obtained from the software is incorrect

Thank you. Then how is the inner diameter determined? For example, my material requirement is 316; the stress required at 350 degrees is 84 MPa, and the design pressure is 20 MPa. If calculated using SCH, the value would be 238, but there is no such standard as SCH238 – so it is rounded up to SCH240

I’ve never used one this thick, so I’m not sure

Why is the inner diameter of the flange larger than the outer diameter of the pipe? ? For this type of flange, which is generally a butt-welding flange, the pipe needs to be inserted into the flange holes and welded there; therefore, the inner diameter of the flange must be larger than the outer diameter of the pipe, otherwise it cannot be inserted. For butt-welded flanges, the pipe and the flange face are welded directly to each other without any need to insert anything in between; as a result, the inner diameter of the flange is smaller than the outer diameter of the pipe. One of the pictures sent by the original poster shows a flange with a neck, and the dimension A corresponds to the outer diameter of the pipe being connected. Speaking of A and B, A is the internationally standard series, commonly known as imperial pipes, while B is the series used in China, commonly known as metric pipes.

For HG/T20615 flanges, the piping used is of Series A type; there is no Series B type.

The A and B I’m referring to are the inner and outer diameters of the straight flange edges, not the A/B series. Thanks anyway. I have another question: if the design pressure is 20 MPa and the allowable stress of the steel pipe at 350 degrees is 84 MPa, then the calculated SCH grade far exceeds this value. How should one determine such a grade?

I think there’s an error in your calculation.