650 how big flanges and valves are used in the pipe?
You mean the inner diameter of the pipe is 650, then the butterfly valve or other valves and flanges are 650. If you have any further questions, you can continue to ask questions
I do not know what kind of valve you want to choose, the pipe pressure is not clear, DN650 valves only non-standard, flange and valve matching, size can refer to standard: HG/T20623-2009 "large-diameter steel pipe flange."
The inner diameter is the nonstandard part of DN650. To be more specific, this is really hard to say. I've also done 550 flanged valves
