How big valves and fittings need flange installation, such as gate valves, DN50, DN80 and the like?.
Specifically, look at the pressure of the pipeline, the environment is not big, if large with flange connection, usually hoop or wire can be connected.
According to user requirements, DN15 also has flanges, in general, DN50 or more are flanges
See, you choose 100 of the pressure is not high, you can not flange
Flanges for piping above DN50,DN50 (below) can be made of wire or flange (flange for pressure piping)