What does this mean in the flange, Pg10Dg50?
Pg10 is the abbreviation of the Pressure Grade pressure level. The common expression is PN10Kg;Dg represents nominal diameter and is often used as a means of DN50;General flange standard does not mean so.
Now generally PN10.0 DN50 nominal pressure 10
10 pressure, 50 way diameter, is only a specification, specific you are what standards need to know.