my country's national standard system (GB) for steel pipe flanges accommodates both the European and American systems. Within the GB standards, the maximum nominal pressure rating for flanges belonging to the European system is 4 MPa, whereas the maximum for those belonging to the American system is 42 MPa. For instance, the six flange pressure ratings of PN0.25, PN0.6, PN1.0, PN1.6, PN2.5, and PN4.0 belong to the European flange system (typified by German standards), while the remaining ratings belong to the American flange system (typified by American standards).
National Standards (GB): GB/T9112-2010 (GB9113.1-2010 to GB9123.4-2010)
Chemical Industry Standards (HG): HG5010-52 to HG5028-58, HGJ44-91 to HGJ65-91, HG20592-2009 series, HG20615-2009 series
Machinery Industry Standards (JB): JB81-59 to JB86-59, JB/T79-94 to JB/T86-94, JB/T74-1994
Pressure Vessel Standards: JB1157-82 to JB1160-82, NB/T47020-2012 to NB/T47027-2012, B16.47A/B, B16.39, B16.
