BS 1873 or ASME B 16.34;
2.Material pressure -- temp standard:
ASME B16.34;
3.End to end dimension standard:
ASME B 16.10;
4.Flange ends dimensioin standard:
CLASS B 16.5(NPS≤24°)
ASME B 16.47(NPS>24°)
5.Inspection and test standard: API 598