STD 150LB 100NB RFSO FLANGE is what flange, preferably with detailed dimensions and reference materials
RF convex, SOFlage hubbed flange, 100NB=4 is the name of the pipe diameter and the 150LB pressure rating, STD should be the pipe wall thickness. For specific dimensions, refer to the ANSI B16.5 flange standard
American Standard, DN100, is 4, 150 pounds of pressure, flange type SO. Standard number B16.5, check what data is out.
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