Specification :

blind flange
BLIND FLANGES are used to blank off the ends of piping, valves and pressure vessel opening. From the standpoint of internal pressure and bolt loading, blind flanges, particularly in the larger sizes, are the most highly stressed of all flange types; however, since the maximum stresses in a blind flange are bending stresses at the center, they can safely be permitted to be higher than in other types of flanges