I am being asked a question, and I don’t know the answer. I am posting it here and appreciate responses from the forum members.

The lapped flanges are used in companion with the stub ends. My engineer received a batch of flanges without their ‘hubs’. His question is, why the lapped flanges need hubs, what are their purposes. I can only say those flanges must meet ASME B16.5, which dictates the flange and hub dimensions. I guess my answer was not a real answer, did not help him much. Any one help me out please.