Steel pipe flange , carbon steel flange , lap joint flange , ASME flange

Lap Joint Pipe Flanges Definition:

A lap joint flange (loose flange) consist two parts,the backing flange and the stud end, the stub end will be butt welded to the pipe,and the lap joint flange will be slip around the stub end.The lap joint flange is not connected to the pipe and stub end directly,so it could be rotated,it is convenient to install the flange connection if there is some misalignment between the bolt holes.

Material of a Lap Joing Flange:

The stub end and lap joint flange is separated,so they could be different material grade,it is very common that a carbon steel lap joint flange work together with a stainless steel stub end.The butt weld end of the stub-end is like the neck of the weld neck flange,the diameter and thickness is according to the pipe for connection.So the material of backing flange in a lap joing flange could be carbon steel commonly for lower cost,the material of stub end could be chosen as per the pipe material and fuild situation.

Sealing Face of Lap Joint Flange:

For other type of flanges like weld neck flange or slip on flange,they could be raised face or flat face or other type of sealing face.But the lap joint flange (Loose flange) only have a flat face,the stub end face is the sealing face in the two lap joint flanges connections,so the stub end should have a same dimensions with the raised face standard.