Benefit of Lap Joint Flanges

The lap joint flange is another important member of flanges and is similar to a slip-on flange. It has a radius at the intersection of the bore and flange face. This radius is imperative to have the flange accommodate a lap joint stub end. The stub end is mated with the lap joint flange and used together in piping systems.  

are used with a corresponding stub-end that "inserts" in the inside of the flange.  The main benefit of this type of flange is that once the pipe welds to the insert stub-end, the flange then can rotate for easier alignment of the bolting holes.  However, lap joint flanges and their stub-ends' ability to hold pressure is about the same as slip-on flanges.  They are not suitable for situations with a high external or changing load of force.  They do provide an advantage in a piping system that needs frequent dismantling for inspection or to remove build-ups.  If high pressure applications are being performed, either a swivel ring flange or an insert flange is recommended to be used instead of a lap joint flange a stub-end.