Lap Joint Flanges have all the same common dimensions as any other flange named on this page however it does not have a raised face, they used in conjunction with a "Lap Joint Stub End".

These flanges are nearly identical to a Slip-On flange with the exception of a radius at the intersection of the flange face and the bore to accommodate the flanged portion of the Stub End.

Their pressure-holding ability is little, if any, better than that of Slip-On flanges and the fatigue life for the assembly is only one-tenth that of Welding Neck flanges.

They may be used at all pressures and are available in a full-size range. These flanges slip over the pipe and are not welded or otherwise fastened to it. Bolting pressure is transmitted to the gasket by the pressure of the flange against the back of the pipe lap (Stub End).

Lap Joint flanges have certain special advantages:

#1 Freedom to swivel around the pipe facilitates the lining up of opposing flange bolt holes.

#2 Lack of contact with the fluid in the pipe often permits the use of inexpensive carbon steel flanges with the corrosion-resistant pipe.

#3 In systems which erode or corrode quickly, the flanges may be salvaged for re-use.