Stub ends used with lap joint flanges where frequent dismantling is needed, or where the flange material needs to differ from the pipe material. Type A and Type B in all grades. MSS SP-43 and ASME B16.9.
A stub end (also called a lap joint stub end) is a short fitting welded to the pipe, with a back face that provides a sealing surface against a lap joint flange. The flange slides over the pipe and rests against the stub end face.
The biggest advantage: the stub end can be an expensive alloy (SS 316L, Duplex) while the flange can be cheap carbon steel — since the flange never contacts the process fluid. Huge cost saving on high-alloy systems.
Lap joint assemblies are easy to rotate and align during installation. The flange is free to rotate around the pipe — bolt holes always align easily. Ideal for systems that require frequent maintenance access.
Type A has a radius at the back face (smoother transition, preferred for most applications). Type B has a flat back face. Type A is the more common choice and what we stock as standard.
Has a full radius (fillet) at the junction of the lap and pipe OD. The radius ensures smooth flow transition and reduces stress concentration. Standard supply for most applications — stainless steel, duplex, alloy, and carbon steel.
Has a square (flat) back face at the lap junction — no radius. Simpler to manufacture. Used in lighter-duty applications and where the Type A radius is not required by the design code. Less common than Type A.
Send type (A or B), grade, size, schedule, quantity. We respond within 4 hours with pricing and availability.