There are two methods for making a fabricated branch connection from the pipe,they are stub-in and stub-on.Both types are allowed by many international codes and standards,such as ASME B31. Because both connections are weak in piping systems,they are limited only for low pressure and low temperature applications.

In a sense, both stub-in and stub-on connections reduce the cost of fittings.They also save installation time because it only needs to be welded around the stub hole instead of three welds that is needed for joining welding tee connections.

What is stub-in?

Stub-ins can replace a reducing tee in joining branch pipes.Drill a hole of the same diameter as the stub-in pipe on the main pipe and assemble the two pipes together.Then welded the stub-in pipe and the main pipe together.The stub-in is usually used when the branch is more than one size smaller than the main pipe.The stub-in connection avoids the cost of buying fittings and saves installation time because it requires welding only once around the stub hole instead of three times around the two connections to the main pipe and joints.

Stub-on connection

What is stub-on?

Stub-on connection is the opposite of the stub-in connection,the hole cut in the running pipe has the same inside diameter (ID) as the branch pipe (not header).

The end profile of the branch tube is the same as the outer diameter (OD) of the header pipe and is then installed outside the hole of the header pipe.The branch appears to be on the head tube.When the length of the branch pipe is equal to or less than one size of the main pipe,stub-in is generally used.For “stub on”, the stub extends only to the outside of the main pipe.

The welding strength of the stub-in connection is as good as butt welding, but the welding procedure is difficult under actual conditions.Stub-in is comparatively stronger than stub on connections.

Haihao Group is experienced in kinds of welding piping products,welcome to contact us for related enquiry.Email:sales@haihaogroup.com