The Stub-In & its Reinforcements

The stub-in is most commonly used as an alternative to the reducing tee.
The stub-in is not an actual fitting but rather a description of how the branch connection is created.
A hole is bored into the header pipe, either the size of the OD or ID of the branch, and the branch is then stubbed into it.

There should be a minimum 3" between welds.

Stub-in Reinforcements :

• Use of the stub-in is limited by the pressure, temperature, and commodity within a pipe
• Cost of purchasing a fitting be avoided, but the stub-in requires only one weld
• Special reinforcement may be necessary to prevent the branch from separating from the header
• Three reinforcing alternatives are:

1.  Reinforcing pad
2.  Welding saddle
3.  O-lets

1) Reinforcing Pad :

The reinforcing pad is a ring cut from steel plate that has a hole in the center equal to the diameter of the branch connection. It is slipped onto the branch pipe then welded to both branch and header.

2) Welding Saddle :

Welding saddle has a short neck designed to give additional support to the branch.

3) Olets :

Olets have one end shaped to the contour of the header and the other end manufactured to accept the type of end connections being used on the branch.

• For branch connections, where standard tee is not available and direct pipe to pipe connection is not allowed due to criticality of the service conditions ,olets are used .Major types of olets being used are 

  Weldolet :- Used for butt welded branch connections

  Sockolet  :- Used for socket welded branch connections

  Threadolet :- Used for threaded branch connection

  Elbowlet  :-  Used for branch connection on elbows .

  Sweepolet  :-  Used for branch connection at an angle. It is also called as Latrolet