How can one know whether stub-in/stub-out or fitting connection is required or not for branch connection & in fitting type whether one should go with Tee or o’let?
Stub-out is not a correct term, this should be stub-on.
Functionally if you are the piping layout designer doing piping layout then you use the information supplied on the “Branch Selection Tables” provided by the Piping Material Engineer (PME) in the Line Class specs.
Functionally if you are the PME developing the “Branch Selection Table” for the Line Class Specs than it is a different role and the answer is different and longer.
As the PME developing the “Branch Selection Table” you need to know:
- The commodity
- The pressure (Design & Operating)
- The temperature (Design & Operating)
- Corrosion allowance
- Along with all the other data used to select the line class base material
Then you make “If – Then” judgment calls based on good engineering practice and economics. For example, assume a Header size of 8”, 10” or 12” (200mm, 250mm or 300mm):
- If – the commodity is Cooling Water at low temperature and low pressure and the branch is size to size – Then you should use a TEE
- If – the commodity is Cooling Water at low temperature and low pressure and the branch is size to one size smaller – Then you should use a Reducing TEE
- If – the commodity is Cooling Water at low temperature and low pressure and the branch is size to two or more sizes smaller – Then you should use a Stub-In (or Stub-On)
- If – the commodity is Hydrocarbon at very high temperature and high pressure and the branch is size to size – Then you should use a TEE
- If – the commodity is Hydrocarbon at very high temperature and high pressure and the branch is size to one size smaller – Then you should use a Reducing TEE
- If – the commodity is Hydrocarbon at very high temperature and high pressure and the branch is size to two or more sizes smaller – Then you should use a Weld-O-Let
Each and every branch situation expected on the job should be considered and the proper calculations run to verify and document the basis of the selection.
This text is an extract from questions gathered from numerous queries of anonymous people in the Piping Engineering and Design profession. The answers or discussion of the topics were provided by James O. Pennock. Images obtained from www.coastalflange.com
