Butt weld tees are used to branch a pipeline at 90 degrees. There are two types of butt weld tees:


For equal tees (otherwise called "straoght tees"), the diameter of the run (tee inlet) and the branch pipe (tee outlet) correspond

Carbon steel equal tee ASME B16.9


For reducing tees, the diameter of the branched pipe is smaller (generally of 2 / 3 sizes maximium) than the diameter of the run pipe. If the branched pipe size has a remarkably lower diameter than the run pipe, a branch connection shall be used instead of a reducing tee.

Carbon steel reducing tee ASME B16.9

The dimensions and the tolerances of butt weld carbon steel / alloy steel straight and reducing tees are set by the ASME B16.19 norm. ASME B16.9 and MSS SP 43 define instead the sizes of butt weld tees in stainless steel and nickel alloys.  

To order a tee, buyers shall indicate the following parameters:

  • Type of tee (equal tee / reducing tee)
  • Dimensions of the run / branched pipe (d1 x d2 x d3, where d1 x d2 = inlets of the run pipe, d3 = tee outlet to the branched pipe)
  • Fitting schedule
  • Construction norm (ASME B16.9 / MSS SP 43)
  • Material grade (ASTM A234, A403, etc)
  • Number of units


Butt weld crossed are used to create two branches from the run pipe. Steel crosses are used way less than all the other butt weld fittings for petrochemical applications and oil & gas pipelines.

Carbon steel cross ASME B16.9



Looking for additional info? Contact the pipingonline expert team

Useful links: ANSI | ASME | ASTM | API | MSS | BS | DIN | ISO