Branch fittings (O’lets)

Branch fittings (O’lets)

Branch fittings are fittings which provide an outlet from one pipe to a larger one, or of the same size. This fitting, also known as ‘branch connection’ is welded on the main pipe which is usually called the run- or header pipe. The branch or outlet pipe is the pipe to which the branch connection provides a channel. A run pipe having a branch connection is weakened by the opening made in it. The branch connection must reinforce the opening and restore the original strength of the run pipe.


The most common of all branch connections is the Weldolet® which is designed for welding onto the outlet pipe. The end is beveled, for a buttweld connection.

The Sockolet® and Threadolet® utilizes the basic Weldolet®, where the major difference is that the branch affixes by way of a socket (Sockolet®) or thread (Threadolet®). Besides these types, there are Elbolets®, Nipolets®, Latrolets® and more. All of these are registered trademarks.

Advantages of branch fittings

Using a Weldolet® instead of a welding Tee, allows more flexible fabrication, because it can be welded on every possible spot, after running the pipe. The design – more specific, the funneled inlet- assures full fluid flow. The wide footing improves mechanical strength, and the short height makes it easy to inspect the inside of the pipeline.


To be able to fit the run side of the branch fitting on all kind of pipe diameters, without adjustments onsite, a variation in range is required. The standard (MSS SP-97) allows a maximum crotch or skirt gap of 1.6mm, as you can see in the image hereunder.

For example: our 2” (pipe size) branch fittings are available from stock in 3 variants with a run size 2 ½-3”/ 3 ½”-6”/ 8”-36”.  These run sizes match the contour radius to the run pipe radius without exceeding the required skirt and crotch gaps.


Arcus provides a wide range of branch fittings in all sizes, types, bores, and classes, in a variety of (stainless) steel, chrome-moly, and other alloys. The common types are available from stock in grades F304/L and F316/L in European quality, and meet the 2009 edition of MSS-SP-97 Standard- “Integrally Reinforced Forged Branch Outlet Fittings”.

How to specify an enquiry or order

1: Quantity

2: Size

  • Outlet size
  • Run size

3: Type

  • (Butt-weld / socket-weld / Threaded)

4: Class / Schedule

  • 3000 / 6000 LBS
  • STD / XS

Generally the schedules of the run pipe and branch pipe are identical.  Where the schedule of the run is greater or less than the schedule of the branch, it is essential that both schedules be specified.)

5: Material grade

6: Design code (if available)

Example: 10 pieces 6”x 1 ½” Weldolet STD  F316L acc. MSS-SP-97

Auteur: Daniel Hage

+31 (0) 78 648 3648

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