Definition and details of O'let Branch Connections
 

Branch Connection Fittings general

Branch Connection fittings (also known as O'lets) are fittings which provide an outlet from a larger pipe to a smaller one (or one of the same size). The main pipe onto which the branch connection is welded is usually called the Run or Header size. The pipe to which the branch connection provides a channel is usually called the Branch or Outlet size. Branch connections are in all sizes, types, bores, and classes, in a wide range of stainless steel, chrome-moly, and other alloys.

Perhaps you know, Bonney Forge has been supplying quality branch fittings (O'lets) for many years. In 1943 when Bonney Forge pioneered the "Shape of Reinforcement" for branch connections, who would have thought it would fast become a recognized industry standard. Today, Bonney Forge Branch Connections offer complete run pipe reinforcement while avoiding cracks, fillet welds, and sharp re-entrant corner reinforcement tapering at the sides, thus preventing abrupt changes in thickness where the fitting joins the header pipe.

Bonney Forge fittings meeting the 100% reinforcement requirement of applicable piping codes i.e. ASME B31.1, B31.3, B31.4 and B31.8. They also meet the 2001 edition of MSS-SP-97 Standard- "Integrally Reinforced Forged Branch Outlet Fittings".

Types of Branch Connection Fittings

Weldolet® Weldolet® is the most common of all branch connections, and is welded onto the outlet pipe. The ends are bevelled to facilitate this process, and therefore the weldolet is considered a butt-weld fitting. Weldolet's are designed to minimize stress concentrations and provide integral reinforcement.
 
Sockolet® Sockolet® utilizes the basic Weldolet® however the branch affixes by way of a socket inside the olet. The bore matches the outlet bore, and the existence of a counter bore roughly the size of the OD of the outlet provides a socket where the pipe can sit, facilitating installation and welding. The Sockolet® is considered a socket fitting, and manufactured in 3000#, 6000# and 9000# classes.
 
Thredolet® Thredolet® utilizes the basic Weldolet® however the branch affixes by way of a thread just inside the top of the olet. The bore matches the outlet bore, and the existence of this threading facilitates installation, as no welding is necessary. The Thredolet® is considered a threaded fitting, andmanufactured in 3000# and 6000# classes.
 
Latrolet® Latrolet®, used for 45° lateral connections, is available butt-weld to meet specific reinforcement requirements, and 3000# or 6000# classes for Socket Weld and threaded applications.
 
Elbolet® Elbolet® is used on 90° Long Radius Elbows (can be manufactured for Short Radius Elbows) for thermowell and instrumentation connections. Available butt-weld to meet specific reinforcement requirements, and 3000# and 6000# classes for Socket Weld and threaded applications.
 
Nipolet® Nipolet® is a one piece fitting for valve take-offs, drains and vents. Manufactured for Extra Strong and Double Extra Strong applications in 3.1/2in to 6.1/2in lengths. Available with male-socket-weld or male threaded outlets.
 
Sweepolet® Sweepolet® is a contoured, integrally reinforced, butt-weld branch connection with a low stress intensification factor for low stresses and long fatigue life. The attachment weld is easily examined by radiography, ultrasound and other standard non-destructive techniques. Manufactured to meet your specific reinforcement requirements.

Specifying the Schedule of both the Run and Branch

Generally the schedules of the run pipe and branch pipe are identical and thus specification of the equivalent schedule Weldolet assures the proper fitting being used.

Example:
16" Standard weight x 6" Standard weight is specified as a 6" standard weight fitting.
Where the schedule of the run is greater or less than the schedule of the branch, it is essential that both schedules be specified since (a) The Weldolet's reinforcing characteristics are a function of the run pipe wall thickness, which in turn designates the schedule of the basic Weldolet® fitting to be used;(b) The wall thickness of the outlet or branch end must match the wall thickness of the branch pipe.

Example:
16" Extra strong x 6" Standard weight
16" Standard weight x 6" Extra strong
Special care is suggested to avoid confusing schedule 40 and standard weight as being identical (above 10" schedule 40 is heavier) and schedule 80 and extra strong (above 8" schedule 80 is heavier).

Example:
8" Schedule 80 x 4" Schedule 80 fitting or extra strong fitting.18" Schedule 80 x 4" Schedule 80 is a considerably heavier fitting, because the reinforcement is for 18" schedule 80 pipe with a wall thickness of approximately 1".
The Weldolet® is available in standard code designs for all combinations of run wall thicknesses up through 3.1/2" thickness and branch wall thicknesses up through double extra strong. Designs for thicknesses greater than these can be developed on request.

Remark(s) of the Author...

Make sure that the supplier has a design approval for the fitting (there are many small outfits out there making their own fittings without any documentation)

Try the site of Bonney Forge. They have all the dimensions and you'll be sure the fittings have a design approval. It seems that the dimensions specified in MSS SP-97, based on Bonney Forge.

Weldolet, Sockolet, Thredolet, Latrolet, Elbolet, Nipolet, Sweepolet are trademarks registered ® for the exclusive use of Bonney Forge.