What are branch connections (or pipe branch outlet fittings aka “Olets”)? Olet fittings are a family of forged products used to make 45 or 90 degrees integrally reinforced branch connections (deviations) from a run pipe (also called, header pipe) to a branch pipe (outlet pipe). The common types of branch fittings are Weldolet, Thredolet, Sockolet, Latrolet, Elbolet, Nipolet, Sweepolet. MSS-SP 97 is the key specification covering reinforced branch connections, introduced by Bonney Forge in the piping market more than 70 years ago.
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PIPE BRANCH FITTINGS
Pipe branch fittings are used to create integrally reinforced connections from a run pipe (header pipe) to an outlet pipe, at 45 or 90 degrees, alternatively to connections made with buttweld tees, reinforcing pads and saddles. This type of forged fittings are otherwise called “branch connections”, or “branch fittings”, or “pipe branch outlet fittings” or, simply, “Olets”.
Outlet fittings are forged products with high strength and clear cost advantages over conventional pipe branching techniques.
How are they installed? Quite easily: on one side, the fittings (example a Weldolet) is fixed onto the run pipe with a full penetration groove weld and, on the other side, welded (or screwed) on the branch pipe. Of course, the header pipe shall be properly cut in the proximity of the area where the pipe needs to be branched.
The use of branch fittings instead of conventional fittings (buttweld tee, reinforcing pads and saddles) has the following advantages (example Weldolet):
- Just 2 welds are needed, instead of 3 (less work and weld inspections)
- Accelerated installation time
- Less space is required, making the piping system design more flexible
- The flow is fully unrestricted, due to the funnel design
Reinforced branch connections are manufactured in a wide range of sizes (to accommodate most size on size or reducing connections), types/designs, connection types (buttweld, socket weld, threaded), and in a wide range of forged steel materials:
- carbon steel (ASTM A105 for high-temperature, A350 LF2/LF3 for low-temperature)
- alloy steel (ASTM A182 Grades F5, F9, F11, F22)
- stainless steel (ASTM A182 F304, F316, and other SS grades)
- nickel alloys (Inconel, Monel, Incoloy, etc).
The MSS-SP 97 specification covers the dimensions, the finishing, the tolerances, the testing methods and procedures, the marking, the material grades, and the minimum tensile strength requirements for 90-degrees integrally reinforced forged branch outlet fittings (welded and threaded). The connection resulting from using branch fittings complies to ASME B31.1 and ASME B31.3 power and process piping codes.
The types of ends of an outlet fitting shall comply to ASME B16.25 (buttweld ends), or ASME B16.11 (socket weld and threaded ends).
BRANCH FITTINGS TYPES
A Weldolet has beveled ends at both ends and is, therefore, welded onto the run pipe on one side and onto the branch pipe on the other side. Weldolets are used to create a 90-degrees (reinforced) pipe branch. The shape of the Weldolet ensures little stress concentration on the branched pipe, providing an integral reinforcement.
On the branch pipe side, Weldolets may have the same schedule of the run pipe or a higher schedule.
How to install a Weldolet: Bonney Forge
A Sockolet is similar to a Weldolet, with the difference that the branch pipe is connected to the run pipe, via the fitting, with a socket weld connection as per ASME B16.11. Likewise Weldolets, Sockolets are used to make a 90-degree pipe branch. Sockolets may be “size on size” or “reducing”.
Fillet welds are used to connect the branch pipe to the branch side of the Sockolet. On the pipe run side, a Sockolet requires a welded connection.
What is the difference between a Sockolet and a Weldolet?
Sockolets belong to the “socket fittings” family and are available in classes 3000#, 6000# and 9000#, whereas Weldolets are buttweld fittings. Sockolets are used for lower pressure applications, and smaller pipe diameters, than Weldolets.
Thredolets are used for low-pressure 90-degree pipe branches. The branch pipe is screwed on the Thredolet, which is welded on the run pipe. The threading is generally of the NPT type and conforms to the ASME B1.20.1 specification.
Thredolets belong to the “threaded fittings” family and are available in classes 3000# and 6000#. Threadolets are used for smaller pipe sizes and low-pressure applications.
Latrolets branch a pipe at 45 degrees. They are available with butt weld connections to meet demanding reinforcement requirements or with socket weld/threaded connections in classes 3000# or 6000#.
Elbolets are used with 90 or 180 degrees long radius and short radius (more rarely) elbows for thermowell and instrumentation connections or as a drain connection when there is too little space for using a Weldolet.
Elbolets are available with butt weld connections or with socket weld/threaded connections in classes 3000# or 6000#.
Nipolets are used for valve take off, drains and vents and are manufactured in lengths between 3 1/2 to 6 1/2 inches and for XS and XXS schedules. A Nipolet is welded onto the run pipe and is manufactured with socket weld or threaded outlets on the branch pipe side.
Sweepolets are contoured, integrally reinforced, buttweld branch fittings used for low stress and long fatigue service. The welded connection on the run pipe side can be easily inspected with radiographic examination (RX or RT), ultrasounds (UT) and other non-destructive tests.
The dimensions of Weldolets are explained in this article.
Sockolet class 3000 “Size on Size”
|Outlet Size (NPT)||A||B||C||D||E||Approx. Weight (lb)|
|3/4||1 1/16||1 5/8||1 3/16||0.824||15/32||0.25|
|1||1 5/16||2||1 7/16||1.049||23/32||0.45|
|1 1/4||1 5/16||2 3/8||1 3/4||1.380||9/16 0.65|
|1 1/2||1 3/8||2 7/8||2||1.610||21/32||0.85|
|2||1 1/2||3 1/2||2 9/16||2.067||15/16||1.40|
|2 1/2||1 9/16||4 1/16||3||2.469||3/4||2.25|
|3||1 3/4||4 13/16||3 11/16||3.068||15/16||3.75|
|3 1/2||1 11/16||5 3/8||4 7/16||3.548||11/16||4.30|
|4||1 7/8||6 1/16||4 3/4||4.026||1 1/16||6.60|
|5||2 7/16||7 1/4||5 1/4||5.047||1||9.00|
|6||2 11/16||8 11/16||6 1/16||6.065||1 3/16||15.50|
- Class 3000 to be used with schedule 80 pipes
- Dimensions and tolerances in accordance with ASME B16.11 and MSS SP-97
- Flat sockolets are used on welding caps, elliptical heads and flat surfaces
- Each outlet size is available to fit any run curvature.
Sockolet class 6000 “Size on Size”
|Outlet Size (NPS)||A||B||C||D||E||Approx. Weight (lb)|
|1/2||1 1/4||1 23/32||3/4||0.466||7/8||0.50|
|3/4||1 7/16||1 61/64||1||0.614||7/8||0.80|
|1||1 9/16||2 7/16||1 5/16||0.815||15/16||1.30|
|1 1/4||1 5/8||2 23/32||1 1/2||1.160||13/16||1.60|
|1 1/2||1 11/16||3 1/4||1 15/16||1.338||7/8||2.00|
|2||2 1/16||4 1/32||2 3/4||1.689||1 3/16||5.15|
- Class 6000 to be used with schedule 160 pipe.
- Dimensions and tolerances in accordance with ASME B16.11 and MSS SP-97
- Flat Sockolets are used on welding caps, elliptical heads and flat surfaces.
- Outlet combinations fit a number of run pipe sizes, and fittings are marked accordingly
|Nominal Size of Elbow (NPS)||Outlet Size (NPS)||CL 3000 Threaded and Socket Weld|
Sch. Standard and XS Buttweld
|CL 6000 Threaded and Socket Weld|
Sch. 160 and XXS Buttweld
|36 – 3/4||1/4||1 1/2||1 19/32||1 1/2||1 19/32|
|36 – 3/4||3/8||1 1/2||1 19/32||1 1/2||1 19/32|
|36 – 3/4||1/2||1 1/2||1 19/32||1 23/32||1 7/8|
|36 – 1||3/4||1 23/32||1 7/8||2 1/4||2 1/4|
|36 – 2||1||2 1/4||2 1/4||2 7/8||2 1/2|
|36 – 2||1 1/4||2 7/8||2 1/2||3 1/8||2 11/16|
|36 – 2||1 1/2||3 1/8||2 11/16||4 3/16||3 1/4|
|36 – 3||2||4 3/16||3 1/4||–||–|
|*2 1/2||4 3/16||3 1/4||bw only||bw only|
|*3||5 1/16||3 7/8||bw only||bw only|
|*4||6 5/8||4 13/16||bw only||bw only|
|*6||9 3/8||6 1/2||bw only||bw only|
|*8||13 5/16||8 1/16||bw only||bw only|
|*10||17 1/32||10 3/8||bw only||bw only|
|*12||19 5/8||11 1/8||bw only||bw only|
- Class 3000 to be used for schedule 80 pipes
- Class 6000 to be used for schedule 160 pipes
- Dimensions and tolerances acc. to ASME B16.9, ASME B16.25 and, MSS SP-97.
- Dimensions and tolerances in accordance with ANSI/ASME B16.11
- Threaded ends in accordance with ANSI/ASME B1.20.1
HOW TO ORDER BRANCH FITTINGS
Suppliers of Weldolets, Thredolets, Sockolets, and other branch fittings need the following information to identify the needed product:
- Header run pipe size (which is generally expressed as a range of possible sizes, example 36-22)
- Branch pipe size (the NPS of the connecting pipe to the run pipe, example 6 inches)
- Branch pipe schedule (which can be STD, XS, 160, XXS) for buttweld types of connections (rating shall be provided for socket weld and NPT threaded Olets)
- Style of branch fitting (Weldolet, Thredolet, Nipolet, Sockolet, etc)
- Material Grade (example A105, A350 LF2, A182 F304)
EXAMPLE: 36-22 | 6 INCH Sch. STD | Weldolet | ASTM A105