BRANCH FITTINGS MSS SP 97 (FORGED OLETS)
Branch fittings (alternatively defined branch connections or “Olets”) are forged products to branch a run pipe. Branch fittings are manufactured in a wide range of sizes, types, bores, classes and material grades (carbon steel, stainless steel, alloy steel, nickel alloys) and are manufactured according to the MSS SP 97 specification. In this article, we give an overview of the most common branch connections as Weldolets, Threadolets and, Sockolets. At the bottom of this page, we indicate how to order a branch fitting connection.
WHAT ARE BRANCH FITTINGS?
Branch fittings provide an outlet for a larger pipe (the run pipe or “header size”) to a smaller or equally sized one (the branched pipe or “outlet size”). Branch connections are manufactured in a wide range of sizes, types, nominal diameters, and, classes, and in a wide range of materials such as carbon steel, stainless steel, chrome-moly, and nickel-alloys. This type of forged fittings have been introduced on the market by Bonney Forge more than 70 years ago, and have become, since then, very popular products for pipeline applications.
The standard MSS SP 97 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 degree integrally reinforced forged branch outlet fittings (both welded and threaded). Branch connections manufactured to the MSS SP 97 standard have to ensure a reinforced joint between two pipes. Branch fittings (Olets) may be manufactured to standard and non-standard dimensions, sizes, shapes, tolerances, or of other wrought material as agreed between the manufacturer and the buyer.
TYPES OF BRANCH FITTINGS
Weldolets are popular branch connections which fall under the category of butt weld fittings. When using a Weldolet, the branch is made by welding the fitting onto the outlet of the run pipe (this type of branch connection has beveled ends to facilitate such activity). Weldolets minimize the stress concentration on the branched connection and provide an integral reinforcement and they can have the same or a higher, schedule than the run pipe. Weldolets are available in multiple material grades and dimensions (Weldolet sizes and weights are illustrated in this article).
Sockolets are similar to Weldolets, with the difference that the branched pipe sits, and can be welded, on the socket present in the inner part of the branch fitting. Sockolets are classified as “socket fittings” and are available in classes 3000#, 6000# and 9000#. They are used for 90 degrees branched pipe connections and can be size on size (the bore of the fitting matches the bore of the run pipe) or reducing (the fitting has a smaller bore size).
SOCKOLETS DIMENSIONS AND WEIGHTS
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
Threadolets are similar to Weldolets, but the branched pipe is in this case screwed with the fitting and not welded. Thredolets belong to the family of “threaded fittings” and are available in classes 3000# and 6000#. The threaded end is generally of the NPT type (National Pipe Thread, the American standard).
Latrolets are used to 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#.
ANSI ELBOLET DIMENSIONS
|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
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. Nipolets are welded onto the run pipe and are manufactured with socket weld or threaded outlets on the branched side.
Sweepolets are contoured, integrally reinforced, butt weld branch connections suited for low stresses and long fatigue service. The weld on the run pipe side can be easily inspected with radiographic examination (RX or RT), ultrasounds (UT) and other non-destructive testing methods.
HOW TO ORDER BRANCH FITTINGS
The following indications are necessary when ordering a branch connection:
- Fitting type
- Weldolet (for buttweld connections)
- Thredolet (for threaded connections)
- Sockolet (for socket weld connections)
- Elbolet, Latrolet, Sweeploet, Insert Weldolet, Nipolet, Brazolet and so on
- Bore sizes
- Outlet size
- Run or Header
- Schedule (butt weld branch connections) and pressure rating (threaded and socket weld connections)
- Class 3000 or 6000 – Threaded or Socket
- Schedule STD, XS, 160, XXS
- Material Grade
- Carbon steel
- Stainless steel
- Nickel Alloys
- Design Code: ASME B16.9/MSS SP 97