Branch Outlets, commonly referred to as Olets, are integrally reinforced forged fittings used to create a branch connection from a larger main pipe (run) to a smaller or equal-sized outlet pipe (branch). Unlike standard tees, Olets are designed to provide integral reinforcement to the run pipe, compensating for the structural strength lost when cutting the branch hole. They are the preferred solution for high-pressure, high-temperature piping systems where minimizing stress concentration factors (SCF) is critical for safety.

Selection depends primarily on the branch size, pressure class, and connection method required by the piping specification :

• Weldolet® (Butt-Weld): The most robust connection, suitable for all pressure classes and sizes. It features a beveled end for a butt weld to the branch pipe, allowing for full radiographic inspection (RT). It is ideal for critical, high-stress services.

• Sockolet® (Socket-Weld): Typically used for smaller branch sizes (≤ 2 inches). It features a socket bore that aligns the branch pipe for a fillet weld. It is faster to install than a Weldolet but requires a 1/16″ expansion gap at the bottom of the socket to prevent weld cracking. Common classes are 3000# and 6000#.

• Thredolet® (Threaded): Used for low-pressure systems or instrumentation connections (e.g., pressure gauges) where welding is not feasible. It uses a tapered pipe thread (NPT) for connection.

he primary manufacturing standard for integrally reinforced forged branch outlet fittings is MSS SP-97. This standard governs the design, dimensions, pressure ratings, and proof-of-design burst testing requirements.

• ASME B16.9 / B16.25: Referenced for the bevel dimensions of Weldolets.

• ASME B16.11: Referenced for the socket dimensions (Sockolet) and thread specifications (Thredolet).

• ASME B31.1 / B31.3: The piping design codes that validate the use of MSS SP-97 components without requiring additional area replacement calculations.

To ensure the correct “consolidated run size” and fit-up, your Request for Quotation (RFQ) or Bill of Materials (BOM) must specify these five data points :

1. Run Size (Header): The Olet is contoured to fit a range of header sizes (e.g., 36″-22″).

2. Branch Size (Outlet): The specific size of the connecting branch pipe (e.g., 4″).

3. Style: The specific type (e.g., Weldolet, Sockolet, Elbolet).

4. Rating/Schedule:

   • For Weldolets: Specify the Schedule (e.g., STD, XS, Sch160) to match the branch pipe wall thickness.

   • For Sockolets/Thredolets: Specify the Pressure Class (e.g., 3000#, 6000#).

5. Material Grade: The material specification (e.g., ASTM A105, A182 F316).

Olets are frequently chosen over standard tees for cost efficiency and installation flexibility :

• Reduced Welding Costs: Installing an Olet requires only 2 welds (one header-to-Olet, one Olet-to-branch), whereas a Tee requires 3 butt welds (cutting the main line). This can reduce welding and inspection labor by 50% to 90% (see chart in report).

• Inventory Optimization: Due to “size consolidation,” a single Olet item code can fit a wide range of run pipe sizes (e.g., one 4″ Weldolet fits all headers from 10″ to 36″), drastically reducing warehouse inventory compared to stocking individual reducing tees for every header size.

• Retrofit Capability: Olets can be installed on existing pipelines via “hot tapping” without cutting the line, which is impossible with standard tees.