Understanding Weld Outlets

1. Types of Stainless Steel Outlets

• Buttweld Outlet (Weldolet): Welded directly to the main pipe and branch pipe, ideal for high-pressure or high-temperature systems.
• Threaded Outlet (Threadolet): Has female threads for connecting to a threaded branch pipe, used in low-to-moderate pressure systems.
• Socket Weld Outlet (Sockolet): Designed for small-diameter branch pipes, where the branch pipe is inserted into the fitting’s socket and welded.

2. Key Sizing Parameters

To size these outlets, you need to match the fitting to both the main (run) pipe and the branch pipe. Here’s what to consider:

A. Nominal Pipe Size (NPS)

• Run Pipe Size: The diameter of the main pipe to which the outlet is attached. Outlets are designed to fit a range of run pipe sizes (e.g., 1/2" to 36").
• Branch Pipe Size: The diameter of the branch pipe connected to the outlet. The branch size is typically smaller than or equal to the run pipe size.
• Example: A 2" threadolet might be used to connect a 2" branch pipe to a 4" main pipe.

B. Schedule or Wall Thickness

• Outlets must match the pipe schedule (wall thickness) of both the run and branch pipes to ensure proper welding and pressure ratings.
• Common schedules: SCH 10, SCH 40, SCH 80, SCH 160, or STD (standard).
• For buttweld olets, the outlet’s wall thickness must align with the branch pipe’s schedule for a smooth weld.
• For socket weld olets, the socket depth must accommodate the branch pipe’s wall thickness.
• For threaded olets, ensure the thread type (e.g., NPT) and pressure class (e.g., 3000#, 6000#) match the branch pipe.

C. Pressure Class

• Outlets are rated for pressure, often in pounds (e.g., 3000#, 6000#) for threaded and socket weld olets, or by schedule for buttweld olets.
• Select a pressure class based on the system’s operating pressure and temperature. Higher pressure systems require thicker-walled (higher schedule) or higher-class fittings.

D. Material Grade

• Stainless steel outlets come in grades like 304/304L, 316/316L, etc., chosen based on corrosion resistance and environmental conditions.
• Ensure the material grade matches the piping system to prevent galvanic corrosion or material failure.

3. How to Size Outlets

• Step 1: Identify Run Pipe Size and Schedule
  • Measure the main pipe’s NPS and schedule (e.g., 6" SCH 40).
  • Check manufacturer charts for outlets compatible with the run pipe size. Outlets often cover a range of run pipe sizes (e.g., 2"–6").
• Step 2: Determine Branch Pipe Size and Schedule
  • Select the branch pipe’s NPS and schedule (e.g., 2" SCH 40).
  • Ensure the outlet’s branch connection matches the branch pipe’s size and schedule.
• Step 3: Choose the Outlet Type
  • Buttweld: For large pipes or high-pressure systems; requires welding expertise.
  • Threaded: For smaller pipes or systems where welding is impractical; check thread type (e.g., NPT, BSP).
  • Socket Weld: For small-diameter, high-pressure systems; easier to install than buttweld but limited to smaller sizes (typically ≤2").
• Step 4: Verify Pressure and Temperature Ratings
  • Cross-reference the outlet’s pressure class (e.g., 3000# for socket weld) or schedule with the system’s requirements.
• Step 5: Check Dimensions
  • Use manufacturer catalogs (e.g., Bonney Forge, Anvil) to confirm the outlet’s physical dimensions (e.g., length, height, socket depth) fit the piping layout.

4. Standards and Specifications

• Standards: Outlets are manufactured to standards like MSS SP-97 (for olets), ASME B16.11 (for threaded/socket weld fittings), or ASME B16.9 (for buttweld fittings).
• Thread Standards: Threaded olets typically use NPT (National Pipe Thread) or BSP (British Standard Pipe).
• Weld Standards: For buttweld and socket weld olets, ensure compliance with welding standards (e.g., ASME B31.3 for process piping).

5. Example Sizing Process

• Scenario: You need to connect a 1" branch pipe to a 4" main pipe in a high-pressure stainless steel system.
  • Run Pipe: 4" NPS, SCH 40.
  • Branch Pipe: 1" NPS, SCH 40.
  • Outlet Choice:
    • Buttweld Outlet: Select a 4" x 1" weldolet, SCH 40, 316 stainless steel.
    • Threaded Outlet: Choose a 1" threadolet, 3000#, 316 stainless steel, with NPT threads.
    • Socket Weld Outlet: Choose a 1" sockolet, 3000#, 316 stainless steel.
  • Verification: Check the manufacturer’s catalog to ensure the outlet fits the 4" run pipe and 1" branch pipe, and confirm pressure ratings (e.g., 3000# for threaded/socket weld).

6. Practical Tips

• Manufacturer Data: Refer to our catalogs for sizing and material offering.
• Welding Considerations: For buttweld and socket weld olets, ensure proper weld preparation (beveling for buttweld, fillet weld for socket weld).
• Code Compliance: Follow ASME B31.1 (power piping) or B31.3 (process piping) for industrial applications, and local codes for plumbing.
• Consult Professionals: For critical systems, consult a piping engineer to verify sizing and installation.