Yes, it is possible to weld an olet (e.g., a Weldolet, Sockolet, or Threadolet) onto a pipe fitting such as a tee, but there are important considerations to ensure the integrity of the weld and compliance with applicable codes and standards.

1. Design Requirements:
   • The fitting and pipe must be strong enough to handle the additional stresses introduced by the olet and any attached piping.
   • Evaluate the system’s design to ensure the added branch does not compromise the fitting’s structural integrity.
2. Code Compliance:
   • Welding olets on fittings is subject to applicable design codes such as ASME B31.3 (Process Piping), ASME B31.1 (Power Piping), or CSA Z662 (Pipelines).
   • The weld configuration must meet the code’s requirements for proper reinforcement and weld size.
3. Material Compatibility:
   • The material of the olet and the tee should be compatible for welding. For example:
     • Carbon steel olet welded to a carbon steel tee.
     • Stainless steel olet welded to a stainless steel tee.
4. Reinforcement and Strength:
   • The addition of an olet to a fitting can change the stress distribution, especially at the tee’s branch or run.
   • Check if the olet requires reinforcement to comply with the code (reinforcing pad or integrally reinforced branch fitting).
5. Welding Procedure:
   • Use a qualified Welding Procedure Specification (WPS) based on the materials and application.
   • Follow preheat, interpass temperature, and post-weld heat treatment (PWHT) requirements as applicable.
6. Inspection and Testing:
   • Perform appropriate non-destructive testing (NDT) to ensure the quality of the weld. Common methods include:
     • Radiographic Testing (RT).
     • Ultrasonic Testing (UT).
     • Magnetic Particle Testing (MT) or Dye Penetrant Testing (PT) for surface defects.
7. Accessibility and Layout:
   • Ensure there is enough space for welding and inspection.
   • Verify the olet placement does not interfere with other piping components or operations.

• Adding an olet to a tee may be required to provide a branch connection where a standard branch on the tee is unavailable or impractical.
• Examples include retrofitting an existing piping system or creating a custom branch layout.

• Welding an olet to a fitting instead of directly to the pipe may create stress concentration points due to the geometry.
• It might be more challenging to achieve a proper fit-up and weld in some configurations.

• Conduct a proper stress analysis.
• Ensure compliance with the governing code and material specifications.
• Use skilled welders qualified for the job and perform thorough inspections.