Everything You Need to Know About Split Tee Fittings: Applications, Manufacturing, and Installation

Split tee fittings are one of the most critical components used in high-pressure pipeline modification and maintenance systems, especially for hot tapping and line stopping operations. Designed for on-line intervention without interrupting the flow of the pipeline medium, these fittings offer unmatched convenience, structural integrity, and operational safety. Whether it’s a pipeline carrying gas, crude oil, chemicals, or water, split tees are essential for branch connections and other inline services where traditional fittings fall short.

This blog explores split tee fittings from a highly technical perspective, detailing their construction, applications, types, design standards, and installation procedures.

What is a Split Tee Fitting?

A split tee fitting is a mechanical fitting used primarily in the oil, gas, petrochemical, and water industries to create a new branch on an existing pipeline without shutdown. It consists of two symmetrical halves that are bolted or welded together around the pipe, creating a tee-connection for subsequent tapping or plugging operations.

Unlike standard tees which are welded during pipeline construction, split tees are used for on-line operations, providing a strong, pressure-resistant solution without the need to stop fluid flow.

Key Components of a Split Tee Fitting

1. Upper and Lower Halves (Shells): The main body of the fitting, typically fabricated from high-strength carbon steel or stainless steel.

2. Reinforcing Saddle or Collar: Ensures structural integrity under internal pressure and flow stress.

3. Flanged or Welded Outlet: Depending on design, may be used to accommodate tapping valves or plugging heads.

4. Gasket and Sealing Materials: Critical for pressure containment; typically made from high-grade elastomers or PTFE.

5. Studs and Nuts (if mechanical type): High-tensile fasteners to join the two halves securely.

Types of Split Tee Fittings

1. Welded Split Tee Fittings: Designed for permanent connections. These are fully welded to the pipeline and offer the highest pressure ratings.

2. Mechanical Split Tee Fittings: Installed using bolted flanges. Ideal for temporary or non-weld operations.

3. Hot Tap Split Tees: Specially designed to integrate with hot tapping machines for branch pipeline installation without interrupting flow.

4. Line Stop Split Tees: Used with line stopping equipment for isolation and maintenance tasks.

Materials Used in Manufacturing

Split tees are manufactured using a range of materials depending on the pipeline media, temperature, and pressure ratings:

• Carbon Steel (ASTM A106, A234 WPB): Most commonly used for oil and gas applications.

• Stainless Steel (304, 316, 321): Used where corrosion resistance is critical.

• Alloy Steels (Inconel, Monel, Hastelloy): For high-temperature or corrosive services.

• Duplex and Super Duplex Steel: Excellent for offshore and highly corrosive environments.

All materials undergo extensive non-destructive testing (NDT), including ultrasonic testing (UT), magnetic particle inspection (MPI), and radiographic testing (RT) for weld integrity.

Design Standards and Codes

Split tee fittings are manufactured and tested according to multiple international standards:

• ASME B31.3 – Process Piping

• ASME Section VIII Div 1 – Pressure Vessel Code

• API 5L – Specification for Line Pipe

• MSS SP-75 – High-Strength Welded Fittings

• ANSI/ASME B16.5 – Flanged Fittings

Engineering calculations for split tee fittings include stress analysis, reinforcement pad design, and compatibility with hot tapping equipment. Finite element analysis (FEA) is often used to simulate pressure behavior and structural integrity before deployment.

Applications of Split Tee Fittings

Split tee fittings are integral in many industries:

1. Oil and Gas Pipelines: For adding branch lines, bypass lines, and temporary pig launchers.

2. Chemical Plants: For system expansion or maintenance without halting production.

3. Power Generation: In steam lines and cooling water circuits.

4. Water Treatment Plants: For tapping or repair operations under continuous service.

5. Marine and Offshore Platforms: For subsea connections and pipeline re-routing.

Installation Procedure of Split Tee Fittings

1. Site Preparation: Marking the location and cleaning the pipe surface to remove scale, rust, or paint.

2. Positioning the Tee: The lower half is clamped to the pipeline followed by the upper half.

3. Welding/Bolting: For welded types, the halves are fully welded using qualified procedures. For mechanical tees, high-strength bolts are used with a calibrated torque wrench.

4. Leak Testing: Hydrostatic or pneumatic tests are conducted to verify joint integrity.

5. Hot Tapping Operation: If required, hot tapping equipment is mounted, and the branch is created under pressure.

6. Final Commissioning: The system is brought back to operational pressure, and monitoring begins.

Advantages of Split Tee Fittings

• Non-intrusive Installation: No need for system shutdown, saving significant time and cost.

• Customizability: Designed to match specific diameter, pressure class, and material requirements.

• High Structural Integrity: Engineered to withstand high pressure and cyclic loading.

• Versatility: Compatible with hot tapping and line stopping equipment.

• Time-Saving Maintenance: Enables maintenance and upgrades with minimal service disruption.

Critical Considerations Before Use

• Pipe Wall Thickness: Must be verified to avoid excessive stress during fitting and tapping.

• Pressure Rating: The tee must be rated to handle full system pressure including transients.

• Weld Quality: High-quality welding procedures (WPS/PQR) must be followed to ensure durability.

• Gasket Material Compatibility: Choose materials resistant to the line medium and temperature.

• Stress Analysis: Ensure fitting does not induce undue stress on the pipeline.

Conclusion

Split tee fittings have revolutionized the way pipeline networks are maintained and expanded. Their ability to facilitate branch connections without service disruption makes them indispensable in modern pipeline systems. With advancements in material science, design simulation, and installation technologies, split tee fittings continue to offer safe, efficient, and cost-effective solutions across critical infrastructure sectors.

Whether you’re working with crude oil pipelines in a remote desert or high-pressure steam lines in a refinery, choosing the right split tee fitting can mean the difference between seamless operations and costly downtime. By adhering to international standards and engineering best practices, industries can fully leverage the technical advantages of split tee fittings in their pipeline networks.