ASME B16.9 Pipe Tee Dimensions

The charts below are intended as a quick reference for engineers, fabricators, contractors, and buyers working with ASME B16.9 butt weld fittings.The dimension charts cover NPS 1/2" to 48" and provide a quick reference for piping design, fabrication, and material selection. The dimensional data is based on the ASME B16.9 standard for factory-made wrought buttwelding fittings.

1. ASME B16.9 Pipe Tee Dimensions

1.1 ASME B16.9 Equal Tee Dimensions

The table below lists the standard dimensions for ASME B16.9 equal tees manufactured in accordance with the ASME B16.9 standard. It includes the nominal pipe size (NPS), outside diameter (OD), and center-to-end dimensions (C and M) for standard butt weld equal tee fittings.

Note: All dimensions are in millimetres (mm) unless otherwise specified. ASME B16.9 specifies fitting dimensions only. Wall thickness is determined by the applicable pipe schedule and is not included in this table.

1.2 ASME B16.9 Reducing Tee Dimensions Chart

The table below provides the standard dimensions for ASME B16.9 reducing tees. The dimensions shown comply with the ASME B16.9 standard for factory-made wrought buttwelding fittings.

2. What Is the ASME B16.9 Standard?

ASME B16.9 is the American Society of Mechanical Engineers (ASME) standard covering factory-made wrought buttwelding fittings. It is one of the most widely adopted piping standards worldwide and is extensively used in the oil and gas, petrochemical, power generation, water treatment, and general industrial sectors.

The standard establishes uniform dimensional requirements for commonly used butt weld fittings, including elbows, tees, reducers, caps, and stub ends. By standardizing these dimensions, ASME B16.9 helps ensure interchangeability between fittings produced by different manufacturers and simplifies piping design, fabrication, and installation.

For pipe tees, the standard specifies the principal dimensions for equal tees and reducing tees, ensuring compatibility with matching pipe sizes and butt weld connections.

3. How to Read an ASME B16.9 Pipe Tee Dimension Chart

ASME B16.9 tee dimensions are typically presented using the nominal pipe size (NPS), outside diameter (OD), and center-to-end dimensions.

For equal tees, the fitting is designated by a single nominal pipe size because all three outlets have the same diameter. For example, NPS 8 × 8 × 8 indicates that the run pipe and the branch outlet are all 8 inches.

For reducing tees, the designation follows the format Run × Run × Branch. For example, NPS 8 × 8 × 4 represents a tee with an 8-inch run pipe and a 4-inch branch outlet.

The dimensions shown in ASME B16.9 tables are identified by standard dimension symbols:

4. Equal Tee vs. Reducing Tee

Equal tees and reducing tees are both standardized under ASME B16.9.

Equal tees are typically used where the main pipe and branch pipe have the same diameter, whereas reducing tees are selected when a smaller branch connection is needed.

5. Selection Considerations for ASME B16.9 Pipe Tees

When selecting an ASME B16.9 pipe tee, confirming the correct dimensions is only one part of the specification. To ensure compatibility with the piping system, the following factors should also be verified before procurement.

- Tee Type – Specify whether an equal tee or a reducing tee is required.

- Nominal Size (NPS) – Confirm the run size and branch size according to the piping layout.

- Pipe Schedule – Select the wall thickness that matches the connected pipe.

- Material Grade – Choose the appropriate material specification, such as ASTM A234 WPB or ASTM A403 WP304/316, based on the service conditions.

- Applicable Standards – Verify compliance with ASME B16.9 and any additional project or material standards.

6. FAQs

Q1. What is the difference between an equal tee and a reducing tee?

An equal tee has three outlets of the same nominal pipe size, while a reducing tee has a smaller branch outlet than the run pipe. The appropriate type depends on whether the branch connection requires the same or a reduced pipe diameter.

Q2. Does ASME B16.9 specify wall thickness?

No. ASME B16.9 specifies the standard dimensions of butt weld fittings. Wall thickness is determined by the applicable pipe schedule and the corresponding material specification.

Q3. What does NPS 8 × 8 × 4 mean?

It represents a reducing tee with an 8-inch run pipe and a 4-inch branch outlet. The first two numbers indicate the run pipe size, while the third number indicates the branch size.

Q4. What is the difference between ASME B16.9 and MSS SP-75?

ASME B16.9 specifies the dimensions of factory-made wrought buttwelding fittings, while MSS SP-75 covers high-strength wrought buttwelding fittings primarily used in pipeline applications.