ASME B16.9 Equal Tee, ASTM A234 WPB, SCH 160 — Dimensions, Properties & Selection Guide
Oct 11, 2025
What Is an Equal Tee?
An equal tee is a butt-weld pipe fitting with three openings of the same nominal bore: two aligned ends forming the run, and one perpendicular branch. In a piping system, it creates a balanced branch take-off - flow continues straight through the run while a controlled portion diverts through the branch.
Equal tees are manufactured by hot forming or cold forming from seamless or welded pipe, followed by end machining and - where the manufacturing route and grade require it - post-forming heat treatment (normalizing or normalizing-and-tempering for hot-formed WPB; stress-relief for cold-formed fittings when specified by the project piping code).
Specification
Product Name: Equal Tee
Standard: ANSI B16.9
Materail: Carbon Steel ASTM A234 WPB
Schedule: SCH 160
Apllication: for Seamless Pipe
End Connection: Butt Welding
Contact us for ASTM A234 WPB Equal Tee：info@gneepipe.com
Applicable Standards
| Standard | Title | What It Covers |
|---|---|---|
| ASME B16.9 | Factory-Made Wrought Butt-Welding Fittings | Dimensions, tolerances, and marking for butt-weld fittings NPS 1/2 through NPS 48. |
| ASTM A234/A234M | Piping Fittings of Wrought Carbon Steel and Alloy Steel for Moderate and High Temperature Service | Material requirements for grades WPB, WPC, WP1, WP5, WP9, WP11, WP22, and WP91. |
| ASME B16.25 | Butt-Welding Ends | Bevel geometry and end preparation for field butt-welding. |
| ASME B36.10 | Welded and Seamless Wrought Steel Pipe | Wall-thickness schedules (SCH 10 through SCH 160, XXS) and corresponding OD/wall tables. |
Note on ANSI B16.9: The designation "ANSI B16.9" is obsolete. ASME assumed responsibility for the B16 committee in the 1980s. Use ASME B16.9 on all purchase specifications, datasheets, and marking requirements.
Chemical Composition - ASTM A234 WPB
Ladle analysis limits per ASTM A234/A234M. Product analysis tolerances apply per the standard.
| Element | Limit (wt%) |
|---|---|
| Carbon (C), max | 0.30 |
| Manganese (Mn) | 0.29 – 1.06 |
| Phosphorus (P), max | 0.050 |
| Sulfur (S), max | 0.058 |
| Silicon (Si), min | 0.10 |
| Chromium (Cr), max | 0.40 |
| Molybdenum (Mo), max | 0.15 |
| Nickel (Ni), max | 0.40 |
| Copper (Cu), max | 0.40 |
| Vanadium (V), max | 0.08 |
The chemistry of A234 WPB is essentially equivalent to ASTM A106 Grade B seamless pipe and ASTM A53 Grade B. The carbon equivalent (CE = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15) is typically below 0.42, which gives WPB good field weldability without mandatory preheat in most conditions.
Mechanical Properties - ASTM A234 WPB
| Property | Minimum Requirement |
|---|---|
| Tensile strength | 415 MPa (60,000 psi) |
| Yield strength (0.2% offset) | 240 MPa (35,000 psi) |
| Elongation in 2 in (50 mm) | 22% (longitudinal); 14% (transverse) |
| Reduction of area, min | 30% |
| Hardness, max | 197 HBW |
Fittings manufactured from plate (rather than pipe) must meet a minimum elongation of 17%. Hardness testing is not mandatory unless specified on the purchase order.
Pressure-Temperature Capability
A common misunderstanding is that butt-weld fittings carry a fixed pressure class such as "Class 300" or "PN 64." ASME B16.9 fittings do not have an intrinsic pressure rating. The pressure capability of an equal tee is a system property - it depends on:
- Material allowable stress (S) at the design temperature, per ASME B31.1 or B31.3 Appendix A
- Wall thickness at the fitting ends (matched to SCH 160 pipe)
- Corrosion allowance and mill undertolerance per the project piping class
Under ASME B31.3, A234 WPB has published allowable stress values from −29 °C to 425 °C. A SCH 160 equal tee in a correctly designed B31.3 line can serve pressures well into the high-pressure range at moderate temperatures. The same tee at 400 °C will have a significantly lower allowable pressure - always calculate per your governing code.
Practical upper limit: For service above 425 °C, switch to an ASTM A234 alloy grade (WP11, WP22, or WP91) matched to ASTM A335 alloy pipe. For service below −29 °C, use ASTM A420 WPL6 (rated to −46 °C) or WPL3 (rated to −73 °C) instead of WPB.
Surface protection such as hot-dip galvanizing (ASTM A153), fusion-bonded epoxy (FBE), or three-layer polyethylene (3PE) coating extends service life in buried, subsea, or corrosive-atmosphere applications. Coating does not change the base metal pressure rating.
SCH 160 Wall Thickness - ASME B36.10
The table below lists the nominal wall thickness for SCH 160 carbon-steel pipe per ASME B36.10. ASME B16.9 requires that fitting wall thickness be at least equal to the nominal wall of the matching pipe.
| NPS | DN | OD (mm) | SCH 160 Wall (mm) | SCH 160 Wall (in) |
|---|---|---|---|---|
| 1/2 | 15 | 21.3 | 4.78 | 0.188 |
| 3/4 | 20 | 26.7 | 5.56 | 0.219 |
| 1 | 25 | 33.4 | 6.35 | 0.250 |
| 1-1/4 | 32 | 42.2 | 6.35 | 0.250 |
| 1-1/2 | 40 | 48.3 | 7.14 | 0.281 |
| 2 | 50 | 60.3 | 8.74 | 0.344 |
| 2-1/2 | 65 | 73.0 | 9.53 | 0.375 |
| 3 | 80 | 88.9 | 11.13 | 0.438 |
| 4 | 100 | 114.3 | 13.49 | 0.531 |
| 5 | 125 | 141.3 | 15.88 | 0.625 |
| 6 | 150 | 168.3 | 18.26 | 0.719 |
| 8 | 200 | 219.1 | 23.01 | 0.906 |
| 10 | 250 | 273.1 | 28.58 | 1.125 |
| 12 | 300 | 323.9 | 33.32 | 1.312 |
Corrected values: The NPS 3, 4, and 6 SCH 160 wall thicknesses have been verified against ASME B36.10. Earlier published versions of some tables contain errors. Always cross-check with the current ASME B36.10 edition.
Manufacturing and Quality Control
Forming
Hot pressing or cold forming from seamless pipe, welded pipe, or plate. Hot-formed WPB fittings are supplied in the normalized condition to refine grain structure. Cold-formed fittings receive stress-relief heat treatment when required by the governing piping code.
Machining
End faces and bevels are machined to ASME B16.25 (37.5° ± 2.5° bevel with 1.6 mm ± 0.8 mm root face). Branch and run bores are verified with go/no-go gauges.
Inspection and Testing
- Dimensional inspection - 100% of fittings or per sampling plan agreed with the purchaser
- Hydrostatic test - when specified on the purchase order
- Non-destructive examination (RT / UT / MT / PT) - per project specification
- Tensile test - one per heat or lot per ASTM A234
- Chemical analysis - ladle analysis per heat
Marking
Each fitting must be legibly marked with manufacturer's name or trademark, material grade (WPB), dimensional standard (B16.9), nominal size and schedule, heat number or lot number.
Applications
- Power plants - main steam, feedwater, blowdown, and condensate lines.
- Oil and gas - gathering lines, transmission piping, and process piping.
- Chemical and petrochemical - process and utility piping.
- Refineries - refinery off-plot and interconnecting piping.
- Shipbuilding and offshore platforms - ballast, bilge, firewater, and utility systems.
Not recommended for untreated water distribution, buried water mains without coating, or services where fluid corrosivity exceeds bare carbon steel capability.
Procurement Checklist
- Specify ASME B16.9 instead of obsolete ANSI B16.9.
- Specify ASTM A234 Grade WPB material.
- State NPS/DN and wall schedule (SCH 160).
- Specify butt-weld bevels per ASME B16.25.
- Require EN 10204 Type 3.1 material test certificates.
- For sour service, add NACE MR0175/ISO 15156 compliance.
- For low-temperature service, specify Charpy impact testing.
- For corrosive environments, specify coating requirements.
FAQs
Q1: What is the difference between an equal tee and a reducing tee?
An equal tee has three openings of the same nominal size; a reducing tee has a smaller branch bore. Use an equal tee when the branch line carries the full line size.
Q2: Can ASTM A234 WPB equal tees be used at temperatures below −29 °C?
Not without qualification. Below −29 °C, impact testing may be required according to ASME B31.3 low-temperature rules. Alternative materials include ASTM A420 WPL6 or WPL3.
Q3: What does SCH 160 mean?
SCH 160 is a wall-thickness designation defined in ASME B36.10. It is a heavy-wall series thicker than SCH 80 and SCH 40.
Q4: Is a seamless or welded equal tee better?
Both manufacturing routes can comply with ASME B16.9 when properly manufactured, heat-treated, and inspected. Selection depends on project requirements, availability, and cost.
Q5: What is the pressure rating of a SCH 160 equal tee?
ASME B16.9 fittings do not carry a fixed pressure rating. Pressure capability must be calculated according to material stress, temperature, wall thickness, and applicable piping code.
References
- ASME B16.9 - Factory-Made Wrought Butt-Welding Fittings
- ASTM A234/A234M - Standard Specification for Piping Fittings of Wrought Carbon Steel and Alloy Steel
- ASME B36.10 - Welded and Seamless Wrought Steel Pipe
- ASME B31.3 - Process Piping
- ASME B16.25 - Butt-Welding Ends
- NACE MR0175 / ISO 15156 - Materials for Use in H₂S-Containing Environments
