High-Integrity Welded Connections for Critical Piping Systems
Buttweld fittings are joined to pipe by circumferential butt welding. They provide the highest integrity connection and are specified for all critical, high-pressure, high-temperature, and hazardous service piping in oil and gas facilities. They are the standard for ASME B31.3 process piping, B31.4 liquid pipelines, and B31.8 gas pipelines.
Available Fitting Types
| Fitting Type | Symbol | Function |
|---|---|---|
| 90° Long Radius Elbow (LR) | 90° LR ELL | Changes direction by 90°. Radius = 1.5 × nominal pipe size |
| 90° Short Radius Elbow (SR) | 90° SR ELL | Changes direction by 90°. Radius = 1.0 × nominal pipe size |
| 45° Elbow | 45° ELL | Changes direction by 45° |
| 180° Return Bend (Long Radius) | 180° LR | Changes direction by 180°. For heat exchangers and coils |
| 180° Return Bend (Short Radius) | 180° SR | Compact U-bend. Back-to-back for tube bundles |
| Straight Tee (Equal Tee) | TEE | Branches flow at 90°. All three ends same size |
| Reducing Tee | RED TEE | Branches flow at 90°. Branch smaller than run |
| Concentric Reducer | CONC RED | Gradual diameter reduction. Centerlines aligned. For horizontal lines |
| Eccentric Reducer | ECC RED | Gradual diameter reduction. Flat side top or bottom. For pump suction and pipe racks |
| Cap (End Cap) | CAP | Closes pipe end. Ellipsoidal, hemispherical, or dished |
| Stub End (Lap Joint Stub End) | STUB END | Used with lap joint flange. Allows flange rotation for bolt-hole alignment |
| Cross (Equal) | CROSS | Four-way branch connection |
| Reducing Cross | RED CROSS | Four-way branch with reduced branches |
Applicable Standards
| Standard | Scope |
|---|---|
| ASME B16.9 | Factory-made wrought buttweld fittings (1/2″ to 48″) |
| ASME B16.28 | Short radius elbows and returns |
| MSS SP-43 | Lightweight corrosion-resistant buttweld fittings (stainless) |
| MSS SP-75 | High-test buttweld fittings for pipeline service (up to 60″, higher yield strength) |
| ASME B16.49 | Induction bends for transportation and distribution piping |
| NACE MR0175 / ISO 15156 | Sour service material requirements |
Size & Wall Thickness
| Parameter | Range |
|---|---|
| Sizes | 1/2″ (DN15) to 60″ (DN1500) |
| Wall Thickness | SCH 5S, 10S, 10, 20, 30, 40S, 40, STD, 60, 80S, 80, XS, 100, 120, 140, 160, XXS |
| End Preparation | Beveled per ASME B16.25 |
Material Options
| Material | ASTM Spec (Pipe) | ASTM Spec (Fitting) | Typical Service |
|---|---|---|---|
| Carbon Steel | A106 Gr.B | A234 WPB | General process, sweet hydrocarbon |
| Carbon Steel (Low Temp) | A333 Gr.6 | A420 WPL6 | Cryogenic, LPG, LNG |
| Carbon Steel (High Temp) | A335 P11/P22 | A234 WP11/WP22 | High temperature, steam |
| Stainless 304/304L | A312 TP304/304L | A403 WP304/304L | Corrosive, food-grade |
| Stainless 316/316L | A312 TP316/316L | A403 WP316/316L | Chlorides, offshore, sour |
| Duplex (UNS S31803/S32205) | A790 | A815 UNS S31803 | High chlorides, seawater |
| Super Duplex (UNS S32750) | A790 | A815 UNS S32750 | Extreme chlorides, subsea |
| Inconel 625 | B444 Gr.1 | B366 WPNICMC | Sour HPHT, extreme corrosion |
Optional Testing & Inspection
- PMI (Positive Material Identification): Verifies alloy composition on finished fitting
- Radiographic Testing (RT): Volumetric inspection of weld area (for welded fittings)
- Magnetic Particle / Dye Penetrant (MPI/DPI): Surface crack detection
- Intergranular Corrosion Test (IGC): Per ASTM A262 for stainless fittings
- Impact Testing: Charpy V-notch at specified temperature
- Hardness Testing: For sour service (NACE MR0175 compliance)