Butt Weld Cap
Butt Weld Cap
A butt weld cap (also called a pipe end cap or butt weld end cap) is a type of pipe fitting used to seal the end of a pipe in a piping system. It is typically welded directly to the pipe using a butt welding process, hence the name.
| Feature | Description |
|---|---|
| Product Name | Butt Weld Cap |
| Function | Seals the end of a pipe or pipeline to prevent leakage, protect pipe ends, or isolate systems for maintenance. |
| Materials | Carbon Steel: ASTM A234 WPB, A420 WPL3, WPL6, WPHY42/52/60/65/70 Stainless Steel: ASTM A403 WP304/304L, 316/316L, 321, 310S, 317, 347 – Duplex Stainless Steel: UNS S31803, S32205, S32550, S32750, S32760 – Alloy Steel: ASTM A234 WP1, WP5, WP9, WP11, WP12, WP22, WP91 – Nickel Alloys: ASTM/ASME SB 111/466 (e.g., Cu-Ni 90/10, 70/30), Monel, Inconel, Hastelloy – Other: Aluminum, Brass, Copper Nickel |
| Sizes | 1/2″ to 48″ (Seamless: up to 24″; Welded: 8″ to 48″) |
| Wall Thickness | Sch 5S, 10S, 20S, STD, 40S, XS, 80S, S100, S120, S140, S160, XXS |
| Standards | ASME B16.9, ASME B16.11, MSS SP-43, MSS SP-75, BS EN 10253-2, DIN, JIS |
| Surface Finish | – Polished (#7 or 32Ra OD, 20Ra ID for sanitary applications) – Unpolished (#5) – Electropolished (15Ra for sanitary fittings) |
| Connection Type | Butt Weld (TIG or MIG welding, 100% penetration for vacuum applications) |
| Applications | – Industrial: Oil & Gas, Chemical, Power Generation, Paper, Cement – Sanitary: Food, Beverage, Pharmaceutical, Biotechnology – Marine: Piping systems, Propellers, Crankshafts – Other: Waste Treatment, Cryogenic Plants, Breweries |
| Manufacturing Process | Cold Drawn, Hot Forming; TIG Welded for vacuum/sanitary applications |
| Key Features | – Corrosion resistance – Leak-proof seal – Durable and sturdy construction – Smooth inner surface to reduce pressure loss – Suitable for high-pressure and high-vacuum systems |
| Certifications | ASTM A403, ASME SA403, API 590-605, 3.1 Test Certification (for heavy wall) |
| Types | Standard Cap, Lap Joint Cap, Long Weld Neck Cap |
Butt Weld Steel Cap Size
| NPS | O.D. D | Length H | Length H(1) | WT |
| 1/2 | 21.3 | 25 | 25 | 4.57 |
| 3/4 | 26.7 | 25 | 25 | 3.81 |
| 1 | 33.4 | 38 | 38 | 4.57 |
| 1.1/4 | 42.2 | 38 | 38 | 4.83 |
| 1.1/2 | 48.3 | 38 | 38 | 5.08 |
| 2 | 60.3 | 38 | 44 | 5.59 |
| 2.1/2 | 73 | 38 | 51 | 7.11 |
| 3 | 88.9 | 51 | 64 | 7.62 |
| 3.1/2 | 101.6 | 64 | 76 | 8.13 |
| 4 | 114.3 | 64 | 76 | 8.64 |
| 5 | 141.3 | 76 | 89 | 9.65 |
| 6 | 168.3 | 89 | 102 | 10.92 |
| 8 | 219.1 | 102 | 127 | 12.70 |
| 10 | 273 | 127 | 152 | 12.70 |
| 12 | 323.8 | 152 | 178 | 12.70 |
| 14 | 355.6 | 165 | 191 | 12.70 |
| 16 | 406.4 | 178 | 203 | 12.70 |
| 18 | 457 | 203 | 229 | 12.70 |
| 20 | 508 | 229 | 254 | 12.70 |
| 22 | 559 | 254 | 254 | 12.70 |
| 24 | 610 | 267 | 305 | 12.70 |
| 26 | 660 | 267 | – | … |
| 28 | 711 | 267 | – | … |
| 30 | 762 | 267 | – | … |
| 32 | 813 | 267 | – | … |
| 34 | 864 | 237 | – | … |
| 36 | 914 | 267 | – | … |
| 38 | 965 | 305 | – | … |
| 40 | 1016 | 305 | – | … |
| 42 | 1067 | 305 | – | … |
| 44 | 1118 | 343 | – | … |
| 46 | 1168 | 343 | – | … |
| 48 | 1219 | 343 | – | … |
Types of Butt Weld Caps
1. Based on Design & Shape
Hemispherical Cap
Most common type
Hemispherical shape for even pressure distribution
Ideal for high-pressure piping systems
Elliptical Cap (2:1 Elliptical Head)
Shallower than hemispherical
Common in pressure vessel applications
Less material and height needed than hemispherical
Flat End Cap
Flat surface at the end
Used in low-pressure systems or where internal cleaning is needed
Economical but less pressure-resistant
2. Based on Standard
ASME B16.9 Butt Weld Cap
Standardized dimensions for high-pressure systems
Widely used in industrial piping systems
MSS SP-43 Cap
Used for light wall thickness, especially in stainless steel systems
Suitable for low-pressure, corrosion-resistant applications
3. Based on End Type
Beveled End Cap
Prepared for butt welding
Angle cut (usually 37.5°) for strong, full-penetration welds
Plain End Cap
Used for non-welded applications
May be temporarily fitted or mechanically secured
4. Based on Material
Carbon Steel Butt Weld Cap
Common in oil & gas, power plants
Example: ASTM A234 WPB
Stainless Steel Butt Weld Cap
Corrosion-resistant; used in chemical, food, and pharma industries
Example: ASTM A403 WP304/304L, WP316/316L
Alloy Steel Butt Weld Cap
Used in high-temperature or pressure environments
Example: ASTM A234 WP5, WP9, WP22
Duplex/Super Duplex Steel Cap
Superior strength and corrosion resistance
For offshore, marine, and chloride-rich environments
Applications:
End termination of a piping run.
Pressure containment (as in pressure vessels).
Future expansion possibilities (can be cut and extended later).
Hydrostatic testing.