Carbon Steel Pipe Cap ASME B16.9 — Factory Direct Supplier
Carbon steel pipe caps are butt-weld fittings used to seal the end of a pipe. They are the most common pipe end closure in process piping, oil and gas, petrochemical, and power plant applications. ASME B16.9 defines the dimensions, tolerances, and marking requirements for butt-weld pipe caps, ensuring interchangeability across manufacturers.
Huaxia-Steel supplies ASME B16.9 carbon steel pipe caps in sizes from 1/2 inch to 48 inch, in schedule 10 through schedule 160 and beyond. Standard material grade is ASTM A234 WPB, with A234 WP1 and WP11 available for low-alloy applications.
Product Overview
| Parameter | Specification |
|---|---|
| Standard | ASME B16.9 / MSS-SP-95 |
| Fitting type | Butt-weld pipe cap |
| Material grade | ASTM A234 WPB (carbon steel) |
| Size range | 1/2 inch to 48 inch (DN15 to DN1200) |
| Wall thickness | Sch 10, Sch 20, Sch 40, Sch 80, Sch 160, XXS |
| End type | Butt-weld (beveled end) |
| Manufacturing method | Cold forming, hot forming, or fabrication |
| Surface finish | As-formed (standard), machined (optional) |
Dimensional Specifications
Standard ASME B16.9 Cap Dimensions
| NPS (inch) | DN | OD of pipe (mm) | Cap height E (mm) | Cap height E1 (mm, at tangent) |
|---|---|---|---|---|
| 1/2 | 15 | 21.3 | 25 | 12.5 |
| 3/4 | 20 | 26.7 | 29 | 12.5 |
| 1 | 25 | 33.4 | 32 | 16 |
| 2 | 50 | 60.3 | 44 | 22 |
| 4 | 100 | 114.3 | 70 | 35 |
| 6 | 150 | 168.3 | 95 | 48 |
| 8 | 200 | 219.1 | 121 | 60 |
| 10 | 250 | 273.1 | 146 | 73 |
| 12 | 300 | 323.9 | 171 | 86 |
| 16 | 400 | 406.4 | 222 | 111 |
| 20 | 500 | 508.0 | 273 | 137 |
| 24 | 600 | 610.0 | 324 | 162 |
| 36 | 900 | 914.0 | 483 | 241 |
| 48 | 1200 | 1219.0 | 635 | 318 |
For caps larger than 24 inch, dimensions may follow MSS-SP-95 or be manufacturer-standard. Always confirm dimensions on the drawing before ordering.
Material Grades
| Grade | Type | Yield (MPa) | Tensile (MPa) | Typical application |
|---|---|---|---|---|
| A234 WPB | Carbon steel | 240 | 415-585 | General purpose, most common |
| A234 WP1 | Low alloy (C-Mo) | 205 | 380-550 | Moderate temperature service |
| A234 WP11 | Low alloy (1.25Cr-0.5Mo) | 205 | 415-585 | High temperature service |
| A234 WP22 | Low alloy (2.25Cr-1Mo) | 205 | 415-585 | High temperature, refinery |
Manufacturing Standards and Quality
- ASME B16.9: Factory-made wrought butt-welding fittings
- ASTM A234/A234M: Piping fittings of carbon and alloy steel
- MSS-SP-95: Swaged nipples and bull plugs (for forged caps)
- Dimensional tolerances: OD within +/- 1.6 mm (up to 12 inch), +/- 3.2 mm (over 12 inch); height within +/- 1.5 mm (up to 10 inch), +/- 3 mm (over 10 inch)
- Wall thickness: Minimum 87.5 percent of nominal pipe wall thickness (ASME B16.9 tolerance)
- Bevel end: 37.5 degrees +/- 2.5 degrees, with 1.6 mm root face per ASME B16.25
Applications
- Process piping: End closure for pipe spools and dead-end lines
- Petrochemical plants: Isolation points, test closures
- Oil and gas pipelines: Pig launcher/receiver closures, temporary isolation
- Power plants: Boiler tube closures, drain line terminations
- Shipbuilding: Pipe system end closures
- Water treatment: Header pipe end caps
Quality Assurance
- Material traceability: heat number stamped on each fitting
- EN 10204 3.1 MTC with chemistry and mechanical test results
- 100 percent visual inspection for surface defects
- Dimensional inspection: OD, height, wall thickness
- PMI (positive material identification) available for alloy grades
- UT or RT examination available for critical applications
- Hardness testing: maximum 197 HB for A234 WPB
Packaging and Shipping
- Small caps (up to 4 inch): Packed in wooden crates, 50-200 pieces per crate
- Medium caps (6-12 inch): Palletized, 10-50 pieces per pallet
- Large caps (14-48 inch): Individual packing with end protection
- Marking: Size, grade, heat number, manufacturer logo per ASME B16.9
- Export packaging: Fumigated wooden pallets, VCI anti-corrosion film
Why Choose Huaxia-Steel?
- Full range of ASME B16.9 caps from 1/2 to 48 inch
- Carbon steel (A234 WPB) and low-alloy grades (WP1, WP11, WP22)
- EN 10204 3.1 MTC included; 3.2 with third-party witnessing available
- Coating options: black painting, FBE, 3LPE for underground service
- Fast delivery: stock sizes ship in 3-5 days; custom sizes in 2-4 weeks
- Competitive pricing for both small and large orders
FAQ
What is the difference between a pipe cap and a plug?
A pipe cap (ASME B16.9) is a butt-weld fitting that fits over the outside of the pipe end. A plug (ASME B16.11) is a threaded fitting that screws into the inside of the pipe. Caps are used for welded systems; plugs are used for threaded systems.
What wall thickness do I need for my pipe cap?
The cap wall thickness must match the pipe schedule. For example, if your pipe is 6-inch Schedule 40, order a 6-inch Schedule 40 cap. ASME B16.9 requires the cap wall thickness to be at least 87.5 percent of the nominal pipe wall thickness at any point.
Can caps be used for high-pressure applications?
Yes. ASME B16.9 caps are rated for the same pressure as the matching pipe. The pressure rating depends on the material grade, wall thickness, and design temperature. For ASME B31.3 process piping, calculate the rating per the code equations.
Get a Quote
Contact Huaxia-Steel for ASME B16.9 carbon steel pipe caps with factory-direct pricing, full material certification, and worldwide shipping. Send your size, schedule, and quantity for a quotation within 24 hours.
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