ASTM A403 WP304 Stainless Steel Pipe Cap Butt Weld Fitting ASME B16.9
Product Overview
ASTM A403 WP304/WP304L Stainless Steel Butt Weld Caps are austenitic stainless steel pipe fittings designed to close the end of piping systems, equipment nozzles and process lines. The caps are supplied with butt-weld ends for direct welding to the adjoining pipe.
Manufactured to ASTM A403/ASME SA403 and dimensioned to ASME B16.9, these stainless steel pipe caps are available in different nominal sizes and wall thicknesses for process piping, petrochemical, oil & gas, power and industrial equipment applications.
Product Specifications
| Item |
Specification |
| Product |
Stainless Steel Butt Weld Cap |
| Material Grade |
ASTM A403 WP304 / WP304L |
| UNS |
S30400 / S30403 |
| Material Type |
Austenitic Stainless Steel |
| Product Type |
Pipe Cap / End Cap |
| Manufacturing Standard |
ASTM A403 / ASME SA403 |
| Dimension Standard |
ASME B16.9 |
| Connection |
Butt Weld (BW) |
| Size Range |
1/8"-48" NB |
| Wall Thickness |
SCH 10S-XXS |
| End Preparation |
ASME B16.25 where applicable |
| Heat Treatment |
Solution Heat Treated |
| Surface |
Pickled / Blasted / Machined as required |
| Inspection |
Dimensional, Visual, PMI, NDT as required |
| Certification |
EN 10204 3.1 available |
ASTM A403 WP304 / WP304L Material
ASTM A403 covers wrought austenitic stainless steel fittings for pressure piping applications. WP304 and WP304L are chromium-nickel stainless steel grades commonly used where corrosion resistance, weldability and general process-service performance are required.
WP304 vs WP304L
The main material distinction is the carbon content.
| Grade |
UNS |
Carbon |
Typical Characteristic |
| WP304 |
S30400 |
≤ 0.08% |
General-purpose 304 stainless steel |
| WP304L |
S30403 |
≤ 0.03% |
Lower-carbon grade for welded applications |
The lower carbon limit of WP304L helps reduce the risk of chromium carbide precipitation during welding and is therefore commonly specified for fabricated piping systems involving extensive welding.
Stainless Steel Butt Weld Cap Design
A butt weld cap is installed over the open end of a pipe or fitting and welded around the circumference. The butt-weld configuration provides:
- Direct pipe-to-fitting welding
- Continuous welded connection
- Compact external profile
- Suitable alignment with piping systems
- Compatibility with ASME B16.9 dimensional requirements
The cap can be supplied for standard piping sizes as well as selected customized requirements.
ASME B16.9 Dimensions
ASME B16.9 provides dimensional requirements for factory-made wrought butt-welding fittings. Available size and wall-thickness combinations can be selected according to the connected pipe specification.
Typical wall designations include:
- SCH 5S
- SCH 10S
- SCH 20S
- SCH 40S
- SCH 80S
- SCH 120
- SCH 160
- XXS
Actual availability depends on size, material grade and applicable dimensional requirements.
Available Stainless Steel Cap Types
YUHONG can supply stainless steel butt weld caps in different configurations and material grades according to project requirements.
WP304 Butt Weld Cap
A403 WP304 stainless steel caps are commonly selected for general process piping and equipment applications where standard 304 stainless steel provides the required corrosion resistance.
WP304L Butt Weld Cap
A403 WP304L stainless steel caps are suitable for welded piping systems where the lower-carbon version of 304 stainless steel is specified.
Custom Stainless Steel Pipe Caps
Special sizes, wall thicknesses and inspection requirements can be considered according to drawings, piping specifications or purchase orders.
Applications
ASTM A403 WP304 / WP304L butt weld caps are used for pipe and equipment termination in:
- Oil & Gas Piping
- Petrochemical Plants
- Chemical Processing
- Refinery Piping
- Power Generation
- Heat Exchanger Systems
- Pressure Vessels
- Process Equipment
- Water Treatment
- Industrial Piping
- Shipbuilding
- General Mechanical Equipment
The cap can be used to close pipe ends, equipment connections and selected process piping branches where a welded end closure is required.
Why Choose WP304 / WP304L Butt Weld Caps?
- Corrosion Resistance - The chromium content of 304 stainless steel provides resistance to many common atmospheric and process environments.
- Weldability - WP304L provides a lower-carbon option for welded fabrication and is frequently selected when welding requirements are an important part of the piping design.
- Butt-Weld Connection - The BW configuration allows the cap to be directly welded to the pipe, producing a compact and continuous piping connection.
- Standardized Dimensions - ASME B16.9 dimensional requirements help ensure compatibility with standard butt-weld piping components.
- Wide Size Availability - The product can be supplied in a broad range of nominal sizes and wall thicknesses according to the applicable specification.
Manufacturing and Inspection
Depending on the project specification, inspection may include:
- Chemical Composition Analysis
- Mechanical Testing
- Heat Treatment Verification
- Visual Inspection
- Dimensional Inspection
- Hardness Testing
- Positive Material Identification (PMI)
- Liquid Penetrant Testing (PT)
- Ultrasonic Testing (UT)
- Other Third-Party Inspection
Material Test Certificates can be supplied according to EN 10204 3.1 or project requirements.
Applicable Standards
The product can be supplied according to:
- ASTM A403 / ASME SA403 - Wrought Austenitic Stainless Steel Piping Fittings
- ASME B16.9 - Factory-Made Wrought Buttwelding Fittings
- ASME B16.25 - Buttwelding Ends
- EN 10204 - Inspection Documents
Additional standards can be considered according to the project specification.
WP304 vs WP304L Stainless Steel Caps
| Item |
WP304 |
WP304L |
| UNS |
S30400 |
S30403 |
| Carbon Limit |
≤ 0.08% |
≤ 0.03% |
| Chromium |
18.0-20.0% |
18.0-20.0% |
| Nickel |
8.0-11.0% |
8.0-12.0% |
| Material Family |
Austenitic Stainless Steel |
Austenitic Stainless Steel |
| Weldability |
Good |
Particularly suitable for welded fabrication |
| Typical Use |
General process piping |
Welded process piping and equipment |
The final grade should be selected according to the piping material specification, welding procedure and operating conditions.
Product Supply Range
YUHONG can supply ASTM A403 WP304 / WP304L stainless steel butt weld caps with:
- 1/8"-48" nominal size range
- SCH 5S-XXS wall thickness options
- Butt weld ends
- Standard and customized dimensions
- Pickled, blasted or machined surfaces
- 3.1 material certification
- PMI and third-party inspection when required
FAQ
What is an ASTM A403 WP304 cap?
It is a wrought austenitic stainless steel pipe fitting manufactured according to ASTM A403 WP304 and designed to close the end of a piping system using a butt-weld connection.
What is the difference between WP304 and WP304L?
The principal difference is the carbon limit. WP304L has a maximum carbon content of 0.03%, compared with 0.08% for WP304, making WP304L a common choice for welded fabrication.
What standard is used for the cap dimensions?
For standard factory-made butt-welding fittings, the dimensional standard is ASME B16.9.
Is this a seamless pipe cap?
The manufacturing route should be confirmed against the specific order specification. ASTM A403 permits different product forms and manufacturing processes depending on the fitting and grade. The supply condition should therefore be specified when seamless construction is required.
What sizes are available?
The existing product specification covers 1/8" to 48" NB, with wall thicknesses from Schedule 10S to XXS. Customized requirements can be reviewed according to drawings or project specifications.
Can you provide WP304L caps for pressure vessel fabrication?
Yes. WP304/WP304L butt weld caps can be supplied for piping and equipment applications, including selected pressure-vessel and process-equipment fabrication projects, subject to the applicable design and material specification.
Related Stainless Steel Butt Weld Fittings
- ASTM A403 WP304 / WP304L Elbow
- ASTM A403 WP304 / WP304L Tee
- ASTM A403 WP304 / WP304L Reducer
- ASTM A403 WP304 / WP304L Cross
- ASTM A403 WP316L Butt Weld Cap
- ASTM A403 WP321 Butt Weld Fittings
- ASTM A403 WP347H Butt Weld Fittings
- Stainless Steel Butt Weld Pipe Fittings ASME B16.9
YUHONG supplies stainless steel, duplex stainless steel and nickel alloy pipes, tubes, butt weld fittings and flanges for industrial piping and process equipment applications.
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