ASME B16.9 Stainless Steel Pipe Cap 304/316L

Product Specification

1. Product Description
This stainless steel pipe cap is a butt-welding fitting manufactured to ASME B16.9, designed to permanently seal the end of a pipeline. It features an ellipsoidal (2:1) dome shape that distributes internal pressure evenly, with a straight cylindrical skirt (tangent length) that moves the weld zone away from the high-stress knuckle radius. Made from ASTM A403 WP304/304L or WP316/316L austenitic stainless steel, it is suitable for corrosive, high-temperature, and critical piping systems. Both ends are beveled for full-penetration butt welding.

2. Key Specifications

• Material: ASTM A403 WP304/304L, WP316/316L

• Chemical Composition (WP304): Cr 18–20%, Ni 8–11%

• Chemical Composition (WP316): Cr 16–18%, Ni 10–14%, Mo 2–3%

• Mechanical Properties (304L/316L): Tensile strength ≥485 MPa, Yield strength ≥170 MPa

• Nominal Size: NPS 1/2 – 48 (DN15 – DN1200)

• Wall Thickness / Schedule: SCH10S, SCH40S, SCH80S, SCH160, XXS (must match pipe schedule)

• Connection: Butt Weld (Beveled End, 37.5° per ASME B16.25)

• Standards: ASME B16.9, ASTM A403

• Surface Treatment: Pickled, passivated, or solution annealed

3. Applications
Widely used in petroleum, chemical processing, power generation, natural gas, water treatment, shipbuilding, and construction. The WP316L grade is particularly suitable for chloride-bearing, marine, and acidic environments due to its molybdenum content. Pipe caps serve as permanent end closures for pipeline terminations, testing, and maintenance points.

4. Product Advantages

• Ellipsoidal shape distributes stress evenly, providing higher strength than flat closures

• Tangent length allows proper butt welding without damaging the dome’s structural integrity

• WP304 offers general corrosion resistance with good weldability

• WP316L provides superior pitting resistance against chlorides and aggressive media

• Low-carbon “L” grades prevent sensitization and intergranular corrosion after welding

• Wall thickness matches the pipe schedule, ensuring the same pressure rating as the connected pipe

5. Product Functions
The pipe cap permanently seals the end of a pipeline, preventing fluid or gas leakage. Unlike flanged blind plates, it is a welded closure that requires cutting for removal. It withstands the same internal pressure, temperature, and corrosive forces as the pipe itself, making it suitable for terminal points, future expansion boundaries, and pressure testing closures.

6. Instruction for Use

• Verify cap size, schedule, and material grade match the pipeline specification. Fitting grade must match pipe grade (e.g., WP316L cap with TP316L pipe).

• Inspect the beveled end for cracks, dents, or deformation before installation.

• Clean the pipe end and cap bevel; remove oil, paint, and debris. Use a stainless-steel wire brush to avoid carbon contamination.

• Align the cap with the pipe; ensure inner diameter matching to prevent turbulence and corrosion.

• Perform at least four tack welds around the circumference to secure alignment and prevent warping.

• Complete butt welding using qualified WPS. Recommended filler: ER308L for WP304, ER316L for WP316.

• Inspect the weld and perform pressure testing as required.

7. Precautions

• Do not subject the cap to impact or drop during storage and handling.

• Keep stainless steel caps away from contact with carbon steel or dissimilar metals to prevent galvanic corrosion.

• Ensure the pipeline is depressurized and drained before installation or maintenance.

• Do not use damaged or deformed caps; inspect bevels for cracks before welding.

• Match filler metal to base metal: ER308L for 304, ER316L for 316.

• Verify that the MTC includes heat number, chemical analysis, mechanical properties, and heat treatment type.

8. Shipping Information

• Standard export packing: wooden case or plywood pallet, with plastic film or bubble bag wrapping.

• Dispatch within 7–30 days depending on order quantity.

• Shipping methods: sea freight, air freight, or express courier depending on quantity and destination.

• Tracking number provided upon dispatch.

9. Payment Terms

• T/T (bank transfer): 30% deposit, 70% balance before shipment.

• L/C at sight accepted for larger orders.

• PayPal / Western Union for sample orders.

• All prices are quoted EXW or FOB unless otherwise specified.

10. Packaging

• Each cap is wrapped in plastic film or bubble bag.

• Multiple pieces are packed in sturdy wooden cases or plywood pallets.

• Desiccant is added for sea shipments to prevent moisture.

• Beveled ends are protected with covers to prevent damage during transport.

• Custom labeling and marking available upon request.

11. Return & After-Sales Policy

• 7-day return or exchange for quality defects (buyer bears return freight unless the defect is verified as our responsibility).

• Custom-made or non-stock items are not eligible for return unless defective.

• Warranty period: 12 months from delivery for manufacturing defects.

• Claims for shortage or damage must be reported within 3 working days of receipt with photo evidence.

• Technical support available for welding procedures, material selection, and installation guidance.