Welded Pipe Cap Manufacture

Welded Pipe Cap – Secure Sealing for Pipeline Terminations

Introduction
A welded pipe cap is a fitting used to close the end of a pipeline, providing a pressure-tight seal for systems during operation or maintenance. Produced from welded steel, these caps ensure safe containment of liquids and gases while allowing for future access when removal is required. Hebei Longrun Pipeline Group Company manufactures welded pipe caps in multiple sizes, pressure classes, and material grades to serve processing plants, utilities, and construction projects.

Material Options
Common materials for welded pipe caps include:

Carbon Steel (A234 WPB): Suitable for general-purpose sealing up to 400 °C and moderate pressures.

Alloy Steel (A182 F11, F22): Designed for high-temperature steam and petrochemical services.

Stainless Steel (A403 WP304, WP316): Ideal for corrosive environments or sanitary applications.

Duplex and Super Duplex: High resistance to chloride stress corrosion for marine and desalination use.

Design and Connection Types

Butt-Weld Caps: Ends are beveled for butt welding to pipeline, producing a smooth transition and minimal flow disturbance.

Socket-Weld Caps: Feature a socket into which the pipe is inserted and fillet-welded, used for small-diameter pipelines (≤ DN 50).

Lap-Joint Caps: Work with stub-end flanges; cap slides over the stub and is secured with a backing flange, facilitating disassembly.

Manufacturing Workflow

Cutting and Forming: Plate or pipe blanks are cut to size; caps are formed by hydraulic pressing or hot spinning machines.

Welding: For fabricated caps, plate sections are butt-welded into hemispherical or elliptical shapes.

Heat Treatment: Post-weld heat treatment relieves residual stresses and aligns metallurgical properties across welded zones.

Machining: Flange surfaces or bevel angles are machined to specified tolerances; surface finishes meet ASME B16.25 requirements.

Testing and Inspection: Hydrostatic testing and radiography confirm weld integrity and absence of internal defects.

Key Specifications

Size Range: DN 15 to DN 2000 (½″ to 80″) and larger.

Pressure Classes: ANSI Class 150–2500.

Caps Shapes: Hemispherical, elliptical, and flat-faced designs.

Standards Compliance: ASME B16.9, B16.11 (socket weld), MSS SP-75, EN 10253.

Applications

Process Piping: Temporarily sealing lines during commissioning, cleaning, or maintenance.

Hydraulic Systems: Closing off unused branches or test ports under high pressure.

Fire Protection: Sealing sprinkler system ends or isolation points.

Storage and Transport: Sealing vessel nozzles and pipe outlets during shipping.

Installation and Removal

Welding Preparation: Clean bevel faces to remove scale and oil; maintain correct root face and gap for weld penetration.

Welding Procedure: Use qualified welders; follow preheat and interpass temperature guidelines.

Future Access: For caps expected to be removed, consider lap-joint or socket-weld types to simplify disassembly.

Maintenance Recommendations
Inspect cap weld seams for signs of corrosion or cracking. Repair or replace caps showing wall thinning or structural faults. Protective coating restoration may be required in corrosive environments.

Conclusion
Hebei Longrun Pipeline Group Company’s welded pipe caps offer dependable pipeline terminations that facilitate both secure operation and ease of future access. With customizable shapes, materials, and pressure ratings, these caps support safe, efficient sealing across diverse industrial networks.