Welded End Cap – Permanent Seals for Pipeline Terminations

  Welded End Cap – Permanent Seals for Pipeline Terminations

Introduction
A welded end cap provides a permanent closure for the end of a pipeline, sealing the system for long-term operation without the intention of future removal. Welded end caps are commonly used in buried pipelines, pressure vessels, and critical process lines where a lasting seal is essential. Hebei Longrun Pipeline Group Company supplies welded end caps in diverse materials and pressure ratings, tailored for secure, maintenance-free service.

Material Options

Carbon Steel (A234 WPB): Robust choice for moderate-temperature services up to 400 °C.

Alloy Steel (A182 F91, F316H): Designed for high-temperature power generation and petrochemical lines.

Stainless Steel (A403 WP304L, WP316L): Preferred for hygienic processes and corrosive media.

Duplex Grades: For high-strength, corrosion-resistant applications in marine and offshore.

Design and Fabrication

Hemispherical Caps: Offer uniform stress distribution under internal pressure; suitable for higher-pressure classes.

Elliptical Caps: Thinner sections reduce material use while maintaining adequate pressure resistance at lower to moderate pressures.

Fabricated Plates: For very large diameters, multiple plate segments are welded and machined into a cap shape.

Manufacturing Steps

Plate Cutting and Profiling: CNC plasma or laser cutting shapes are profiled for precise geometry.

Forming: Hydraulic pressing or hammer forming creates the basic cap curvature.

Welding: If fabricated, plate segments are welded with full penetration girth welds; filler metal matches base alloy composition.

Heat Treatment: Post-weld heat treatment relieves residual stresses and ensures uniform mechanical properties.

Finishing and Inspection: Machined edges are beveled to specification; hydrostatic testing verifies seal integrity.

Specifications

Size Range: From DN 50 (2″) to DN 3000 (120″) custom-manufactured for project requirements.

Pressure Ratings: ANSI Class 150–2500.

Standards: ASME B16.9 (butt-weld caps), EN 1329, ISO 1127.

Applications

Buried Pipelines: Permanent termination points in water, sewage, and gas distribution mains.

Process Vessels: Closing vessel nozzles where future access is not anticipated.

Structural Piping: End closures for structural steel bracing or support pipelines.

Hydraulic Accumulators: Sealing high-pressure accumulator shells in power units.

Installation Considerations

Welding Preparations: Precise bevel angles and clean root faces are critical for full-penetration welds.

Non-Destructive Examination: Radiographic or ultrasonic testing confirms weld quality before commissioning.

Corrosion Protection: External coatings or cathodic protection systems applied for buried or marine service.

Maintenance
Although designed for permanent use, periodic external inspections and cathodic protection checks help ensure long-term integrity. In the event of system modifications, the cap may be removed by cutting and re-welded as needed.

Conclusion
Hebei Longrun Pipeline Group Company’s welded end caps provide robust, maintenance-free seals for critical pipeline terminations. Engineered with precise fabrication and rigorous testing, these caps support the safe and reliable operation of industrial and utility systems.