Welded End Cap

Welded End Cap – Precision Sealing for Operational Reliability

Introduction

A Welded End Cap provides a permanent closure for pipe ends in both pressure and non-pressure applications. Hebei Longrun Pipeline Group Company’s welded end caps combine precise fabrication with thorough testing, resulting in secure seals for pipelines in industries such as petrochemical, utilities, and manufacturing.

Types of Welded End Caps

Butt-Weld Caps: Hemispherical or ellipsoidal domes welded directly to pipe ends.

Socket-Weld Caps: Fitted over pipe OD then fillet-welded; used in smaller-diameter, high-pressure lines.

Threaded Caps: Rarely welded but available for temporary closures; our welded end caps focus on permanent solutions.

Material Grades

Carbon Steel: ASTM A234 WPB for general industrial use.

Alloy Steels: Grades F5–F91 for high-temperature steam service.

Stainless Steel: A403 WP304/316 for corrosion resistance.

Duplex: Offshore and seawater applications.

Fabrication Steps

Forming: Pressing or spinning plate to spherical/ellipsoidal shape.

Bevel Machining: Preparing pipe end and cap edge per ASME B16.25.

Welding:

Butt Weld: Full-penetration join with controlled heat input.

Socket-Weld: Cap slip-fit then fillet weld; ensures rapid assembly.

Heat Treatment: PWHT for high-alloy materials; stress relieving for carbon steel.

Testing & Certification

RT/UT: Inspect weld roots and cap body for internal defects.

Dye Penetrant: Verify surface integrity around weld toes.

Mechanical Tests: Tensile, impact, and hardness tests on representative samples.

Applications

Pipeline Termination: Permanent closure of branch lines or dead ends.

Pressure Vessel Nozzles: Sealing unused flanged or welded connections.

Hydrostatic Test Caps: Temporary, though our welded end caps are designed for permanent service.

Installation and Inspection

Root Gap Control: Essential for butt-weld caps to achieve full penetration.

Weld Procedure: ASME Section IX qualified; back-purge stainless welds to avoid discoloration.

Final Inspection: Confirm cap geometry and weld quality before pressure testing.

Maintenance
Welded end caps are inherently low-maintenance; visual inspections and occasional coating renewal suffice for long service life.