As demands for precision in boiler tube fabrication continue to rise, Metro Boiler Tube Co., Inc. has announced the expansion of its in-house swaging capabilities with two Mitchell Swagers machines. This strategic investment enables the company to maintain tighter control over finished tube wall thickness, significantly improving both manufacturing efficiency and product reliability.
Understanding Tube Swaging
Tube swaging is a cold-forming process that uses hydraulic pressure to reshape pipe or tube ends through dies, altering their outer diameter (OD) without heat application. While classified as a "cold working" technique, the material compaction during swaging induces work hardening, often necessitating subsequent heat treatment or annealing to meet material specifications.
The process naturally increases wall thickness while reducing inner diameter (ID). For applications requiring precise dimensional control—such as tube-to-drum rolling—Metro Boiler Tube employs counter-pull mandrel technology to maintain consistent ID throughout the swaged section. This specialized approach ensures smooth internal profiles and uniform wall thickness.
Metro Boiler Tube's Technical Advantages
The company's Ringgold, Georgia facility features an advanced induction heating system capable of performing ASME-compliant annealing on swaged tube ends. Heat treatment parameters vary by material classification:
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P1 materials: 1,600°F–2,100°F (max wall 0.750")
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P-3/P-4/P-5A: 1,600°F–2,100°F (max wall 0.50")
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P-5B: 1,650°F–1,950°F (max wall 0.50")
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P-8: 1,400°F–2,100°F
For wall thicknesses exceeding these thresholds or materials not listed, Metro Boiler Tube utilizes furnace heat treatment for superior process control.
Material Hardness Standards
The table below outlines maximum hardness values for common boiler tube materials post-processing:
|
Material
|
P-Number
|
Max Hardness
|
|
SA 178 A
|
P1
|
72 HRB
|
|
SA 210 C
|
P1
|
89 HRB
|
|
SA 213 T11
|
P4
|
85 HRB
|
|
SA213 T91
|
P15E
|
100 HRB
|
Hardness typically returns to the as-received condition from the original tube mill.
Comprehensive Fabrication Services
Beyond swaging, Metro Boiler Tube provides full-service tube bending and welding capabilities, supported by over 500,000 feet of commonly used boiler tube inventory. This integrated approach enables rapid turnaround for complete tube bundle assemblies.
Quality Assurance Protocols
The company's quality control department implements rigorous inspection protocols:
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10% of all swages undergo dimensional verification (OD, ID, wall thickness, length)
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Full hardness testing and surface inspection
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Dimensional tolerances: ±0.012" (OD), ±0.010" (ID for counter-pull)
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Maximum concentricity deviation: 0.0625"
Post-processing includes lubricant removal and optional steam cleaning. Swaged ends may receive polishing for oxide removal and ease of drum insertion, with protective vinyl capping available for shipment.
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