Stainless Steel Coil Tube (Coiltube) — Ultra-Long Continuous Coil Piping System
1. Product Overview
The Stainless Steel Coil Tube (hereinafter referred to as "Coiltube") is a continuously formed, non-welded tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. Unlike conventional straight-segment piping, Coiltube is produced in a continuous spiral coil configuration, enabling lengths up to 800 meters or beyond without intermediate butt-weld joints. This design fundamentally eliminates the weak points associated with welded connections, offering superior structural integrity, enhanced pressure resistance, and significantly reduced installation time in complex piping networks.
Coiltube is engineered for applications requiring long-reach fluid or material transport, including hydraulic systems, chemical processing lines, food-grade pipelines, and specialized construction scenarios such as ultra-long concrete pumping circuits. The continuous coil architecture ensures uniform mechanical properties along the entire tube length, free from the heterogeneity introduced by segmented welding.
2. Material & Properties
Coiltube products are fabricated from high-grade austenitic stainless steel grades, with the following material specifications:
- Primary Grades: SUS304 (UNS S30400), SUS316L (UNS S31603), SUS321 (UNS S32100), and custom alloy compositions upon request
- Composition (SUS304 typical): Cr 18.0–20.0%, Ni 8.0–10.5%, C ≤ 0.08%, Mn ≤ 2.0%, Si ≤ 1.0%, P ≤ 0.045%, S ≤ 0.030%
- Tensile Strength: ≥ 520 MPa (75 ksi)
- Yield Strength (0.2% offset): ≥ 205 MPa (30 ksi)
- Elongation: ≥ 40% (minimum, in 50 mm gauge length)
- Hardness: ≤ 92 HRB (annealed condition)
- Corrosion Resistance: Excellent resistance to atmospheric, aqueous, and acidic environments; pitting resistance equivalent number (PREN) ≥ 19 for 316L grade
- Operating Temperature Range: −196°C to +870°C (vacuum) / +870°C to +1150°C (atmospheric)
- Surface Finish: 2B, BA (Bright Annealed), No. 4 Brushed, or custom finish (Ra ≤ 0.4 μm available)
3. Technical Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 6 mm – 168.3 mm (1/4" – 6-5/8") |
| Wall Thickness | 0.3 mm – 12.7 mm (0.012" – 0.5") |
| Coil Length (Continuous) | Up to 800 m (2,625 ft) or customized |
| Coil Diameter (Coil OD) | 1,000 mm – 3,500 mm (adjustable per application) |
| Dimensional Tolerance (OD) | ±0.1 mm – ±0.5 mm (per ASTM A213 / EN 10216) |
| Dimensional Tolerance (Wall) | ±10% of nominal thickness |
| End Condition | Plain end, beveled (V-cut), or cap-fitted |
| Coil Form | Flat coil (flat-pack) or helical coil |
| Standard References | ASTM A213/A213M, ASTM A269/A269M, EN 10216-5, GB/T 14976 |
| Maximum Working Pressure | Up to 40 MPa (5,800 psi), grade-dependent |
| Hydrostatic Test Pressure | 1.5× working pressure (100% inline tested) |
| Packaging | Steel band-strapped coil on wooden reel; moisture-proof wrapping |
4. Manufacturing Process
The production of Coiltube follows a rigorous multi-stage process to ensure dimensional accuracy, metallurgical homogeneity, and mechanical performance:
- Raw Material Selection & Inspection: Cold-rolled stainless steel strip is procured from certified mills. Incoming material undergoes spectroscopic analysis (OES), mechanical property verification, and surface quality inspection.
- Strip Preparation: The coil strip is slit, leveled, and trimmed to precise width specifications. Surface defects are removed, and edges are deburred to prevent stress concentration during forming.
- Continuous Forming: The strip passes through a multi-stand roll-forming system (typically 12–20 forming stations) that progressively shapes the flat strip into a tubular cross-section with controlled wall thickness and ovality tolerance.
- Welding (if applicable): For welded coil tube, a TIG (Tungsten Inert Gas) or laser welding process is applied to the longitudinal seam with argon back-gas shielding to maintain internal surface integrity. Weld quality is verified via inline eddy current testing.
- Continuous Annealing: The formed tube undergoes in-line annealing in a protective atmosphere (H₂/N₂ mixture or vacuum) to relieve forming stresses, restore full austenitic microstructure, and achieve specified mechanical properties.
- Pickling & Passivation: The tube is pickled to remove oxide scale and passivated with nitric or citric acid to establish a chromium oxide passive film for maximum corrosion resistance.
- Hydrostatic Testing: Each coil is subjected to 100% hydrostatic pressure testing at 1.5× the maximum working pressure to verify weld integrity and wall uniformity.
- Coiling & Packaging: The finished tube is coiled onto precision-engineered reels, strapped with steel bands, and packaged for shipment.
5. Applications
The unique continuous-coil architecture and stainless steel material properties make Coiltube suitable for a wide spectrum of demanding applications:
- Ultra-Long Fluid Transport: Hydraulic power systems, pneumatic conveying lines, and chemical process piping where joint-free continuity is critical for pressure integrity and leak prevention.
- Construction & Civil Engineering: Long-reach concrete pumping circuits (up to 800 m), grouting pipelines, and post-tensioning ducts where the continuous tube eliminates joint failure risks.
- Food & Pharmaceutical Industry: Sanitary-grade piping (316L, BA finish) for dairy, beverage, and pharmaceutical processing where CIP (Clean-in-Place) compatibility and corrosion resistance are mandatory.
- Oil & Gas: Subsea flow lines, wellhead instrumentation tubing, and offshore platform piping systems requiring resistance to chloride-induced stress corrosion cracking.
- Automotive & Aerospace: Fuel lines, brake lines, exhaust systems, and hydraulic actuator tubing requiring lightweight, high-strength, and fatigue-resistant piping.
- Heat Exchangers & Cooling Systems: Coil tube for shell-and-coil heat exchangers, condenser tubes, and refrigeration circuit piping.
- Medical Devices: Endoscopic tubing, dialysis fluid lines, and surgical instrument housings requiring biocompatibility and sterilization resistance.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and product certifications to ensure traceability, conformance, and international acceptance:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- EN 10204 3.1/3.2 — Material test certificates (ENAC/DAkkS accredited inspection)
- ASTM A213 / A269 — Conformance to American standards for austenitic stainless steel seamless and welded tubing
- EN 10216-5 — European standard for welded stainless steel tubes
- GB/T 14976 — Chinese national standard for seamless stainless steel tubes
- PED 2014/68/EU — Pressure Equipment Directive compliance (CE marking available)
- ASME B31.3 — Process piping design and fabrication compliance
- NSF/ANSI 61 — Drinking water system components certification (select grades)
- 3-A Sanitary Standards — Dairy and food processing industry certification (BA finish, 316L)
7. Unique Selling Points
Joint-Free Ultra-Long Reach: The ability to deliver continuous coil tube lengths up to 800 meters eliminates the need for field welding, reducing installation time by up to 60% and virtually eliminating leak points in critical pressure systems.
- Metallurgical Homogeneity: In-line continuous annealing ensures uniform grain structure and mechanical properties along the entire tube length, unlike segmented pipe where weld HAZ (Heat-Affected Zone) creates property discontinuities.
- Superior Fatigue Resistance: The absence of weld joints provides exceptional fatigue life in cyclic-loading applications such as hydraulic systems and automotive fuel lines.
- Dimensional Consistency: Multi-stand forming with inline laser diameter monitoring ensures tight OD and wall thickness tolerances throughout the coil length.
- Corrosion-Free Integrity: Full-length pickling and passivation ensures no localized corrosion initiation at joints or weld seams.
- Cost Efficiency: Reduced field labor, fewer fittings, and lower maintenance costs result in total installed cost savings of 25–40% compared to segmented pipe systems.
- Customization Flexibility: Available in multiple grades, wall thicknesses, and surface finishes to meet specific application requirements, with custom coil diameters for compatibility with existing reel-handling equipment.
Wenzhou Jixing Metal Materials Co., Ltd. is committed to delivering world-class stainless steel coil tube solutions that combine engineering excellence, material science innovation, and rigorous quality assurance to serve the global industrial market.