Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
Product Overview
The Stainless Steel Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered continuous-length tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is supplied in a coiled configuration, offering significant advantages in storage efficiency, transportation logistics, and downstream processing flexibility. The Coiltube is specifically designed for applications in Fan Coil Units (FCUs), heat exchangers, refrigeration systems, and industrial fluid transfer systems where corrosion resistance, thermal conductivity, and mechanical integrity are paramount.
As a continuous coil product, the Coiltube eliminates the need for butt-welding joints during installation, thereby reducing potential leak points and enhancing system reliability. The coiled form factor also enables seamless integration with automated coil-forming and bending equipment, significantly reducing fabrication time and labor costs.
Material Composition & Properties
Base Materials
- Austenitic Stainless Steel: Commonly supplied in grades AISI 304 (UNS S30400), AISI 304L (UNS S30403), AISI 316 (UNS S31600), and AISI 316L (UNS S31603), selected based on the end-use environment and corrosion resistance requirements.
- Duplex Stainless Steel: Grade AISI 2205 (UNS S32205) available for applications demanding superior mechanical strength and chloride stress corrosion cracking (SCC) resistance.
Mechanical Properties
- Tensile Strength (UTS): ≥ 520 MPa (AISI 304); ≥ 550 MPa (AISI 316); ≥ 550 MPa (AISI 2205)
- Yield Strength (0.2% offset): ≥ 205 MPa (AISI 304); ≥ 205 MPa (AISI 316); ≥ 450 MPa (AISI 2205)
- Elongation (A50mm): ≥ 35% (AISI 304); ≥ 30% (AISI 316); ≥ 25% (AISI 2205)
- Hardness: ≤ 220 HB (Annealed condition)
Corrosion Resistance
- Pitting Resistance (PREN): ≥ 18 (AISI 304); ≥ 24 (AISI 316); ≥ 35 (AISI 2205)
- Excellent resistance to atmospheric corrosion, aqueous environments, and moderate chloride exposure
- Resistance to intergranular corrosion (IGC) verified per ASTM A240 Appendix A
Thermal Properties
- Thermal Conductivity: 14–16 W/(m·K) at 20°C (AISI 304)
- Linear Thermal Expansion: 17.3 × 10⁻⁶ /°C (AISI 304)
- Maximum Service Temperature: 870°C (AISI 304); 870°C (AISI 316); 300°C (AISI 2205)
Specifications
| Parameter | Specification / Range |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Product Code | 1259 |
| Outer Diameter (OD) | Φ3.0 mm – Φ35.0 mm (customizable) |
| Wall Thickness | 0.3 mm – 3.0 mm (customizable) |
| Coil Inner Diameter (ID) | Φ150 mm – Φ600 mm |
| Coil Length per Spool | 50 m – 500 m (typical); up to 1000 m on request |
| Coil Weight per Spool | 50 kg – 500 kg (typical) |
| Surface Finish | No.1 Pickled, 2B Annealed, BA (Bright Annealed), No.4 Brushed |
| Surface Roughness (Ra) | ≤ 0.4 μm (BA); ≤ 1.6 μm (2B); ≤ 3.2 μm (No.4) |
| Roundness Tolerance | ±1% of OD |
| Wall Thickness Tolerance | ±10% (standard); ±5% (precision grade) |
| OD Tolerance | ±0.1 mm (standard); ±0.05 mm (precision grade) |
| Straightness (per meter) | ≤ 1.0 mm/m (for cut-to-length sections) |
| End Form | Plain end, chamfered end, or with protective caps |
| Packaging | Wooden pallet with VCI (Vapor Corrosion Inhibitor) film wrap and moisture indicator |
| Applicable Standards | ASTM A554, ASTM A213, GB/T 12771, EN 10217-7, JIS G3446 |
Manufacturing Process
Process Flow
- Raw Material Selection: Cold-rolled stainless steel strip sourced from certified mills (e.g., POSCO, Outokumpu, Taigang) with full chemical composition and mechanical property documentation.
- Strip Inspection: Incoming material subjected to visual inspection, ultrasonic testing (UT) for internal defects, and chemical spot analysis per ASTM E1926 (OES) or ASTM E415 (wet chemistry).
- Coil Forming (Cold Bending): The strip is precisely formed into a tubular cross-section using a high-precision cold-forming roll set. The roll configuration is engineered to produce uniform wall thickness and minimal ovality.
- Welding: A continuous longitudinal seam is produced using Gas Metal Arc Welding (GMAW) or Tungsten Inert Gas (TIG) welding under argon shielding atmosphere. The welding parameters (current, voltage, wire feed speed, shielding gas flow rate) are optimized to achieve full penetration with a narrow heat-affected zone (HAZ).
- Weld Seam Inspection: 100% inline visual inspection of the weld seam. Additional Eddy Current Testing (ECT) or Optical Eddy Current (OEC) scanning is performed to detect surface and near-surface discontinuities.
- Post-Weld Heat Treatment (PWHT): For grades requiring sensitization control (e.g., 304L, 316L), solution annealing at 1050–1100°C followed by rapid quenching is performed to restore full corrosion resistance and relieve residual welding stresses.
- Pickling & Passivation: The tube is immersed in a mixed acid bath (nitric acid / hydrofluoric acid) to remove the weld discoloration and mill scale, followed by passivation in a nitric acid or citric acid solution to restore the chromium oxide passive film.
- Surface Finishing: Electropolishing or mechanical polishing is available for applications requiring enhanced surface smoothness and biocompatibility.
- Diameter & Roundness Verification: Final dimensional inspection using laser micrometers or optical gauges. Each coil is sampled and measured at multiple points along its length.
- Coiling & Packaging: The finished tube is wound onto a protective core and coiled with controlled tension to prevent deformation. Each coil is wrapped with VCI-impregnated film and shrink-wrapped for moisture protection.
Key Manufacturing Advantages
- Continuous production process enables high throughput with consistent quality
- Inline automated inspection systems ensure zero-defect tolerance for critical dimensions
- Customizable coil diameter and length to match downstream customer processing equipment
Applications
Primary Application: Fan Coil Units (FCUs)
The Coiltube is a critical component in Fan Coil Units (FCUs) — the terminal heat exchange devices used in hydronic air conditioning systems. The coil tube serves as the refrigerant or hot/cold water circuit within the FCU heat exchanger, transferring thermal energy between the fluid and the airstream. Key performance requirements for FCU applications include:
- High thermal efficiency and rapid heat transfer response
- Resistance to condensation corrosion in high-humidity environments
- Long service life with minimal maintenance
- Compliance with energy efficiency standards (e.g., ASHRAE 90.1, EN 14511)
Additional Applications
- Refrigeration & Heat Exchangers: Evaporator coils, condenser coils, and plate-fin heat exchangers in commercial and industrial refrigeration systems
- Automotive Industry: Radiator tubes, intercooler tubes, and HVAC system tubing for passenger and commercial vehicles
- Food & Beverage Processing: Sanitary-grade tubing for pasteurization systems, CIP (Clean-in-Place) loops, and process piping (BA finish, AISI 316L)
- Pharmaceutical Equipment: Clean steam lines, condensate return systems, and heat exchanger elements requiring electropolished surfaces (Ra ≤ 0.25 μm)
- Chemical Processing: Corrosive fluid transfer lines, reactor coil elements, and heat tracing systems
- Building Services: Radiator tubes, solar thermal collectors, and district heating loop tubing
- Marine & Offshore: Seawater cooling circuits, desalination plant tubing, and ballast water system piping
Quality Certifications & Compliance
Management System Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health and Safety Management System
Product & Industry Certifications
- EN 10204 3.1 — Material Test Certificate (independent third-party inspection)
- CE Marking — Compliance with European Pressure Equipment Directive (PED) 2014/68/EU where applicable
- EN 10217-7 — Seamless and welded stainless steel tubes for pressure purposes
- ASME B31.3 — Process piping code compliance for industrial applications
- ASME B31.9 — Building services piping code compliance
- NSF/ANSI 61 — Drinking water system components (available upon request)
- 3-A Sanitary Standards — Dairy and food processing equipment (available upon request)
Testing & Inspection Regime
- Hydrostatic Testing: 100% of coils tested at 1.5× maximum working pressure per ASTM A554
- Chemical Analysis: Every heat number verified per ASTM E415 or OES (ASTM E1926)
- Mechanical Testing: Tensile testing per ASTM A370; hardness testing per ASTM E92
- Corrosion Testing: Intercrystalline corrosion testing per ASTM A240 Appendix A; salt spray testing per ASTM B117 (≥ 500 hours, no pitting for 316L)
- Dimensional Verification: Inline laser measurement with statistical process control (SPC) documentation
Unique Selling Points
1. Engineering Excellence for FCU Applications: Wenzhou Jixing Metal Materials Co., Ltd has developed specialized Coiltube product lines optimized for Fan Coil Unit heat exchangers, with precise OD/wall thickness tolerances that ensure optimal fin-tube contact resistance and maximum heat transfer coefficient (h).
2. Continuous Coil Supply Advantage: The coiled format eliminates butt-weld joints, reducing installation time by up to 40% and eliminating potential leak paths — a critical advantage for sealed refrigerant systems and pressurized hydronic circuits.
3. Customization Capability: Full customization of OD, wall thickness, coil diameter, surface finish, and cut-to-length options to match specific OEM (Original Equipment Manufacturer) requirements.
4. End-to-End Quality Traceability: Each coil is traceable from raw material heat number through every manufacturing stage, supported by complete test documentation and digital quality records.
5. Competitive Cost-Efficiency: The continuous manufacturing process and lean production methodology deliver premium-quality Coiltube at competitive pricing, enabling customers to achieve optimal total cost of ownership (TCO).
Storage & Handling Recommendations
- Store in a dry, well-ventilated warehouse with relative humidity below 60%
- Do not stack coils vertically; store horizontally on wooden pallets or coil saddles
- Protect from direct contact with carbon steel to prevent galvanic corrosion
- Maintain protective wrapping intact until immediately prior to installation
- Recommended maximum storage duration: 12 months in ambient conditions
Technical Support & Consultation
Wenzhou Jixing Metal Materials Co., Ltd provides comprehensive technical support including material selection guidance, application engineering, welding procedure qualification assistance, and post-delivery quality assurance. Customers are encouraged to consult with our technical team for project-specific recommendations to ensure optimal product selection and performance.