Stainless Steel Coil Tube (Coiltube) — Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product formed into continuous helical or spiral configurations. Designed for use in heat exchanger assemblies, fan coil units (FCU), HVAC systems, and thermal management applications, this coil tube offers superior thermal conductivity, corrosion resistance, and mechanical integrity under cyclic loading conditions.
Unlike conventional straight pipe sections, the coil tube geometry maximizes the surface-area-to-volume ratio, enabling enhanced heat transfer efficiency in compact system footprints. The product is available in a range of diameters, wall thicknesses, and coil pitch configurations to accommodate diverse engineering requirements.
2. Material & Properties
2.1 Base Material Composition
- Austenitic Stainless Steel Grades: AISI 304, AISI 304L, AISI 316, AISI 316L, AISI 321, AISI 310S
- Ferritic & Duplex Grades (on request): AISI 430, UNS S31803 (2205 Duplex)
2.2 Key Mechanical & Physical Properties
- Tensile Strength (UTS): 515–720 MPa (depending on grade and condition)
- Yield Strength: 205–310 MPa (0.2% offset)
- Elongation: ≥40% (at break)
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 25°C
- Operating Temperature Range: −196°C to +870°C (grade-dependent)
- Corrosion Resistance: Excellent resistance to pitting, crevice corrosion, and intergranular corrosion in chloride-containing environments (particularly 316/316L grades)
- Cold Workability: Suitable for cold forming, coiling, and bending without pre-heating
3. Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 50.8 mm (1/8" – 2") | ASTM A511 / GB/T 12771 |
| Wall Thickness | 0.3 mm – 3.0 mm | ASTM A511 / GB/T 12771 |
| Coil Pitch | 5 mm – 50 mm (customizable) | Custom / Project-Specific |
| Coil Length | 1 m – 100 m (continuous or segmented) | Custom / Project-Specific |
| Surface Finish | Bright Annealed, Pickled & Passivated (P&P), No. 4 Brushed, Mirror (8K) | ASTM A473 / GB/T 4237 |
| Tolerance (OD) | ±0.05 mm – ±0.15 mm | ASTM A511 |
| Tolerance (Wall) | ±10% of nominal | ASTM A511 |
| End Treatment | Plain cut, Beveled, Flanged, Threaded, or Solder-Ready | Custom / Project-Specific |
| Coil Diameter (Bundle) | 100 mm – 800 mm | Custom / Project-Specific |
4. Manufacturing Process
- Raw Material Procurement & Inspection: Certified stainless steel strip or seamless tube stock is sourced from approved mills with full mill test certificates (MTC) conforming to EN 10204 3.1 or 3.2.
- Blanking & Annealing: Raw stock undergoes solution annealing at 1050–1150°C followed by controlled cooling to ensure a uniform austenitic microstructure and eliminate residual stresses.
- Forming & Coiling: Precision CNC-controlled forming machinery shapes the tube into the required helical geometry. Multi-axis servo-controlled rollers ensure consistent coil pitch and dimensional accuracy throughout the production run.
- Welding (if applicable): For seamless coil tubes formed from strip, longitudinal seams are welded via Automatic Welding (AW) or TIG (Tungsten Inert Gas) welding with full penetration, followed by post-weld annealing.
- Heat Treatment: Final annealing at 1040–1120°C in a protective atmosphere (argon or vacuum) to restore ductility and enhance corrosion resistance.
- Pickling & Passivation: Chemical treatment to remove oxide scale and form a protective chromium oxide passive layer, ensuring long-term corrosion resistance.
- Quality Inspection: Non-Destructive Testing (NDT) including eddy current testing, hydrostatic pressure testing (2–3× working pressure), dimensional verification via coordinate measuring machines (CMM), and visual inspection.
- Packaging: Coils are wrapped in protective film, placed in moisture-proof bags, and secured on wooden pallets or steel frames for shipping.
5. Applications
5.1 HVAC & Thermal Management
- Fan Coil Units (FCU) — coil tubes serve as the primary heat exchange element in air handling systems, where the helical geometry maximizes contact area between the refrigerant and air stream.
- Chilled water and hot water distribution coils
- Air-to-water heat exchangers
5.2 Industrial Heat Exchangers
- Shell-and-tube heat exchanger tube bundles
- Plate-fin heat exchanger channels
- Condensers and evaporators in refrigeration systems
5.3 Process & Chemical Industry
- Corrosive fluid transfer in chemical processing
- Food and beverage industry heat transfer (316L grade for sanitary compliance)
- Pharmaceutical equipment and clean-in-place (CIP) systems
5.4 Marine & Offshore
- Seawater cooling systems (316L and duplex grades)
- Marine HVAC and ballast water heat exchangers
5.5 Specialized Applications
- High-temperature exhaust gas heat recovery (321, 310S grades)
- Cryogenic applications (304L, 316L grades down to −196°C)
- Solar thermal collector absorber tubes
6. Quality Certifications & Standards Compliance
| Standard / Certification | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification for manufacturing processes |
| ISO 14001:2015 | Environmental Management System certification |
| EN 10204 3.1 / 3.2 | Material Test Certificate (Mill Certificate) with full traceability |
| ASTM A511 | Standard Specification for Seamless and Wrought Stainless Steel Tubes for Heat-Transfer Equipment |
| ASTM A554 | Standard Specification for Seamless and Wrought Austenitic Stainless Steel Tubing and Pipe for Chemical and Similar Service |
| GB/T 12771 | Chinese National Standard for Stainless Steel Tubes for General Purposes |
| GB/T 17705 | Chinese National Standard for Stainless Steel Tubes for Heat Exchangers and Condensers |
| ASME SB 167 / SB 168 | American Society of Mechanical Engineers boiler and pressure vessel tube specifications |
| EN 10217-7 | European standard for stainless steel tubes for heat exchangers and condensers |
| CE Marking | Compliance with European health, safety, and environmental protection standards |
| NSF / FDA (on request) | Food-safe certification for sanitary applications (316L grade) |
7. Unique Selling Points
Wenzhou Jixing Metal Materials Co., Ltd. differentiates its Stainless Steel Coil Tube product line through the following value propositions:
- Integrated Centralized Control Technology: Drawing from advanced research in centralized silicon-controlled rectifier (SCR) speed regulation for fan coil unit applications, the company integrates intelligent thermal management design principles into coil tube geometry optimization, ensuring peak efficiency when paired with variable-speed FCU systems.
- Full Traceability: Every coil tube batch is traceable to its raw material origin through a digital quality management system, with complete documentation of chemical composition, mechanical testing, and dimensional inspection records.
- Custom Engineering Capability: The company offers fully customized coil geometry, pitch, length, and surface finish configurations to meet project-specific thermal performance targets, supported by finite element analysis (FEA) and computational fluid dynamics (CFD) simulation.
- Multi-Grade Material Availability: A comprehensive inventory of austenitic, ferritic, and duplex stainless steel grades ensures that the correct material solution is available for any service environment — from aggressive chloride atmospheres to cryogenic temperatures.
- Quality Assurance at Every Stage: From incoming material inspection through final packaging, a multi-stage quality control protocol ensures that every product meets or exceeds the specified standards before dispatch.
- Competitive Lead Times: Strategic inventory management and flexible manufacturing capacity enable rapid response to both standard and custom orders, minimizing project downtime.
8. Technical Notes
When integrating Stainless Steel Coil Tubes into Fan Coil Unit (FCU) systems employing centralized Silicon Controlled Rectifier (SCR) motor speed regulation, the coil geometry — including pitch, diameter, and tube count per circuit — should be optimized to maintain consistent heat transfer coefficients across the full operating speed range. The helical form factor of the coil tube inherently promotes turbulent flow development at lower Reynolds numbers compared to straight tube configurations, which contributes to stable thermal performance even at reduced fan speeds. This characteristic makes the product particularly well-suited for energy-efficient HVAC systems that operate across variable load conditions.
For applications requiring enhanced fouling resistance in water-side service, the Pickled & Passivated (P&P) surface finish is recommended, as the smooth, oxide-free surface minimizes scale adhesion and facilitates cleaning cycles.