Stainless Steel Coil Tube (Coiltube) — Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (also referred to as Coiltube or Coil Pipe) is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is supplied in continuous coil form, offering exceptional flexibility in downstream processing, installation, and integration into complex system architectures. The coil tube is designed to deliver superior mechanical strength, outstanding corrosion resistance, and long-term structural integrity across a wide range of industrial and commercial environments.
Coiltube products are extensively utilized in Heat Recovery Ventilation (HRV) systems, Heat Exchanger (HX) assemblies, Building Management Systems (BMS), and Building Automation Systems (BAS), where seamless fluid transfer and thermal management are critical performance parameters. The continuous coil configuration eliminates the need for field welding or brazing at intermediate joints, thereby reducing potential leak points and enhancing system reliability.
2. Material Composition & Properties
2.1 Base Material Grades
- AISI 304 / 1.4301 — General-purpose austenitic stainless steel with excellent formability and moderate corrosion resistance; suitable for non-aggressive environments.
- AISI 316 / 1.4401 — Molybdenum-enhanced austenitic stainless steel offering superior resistance to chlorides, acids, and marine environments.
- AISI 316L / 1.4404 — Low-carbon variant of 316, optimized for welding applications and cryogenic service conditions.
- AISI 321 / 1.4541 — Titanium-stabilized grade with enhanced resistance to intergranular corrosion at elevated temperatures.
2.2 Mechanical Properties
| Property | Unit | AISI 304 | AISI 316 | AISI 316L |
|---|---|---|---|---|
| Tensile Strength (Ultimate) | MPa | ≥ 520 | ≥ 515 | ≥ 485 |
| Yield Strength (0.2% Proof) | MPa | ≥ 205 | ≥ 205 | ≥ 170 |
| Elongation (at Break) | % | ≥ 40 | ≥ 40 | ≥ 45 |
| Density | g/cm³ | 8.0 | 8.0 | 8.0 |
| Thermal Conductivity (20°C) | W/(m·K) | 16.3 | 14.6 | 14.6 |
| Thermal Expansion Coefficient (20–100°C) | ×10⁻⁶ /K | 17.3 | 16.0 | 16.0 |
| Maximum Service Temperature | °C | 870 | 870 | 870 |
2.3 Chemical Composition (Typical, wt%)
| Element | AISI 304 | AISI 316 | AISI 316L |
|---|---|---|---|
| C (Carbon) | ≤ 0.08 | ≤ 0.08 | ≤ 0.03 |
| Cr (Chromium) | 18.0–20.0 | 16.0–18.0 | 16.0–18.0 |
| Ni (Nickel) | 8.0–10.5 | 10.0–14.0 | 10.0–14.0 |
| Mo (Molybdenum) | — | 2.0–3.0 | 2.0–3.0 |
| Mn (Manganese) | ≤ 2.0 | ≤ 2.0 | ≤ 2.0 |
| Si (Silicon) | ≤ 1.0 | ≤ 1.0 | ≤ 1.0 |
| P (Phosphorus) | ≤ 0.045 | ≤ 0.045 | ≤ 0.045 |
| S (Sulfur) | ≤ 0.030 | ≤ 0.030 | ≤ 0.030 |
3. Dimensional Specifications
| Parameter | Specification Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 50.8 mm | ASTM A554 / ASME SA-554 |
| Wall Thickness (WT) | 0.3 mm – 3.0 mm | ASTM A554 / ASME SA-554 | Coil Length (per spool) | 20 m – 200 m (customizable) | Manufacturer Specification |
| Coil Winding Diameter | 300 mm – 1200 mm | Manufacturer Specification |
| Surface Finish | Bright Annealed (BA) / Pickled & Passivated (P&P) / Hairline | ASTM A473 |
| Tolerance on OD | ±0.05 mm (precision grade) / ±0.10 mm (standard grade) | EN 10217 / ASTM A554 |
| Tolerance on WT | ±10% (standard) / ±5% (precision) | EN 10217 / ASTM A554 |
| End Condition | Plain cut / Beveled / Flanged / Threaded (on request) | Customer Specification |
| Maximum Pressure Rating | Up to 16 MPa (depending on OD/WT combination) | PV-RT-10 / PED 2014/68/EU |
| Temperature Range | −196 °C to +870 °C | Material-dependent |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Procurement: High-purity stainless steel strip or rod sourced from certified mills (e.g., Outokumpu, Posco, Baosteel) with full chemical composition and mechanical property documentation.
- Coil Straightening & Forming: The strip material is fed through a series of precision rolls to achieve the target outer diameter and wall thickness with minimal residual stress.
- Seam Welding: High-frequency induction welding (HF-IW) or TIG (Tungsten Inert Gas) orbital welding is employed to create a continuous, defect-free longitudinal seam. Seam weld quality is verified via ultrasonic testing (UT) and dye penetrant inspection (DPI).
- Heat Treatment: Solution annealing is performed at 1010–1150 °C followed by rapid water quenching to achieve full austenitic microstructure and maximize corrosion resistance. For 316L grades, a sub-solution treatment at 870 °C may be applied to prevent sensitization.
- Pickling & Passivation: Post-welding acid pickling removes oxide scale; subsequent passivation with nitric acid or citric acid forms a stable chromium oxide (Cr₂O₃) passive film on the surface.
- Coil Winding: The formed tube is wound onto a precision spool with controlled winding tension to prevent deformation or ovality.
- Quality Inspection: Every coil undergoes comprehensive non-destructive testing (NDT) including ultrasonic testing, eddy current testing (ECT), hydrostatic pressure testing (per ASTM A554), and dimensional verification via laser diameter gauges.
- Packaging & Shipping: Coils are wrapped in moisture-proof polyethylene film, secured with steel strapping, and palletized for export or domestic distribution.
4.2 Key Process Controls
- Weld seam quality maintained to Class A per ASTM A554 (continuous, uniform, and free from porosity or lack of fusion).
- Dimensional tolerances controlled to ±5% on wall thickness for precision-grade applications.
- Surface roughness (Ra) maintained at ≤ 0.8 μm for BA finish and ≤ 1.6 μm for P&P finish.
- Every production batch is traceable via unique heat number and mill certificate.
5. Applications
5.1 HVAC & Building Energy Systems
Stainless steel coil tubes are integral components in Heat Recovery Ventilation (HRV) systems, Variable Refrigerant Flow (VRF) air conditioning units, and fan coil units (FCU). Their seamless construction and corrosion resistance make them ideal for heat exchanger cores where thermal efficiency and long service life are paramount. In smart building environments, coil tubes serve as the fluid transport medium in Building Automation Systems (BAS) and networked temperature control solutions, enabling precise energy metering and billing.
5.2 Additional Applications
- Medical Equipment: Sterilization equipment, dialysis machines, and pharmaceutical fluid transfer lines (requires 316L grade).
- Food & Beverage Processing: Sanitary piping for dairy, brewing, and beverage production lines (FDA-compliant surface finish).
- Automotive Industry: Exhaust systems, turbocharger intercooler piping, and fuel delivery lines.
- Petrochemical & Marine: Seawater cooling circuits, offshore platform piping, and chemical processing reactors (316/316L grade recommended).
- Solar Thermal & Geothermal: Heat transfer loops in concentrated solar power (CSP) plants and geothermal energy extraction systems.
- Furniture & Architectural Decoration: Structural supports and decorative elements in high-end interior design.
6. Quality Certifications & Standards Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System — ensures consistent product quality and process control. |
| ISO 14001:2015 | Environmental Management System — demonstrates commitment to sustainable manufacturing. |
| ISO 45001:2018 | Occupational Health & Safety Management System. |
| EN 10217-7 | European standard for stainless steel seamless and welded tubes for pressure purposes. |
| ASTM A554 / ASME SA-554 | American standard for seamless and welded austenitic stainless steel tubing for general purposes. |
| ASTM A213 | Standard for austenitic stainless steel seamless, welded, and heavily cold-worked tubing for heat-exchanger and heat-sink applications. |
| PED 2014/68/EU | European Pressure Equipment Directive compliance for pressure-rated applications. |
| CE Marking | Conformity to European health, safety, and environmental protection standards. |
| NSF 61 | Drinking water system components certification (for potable water applications). |
| Mill Test Certificate (MTC) — EN 10204 3.1 | Third-party verified material certificate accompanying every shipment. |
7. Unique Selling Points
- Seamless Corrosion Resistance: The continuous coil form with fully welded and annealed seams eliminates galvanic corrosion risk at joints, extending service life beyond 25 years in aggressive environments.
- Installation Efficiency: Coil supply format reduces on-site assembly time by up to 60% compared to straight pipe sections, minimizing labor costs and project schedules.
- Design Flexibility: Continuous coil configuration allows for custom bending, routing, and forming without additional welding — ideal for complex geometries in heat exchangers and piping systems.
- Thermal Performance: Optimized wall thickness and high-purity alloy composition deliver superior heat transfer coefficients, critical for HVAC and energy recovery applications.
- Full Traceability: Every coil is accompanied by a complete quality dossier including heat number, chemical analysis, mechanical test results, and dimensional inspection records.
- Custom Engineering: Wenzhou Jixing Metal Materials Co., Ltd. offers tailored specifications including custom OD/WT combinations, special surface finishes, and application-specific end treatments.
8. Ordering & Technical Support
For detailed quotations, sample requests, or custom engineering consultations, contact Wenzhou Jixing Metal Materials Co., Ltd. directly. Technical support is available in English and Chinese to assist with material selection, specification validation, and compliance documentation for international projects.
Reference: Product Catalog No. 1