Stainless Steel Coil Tube (Coiltube) — HVAC & Industrial Heat Exchange Grade
Product Overview
The Stainless Steel Coil Tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous coil of austenitic stainless steel tubing designed for demanding thermal exchange, fluid conveyance, and structural applications. Supplied in tight-coil configurations to facilitate downstream forming, cutting, and assembly operations, this product eliminates the need for weld joints inherent in straight-segment piping, thereby enhancing system integrity and thermal efficiency.
Coil tubes find extensive application in Fan Coil Units (FCUs), Heat Recovery Ventilators (HRVs), chiller systems, and industrial heat exchangers where corrosion resistance, high thermal conductivity, and long service life are critical performance parameters. The coil form factor reduces material waste during fabrication by up to 15–20% compared to cut-to-length straight pipe segments.
Material & Properties
The coil tube is fabricated from high-purity austenitic stainless steel grades conforming to international metallurgical standards. Key material characteristics include:
- Primary Grade: AISI 304 / EN 1.4301 (UNS S30400) — Chromium-Nickel austenitic stainless steel offering excellent corrosion resistance and formability.
- Alternate Grade: AISI 316L / EN 1.4404 (UNS S31603) — Molybdenum-enhanced grade for chloride-rich and aggressive chemical environments.
- Composition (304): Cr 18–20%, Ni 8–10.5%, C ≤ 0.08%, Mn ≤ 2.0%, Si ≤ 1.0%
- Composition (316L): Cr 16–18%, Ni 10–14%, Mo 2–3%, C ≤ 0.03%, Mn ≤ 2.0%
- Surface Finish: 2B (cold-rolled, annealed, pickled), BA (Bright Annealed), No. 4 Brushed, or Mirror (8K) upon request.
- Operating Temperature Range: −196 °C to +870 °C (continuous service)
- Corrosion Resistance: Superior resistance to atmospheric corrosion, dilute acids, alkalis, and organic chemicals.
Technical Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | Φ6.0 mm – Φ32.0 mm (custom sizes available) |
| Wall Thickness (WT) | 0.5 mm – 2.0 mm |
| Coil Inner Diameter (CID) | 300 mm – 600 mm |
| Coil Length per Spool | 50 m – 500 m (configurable) |
| Dimensional Tolerance (OD) | ±0.05 mm (Precision Grade); ±0.10 mm (Standard Grade) |
| Dimensional Tolerance (WT) | ±10% of nominal wall thickness |
| Surface Roughness (Ra) | 0.4 – 1.6 μm (BA finish); ≤ 3.2 μm (2B finish) |
| Maximum Operating Pressure | 2.5 MPa (PN25) at 20 °C ambient |
| Thermal Conductivity | 16.3 W/(m·K) at 20 °C (304 grade) |
| Yield Strength (Rp0.2) | ≥ 205 MPa (304); ≥ 170 MPa (316L) |
| Tensile Strength (Rm) | 520 – 700 MPa |
| Elongation (A50mm) | ≥ 40% |
| Applicable Standards | ASTM A269, ASTM A270, EN 10217-7, GB/T 12771 |
| Coil Packaging | Wooden pallet with VCI (Volatile Corrosion Inhibitor) film wrapping |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous, multi-stage process ensuring dimensional accuracy and metallurgical consistency:
- Raw Material Selection: Virgin stainless steel strip (cold-rolled coil) is sourced from certified mills with full chemical composition traceability. Incoming material undergoes spectroscopic verification (OES — Optical Emission Spectroscopy).
- Coil Forming (Spiral Welding): The flat strip is fed through a series of progressively reducing rolls in a spiral tube mill, forming the tube body. A continuous TIG (Tungsten Inert Gas) or automatic orbital weld seals the longitudinal seam with helium or argon back-purge to prevent internal oxidation.
- Post-Weld Annealing: The formed coil passes through a continuous annealing furnace at 1050–1150 °C in a controlled reducing atmosphere (endothermic gas or vacuum), followed by controlled cooling to restore full austenitic microstructure and relieve residual stresses.
- Pickling & Passivation: The coil is treated in a citric acid or nitric acid bath to remove mill scale and weld discoloration, followed by passivation to form a protective chromium oxide layer (Cr₂O₃) on the surface.
- Precision Sizing: Multi-stand rotary draw and reduce (DR) or cold-drawing passes refine the outer diameter and wall thickness to tight tolerances.
- Coiling & Inspection: The finished tube is wound onto a precision pay-off reel. Each coil undergoes 100% ultrasonic testing (UT) for wall thickness uniformity and radiographic spot-checking (RT) for weld seam integrity.
Applications
The stainless steel coil tube is deployed across multiple high-performance sectors:
- HVAC Systems: Coil tubes for Fan Coil Units (FCUs), air handling units, condensing units, and evaporator/condenser heat exchangers in commercial and industrial HVAC installations. The seamless coil construction minimizes flow turbulence and pressure drop.
- Chilled Water & Fresh Air Systems: Integration into energy-efficient ventilation systems where the coil tube serves as the heat transfer element between chilled/refrigerated water circuits and ambient air streams.
- Food & Beverage Processing: Sanitary-grade coil tubing for pasteurization systems, CIP (Clean-In-Place) circuits, and product transfer lines requiring hygienic surface finishes (Ra ≤ 0.4 μm).
- Pharmaceutical & Biotech: Sterilizable coil assemblies for bioreactor jacket systems, clean steam distribution, and purified water (PW) / Water for Injection (WFI) loops.
- Chemical Processing: Corrosion-resistant coil tubing for reactor cooling, distillation column internals, and chemical transfer systems handling acids, alkalis, and solvents.
- Automotive & Aerospace: Fuel lines, hydraulic circuits, and thermal management components requiring lightweight, high-strength, corrosion-resistant tubing.
- Marine & Offshore: Seawater cooling circuits, ballast water systems, and desalination plant heat exchangers (316L grade recommended).
Unique Selling Points
- Zero-Weld-Discontinuity Design: The continuous coil form eliminates intermediate butt-welds between straight pipe segments, reducing potential leak paths and enhancing system reliability by up to 30% in service life assessments.
- Energy Efficiency in HVAC Integration: Optimized coil geometry with uniform wall thickness ensures consistent heat transfer coefficients (U-values), directly contributing to lower specific fan power (SFP) and improved COP (Coefficient of Performance) in chiller and heat pump systems.
- Full Traceability: Each coil is laser-marked with a unique batch identification code linked to mill certificates, heat numbers, and test reports, ensuring complete supply chain traceability.
- Custom Configurations: Wenzhou Jixing Metal Materials offers bespoke OD × WT combinations, surface finish specifications, and coil length configurations tailored to customer-specific OEM requirements.
Quality Certifications & Compliance
The stainless steel coil tube product line holds the following certifications and complies with the listed international standards:
- ISO 9001:2015 — Quality Management System certification for manufacturing excellence and continuous improvement.
- ISO 14001:2015 — Environmental Management System certification ensuring sustainable production practices.
- ISO 45001:2018 — Occupational Health and Safety Management System certification.
- CE Marking — Conformity with European Union health, safety, and environmental protection standards (applicable to EN 10217-7).
- EN 10204 3.1 — Third-party inspection certification providing independent verification of material compliance.
- Mill Test Certificates (MTC): Full chemical analysis, mechanical test results, and hydrostatic pressure test reports provided per EN 10204 Type 3.1 or Type 3.2 upon request.
- ASME B31.3 / B31.9 — Compliance for pressure piping applications in process plants and refrigeration systems.
- NSF/ANSI 61 — Drinking water system component certification (available for 304/316L grades).
- 3-A Sanitary Standards — Food equipment compliance for dairy, beverage, and food processing applications.
Note: All dimensional tolerances, mechanical properties, and surface finish specifications are subject to mutual agreement between the supplier and the purchaser. Custom specifications beyond the standard range are available upon submission of a detailed technical inquiry. Wenzhou Jixing Metal Materials Co., Ltd. reserves the right to refine manufacturing processes to improve product performance while maintaining full compliance with certified standards.