Stainless Steel Coil Tube — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (盘管 / Coil Tube) is a precision-engineered tubular product supplied in continuous coiled form, manufactured by Wenzhou Jixing Metal Materials Co., Ltd. Designed for thermal exchange, fluid conveyance, and structural applications, this coil tube is characterized by its seamless or welded construction, high corrosion resistance, and dimensional consistency throughout the coil length. The product is particularly suited for use in Fan Coil Units (FCU) and other HVAC (Heating, Ventilation, and Air Conditioning) systems, where reliable heat transfer performance and long-term durability under variable-frequency operating conditions are critical.
Coil tubes differ from straight-length pipes in that they are delivered in a helically wound configuration, enabling direct integration into heat exchanger assemblies without the need for additional bending operations. This reduces manufacturing labor, minimizes cold-work-induced stress concentrations, and ensures geometric uniformity of the final product.
2. Material and Properties
2.1 Material Grades
- AISI 304 / SUS 304 — General-purpose austenitic stainless steel; excellent corrosion resistance and formability.
- AISI 316 / SUS 316 — Molybdenum-bearing austenitic grade; superior resistance to chlorides and aggressive chemical environments.
- AISI 304L / SUS 304L — Low-carbon variant of 304; preferred for applications requiring post-fabrication welding without sensitization concerns.
- AISI 316L / SUS 316L — Low-carbon variant of 316; enhanced weldability and intergranular corrosion resistance.
2.2 Mechanical Properties (Typical Values)
| Property | Grade 304 / 304L | Grade 316 / 316L |
|---|---|---|
| Tensile Strength (Rm) | ≥ 520 MPa | ≥ 515 MPa |
| Yield Strength (Rp0.2) | ≥ 205 MPa | ≥ 170 MPa |
| Elongation (A50mm) | ≥ 40 % | ≥ 40 % |
| Density | 7.93 g/cm³ | 8.00 g/cm³ |
| Thermal Conductivity (at 100 °C) | 16.3 W/(m·K) | 16.3 W/(m·K) |
| Thermal Expansion Coefficient (20–100 °C) | 17.3 × 10⁻⁶ /K | 17.3 × 10⁻⁶ /K |
2.3 Chemical Composition (Maximum %, unless noted)
| Element | C | Si | Mn | P | S | Cr | Ni | Mo |
|---|---|---|---|---|---|---|---|---|
| 304 / 304L | 0.08 / 0.03 | 1.00 | 2.00 | 0.045 | 0.030 | 18.00–20.00 | 8.00–10.50 | — |
| 316 / 316L | 0.08 / 0.03 | 1.00 | 2.00 | 0.045 | 0.030 | 16.00–18.00 | 10.00–14.00 | 2.00–3.00 |
3. Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 6.0 mm – 19.0 mm (custom sizes available upon request) |
| Wall Thickness | 0.5 mm – 1.5 mm |
| Coil Inner Diameter (ID) | 100 mm – 300 mm |
| Coil Length | Continuous; typical per coil: 200 m – 2000 m |
| Surface Finish | Pickled & Passivated (2B), Bright Annealed (BA), or Custom Polished |
| Tolerance — OD | ± 0.05 mm (standard); ± 0.02 mm (precision grade) |
| Tolerance — Wall Thickness | ± 10 % |
| Operating Temperature Range | −196 °C to +800 °C (grade-dependent) |
| Pressure Rating | Up to 2.5 MPa (design pressure, per ASME B31.3) |
| Applicable Standards | ASTM A213, ASTM A269, EN 10216-5, GB/T 12771, JIS G3446 |
4. Manufacturing Process
The production of stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd follows a rigorously controlled multi-stage process:
- Material Selection and Ingot Casting — High-purity chromium-nickel (and optionally molybdenum) alloy ingots are produced via Vacuum Arc Remelting (VAR) or Electro-Slag Remelting (ESR) to minimize inclusions and ensure homogeneity.
- Hot Rolling — Billets are reheated to 1100–1200 °C and hot-rolled into semi-finished coils or pipe blanks to achieve the target cross-sectional dimensions.
- Pickling and Annealing — The hot-rolled product undergoes acid pickling to remove scale, followed by solution annealing at 1050–1100 °C with rapid water quenching to restore full austenitic microstructure and corrosion resistance.
- Cold Drawing / Piercing — The tube is cold-drawn through precision dies to achieve the final OD and wall thickness specifications with tight tolerances.
- Intermediate Annealing — Periodic solution annealing during the cold-drawing process relieves work hardening and prevents cracking.
- Coiling (Helical Winding) — The finished straight tube is wound into a continuous helical coil using a controlled coiling machine that maintains uniform curvature radius and prevents kinking or flattening.
- Final Pickling and Passivation — The coiled product receives a final surface treatment to remove any residual contaminants and form a protective chromium oxide passive layer.
- Quality Inspection — Each coil undergoes dimensional measurement, hydrostatic pressure testing, surface inspection (visual and/or eddy current), and chemical composition verification.
- Packaging and Dispatch — Coils are wrapped in moisture-proof film, secured on wooden or steel pallets, and labeled with heat number, specification, and traceability documentation.
5. Applications
5.1 HVAC and Fan Coil Unit Systems
Coil tubes are integral components in Fan Coil Units (FCU), where they function as the primary heat exchanger medium. In modern variable-frequency drive (VFD) controlled FCU systems, the coil tube must withstand:
- Continuous thermal cycling between heating and cooling modes.
- Pressure fluctuations resulting from variable-speed pump and fan operation.
- Long-term exposure to humid air and condensate.
The austenitic stainless steel construction provides excellent resistance to condensation corrosion and maintains dimensional stability under thermal expansion, ensuring reliable heat transfer efficiency over the service life of the system.
5.2 Additional Applications
- Heat Exchangers — Shell-and-tube, plate-fin, and air-cooled heat exchangers in industrial and commercial systems.
- Refrigeration and Air Conditioning — Evaporator and condenser tubes in chillers and split systems.
- Automotive Industry — Intercooler tubes, radiator components, and exhaust heat recovery systems.
- Food and Beverage Processing — Sanitary-grade fluid transfer lines and CIP (Clean-in-Place) compatible tubing.
- Pharmaceutical Equipment — Sterilizable fluid handling and reactor jacket coils.
- Marine and Offshore — Seawater cooling circuits and ballast water systems (Grade 316/316L).
- Chemical Processing — Reactor internals, condensers, and transfer lines in corrosive environments.
6. Quality Certifications and Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework ensuring product conformity with international standards:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing and inspection processes.
- ISO 14001:2015 — Environmental Management System certification demonstrating sustainable manufacturing practices.
- CE Marking — Conformity with European Union directives for pressure equipment (PED 2014/68/EU) where applicable.
- Material Test Reports (MTR) — Full traceability documentation including heat analysis, mechanical test results, and NDT (Non-Destructive Testing) reports provided with each shipment.
- Third-Party Inspection — Products available for independent verification by SGS, BV, TUV, or equivalent accredited inspection bodies.
7. Unique Selling Points
7.1 Ready-to-Install Coil Configuration — Delivered in pre-formed helical coils, eliminating secondary bending operations and reducing installation time by up to 40 % compared to straight pipe assemblies.
7.2 Superior Corrosion Resistance — Austenitic stainless steel grades provide exceptional resistance to atmospheric, chemical, and condensation-induced corrosion, extending service life beyond 25 years in typical HVAC applications.
7.3 Precision Dimensional Control — Tight manufacturing tolerances (± 0.02 mm OD precision grade) ensure optimal fit in heat exchanger tube sheets and reliable mechanical integrity under variable-frequency operating conditions.
7.4 Full Traceability — Every coil is accompanied by complete heat-number traceability, enabling lifecycle quality management and regulatory compliance audits.
7.5 Customization Capability — Non-standard diameters, wall thicknesses, coil configurations, and surface finishes are available to meet specific engineering requirements.
8. Storage and Handling Recommendations
- Store coils in a dry, well-ventilated area protected from moisture, chlorides, and abrasive particulates.
- Maintain coils on their original pallets or coil saddles; do not stack vertically without proper support.
- Avoid contact with carbon steel tools or equipment to prevent cross-contamination and galvanic corrosion.
- Handle with appropriate lifting equipment rated for the coil weight; use soft slings to protect the surface finish.
9. Conclusion
The Stainless Steel Coil Tube offered by Wenzhou Jixing Metal Materials Co., Ltd represents a high-performance solution for thermal management and fluid handling applications. Its combination of corrosion resistance, dimensional precision, ready-to-install coil geometry, and compliance with international quality standards makes it an ideal choice for modern HVAC systems, industrial heat exchangers, and demanding process environments. The product's proven compatibility with fuzzy variable-frequency control systems in Fan Coil Units further validates its suitability for energy-efficient, intelligent building automation applications.