Stainless Steel Coil Tube (Coiltube) — Model No. 1253
Product Overview
The Stainless Steel Coil Tube (Coiltube), designated as Model No. 1253, is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This coil tube is specifically designed for application in HVAC (Heating, Ventilation, and Air Conditioning) systems, particularly in dry-condition fan coil units (Fan Coil Units, FCUs) integrated with ice thermal storage fresh air systems. The product is supplied in continuous coil form, enabling efficient downstream forming, bending, and assembly operations with minimal material waste.
This coil tube serves as a critical heat exchange component in advanced air conditioning architectures that combine sensible cooling (dry condition) with latent heat management through ice thermal storage. The dry-condition operation ensures dehumidification-free cooling, maintaining indoor relative humidity at optimal levels while delivering superior thermal comfort.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, conforming to the following material specifications:
- Base Alloy: Type 304 (UNS S30400) or Type 316L (UNS S31603) austenitic stainless steel, selected based on corrosion resistance requirements of the specific application environment.
- Carbon Equivalent (Ceq): < 0.08% (304); < 0.03% (316L), ensuring excellent weldability and resistance to intergranular corrosion.
- Chromium (Cr) Content: 18.0–20.0 wt% (304); 16.0–18.0 wt% (316L), providing robust passive film formation and oxidation resistance.
- Nickel (Ni) Content: 8.0–10.5 wt% (304); 10.0–14.0 wt% (316L), stabilizing the austenitic crystal structure.
- Molybdenum (Mo) Content: < 0.10 wt% (304); 2.0–3.0 wt% (316L), enhancing resistance to pitting and crevice corrosion in chloride environments.
- Thermal Conductivity: 16.3 W/(m·K) at 20°C (304), ensuring efficient heat transfer in cooling and heating cycles.
- Corrosion Resistance: Passivation potential (Ecorr) > +200 mV vs. Ag/AgCl in neutral aqueous environments; resistance to atmospheric, industrial, and marine corrosion.
- Operating Temperature Range: −196°C to +870°C (304); −273°C to +870°C (316L), accommodating cryogenic ice thermal storage applications.
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Product Model | 1253 | — |
| Outer Diameter (OD) | 6.35 mm / 9.53 mm / 12.7 mm / 15.88 mm (1/4" / 3/8" / 1/2" / 5/8") | ASTM A213 |
| Wall Thickness | 0.50 mm / 0.80 mm / 1.00 mm / 1.20 mm | ASTM A213 |
| Material Grade | SUS304 / SUS316L / 304L / 316L | ASTM A213 / JIS G4304 |
| Surface Finish | No. 4 Brushed / No. 8 Mirror / 2B Annealed / Pickled | ASTM A480 |
| Coil Inner Diameter | 150 mm / 200 mm / 250 mm / 300 mm | Internal Specification |
| Coil Length (Continuous) | 50 m – 200 m (standard); up to 500 m (custom) | Internal Specification |
| Tolerance on OD | ±0.05 mm | ASTM A213 |
| Tolerance on Wall Thickness | ±10% of nominal | ASTM A213 |
| Maximum Working Pressure | ≤ 1.6 MPa (at 25°C) | ASME B31.5 |
| Heat Treatment | Solution Annealed (1050–1150°C) followed by water quenching | ASTM A213 |
| Delivery Condition | Continuous coil, protected against mechanical damage and moisture | — |
| Applicable Fluids | Chilled water, glycol-water mixtures, refrigerants, air | ASHRAE 15 |
Manufacturing Process
The production of the Model 1253 Stainless Steel Coil Tube follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection: Cold-rolled stainless steel strip (CRSS) conforming to ASTM A480, with certified chemical composition and mechanical properties. Incoming material undergoes spectroscopic analysis (OES) to verify alloying element concentrations.
- Slitting and Leveling: The coil strip is slit to the required width and leveled to eliminate residual stresses and ensure flatness within ±0.1 mm/m.
- Roll Forming (Tube Forming): The leveled strip passes through a series of progressive forming rolls that shape it into a seamless tubular geometry. Forming parameters are precisely controlled to maintain dimensional tolerances and prevent surface defects.
- Welding (where applicable): For welded coil tubes, a high-purity TIG (Tungsten Inert Gas) welding process is employed with argon shielding to produce a fully penetrated weld seam. Weld bead height is controlled to ≤ 0.1 mm internal protrusion to minimize flow resistance and erosion corrosion.
- Solution Annealing: The formed tube is solution annealed at 1050–1150°C in a controlled atmosphere furnace (dew point < −60°C) to dissolve carbide precipitates, restore full austenitic structure, and achieve maximum corrosion resistance. Water quenching follows immediately to lock in the solution-treated microstructure.
- Pickling and Passivation: The annealed tube undergoes acid pickling (HNO3/H2SO4 or HNO3/HF blend) to remove mill scale and oxide films, followed by passivation treatment to restore the chromium-rich passive layer.
- Surface Finishing: Depending on the specified finish grade, the tube may undergo brushing, polishing, or mechanical finishing to achieve the target surface roughness (Ra ≤ 0.8 μm for standard; Ra ≤ 0.2 μm for mirror finish).
- Coiling and Packaging: The finished tube is coiled onto a mandrel of the specified inner diameter. Each coil is wrapped in moisture-barrier film, placed in protective packaging, and labeled with full traceability documentation.
Applications
The Model 1253 Stainless Steel Coil Tube is engineered for demanding applications in the HVAC and thermal management sectors:
- Dry-Condition Fan Coil Units: Serves as the primary heat exchange coil in FCUs operating in sensible-only cooling mode, where the coil surface temperature remains above the dew point to prevent condensation and maintain indoor humidity control.
- Ice Thermal Storage Systems: Functions as the heat transfer medium in ice-on-chilled-water (IOW) or ice-in-chilled-water (ICW) thermal storage systems, where the coil tube transports low-temperature brine or glycol-water solutions to melt or form ice packs.
- Fresh Air Systems: Integrated into dedicated outdoor air systems (DOAS) that combine sensible cooling with heat recovery, enabling energy-efficient ventilation in commercial and institutional buildings.
- Process Cooling: Applicable in food and beverage processing, pharmaceutical manufacturing, and laboratory environments where corrosion resistance and hygienic surface conditions are critical.
- Marine and Coastal HVAC: Suitable for air conditioning systems in marine vessels, offshore platforms, and coastal facilities due to the superior chloride resistance of 316L-grade coil tubes.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system with the following certifications and compliance standards:
- ISO 9001:2015 — Quality Management System certification for consistent product quality and process control.
- ISO 14001:2015 — Environmental Management System certification, ensuring environmentally responsible manufacturing practices.
- ISO 45001:2018 — Occupational Health and Safety Management System certification.
- CE Marking — Compliance with European Union directives for safety and performance.
- ASME A213 — Conformity with the American Society of Mechanical Engineers standard for seamless and welded austenitic stainless steel tubing.
- JIS G4304 — Compliance with the Japanese Industrial Standard for stainless steel tubing.
- EN 10216-5 — Compliance with the European standard for welded austenitic stainless steel tubes.
- Mill Test Certificates (MTC) — Full EN 10204 3.1 and 3.2 test documentation provided for every production lot, including chemical analysis, mechanical test results, and heat treatment records.
Unique Selling Points
1. Superior Thermal Performance: The austenitic stainless steel matrix provides a thermal conductivity of 16.3 W/(m·K), combined with the continuous coil geometry that maximizes heat transfer surface area per unit volume — critical for the high-efficiency operation of dry-condition fan coil units.
2. Cryogenic Compatibility: The material retains full ductility and mechanical integrity at temperatures as low as −196°C, making it uniquely suited for ice thermal storage systems that operate at sub-zero temperatures without risk of brittle fracture.
3. Extended Service Life: With proper passivation and in compatible fluid environments, the expected service life exceeds 25 years, significantly outperforming carbon steel alternatives in corrosive HVAC applications.
4. Continuous Coil Supply: The coil form factor eliminates the need for field welding of straight tube sections, reducing installation time by up to 40% and minimizing leak points in the assembled system.
5. Full Traceability: Every coil is accompanied by comprehensive mill documentation enabling complete material traceability from raw steel melt to finished product, satisfying stringent regulatory requirements in pharmaceutical and food-grade applications.
6. Customization Capability: Flexible manufacturing parameters allow customization of outer diameter, wall thickness, surface finish, and coil dimensions to meet specific OEM (Original Equipment Manufacturer) design requirements.
Conclusion
The Model 1253 Stainless Steel Coil Tube represents a state-of-the-art solution for HVAC applications demanding high corrosion resistance, thermal efficiency, and cryogenic reliability. Its application in dry-condition fan coil units coupled with ice thermal storage fresh air systems exemplifies the integration of advanced materials science with sustainable building energy management strategies. Wenzhou Jixing Metal Materials Co., Ltd. is committed to delivering products that meet the highest international standards while supporting the global transition toward energy-efficient, environmentally responsible air conditioning technologies.