Stainless Steel Coil Tube (Coiltube) — Model No. 901
Product Overview
The Model No. 901 Stainless Steel Coil Tube (盘管) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous-length tubing product designed for thermal regulation and fluid transfer applications. Unlike traditional straight-length seamless or welded tubes, coil tubes are supplied in continuous coil form, enabling on-site forming and installation with minimal cutting and welding, thereby reducing material waste and labor costs. This product category has gained significant traction in industrial aquaculture systems, HVAC (Heating, Ventilation, and Air Conditioning) applications, heat exchangers, and chemical processing plants where reliable thermal conductivity, corrosion resistance, and hygienic surfaces are critical performance requirements.
The economic comparison study conducted in Ningbo marine fishing villages demonstrated that stainless steel coil tubes outperform conventional carbon steel alternatives in factory-based aquaculture pond temperature control systems, offering superior lifecycle cost efficiency despite higher initial material investment. This validation underscores the product's suitability for demanding, long-duration operational environments.
Material & Properties
Material Grades
- AISI 304 (UNS S30400): The most widely specified grade for general-purpose coil tubes. Contains approximately 18–20% Chromium (Cr) and 8–10.5% Nickel (Ni), providing excellent general corrosion resistance, good formability, and weldability. Suitable for food-grade, pharmaceutical, and marine aquaculture applications.
- AISI 316 (UNS S31600): Enhanced grade incorporating 2–3% Molybdenum (Mo), delivering superior resistance to pitting and crevice corrosion, particularly in chloride-rich environments such as seawater aquaculture systems. Recommended for high-chloride and high-temperature applications.
- AISI 316L (UNS S31603): Low-carbon variant of 316 (carbon ≤ 0.03%), optimized for welded assemblies and applications requiring resistance to intergranular corrosion (IGC) during heat-affected zone exposure.
- AISI 321 (UNS S32100): Titanium-stabilized grade suitable for elevated-temperature service up to 870°C, with enhanced resistance to stress corrosion cracking (SCC).
Key Physical and Mechanical Properties (AISI 304 Reference)
- Density: 7.93 g/cm³
- Thermal Conductivity: 16.3 W/(m·K) at 20°C
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (20–100°C)
- Yield Strength (0.2% Offset): ≥ 205 MPa (annealed condition)
- Tensile Strength (Rm): ≥ 520 MPa (annealed condition)
- Elongation (A50mm): ≥ 40%
- Operating Temperature Range: −196°C to +870°C
Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | Φ6.0 mm – Φ108 mm | ASTM A213 / GB/T 14976 |
| Wall Thickness (WT) | 0.5 mm – 3.0 mm | ASTM A213 / GB/T 14976 |
| Tolerance on OD | ±0.10 mm (standard); ±0.05 mm (precision grade) | ISO 4287 |
| Tolerance on Wall Thickness | ±10% (standard); ±5% (precision grade) | ASTM A213 |
| Coil Length | 20 m – 60 m (continuous coil) | — |
| Coil Inner Diameter (Coil ID) | Φ500 mm – Φ1500 mm | — |
| Surface Finish | 2B (cold-rolled), No. 4 Brushed, BA (Bright Annealed), Electropolished (Ra ≤ 0.4 μm) | ASTM A480 / GB/T 4237 |
| End Condition | Plain cut, beveled (15°/30°), or threaded | ASME B1.20.1 |
| Heat Treatment Condition | Annealed (Solution Annealed) — 1050–1100°C water/quench | ASTM A213 |
| Maximum Working Pressure | Up to 1.6 MPa (PN16) at 20°C (grade-dependent) | ASME B31.3 |
| Test Standards | Hydrostatic test, Eddy Current (EC) inspection, Spectroscopic analysis | ASTM A269 / GB/T 12451 |
Manufacturing Process
- Raw Material Selection and Mill Certification: Virgin stainless steel strip or billet sourced from certified mills (e.g., Outokumpu, POSCO, Taigang) with full mill test certificates (MTC) conforming to EN 10204 Type 3.1. Incoming material undergoes spectroscopic verification via Optical Emission Spectrometry (OES) to confirm chemical composition within ASTM A240/A213 limits.
- Coil Slitting and Leveling: Wide stainless steel coil is slit to the required blank width using precision slitting lines with optical edge detection. The slit coil passes through a tension-leveling unit to achieve flatness tolerance of ≤ 0.15% of length.
- Forming (Cold Roll Forming / Multi-Stand Rolling): The leveled strip is fed through a multi-stand cold rolling mill (typically 20–30 stands) where progressive die sets incrementally reduce the strip to the target OD and wall thickness. This process maintains tight dimensional tolerances and eliminates the need for post-forming annealing in most cases.
- In-Line Inspection: Each coil undergoes automated ultrasonic thickness measurement (UT), eddy current flaw detection (for subsurface and surface discontinuities), and optical diameter measurement. Non-conforming segments are automatically marked or rejected.
- Solution Annealing (if required): For orders specifying a fully annealed condition, the formed coil is solution-annealed in a continuous belt furnace at 1050–1100°C followed by controlled quenching (water or air) to achieve a fully recrystallized, stress-free microstructure with optimal mechanical properties.
- Pickling and Passivation: Annealed coils are subjected to acid pickling (HNO₃/HF or citric acid blend) to remove oxide scale, followed by passivation treatment to restore the protective chromium oxide passive layer (Cr₂O₃) on the surface.
- Surface Finishing: Depending on the order specification, coils may undergo mechanical brushing (No. 4 finish), electropolishing, or bead blasting. Electropolished surfaces achieve a surface roughness (Ra) as low as 0.2–0.4 μm, critical for hygienic and pharmaceutical applications.
- Final Coiling and Packaging: The finished tube is re-coiled onto a steel core with the specified coil ID. Each coil is wrapped in protective film, placed in a moisture-proof polyethylene bag, and secured on a wooden pallet or steel skid for transport. Desiccant packs are included to prevent transit corrosion.
Applications
Primary Applications
- Industrial Aquaculture and Mariculture: As validated in the Ningbo marine fishing village study, stainless steel coil tubes serve as heat exchange elements in factory-based aquaculture pond temperature control systems. The coils are immersed in water tanks or integrated into heat exchanger bundles to precisely regulate water temperature (typically 15–30°C) for optimal fish and shellfish growth. The corrosion resistance of AISI 316/316L grades in chloride-rich seawater environments is a decisive advantage over carbon steel alternatives, significantly extending service life from 2–3 years to 10–15 years.
- Heat Exchangers and Radiators: Coil tubes are the core component of plate-fin heat exchangers, air-to-water heat pumps, and industrial process heaters. The continuous coil form allows tight winding patterns that maximize heat transfer surface area per unit volume.
- HVAC and Refrigeration Systems: Used as refrigerant circuit tubing in commercial and industrial refrigeration units, condensing units, and evaporator coils. The high thermal conductivity and low thermal resistance of stainless steel support efficient phase-change heat transfer.
- Chemical Processing and Petrochemical: Coil tubes are employed in chemical reactors, distillation columns, and heat recovery systems where resistance to aggressive process media (acids, alkalis, halides) is essential.
- Food and Beverage Processing: Hygienic-grade electropolished coil tubes are used in dairy pasteurization systems, brewing equipment, and pharmaceutical CIP (Clean-In-Place) systems where surface cleanliness and non-reactivity are regulatory requirements (FDA, 3-A Sanitary Standards).
- Oil and Gas (Upstream and Downstream): AISI 316L and duplex stainless steel coil tubes are used in subsea production systems, gas processing plants, and refinery heat exchangers operating in high-pressure, high-temperature, high-chloride (H₂S-containing) environments.
Economic Performance in Aquaculture Applications
The comparative economic analysis conducted in Ningbo demonstrated that while the initial capital expenditure (CAPEX) for stainless steel coil tubes is approximately 2.5–3.5× that of carbon steel equivalents, the total cost of ownership (TCO) over a 10-year operational period is 35–50% lower due to:
- Elimination of frequent replacement cycles (10–15 year service life vs. 2–3 years for carbon steel)
- Reduced maintenance and downtime costs (no rust-related fouling or tube blockage)
- Improved thermal efficiency over the service life (no oxide layer degradation of heat transfer)
- Lower environmental and disposal costs associated with corrosive waste
Quality Certifications and Compliance
Product Certifications
- ISO 9001:2015 — Quality Management System certification covering all manufacturing processes at Wenzhou Jixing Metal Materials Co., Ltd.
- ISO 14001:2015 — Environmental Management System certification, demonstrating commitment to sustainable manufacturing practices and waste minimization.
- ISO 45001:2018 — Occupational Health and Safety Management System certification.
Material and Product Standards Compliance
- ASTM A213: Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubes for High-temperature Service.
- ASTM A269: Standard Specification for Welded Austenitic Stainless Steel Tube for Chemical and Similar Severe Service.
- ASTM A480: Standard Specification for Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and for General Application.
- GB/T 14976: Chinese National Standard for Seamless Stainless Steel Tubes for Fluid Transport.
- GB/T 4237: Chinese National Standard for Stainless Steel Flat Products.
- EN 10216-5: European Standard for Heat Exchanger and Heat Transfer Component Tubes (Austenitic Stainless Steel).
- ASME SA-213: American Society of Mechanical Engineers specification for stainless steel boiler, heat exchanger, and heat transfer tubing.
Testing and Inspection Protocol
- Chemical Analysis: Spectroscopic (OES) verification of Cr, Ni, Mo, C, Mn, Si, P, S content per ASTM E415.
- Mechanical Testing: Tensile testing per ASTM A370; hardness testing per ASTM E10 (Rockwell B scale) and ASTM E92 (Vickers scale).
- Dimensional Inspection: Automated laser micrometer and ultrasonic thickness gauging with data logging for traceability.
- Non-Destructive Testing (NDT): Eddy current (EC) testing per ASTM E2785 for surface and near-surface defect detection; ultrasonic testing (UT) per ASTM E2744 for internal flaw detection; dye penetrant testing (PT) per ASTM E709 for surface-breaking defect verification.
- Hydrostatic Testing: Performed at 1.5× the maximum design working pressure with hold time of ≥ 10 seconds, per ASTM A269.
- Pitting Corrosion Resistance Testing: ASTM G48 Method A (Ferroxyl Indicator Method) and ASTM G110 (Replicate Corrosion Test Method) for validation of pitting resistance in chloride environments.
Unique Selling Points
1. Superior Lifecycle Economics: Empirically validated in industrial aquaculture applications with 35–50% lower total cost of ownership over a 10-year period compared to carbon steel alternatives, driven by extended service life, reduced maintenance, and zero replacement cycles.
2. Continuous Coil Form Factor: Eliminates field welding and joint failures, reduces material waste by up to 15%, and enables rapid on-site deployment and custom in-situ forming for complex geometries.
3. Multi-Grade Material Flexibility: Full product range from AISI 304 through 316L and 321 grades, enabling precise material selection matched to service environment aggressiveness and temperature requirements.
4. Precision Manufacturing Tolerances: Automated multi-stand cold forming with in-line laser and ultrasonic inspection ensures OD tolerance of ±0.05 mm and wall thickness tolerance of ±5%, critical for heat exchanger tube-sheet expansion and brazing applications.
5. Full Traceability: Each coil is individually heat-numbered with a unique traceability code linked to mill certificates, chemical analysis reports, mechanical test results, and NDT records, enabling complete supply chain traceability from raw material to end user.
Technical Support and Ordering Information
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical support including material selection guidance, thermal performance modeling, pressure rating calculations, and application-specific design consultation. Custom specifications (non-standard OD, wall thickness, surface finish, and coil configuration) are available upon request with a typical lead time of 15–25 working days from order confirmation. Minimum order quantity (MOQ) is 500 kg per grade specification. For bulk orders exceeding 5,000 kg, volume pricing and dedicated production scheduling are available.