Stainless Steel Coil Tube (Coiltube) — Series 962
1. Product Overview
The Stainless Steel Coil Tube (Coiltube), catalogued as Series 962 by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered tubular product manufactured in continuous coil form. Designed for demanding applications in HVAC (Heating, Ventilation, and Air Conditioning), fluid transfer, and industrial heat exchange systems, this coil tube integrates the corrosion resistance and mechanical integrity of stainless steel with the compact, space-efficient geometry of a coiled configuration. The product is particularly suited for applications where energy efficiency, intelligent control, and long-term durability are paramount — areas extensively studied in the field of fan coil unit (FCU) optimization.
The coil tube is supplied as a continuous rolled coil, enabling downstream users to cut, form, and fabricate components to exact specifications without the need for welding seams at intermediate joints. This seamless continuity ensures uniform hydraulic performance, minimizes leakage risk, and extends the service life of the end product.
2. Material Composition & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its superior balance of mechanical strength, corrosion resistance, and formability. The following table summarizes the key material grades and their properties:
| Property | Specification | Standard Reference |
|---|---|---|
| Base Material Grade | 304 / 316 / 316L Austenitic Stainless Steel | ASTM A213 / EN 10216-5 |
| Chromium (Cr) Content | 18.0% – 20.0% (304); 16.0% – 18.0% (316) | ASTM A240 |
| Nickel (Ni) Content | 8.0% – 10.5% (304); 10.0% – 14.0% (316) | ASTM A240 |
| Molybdenum (Mo) Content | — (304); 2.0% – 3.0% (316) | ASTM A240 |
| Maximum Carbon (C) Content | ≤ 0.08% (304); ≤ 0.03% (316L) | ASTM A213 |
| Yield Strength (Rp0.2) | ≥ 205 MPa (304); ≥ 170 MPa (316L) | ISO 6892-1 |
| Tensile Strength (Rm) | 515 – 730 MPa (304); 485 – 720 MPa (316L) | ISO 6892-1 |
| Elongation (A50) | ≥ 35% (304); ≥ 30% (316L) | ISO 6892-1 |
| Surface Finish | No. 1 (Annealed & Pickled), 2B, BA (Bright Annealed), or Custom | ASTM A480 |
| Corrosion Resistance | Excellent in atmospheric, aqueous, and mild chemical environments; 316 grade offers superior resistance to chlorides and pitting | ASTM G48 / ISO 9407 |
| Operating Temperature Range | −196 °C to +870 °C (304); −196 °C to +800 °C (316L) | ASTM A213 |
| Magnetic Susceptibility | Non-magnetic in annealed condition; may exhibit slight magnetism after cold working | — |
3. Technical Specifications
The following table details the dimensional and performance specifications available for the Series 962 coil tube:
| Parameter | Range / Value | Tolerance | Standard |
|---|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 50.8 mm (1/8" – 2") | ±0.05 mm | ASTM A213 |
| Wall Thickness | 0.3 mm – 3.0 mm | ±10% of nominal | EN 10216-5 |
| Coil Width | Up to 1500 mm (configurable) | ±1.0 mm | — |
| Coil Weight | 200 kg – 2000 kg (per coil) | — | — |
| Coil Inner Diameter (ID) | 200 mm / 300 mm / 500 mm (standard options) | ±3.0 mm | — |
| Surface Roughness (Ra) | 0.2 – 1.6 μm (BA finish); ≤ 3.2 μm (2B finish) | — | ASTM A480 |
| Maximum Bending Radius | ≥ 3 × OD (cold bending); ≥ 5 × OD (severe forming) | — | — |
| Maximum Working Pressure | Up to 10 MPa (grade- and dimension-dependent) | — | ASME B31.3 |
| Heat Transfer Coefficient | Optimized for HVAC and thermal exchange applications | — | ASHRAE Handbook |
| Available Lengths (Cut Coil) | Custom cut lengths available upon request | ±1.0 mm | — |
4. Manufacturing Process
The production of the Series 962 coil tube follows a rigorous, multi-stage manufacturing workflow designed to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection: High-purity stainless steel ingots or continuous cast slabs are sourced from certified mills, with chemical composition verified via Optical Emission Spectrometry (OES) and confirmed against ASTM A240 / EN 10088-1 requirements.
- Hot Rolling: Billets are reheated to temperatures between 1150 °C and 1250 °C and passed through a hot rolling mill to produce a seamless or welded tube blank with the desired outer diameter and wall thickness.
- Piercing & Forming: For seamless variants, the hot billet is pierced on a Mannesmann-type piercing mill and subsequently drawn through a series of reducing stands to achieve precise dimensional tolerances.
- Cold Drawing / Cold Reduction: The hot-rolled tube blank undergoes cold drawing through precision dies to achieve the final dimensional tolerances (±0.05 mm on OD), improved surface finish, and enhanced mechanical properties through strain hardening.
- Solution Annealing: The cold-worked tube is annealed at temperatures of 1050 °C – 1150 °C in a protective atmosphere (argon or vacuum) to relieve residual stresses, restore ductility, and dissolve carbide precipitation — critical for maintaining corrosion resistance, especially in 316/316L grades.
- Pickling & Passivation: The annealed tube is immersed in a hydrofluoric/nitric acid bath to remove oxide scale, followed by a passivation treatment to form a stable chromium oxide (Cr₂O₃) protective layer on the surface.
- Coil Winding: The finished tube is wound onto a precision-controlled winding reel to form the coil configuration. Tension is carefully regulated to prevent deformation, kinking, or inter-coil contact damage.
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Quality Inspection: Every coil undergoes comprehensive inspection including:
- Dimensional verification via laser diameter measurement and ultrasonic wall thickness gauging.
- Hydrostatic testing at 1.5× the maximum working pressure to detect porosity, cracks, or leaks (per ASTM A213 / EN 10216-5).
- Surface inspection using automated optical systems to detect scratches, inclusions, or oxidation defects.
- Mechanical testing (tensile, hardness, impact) on representative samples per ISO 6892-1 and ISO 6508.
- Corrosion testing including salt spray (ASTM B117) and intergranular corrosion (ASTM A240 Table 16) verification.
- Packaging & Labeling: The coil is wrapped in moisture-proof polyethylene film and protective cardboard, secured with steel strapping, and labeled with full traceability data including mill test certificate (MTC), heat number, chemical composition, and dimensional data.
5. Applications
The Series 962 coil tube finds extensive application across multiple industrial sectors, with particular emphasis on energy-efficient and intelligent systems:
- HVAC (Heating, Ventilation, and Air Conditioning) Systems: The coil tube is a core component in fan coil units (FCUs), air handling units (AHUs), and chiller/boiler heat exchangers. Its high thermal conductivity and corrosion resistance make it ideal for condenser and evaporator coils, where it facilitates efficient heat transfer between refrigerant and air/water media. Research on FCU energy optimization has demonstrated that stainless steel coil tubes with optimized geometry can improve seasonal energy efficiency ratios (SEER) by up to 15% compared to conventional copper alternatives.
- Refrigeration & Cryogenic Systems: Used in refrigerant piping, expansion coils, and cryogenic fluid transfer lines, where the material's low-temperature toughness (−196 °C) and resistance to thermal cycling are critical.
- Water Heating & Solar Thermal Systems: Employed in solar water heater absorber plates, domestic hot water storage coils, and district heating network components.
- Food & Beverage Processing: Compliant with FDA and 3-A Sanitary Standards, the coil tube is used in pasteurization systems, CIP (Clean-in-Place) loops, and beverage dispensing lines where hygienic fluid transfer is required.
- Pharmaceutical & Biotechnology: Used in sterile fluid processing, bioreactor jacket coils, and clean-in-place systems where biocompatibility and resistance to aggressive cleaning agents are essential.
- Chemical & Petrochemical Industry: 316/316L grade coil tubes are utilized in chemical dosing lines, acid handling systems, and process heat exchangers where resistance to chlorides, sulfides, and organic acids is required.
- Marine & Offshore Applications: Resistant to seawater corrosion, the coil tube is suitable for desalination plant heat exchangers, ballast water systems, and offshore platform fluid transfer lines.
- Intelligent Building Systems: In modern smart-building HVAC architectures, the coil tube serves as the thermal interface for IoT-enabled fan coil units equipped with variable-frequency drives (VFDs), temperature sensors, and BMS (Building Management System) integration for demand-responsive energy management.
6. Quality Certifications & Compliance
The Series 962 coil tube is manufactured under a certified quality management system and complies with the following international standards and certifications:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification ensuring consistent product quality and continuous improvement |
| ISO 14001:2015 | Environmental Management System certification demonstrating commitment to sustainable manufacturing practices |
| ISO 45001:2018 | Occupational Health and Safety Management System certification |
| CE Marking | Compliance with European Union directives for machinery, pressure equipment, and construction products |
| EN 10216-5 | European standard for stainless steel seamless and welded tubes for pressure purposes |
| ASTM A213 | American standard for austenitic stainless steel tubes for heat-exchange and similar service |
| EN 10217-7 | European standard for austenitic stainless steel tubes for heat exchangers |
| GB/T 14976 | Chinese national standard for cold-rolled or cold-drawn seamless stainless steel tubes |
| GB/T 13296 | Chinese national standard for cold-rolled or cold-drawn seamless stainless steel tubes for heat exchangers |
| ASME B31.3 | Compliance with ASME Code for Process Piping design and fabrication |
| Mill Test Certificate (MTC) | EN 10204 Type 3.1 Certificate provided with each shipment, including chemical composition, mechanical properties, and dimensional data |
7. Unique Selling Points
- Superior Corrosion Resistance: The austenitic stainless steel composition provides exceptional resistance to atmospheric, aqueous, and chemical corrosion, significantly outperforming carbon steel alternatives and offering competitive advantages over copper in chloride-rich environments.
- Seamless Continuity: The coil form eliminates intermediate weld joints, reducing potential failure points and ensuring uniform hydraulic and thermal performance throughout the entire length.
- Energy Efficiency: