Stainless Steel Coil Tube — Product Technical Specification
Product Overview
The Stainless Steel Coil Tube (盘管, Coiltube) is a precision-engineered continuous tube product manufactured by Wenzhou Jixing Metal Materials Co., Ltd (Product No. 1056). This product is designed as a seamless, helically wound tubular component fabricated from austenitic stainless steel alloys, optimized for thermal-fluid exchange applications in HVAC (Heating, Ventilation, and Air Conditioning) systems, industrial process cooling, and heat exchanger assemblies. The coil tube geometry provides a high surface-area-to-volume ratio, enabling efficient heat transfer under variable operating conditions — a characteristic extensively validated through experimental research on Fan Coil Unit (FCU) variable-load performance.
Unlike straight-section tubing, coil tubes are delivered in continuous spiral or helical form, eliminating the need for field welding or brazing at installation sites. This design inherently reduces leak points, improves structural integrity, and facilitates rapid deployment in compact heat exchange configurations.
Material & Properties
Base Alloy Composition
The coil tube is predominantly manufactured from austenitic stainless steel grades conforming to the following standards:
- SUS304 / AISI 304 — General-purpose corrosion-resistant alloy with excellent formability
- SUS316 / AISI 316 — Enhanced molybdenum content for superior chloride resistance
- SUS304L / AISI 304L — Low-carbon variant for improved weldability and stress-corrosion cracking resistance
Mechanical Properties (Typical)
| Property | Grade 304 | Grade 316 | Test Standard |
|---|---|---|---|
| Tensile Strength (抗拉强度) | ≥ 520 MPa | ≥ 515 MPa | ASTM A270 / GB/T 249 |
| Yield Strength (屈服强度) | ≥ 205 MPa | ≥ 205 MPa | ASTM A270 |
| Elongation (延伸率) | ≥ 40% | ≥ 40% | ASTM A270 |
| Hardness (硬度) | ≤ 92 HRB | ≤ 92 HRB | ASTM E18 |
| Thermal Conductivity (导热系数, 20°C) | 16.3 W/(m·K) | 14.6 W/(m·K) | ASTM E153 |
Corrosion Resistance
The austenitic microstructure (面心立方, FCC) provides excellent resistance to atmospheric corrosion, weak acids, and oxidizing environments. Grade 316 variants demonstrate superior performance in chloride-containing media due to 2.0–2.5% Mo (Molybdenum) addition, making them suitable for marine and chemical processing environments.
Specifications
| Parameter (参数) | Specification Range (规格范围) | Standard Reference |
|---|---|---|
| Outer Diameter (外径, OD) | Φ6.0 mm – Φ25.0 mm | GB/T 14976 / ASTM A554 |
| Wall Thickness (壁厚) | 0.5 mm – 2.0 mm | GB/T 14976 |
| Coil Mean Diameter (盘管平均直径) | Φ80 mm – Φ300 mm | Custom / OEM |
| Coil Length (盘管展开长度) | 1 m – 50 m (continuous) | Customer Specification | Coil Pitch (螺距) | 5 mm – 25 mm (adjustable) | Design Requirement |
| Surface Finish (表面状态) | 2B, BA (Bright Annealed), No.4 Polished | ASTM A478 |
| Surface Roughness (表面粗糙度) | Ra ≤ 0.8 μm (BA finish) | ISO 1302 |
| Pressure Rating (耐压等级) | Up to 2.5 MPa (PN25) | ASME B31.3 |
| Operating Temperature (工作温度) | −196°C to +870°C | Material-dependent |
| Tolerance (公差) | OD: ±0.05 mm; Wall: ±0.03 mm | GB/T 14976 |
Manufacturing Process
The production of stainless steel coil tubes involves a multi-stage metallurgical and forming process:
- Raw Material Selection (原材料选择) — Cold-rolled stainless steel strip or seamless tube stock is inspected for chemical composition (via Spark OES analysis) and mechanical properties.
- Tube Forming (管材成型) — The tube blank is formed through cold-drawing or cold-rolling processes to achieve precise OD and wall thickness tolerances.
- Solid-Solution Annealing (固溶退火) — Tubes are heated to 1050–1100°C and rapidly quenched in water to dissolve carbide precipitates, restoring full austenitic corrosion resistance and mechanical ductility.
- Pickling & Passivation (酸洗钝化) — Surface oxides are removed via citric acid or nitric-hydrofluoric acid solutions, followed by passivation treatment to establish a protective chromium oxide (Cr₂O₃) film.
- Coil Winding (盘绕成型) — The formed tube is helically wound around a precision mandrel using CNC-controlled coiling equipment. The winding parameters (pitch, tension, diameter) are programmatically controlled to ensure uniform geometry and dimensional accuracy.
- Post-Coil Heat Treatment (盘绕后热处理) — Where required, a controlled stress-relief anneal is performed to eliminate residual stresses introduced during coiling, preventing springback and dimensional drift.
- End Sealing & Inspection (端部密封与检测) — Tube ends are sealed to prevent contamination; dimensional verification is conducted via optical measurement systems and eddy-current wall-thickness gauging.
- Packaging (包装) — Coils are protected with moisture-absorbent desiccants, wrapped in polyethylene film, and secured on wooden or steel cradles for transport.
Applications
Primary Application Domains
- Fan Coil Units (风机盘管机组, FCU) — The coil tube serves as the core heat transfer element in FCUs, enabling efficient air-side and water-side thermal exchange. Experimental research on variable operating conditions has demonstrated that stainless steel coil tubes maintain stable thermal performance across part-load ratios (PLR) of 20%–100%, with minimal degradation in heat transfer coefficient (传热系数, U-value).
- Industrial Heat Exchangers (工业换热器) — Used in shell-and-tube and plate-fin heat exchangers for chemical processing, pharmaceutical manufacturing, and food-grade thermal systems.
- Chilled Water Distribution (冷冻水分配系统) — Employed in commercial HVAC chilled water loops where corrosion resistance and long service life are critical.
- Refrigeration Systems (制冷系统) — Utilized in evaporator and condenser coil assemblies for refrigerant circulation.
- Marine & Offshore Applications (海洋与海上工程) — Grade 316 coil tubes provide essential resistance to saltwater corrosion in marine HVAC and process systems.
- Medical & Laboratory Equipment (医疗与实验室设备) — Hygienic-grade BA-finish coil tubes used in cleanroom air handling and sterilization systems.
Variable Operating Condition Performance
Based on experimental investigation of Fan Coil Unit variable-load characteristics, stainless steel coil tubes exhibit the following performance advantages under transient conditions:
- Stable heat transfer coefficient variation (≤5% deviation) across water flow rates of 0.5–3.0 L/s
- Superior resistance to thermal cycling fatigue compared to carbon steel alternatives
- Consistent hydraulic resistance characteristics enabling predictable fan energy consumption
- No scaling or fouling accumulation under long-term operation in treated water systems
Quality Certifications & Standards Compliance
Applicable Standards
- GB/T 14976 — Welded seamless steel tubes for fluid transport (Chinese National Standard)
- GB/T 21832 — Stainless steel tubes for heat exchange (Chinese National Standard)
- ASTM A270 — Seamless and welded austenitic stainless steel tubing
- ASTM A554 — Seamless and welded austenitic stainless steel tube for heat exchangers
- ASME BPV Section I — Power piping and pressure vessel components
- EN 10217-7 — European standard for stainless steel tubes for heat exchangers
Certification Body Approvals
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System
- CE Marking — European Conformity for pressure equipment (PED 2014/68/EU)
- Mill Test Reports (MTR) — Provided per EN 10204 Type 3.1
Quality Assurance Measures
- 100% Eddy Current Testing (涡流检测) for wall thickness uniformity and defect detection
- Hydrostatic Pressure Testing (水压试验) at 1.5× working pressure
- Spectroscopic Chemical Analysis (光谱成分分析) on every heat lot
- Dye Penetrant Testing (渗透检测) for surface discontinuities
- Dimensional verification via laser measurement (±0.02 mm accuracy)
Unique Selling Points
- Seamless Continuous Geometry — Eliminates field joints, reducing installation time by up to 60% and eliminating potential leak paths
- Superior Corrosion Longevity — Service life exceeding 25 years in aggressive environments versus 8–12 years for carbon steel alternatives
- Variable-Load Thermal Stability — Proven performance consistency across the full operating range, validated by experimental FCU testing
- Hygienic Surface Finish — BA (Bright Annealed) finish with Ra ≤ 0.8 μm prevents microbial adhesion in food-grade and pharmaceutical applications
- Customizable Geometry — CNC-controlled coiling enables precise pitch, diameter, and length configurations tailored to specific OEM requirements
- Low Thermal Conductivity Coating Compatibility — Surface is suitable for subsequent PTFE or ceramic anti-fouling coatings where enhanced efficiency is required
Conclusion
The Stainless Steel Coil Tube (Product No. 1056) manufactured by Wenzhou Jixing Metal Materials Co., Ltd represents a high-performance, precision-engineered solution for thermal-fluid exchange applications. Its metallurgical integrity, dimensional accuracy, and proven variable-condition performance make it an ideal selection for demanding industrial and commercial HVAC systems, heat exchangers, and process engineering applications where reliability, corrosion resistance, and thermal efficiency are paramount.