Stainless Steel Coil Tube — Heating Fan Coil Unit Application (Model No. 1140)
1. Product Overview
The Stainless Steel Coil Tube (盘管 / Coil Tube), designated as Model No. 1140 by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered tubular product designed for integration into heating fan coil unit systems. This product represents a critical component in hydronic heating and cooling infrastructure, where the coil tube serves as the primary heat exchange surface within fan coil units (FCUs). The coil tube is manufactured to meet rigorous dimensional tolerances and mechanical performance standards, ensuring optimal thermal transfer efficiency in commercial and residential HVAC (Heating, Ventilation, and Air Conditioning) applications.
Coil tubes are formed by coiling straight seamless or welded stainless steel tubing into precise helical configurations, creating a compact heat exchange surface area within a confined envelope. The product is particularly suited for heating-type fan coil units where thermal efficiency, corrosion resistance, and long-term structural integrity are paramount.
2. Material & Properties
2.1 Base Material
The coil tube is fabricated from high-grade austenitic stainless steel, conforming to the following material specifications:
- Primary Grade: SUS304 (UNS S30408) — Chromium-Nickel austenitic stainless steel
- Alternative Grade: SUS316L (UNS S31603) — Molybdenum-enhanced austenitic stainless steel for aggressive environments
- Standard Reference: ASTM A213 / ASTM A312 / GB/T 12771 / EN 10216-5
2.2 Mechanical Properties
| Property | SUS304 Specification | SUS316L Specification |
|---|---|---|
| Tensile Strength (抗拉强度) | ≥ 520 MPa | ≥ 485 MPa |
| Yield Strength (屈服强度) | ≥ 205 MPa | ≥ 170 MPa |
| Elongation (延伸率) | ≥ 40% | ≥ 40% |
| Hardness (硬度) | ≤ 217 HB | ≤ 217 HB |
| Thermal Conductivity (热导率, 20°C) | 16.3 W/(m·K) | 14.6 W/(m·K) |
| Specific Heat (比热容) | 500 J/(kg·K) | 500 J/(kg·K) |
2.3 Chemical Composition
| Element | SUS304 (%) | SUS316L (%) |
|---|---|---|
| C (Carbon, 碳) | ≤ 0.08 | ≤ 0.03 |
| Cr (Chromium, 铬) | 18.00–20.00 | 16.00–18.00 |
| Ni (Nickel, 镍) | 8.00–10.50 | 10.00–14.00 |
| Mo (Molybdenum, 钼) | — | 2.00–3.00 |
| Si (Silicon, 硅) | ≤ 1.00 | ≤ 1.00 |
| Mn (Manganese, 锰) | ≤ 2.00 | ≤ 2.00 |
| P (Phosphorus, 磷) | ≤ 0.045 | ≤ 0.045 |
| S (Sulfur, 硫) | ≤ 0.030 | ≤ 0.030 |
3. Specifications
| Parameter | Specification |
|---|---|
| Product Designation (产品型号) | No. 1140 — Coil Tube (盘管) |
| Tube Outer Diameter (外径) | 6.35 mm / 9.52 mm / 12.70 mm (1/4" / 3/8" / 1/2") |
| Tube Wall Thickness (壁厚) | 0.50 mm – 1.20 mm (customizable) |
| Coil Pitch (盘管节距) | 12 mm – 25 mm (adjustable per application) |
| Coil Diameter (盘管直径) | 100 mm – 300 mm |
| Tube Length per Coil (单圈长度) | 0.5 m – 5.0 m (continuous) |
| Surface Finish (表面处理) | No. 4 Brushed / Mirror Polish / Passivated |
| Operating Temperature (工作温度) | -196°C to +870°C |
| Operating Pressure (工作压力) | ≤ 1.6 MPa (standard); ≤ 2.5 MPa (reinforced) |
| Hydrostatic Test Pressure (水压试验压力) | 2.5× working pressure |
| Tolerance on OD (外径公差) | ± 0.05 mm |
| Tolerance on Wall Thickness (壁厚公差) | ± 10% |
| End Treatment (端部处理) | Flat cut / Flared / Threaded / Fitted (per customer requirement) |
4. Manufacturing Process
The production of the No. 1140 Stainless Steel Coil Tube follows a multi-stage manufacturing workflow ensuring dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Procurement (原材料采购): High-purity stainless steel strip or wire is sourced from certified mills, with each batch accompanied by a Mill Test Certificate (MTC) verifying chemical composition and mechanical properties.
- Tube Forming (管材成型): Seamless tubing is produced via cold drawing or hot rolling processes, or welded tubing is manufactured through ERW (Electric Resistance Welding) with subsequent weld annealing to homogenize microstructure.
- Heat Treatment (热处理): Solution annealing at 1050°C–1100°C followed by rapid water quenching ensures full austenitic microstructure and maximum corrosion resistance.
- Precision Coiling (精密盘绕): The straight tube is coiled using CNC-controlled coiling machines with hydraulic tension control, maintaining consistent pitch and coil diameter throughout the entire length.
- Surface Treatment (表面处理): Pickling and passivation remove oxide scale and form a protective chromium oxide layer, enhancing passive film stability.
- Quality Inspection (质量检验): Each coil tube undergoes dimensional verification, visual inspection, pressure testing, and (where applicable) eddy current testing for wall thickness and defect detection.
- Packaging and Shipping (包装与发货): Products are packaged with protective wrapping, desiccants, and wooden crates to prevent mechanical damage and moisture exposure during transit.
5. Applications
The No. 1140 Stainless Steel Coil Tube is engineered for use in heating-type fan coil units and related HVAC systems. Primary application domains include:
5.1 Heating Fan Coil Units (采暖型风机盘管)
- Commercial building HVAC systems — offices, hotels, hospitals, and educational facilities
- Residential radiant heating systems with hydronic distribution
- Industrial process heating applications requiring corrosion-resistant heat exchangers
- Clean room environments where stainless steel's hygienic properties are required
5.2 Additional Application Areas
- Refrigeration and air conditioning heat exchangers
- Boiler feed water heating systems
- Marine and coastal HVAC installations (SUS316L grade)
- Food and pharmaceutical processing equipment
- Chemical processing heat transfer applications
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management systems and product certifications ensuring international market compliance:
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System Certification |
| ISO 14001 | Environmental Management System |
| CE Marking | European Conformity for HVAC components |
| ASTM A213 / A312 | Material standard compliance for seamless and welded stainless steel tubing |
| GB/T 12771 | Chinese national standard for stainless steel welded tubes for general purposes |
| EN 10216-5 | European standard for non-alloy and alloy steel tubes — austenitic stainless steel |
| JIS G3446 | Japanese Industrial Standard for stainless steel tubes |
| NACE MR0175 | Compliance for sour service applications (where applicable) |
Every production batch is accompanied by a Mill Test Certificate (MTC / EN 10204 3.1) documenting chemical analysis, mechanical test results, and dimensional verification data.
7. Unique Selling Points
Exceptional Corrosion Resistance: The austenitic stainless steel composition provides superior resistance to oxidation, pitting, and general corrosion, extending service life significantly beyond carbon steel alternatives in hydronic heating applications.
Precision Coiling Geometry: CNC-controlled coiling ensures uniform pitch and coil diameter, maximizing heat transfer surface area and ensuring balanced fluid flow distribution throughout the fan coil unit.
Hygienic Surface Finish: Passivated and optionally mirror-polished surfaces resist bacterial adhesion, making the product suitable for pharmaceutical, food processing, and clean-room HVAC applications.
Thermal Efficiency: Optimized wall thickness and material selection balance thermal conductivity with structural integrity, achieving high heat exchange coefficients while maintaining pressure vessel-grade strength.
Full Customization Capability: Wenzhou Jixing Metal Materials Co., Ltd. offers flexible customization of tube diameter, wall thickness, coil pitch, coil diameter, and end treatments to match specific fan coil unit design requirements.
Comprehensive Traceability: Each product batch maintains full material traceability from raw steel mill through final inspection, ensuring supply chain transparency and quality accountability.
8. Technical Notes for Fan Coil Unit Integration
When integrating the No. 1140 Coil Tube into heating-type fan coil units, the following engineering considerations should be observed:
- Thermal Expansion: Stainless steel exhibits a linear thermal expansion coefficient of approximately 17.3 × 10⁻⁶ /°C. Expansion loops or flexible connections must be incorporated in the piping layout to accommodate differential thermal movement between the coil tube and connected piping.
- Flow Velocity: Recommended internal flow velocity for hydronic heating applications is 0.5–2.0 m/s to prevent erosion-corrosion while maintaining adequate heat transfer rates.
- Welding Considerations: If field welding is required, use matching filler metals (ER308L for SUS304, ER316L for SUS316L) with argon shielding gas to prevent chromium carbide precipitation at weld zones.
- Insulation: External thermal insulation is recommended to minimize radiant heat loss and prevent condensation in heating applications operating above ambient dew point temperatures.
Document Classification: Technical Product Specification | Reference No. 1140 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd. | Product Category: Stainless Steel Coil Tube for Heating Fan Coil Units