Stainless Steel Coil Tube for HVAC and Radiant Heating Systems
Product Overview
The Stainless Steel Coil Tube (盘管 / Coiltube) is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd., specifically designed for integration into fan coil units (FCU), floor radiant heating systems, and combined hybrid heating/cooling applications. As a critical heat exchange medium, this coil tube delivers superior thermal conductivity, long-term corrosion resistance, and mechanical integrity under sustained cyclic thermal and hydraulic loading conditions. The product is engineered to meet the rigorous demands of modern building services engineering, where efficiency, durability, and compliance with international standards are paramount.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, thermal performance, and structural reliability. The material composition and resulting mechanical properties are as follows:
- Base Material: Austenitic stainless steel (奥氏体不锈钢), typically conforming to grades such as AISI 304 (S30408), AISI 316 (S31603), or equivalent Chinese national standard designations (GB/T 12771, GB/T 14976).
- Corrosion Resistance: Demonstrates excellent resistance to atmospheric corrosion, acidic/alkaline environments, and chloride-induced pitting (particularly in 316 grade), ensuring service life exceeding 25 years under typical HVAC operating conditions.
- Thermal Conductivity: Approximately 15–16 W/(m·K), providing efficient heat transfer between the circulating medium and the surrounding environment.
- Mechanical Strength: Tensile strength (抗拉强度) ranging from 520–720 MPa, with elongation (延伸率) of ≥30%, ensuring resistance to thermal expansion stresses and pressure cycling.
- Operating Temperature Range: Suitable for continuous operation from -40°C to +200°C, accommodating both heating and cooling duty cycles.
- Operating Pressure: Designed for working pressures up to 1.6 MPa (standard) and 2.5 MPa (high-pressure variants).
Specifications
| Parameter (参数) | Specification (规格) | Standard / Reference (标准/参考) |
|---|---|---|
| Outer Diameter (外径) | 6 mm – 22 mm (customizable) | GB/T 14976, ASTM A269 |
| Wall Thickness (壁厚) | 0.5 mm – 1.5 mm | GB/T 14976 |
| Coil Diameter (盘绕直径) | 50 mm – 300 mm | Manufacturer specification |
| Coil Length (盘管长度) | 1 m – 100 m (continuous coil) | Custom order |
| Surface Finish (表面光洁度) | Mill finish / Electropolished (Ra ≤ 0.4 μm) | ASTM A270 |
| Heat Treatment (热处理) | Solution annealed (固溶处理), 1010°C – 1100°C, water quench | GB/T 12771 |
| Tolerance – OD (外径公差) | ±0.05 mm (precision grade) | GB/T 14976 |
| Tolerance – Wall Thickness (壁厚公差) | ±10% | GB/T 14976 |
| Hydrostatic Test Pressure (水压试验压力) | 2.5 × working pressure (≥ 4.0 MPa) | ISO 4427 |
| Delivery Form (交货形态) | Coiled coil tube (盘管), cut-to-length, or formed assembly | Per customer requirement |
Manufacturing Process
The production of the stainless steel coil tube follows a tightly controlled multi-stage process to ensure dimensional accuracy, metallurgical quality, and surface integrity:
- Raw Material Selection (原材料选择): Cold-rolled stainless steel strip (冷轧不锈钢带) or seamless tube blanks (无缝管坯) are sourced from certified mills, with full chemical composition analysis (化学成分分析) and mechanical property verification prior to acceptance.
- Tubing Forming (制管成形): Precision cold-drawing (冷拔) or roll-forming (卷制) processes are employed to achieve the target outer diameter and wall thickness. Seamless tubes are preferred for high-pressure applications to eliminate weld-induced weaknesses.
- Solution Annealing (固溶退火): The formed tube is heated to 1010°C–1100°C and rapidly quenched to dissolve carbide precipitates, restoring full austenitic microstructure and maximizing corrosion resistance.
- Pickling & Passivation (酸洗钝化): Surface oxide layers and residual contaminants are removed via nitric acid/hydrofluoric acid pickling, followed by passivation treatment to form a stable chromium oxide protective film (Cr₂O₃).
- Coil Winding (盘绕成形): The annealed and passivated tube is wound into the specified coil geometry using CNC-controlled winding equipment to ensure uniform coil spacing, minimal plastic deformation, and consistent curvature radius.
- Quality Inspection (质量检测): Each coil undergoes hydrostatic pressure testing, dimensional measurement (caliper, ultrasonic thickness gauge), visual inspection, and non-destructive testing (NDT, 无损检测) including eddy current testing (涡流检测) for internal defect detection.
- Packaging & Marking (包装标识): Approved coils are wrapped in protective film, labeled with heat number, grade, dimensions, and traceability codes, and packed for shipment.
Applications
The coil tube is engineered for use across a broad spectrum of HVAC and building services applications:
- Fan Coil Units (风机盘管, FCU): Serves as the core heat exchange element in air-handling terminals, facilitating both heating and cooling of indoor air streams in commercial buildings, hotels, and residential complexes.
- Floor Radiant Heating Systems (地板辐射供暖系统): Installed beneath floor screed or tiles to provide uniform, low-temperature radiant heat distribution, enhancing occupant comfort and energy efficiency.
- Combined Hybrid Heating/Cooling Systems (联合供暖制冷系统): Enables dual-mode operation in integrated building management systems, providing seasonal flexibility and reduced peak load.
- Industrial Process Cooling/Heating (工业过程冷却/加热): Utilized in chemical, pharmaceutical, and food processing plants where hygienic, corrosion-resistant heat exchange is required.
- Domestic Water Heating & Heat Recovery (生活热水及热回收): Applied in plate heat exchangers and spiral heat exchangers for domestic hot water generation and waste heat recovery.
- Marine & Coastal Environments (海洋及沿海环境): 316-grade coil tubes are suitable for HVAC systems in marine vessels, offshore platforms, and coastal facilities due to superior chloride resistance.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring product conformity to international and national standards:
- ISO 9001:2015 – Quality Management System certification, demonstrating systematic process control and continuous improvement.
- ISO 14001:2015 – Environmental Management System certification, reflecting commitment to sustainable manufacturing practices.
- CE Marking (欧盟CE认证) – Conformity with European health, safety, and environmental protection requirements for construction products (CPR – Construction Products Regulation, EU 305/2011).
- GB/T 14976 – Chinese National Standard for seamless stainless steel tubes, ensuring compliance with domestic regulatory requirements.
- ASTM A269 / A270 – American Society for Testing and Materials standards for seamless and welded austenitic stainless steel tubing.
- EN 10217 / EN 10216 – European standards for austenitic stainless steel tubes for pressure purposes.
- Third-Party Inspection (第三方检测): Products are available for independent verification by SGS, BV (Bureau Veritas), or TÜV, with full material test certificates (MTC, 材质证明书) and heat traceability documentation provided.
Unique Selling Points
- Integrated System Compatibility: Specifically designed and validated for fan coil unit and floor radiant heating combined systems, ensuring optimal thermal-hydraulic performance when used as a unified heating/cooling solution.
- Full Traceability: Every coil tube is accompanied by a complete material test certificate (MTC) with heat number traceability, enabling end-to-end quality accountability from raw material to finished product.
- Custom Engineering: Flexible customization of outer diameter, wall thickness, coil geometry, and surface finish to meet specific OEM and project requirements.
- Hygienic Surface Quality: Electropolished variants achieve Ra ≤ 0.4 μm surface roughness, ideal for pharmaceutical, food, and medical HVAC applications where biofilm resistance is critical.
- Extended Service Life: Austenitic stainless steel construction eliminates the need for internal linings or cathodic protection, reducing lifecycle maintenance costs by up to 60% compared to carbon steel alternatives.
Note: All specifications listed herein are based on standard product configurations. Custom specifications, non-standard grades, and special surface treatments are available upon request. Wenzhou Jixing Metal Materials Co., Ltd. provides technical consultation, sample testing, and on-site installation guidance to support successful project integration.