Stainless Steel Coil Tube — HVAC Steam Heating Coil Series (Model No. 1304)
1. Product Overview
The Stainless Steel Coil Tube (盘管 / Coil Tube), designated as Model No. 1304 by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered tubular product specifically designed for use in central air conditioning (HVAC) heating sections and industrial heat exchange systems. This product series addresses critical performance challenges observed in conventional steam coil assemblies, particularly the recurring issue of steam leakage (steam coil leakage) at connection interfaces and within the coil body itself.
Unlike standard carbon steel or copper coils, the Model 1304 stainless steel coil tube offers superior corrosion resistance, thermal conductivity, and mechanical durability, making it an ideal solution for high-temperature steam environments where long-term reliability and minimal maintenance are paramount. The product is manufactured to meet stringent international standards and is suitable for applications ranging from commercial building HVAC systems to industrial process heating.
2. Material & Properties
The coil tube is fabricated from high-grade stainless steel materials selected for their exceptional performance in high-temperature and corrosive environments. The primary material grades include:
- SUS304 (AISI 304 / 1.4301) — General-purpose austenitic stainless steel with excellent formability and corrosion resistance in most atmospheric and chemical environments.
- SUS316 (AISI 316 / 1.4401) — Enhanced molybdenum-bearing grade offering superior resistance to pitting and crevice corrosion, particularly suitable for chloride-containing or humid environments.
- SUS321 (AISI 321 / 1.4541) — Titanium-stabilized grade providing excellent resistance to intergranular corrosion and thermal cycling fatigue.
Key Material Properties:
- Operating Temperature Range: −196 °C to +870 °C (depending on grade)
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20 °C (SUS304)
- Specific Heat Capacity: 500 J/(kg·K)
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C
- Tensile Strength: ≥ 520 MPa (annealed condition)
- Yield Strength: ≥ 205 MPa
- Corrosion Resistance: Excellent resistance to oxidation, scaling, and steam-side corrosion up to 800 °C
3. Specifications
| Parameter | Specification |
|---|---|
| Product Model | 1304 (Coil Tube Series) |
| Product Name | Stainless Steel Coil Tube (盘管 / Coil Tube) |
| Outer Diameter (OD) | 6.35 mm / 9.52 mm / 12.7 mm / 15.88 mm / 19.05 mm / 25.4 mm / 31.75 mm (customizable) |
| Wall Thickness | 0.5 mm – 3.0 mm (customizable) |
| Coil Pitch (Spacing) | 15 mm – 50 mm (adjustable based on application) |
| Material Grade | SUS304 / SUS316 / SUS321 (as specified) |
| Surface Finish | Mirror polish (Ra ≤ 0.4 μm) / Satin finish / Industrial finish |
| Maximum Operating Pressure | 1.6 MPa (standard) / up to 4.0 MPa (reinforced) |
| Maximum Operating Temperature | 450 °C (continuous) / 870 °C (intermittent) |
| End Connection Type | Threaded (NPT / BSP) / Flanged / Welded (butt / socket) |
| Heat Treatment | Solution annealing at 1050–1150 °C followed by water quench |
| Standards Compliance | ASTM A269 / ASTM A213 / GB/T 12771 / JIS G3459 / EN 10216-5 |
| Minimum Order Quantity | 500 meters (standard) / Custom batch sizes available |
4. Manufacturing Process
The production of the Model 1304 stainless steel coil tube follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, material integrity, and long-term service reliability:
- Raw Material Selection & Inspection: High-purity stainless steel wire rod is sourced from certified mills and subjected to spectroscopic analysis (OES) to verify chemical composition compliance with the specified grade.
- Wire Drawing: The raw wire rod undergoes multi-pass cold drawing to achieve the required outer diameter and wall thickness with tight tolerance (±0.05 mm). Intermediate annealing is performed to prevent work hardening and maintain ductility.
- Seam Welding: Precision high-frequency resistance welding (HFW) is employed to form a continuous, defect-free weld seam. The weld zone is controlled to ensure metallurgical homogeneity and mechanical strength equivalent to the base material.
- Heat Treatment: The welded tube undergoes solution annealing at 1050–1150 °C followed by rapid water quenching to dissolve carbides and restore full austenitic microstructure, ensuring optimal corrosion resistance and mechanical properties.
- Coil Forming (Coiling): The straight tube is cold-formed into the required coil geometry using precision CNC coiling machines. The forming process maintains dimensional accuracy and prevents micro-cracking in the material.
- Surface Finishing: Depending on the application, the coil tube receives mirror polishing (electropolishing), satin finishing, or industrial-grade surface treatment to achieve the specified surface roughness (Ra).
- Quality Inspection & Testing: Each batch undergoes comprehensive testing including:
- Hydrostatic Pressure Testing at 1.5× the maximum operating pressure
- Dimensional Inspection using laser measurement systems
- Visual & Dye Penetrant Inspection of weld seams
- Chemical Composition Verification via portable XRF analysis
- Corrosion Testing (salt spray test per ASTM B117, minimum 1000 hours)
- Packaging & Delivery: The finished coil tubes are packaged with protective end caps, moisture barriers, and wooden crates to ensure safe transportation.
5. Applications
The Model 1304 stainless steel coil tube is engineered for demanding thermal and fluid handling applications:
- Central Air Conditioning Heating Sections (HVAC): Primary application for steam heating coils in commercial and industrial HVAC systems, where the coil tube serves as the heat transfer element between steam and air. The stainless steel construction directly addresses the steam leakage problem commonly encountered in carbon steel coil assemblies.
- Industrial Process Heating: Steam heating coils for food processing, pharmaceutical manufacturing, and chemical production environments where sanitary and corrosion-resistant requirements are critical.
- Boiler & Heat Exchanger Systems: Used as coil elements in shell-and-tube heat exchangers, steam generators, and condensate recovery systems.
- Marine & Offshore Applications: Corrosion-resistant heating coils for shipboard HVAC systems and offshore platform thermal management.
- Automotive & Transportation: Precision coil tubes for vehicle heating systems and air conditioning components.
- Building Services Engineering: Fan coil units, air handling units (AHU), and rooftop units (RTU) in commercial and residential buildings.
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and standards compliance for the Model 1304 Coil Tube Series:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- CE Marking — Conformity with European Union directives
- ASTM A269 — Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubes for General Applications
- ASTM A213 — Standard Specification for Seamless Austenitic Chromium-Chromium-Nickel Alloy Boilers, Heat Exchanger, and Condenser Tubes
- GB/T 12771 — Chinese National Standard for Stainless Steel Seamless Tubes for Fluid Transport
- EN 10216-5 — European Standard for Non-Alloy and Alloy Steel Tubes for Pressure Purposes
- JIS G3459 — Japanese Industrial Standard for Austenitic Stainless Steel Tubes
- PED (Pressure Equipment Directive) 2014/68/EU — Compliance for pressure equipment applications
7. Unique Selling Points
"Engineered to Eliminate Steam Leakage — The Definitive Solution for HVAC Heating Coils"
- Superior Corrosion Resistance: Stainless steel construction provides 5–10× longer service life compared to carbon steel coils, significantly reducing maintenance frequency and total cost of ownership (TCO).
- Leakage-Free Design: Precision seam welding and comprehensive hydrostatic testing ensure zero steam leakage at the coil body level, directly addressing the industry's most common failure mode in HVAC heating sections.
- High Thermal Efficiency: Optimized coil geometry and surface finish maximize heat transfer coefficients, improving system efficiency by up to 15% compared to conventional coil designs.
- Customizable Specifications: Full range of OD, wall thickness, coil pitch, and end connection types available to meet project-specific requirements.
- Multi-Grade Material Options: SUS304, SUS316, and SUS321 grades available to match specific environmental and performance demands.
- Full Traceability: Each production batch includes material mill certificates (MTC), heat number traceability, and complete test reports for full supply chain transparency.
- Scalable Production Capacity: Capable of both small-batch custom orders and large-volume production runs with consistent quality assurance.
8. Technical Note: Steam Coil Leakage Prevention
Based on extensive engineering analysis of central air conditioning heating section steam coil leakage (中央空调加热段蒸汽盘管漏汽问题), the Model 1304 coil tube incorporates several design features specifically engineered to prevent and mitigate leakage:
- Enhanced Wall Thickness: Minimum wall thickness of 0.8 mm (vs. industry standard 0.5 mm) provides additional structural margin against thermal fatigue and pressure cycling.
- Optimized Weld Geometry: The seam weld is designed with a smooth internal profile to minimize turbulence-induced erosion at the weld zone, which is a common failure initiation point.
- Thermal Stress Compensation: The coil pitch and bend radius are calculated to accommodate differential thermal expansion between the tube and the coil support structure, preventing stress-induced micro-cracking.
- Material Compatibility: Stainless steel eliminates galvanic corrosion risks when in contact with dissimilar metals (e.g., copper headers, aluminum fins) commonly found in HVAC coil assemblies.
These engineering enhancements make the Model 1304 stainless steel coil tube the preferred choice for HVAC system designers and engineers seeking reliable, low-maintenance steam heating solutions.