Stainless Steel Dry Coil Tube — Wenzhou Jixing Metal Materials Co., Ltd.
1. Product Overview
The Stainless Steel Dry Coil Tube (Product No. 1143) is a precision-engineered coil tube system designed for application in building heating, ventilation, and air conditioning (HVAC) systems, particularly within office-class commercial buildings. This product represents an advanced dry coil technology (干盘管技术) that eliminates the need for water circulation within the coil itself, thereby significantly reducing the risk of condensation-related issues, microbial growth, and structural corrosion in indoor air distribution systems.
Dry coil tubes operate by utilizing dehumidified air as the primary heat exchange medium rather than relying on direct water-air contact. This technology addresses critical challenges in office building environments where maintaining optimal indoor air quality (IAQ), thermal comfort, and energy efficiency are paramount. The product is manufactured to international standards and is suitable for integration into radiant cooling/heating systems, air handling units (AHUs), and fan coil units (FCUs).
2. Material & Properties
2.1 Base Material
The coil tube is fabricated from austenitic stainless steel, conforming to the following material specifications:
- Grade 304 (UNS S30400 / AISI 304) — Chromium (Cr) 18–20%, Nickel (Ni) 8–10.5%; provides excellent general corrosion resistance and formability.
- Grade 316 (UNS S31600 / AISI 316) — Chromium (Cr) 16–18%, Nickel (Ni) 10–14%, Molybdenum (Mo) 2–3%; offers superior resistance to chlorides and aggressive chemical environments.
- Surface Treatment — Electropolished or passivated finish to enhance corrosion resistance and facilitate cleaning.
2.2 Mechanical Properties
- Tensile Strength: ≥ 520 MPa (Grade 304); ≥ 550 MPa (Grade 316)
- Yield Strength: ≥ 205 MPa
- Elongation at Break: ≥ 40%
- Hardness: ≤ 220 HB (annealed condition)
- Thermal Conductivity: 16.3 W/(m·K) at 20°C
- Coefficient of Thermal Expansion: 17.3 × 10⁻⁶ /°C (20–100°C)
2.3 Thermal & Corrosion Performance
- Operating temperature range: −196°C to +450°C
- Outstanding resistance to pitting, crevice corrosion, and stress corrosion cracking (SCC)
- Non-toxic, non-magnetic (in annealed condition), and fully recyclable
- Compliant with NSF/ANSI 61 for potable water contact applications
3. Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | Φ6.0 mm – Φ12.7 mm (1/4" – 1/2") | ASTM A269 / ASTM A213 |
| Wall Thickness (WT) | 0.5 mm – 1.5 mm | ASME B36.19M |
| Coil Pitch | 10 mm – 30 mm (adjustable) | Manufacturer Specification |
| Coil Diameter | Φ150 mm – Φ600 mm | Project-Specific |
| Tube Length | Up to 200 m per continuous coil | — |
| Surface Roughness | Ra ≤ 0.4 μm (electropolished) | ASTM A967 |
| Hydrostatic Test Pressure | 2.0 × Working Pressure (minimum) | ASME B31.9 |
| Maximum Operating Pressure | 1.6 MPa (232 psi) | — |
| Heat Exchange Efficiency | U-value: 45–75 W/(m²·K) | ASHRAE Handbook |
| Fin Configuration | Aluminum or Stainless Steel fins; FPI: 8–14 | — |
| Weight (Typical) | 0.35 – 0.85 kg/m (depending on OD/WT) | — |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Procurement — Certified stainless steel coils or bars sourced from accredited mills (e.g., Outokumpu, POSCO, Baosteel), accompanied by mill test certificates (MTC) per EN 10204 Type 3.1.
- Coil Unwinding & Straightening — Precision leveling to eliminate residual stresses and ensure dimensional uniformity.
- Cold Forming / Coiling — The tube is mechanically formed into the designated coil geometry using CNC-controlled forming equipment to maintain consistent pitch and diameter.
- Welding (if applicable) — Automatic orbital TIG welding (Gas Tungsten Arc Welding) with inert gas backing (Argon, 99.99% purity) to ensure penetration integrity.
- Fin Attachment — Fins are either mechanically pressed onto the tube (mechanical finning) or bonded using high-temperature adhesive, depending on the thermal performance requirement.
- Surface Treatment — Acid pickling and passivation (per ASTM A967) or electropolishing to achieve a chromium-rich passive film thickness of ≥ 2 nm.
- Quality Inspection — Includes visual inspection, dimensional measurement, hydrostatic pressure testing, and destructive testing (tensile, impact) on sample lots.
- Packaging & Dispatch — Protective wrapping with moisture-absorbing desiccants; clearly labeled with material grade, heat number, and traceability codes.
4.2 Key Process Controls
- Intergranular corrosion resistance verified per ASTM A262 Practice No. 1E
- Weld seam integrity confirmed by radiographic testing (RT) or eddy current testing (ECT)
- Dimensional tolerance maintained within ±0.1 mm for OD and ±0.05 mm for wall thickness
5. Applications
5.1 Primary Application: Office Building HVAC Systems
Based on static feasibility analysis of dry coil tube technology in office-class buildings, the following application scenarios are identified:
- Radiant Cooling & Heating Panels — Embedded in ceilings or walls of open-plan offices to provide zonal temperature control with minimal noise.
- Fresh Air Handling Units — Used as pre-cooling or dehumidification coils in outdoor air handling systems to reduce latent load on main chillers.
- Displacement Ventilation Systems — Integrated into under-floor or under-desk air supply systems for superior IAQ in high-occupancy office spaces.
- Heat Recovery Systems — Employed in run-around coil configurations for energy-efficient air-to-air heat exchange between supply and exhaust air streams.
5.2 Additional Applications
- Commercial and institutional buildings (hospitals, laboratories, data centers)
- Industrial process heating and cooling circuits
- Food and pharmaceutical processing equipment (hygienic grade)
- Marine and offshore HVAC systems (Grade 316)
6. Quality Certifications & Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System — Certified by accredited third-party body |
| ISO 14001:2015 | Environmental Management System |
| ISO 45001:2018 | Occupational Health and Safety Management System |
| CE Marking | Compliance with EU Construction Products Regulation (CPR) 305/2011 |
| EN 10204 3.1 | Material Test Certificate — Full chemical and mechanical analysis |
| ASME B31.9 | Pressure Piping — Nonlethal Applications |
| ASTM A269 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing |
| NSF/ANSI 61 | Health Effects — Drinking Water System Components |
| GB/T 14976 | Chinese National Standard for Seamless Stainless Steel Tubes |
| JIS G3445 | Japanese Industrial Standard for Seamless Stainless Steel Tubes |
7. Unique Selling Points
- Condensation-Free Operation — Eliminates the risk of water droplet formation and subsequent microbial proliferation, ensuring superior indoor air quality in office environments.
- Energy Efficiency — Static analysis demonstrates potential energy savings of 15–30% compared to conventional wet coil systems by reducing fan power consumption and chiller load.
- Corrosion Resistance — Austenitic stainless steel construction ensures a service life exceeding 25 years even in aggressive indoor environments.
- Low Maintenance — Dry operation eliminates scale buildup, biofilm formation, and the need for chemical treatment of circulating water.
- Sustainability — 100% recyclable material; reduces water consumption in building operations; contributes to LEED and Green Star certification credits.
- Precision Manufacturing — CNC-controlled coiling and forming ensures repeatable geometric accuracy, critical for optimal heat transfer performance.
- Traceability — Full material traceability from mill to finished product with documented heat numbers and test certificates.
8. Conclusion
The Wenzhou Jixing Metal Materials Co., Ltd. Stainless Steel Dry Coil Tube (Product No. 1143) represents a state-of-the-art solution for building HVAC systems, combining proven austenitic stainless steel metallurgy with advanced dry-coil thermal management technology. Static feasibility analysis confirms its technical viability and economic advantage in office-class buildings, offering a sustainable, energy-efficient, and high-performance alternative to conventional wet coil systems.