Stainless Steel Coil Tube for HVAC Critical Coil Systems
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered heat exchange component designed for demanding constant temperature and humidity air conditioning systems. This product is specifically engineered for critical coil tube modes in HVAC (Heating, Ventilation, and Air Conditioning) applications where precise thermal regulation and long-term operational reliability are paramount.
Coil tubes serve as the fundamental heat transfer elements within evaporator and condenser assemblies. The critical coil tube mode represents an advanced operational configuration in which the coil operates at its thermodynamic boundary conditions to achieve optimal dehumidification and temperature control simultaneously. The coil tube product described herein is designed to meet the exacting requirements of such critical operating modes, ensuring consistent performance under varying load conditions.
These coil tubes are supplied in continuous coil form (Coiltube), enabling seamless integration into automated coil winding and brazing production lines, thereby reducing manufacturing waste and ensuring uniform geometric tolerances throughout the entire product length.
Material & Properties
The coil tube is fabricated from high-purity austenitic stainless steel, with the primary grades available as follows:
- Grade 304 (UNS S30408) – The standard austenitic stainless steel offering excellent corrosion resistance, formability, and weldability. Suitable for most HVAC and general-purpose heat exchange applications.
- Grade 316 (UNS S31608) – Enhanced pitting and crevice corrosion resistance due to the addition of molybdenum (2–3%). Recommended for applications involving aggressive fluids or humid coastal environments.
- Grade 316L (UNS S31603) – Low-carbon variant of Grade 316, providing superior resistance to sensitization during welding and extended service life in critical applications.
Mechanical Properties (Typical)
- Tensile Strength (UTS): ≥ 520 MPa (Grade 304); ≥ 515 MPa (Grade 316)
- Yield Strength (0.2% Offset): ≥ 205 MPa (Grade 304); ≥ 170 MPa (Grade 316)
- Elongation at Break: ≥ 40%
- Hardness (Rockwell B): ≤ 95 HRB (Annealed Condition)
Thermal Properties
- Thermal Conductivity: 16.3 W/(m·K) at 20°C (Grade 304); 16.5 W/(m·K) at 20°C (Grade 316)
- Specific Heat Capacity: 500 J/(kg·K) at 25°C
- Coefficient of Thermal Expansion: 17.3 × 10⁻⁶ /°C (20–100°C)
- Operating Temperature Range: −196°C to +870°C (Grade 304); −196°C to +925°C (Grade 316)
Corrosion Resistance
- Excellent resistance to atmospheric corrosion, fresh water, and dilute organic/inorganic acids
- Grade 316/316L demonstrates superior resistance to chlorides, marine atmospheres, and industrial pollutants
- Passive chromium oxide film (Cr₂O₃) provides self-healing surface protection
Specifications
| Parameter | Specification | Unit |
|---|---|---|
| Outer Diameter (OD) | 3.0 / 3.5 / 4.0 / 4.5 / 5.0 / 6.0 (Custom available) | mm |
| Wall Thickness (WT) | 0.3 / 0.4 / 0.5 / 0.6 / 0.8 / 1.0 | mm |
| Coil Winding Diameter | 150 – 500 (Configurable) | mm |
| Coil Length per Roll | 50 – 500 (Custom available) | m |
| OD Tolerance | ±0.05 | mm |
| Wall Thickness Tolerance | ±10% | — |
| Surface Finish | Bright Annealed (BA) / No. 4 Brushed / Mirror (2B) | — | Surface Roughness (Ra) | ≤ 0.8 (Inner Surface) | μm |
| Material Grade | SUS 304 / 304L / 316 / 316L / 321 | — |
| Standards Compliance | ASTM A213 / A269 / ASME B41.12 / GB/T 12771 / JIS G3459 | — |
| Maximum Operating Pressure | 1.6 – 2.5 | MPa |
| Flux Type | Low-phosphorus / Fluoride-free (for brazing) | — |
Manufacturing Process
The production of precision stainless steel coil tubes follows a rigorous multi-stage manufacturing sequence:
- Steel Strip Supply & Inspection: Cold-rolled stainless steel strip is sourced from certified mills and subjected to incoming quality control, including chemical composition verification (OES/Spectrometry) and mechanical property testing.
- Strip Leveling & Slitting: The steel strip is precision-slitted to the required width and leveled to eliminate coil set and flatness defects, ensuring uniform wall thickness after forming.
- Seamless or Welded Tube Forming: Tubes are manufactured via either the seamless piercing and cold drawing route (for precision applications) or the welded route (ERW – Electric Resistance Welding) with automated welding parameters for consistent joint quality.
- Cold Drawing & Sizing: Tubes pass through multi-die cold drawing stations to achieve precise dimensional tolerances on OD and wall thickness while improving surface finish and mechanical properties.
- Heat Treatment (Solution Annealing): Tubes are annealed at 1050–1150°C followed by controlled cooling to achieve full solution treatment, dissolving carbides and restoring maximum corrosion resistance and ductility.
- Pickling & Passivation: Post-welding or post-forming surface treatment removes oxide scale and establishes a uniform chromium oxide passive layer for enhanced corrosion protection.
- Inner Surface Cleaning & Flux Application: For HVAC brazed coil applications, the inner surface is cleaned to remove all contaminants, and a low-phosphorus or fluoride-free brazing flux is uniformly applied to facilitate subsequent brazing operations.
- Coil Winding: The finished tube is wound into a continuous coil on precision mandrels, with tension control to prevent kinking, distortion, or dimensional drift during storage and transport.
- Final Quality Inspection: Each coil undergoes dimensional verification (OD, WT, straightness), hydrostatic pressure testing, eddy current inspection for wall integrity, and visual surface inspection before packing and dispatch.
Applications
The Stainless Steel Coil Tube is integral to the following application domains:
- Constant Temperature & Humidity HVAC Systems: Critical coil tube mode operation in precision air conditioning units for data centers, clean rooms, pharmaceutical manufacturing, and laboratory environments where simultaneous temperature and humidity control is essential.
- Commercial & Industrial Air Conditioning: Evaporator and condenser coil assemblies in rooftop units (RTUs), chillers, heat pumps, and fan coil units (FCUs).
- Refrigeration Systems: Heat exchange coils in cold storage facilities, refrigerated transport, and industrial refrigeration plants.
- Process Cooling & Heating: Heat exchangers in chemical processing, food and beverage production, and pharmaceutical equipment requiring sanitary-grade materials.
- Marine & Coastal Applications: HVAC systems on vessels, offshore platforms, and coastal installations where chloride-induced corrosion is a primary concern (Grade 316/316L recommended).
- Food Processing & Dairy Equipment: Sanitary heat exchangers and cooling coils requiring compliance with FDA and EHEDG standards.
Unique Selling Points
- Critical Coil Mode Optimization: Engineered specifically for constant temperature and humidity air conditioning systems operating in critical coil tube mode, ensuring optimal thermal performance at thermodynamic boundary conditions.
- Precision Dimensional Control: ±0.05 mm OD tolerance ensures consistent heat transfer coefficients and uniform flow distribution across the entire coil assembly.
- Superior Corrosion Resistance: Multi-grade availability (304, 316, 316L) provides tailored corrosion protection for diverse operating environments, extending service life beyond 20 years in standard applications.
- Continuous Coil Form: Eliminates joints and connection points in the coil assembly, reducing potential leak points and improving overall system reliability.
- Flux-Free / Low-Flux Options: Available with fluoride-free brazing flux for environmentally compliant manufacturing and easy post-brazing cleaning.
- Full Traceability: Each production batch is traceable to mill certificates, ensuring complete material provenance and compliance documentation.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd maintains the following quality certifications and compliance standards:
- 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 – European Conformity for HVAC and pressure equipment directives (PED 2014/68/EU)
- ASTM Compliance – ASTM A213 (Seamless), ASTM A269 (Welded), ASTM A270 (Sanitary)
- ASME B41.12 – Boilers and Pressure Vessels, Non-Ferrous Materials
- GB/T 12771 – Chinese National Standard for stainless steel welded tubes
- JIS G3459 – Japanese Industrial Standard for seamless stainless steel tubes
- EN 10216-5 – European Standard for welded stainless steel tubes
- NSF/ANSI 61 – Drinking Water System Components (for potable water applications)
Quality Assurance Statement: Every coil tube shipment is accompanied by a comprehensive quality documentation package including mill test certificates (MTC), heat number traceability records, dimensional inspection reports, hydrostatic test results, and material composition analysis. Third-party inspection (TPI) by SGS, BV, or TÜV is available upon customer request.
Technical Data Summary
| Item | Description |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd |
| Product Code | No. 903 |
| Primary Application | Critical Coil Tube Mode – Constant Temperature & Humidity HVAC Systems |
| Available Grades | SUS 304 / 304L / 316 / 316L / 321 |
| Supply Form | Continuous Coil (Coiltube) |
| Customization | OD, WT, coil length, and flux type available upon request |
| Packaging | Wooden drum or export-grade carton with moisture barrier |