Stainless Steel Coil Tube for Fan Coil Unit Systems
Product Overview
The Stainless Steel Coil Tube (盘管) is a precision-engineered coiled piping product manufactured by Wenzhou Jixing Metal Materials Co., Ltd, designed specifically for integration into fan coil unit (FCU) systems and thermostatic control valve assemblies. This product serves as the core heat exchange conduit in modern HVAC (Heating, Ventilation, and Air Conditioning) applications, where thermal efficiency, corrosion resistance, and long-term structural integrity are paramount. The coil tube is engineered to accommodate the next-generation floating-point electric thermostatic valve technology, ensuring seamless compatibility with advanced building automation and climate control systems.
As a critical component in hydronic heating and cooling circuits, the stainless steel coil tube provides a closed-loop pathway for water or glycol-based heat transfer media, enabling precise temperature regulation within commercial, industrial, and residential environments.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its superior combination of mechanical strength, corrosion resistance, and thermal conductivity. The primary material grades employed include:
- SUS304 (ASTM 304) — Chromium-Nickel austenitic stainless steel (18% Cr, 8% Ni), offering excellent general corrosion resistance and weldability
- SUS316 (ASTM 316) — Chromium-Nickel-Molybdenum austenitic stainless steel (16–18% Cr, 10–14% Ni, 2–3% Mo), providing enhanced resistance to pitting and crevice corrosion in aggressive environments
- SUS316L (ASTM 316L) — Low-carbon variant of 316 with improved weldability and resistance to intergranular corrosion
Key Physical and Mechanical Properties
| Property | SUS304 | SUS316 / 316L |
|---|---|---|
| Density (kg/m³) | 8,000 | 8,000 |
| Thermal Conductivity at 20°C (W/m·K) | 16.3 | 16.3 |
| Specific Heat Capacity (J/kg·K) | 500 | 500 |
| Young's Modulus (GPa) | 193 | 193 |
| Tensile Strength (MPa, min.) | 515 | 515 |
| Yield Strength (MPa, min.) | 205 | 205 |
| Elongation at Break (% , min.) | 40 | 40 |
| Maximum Operating Temperature (°C) | 870 | 870 |
| Corrosion Resistance (Pitting Resistance Equivalent Number, PREN) | 19 | 24–26 |
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (盘管 / Coiltube) |
| Product Code | 1020 |
| Material Grade | SUS304 / SUS316 / SUS316L |
| Outer Diameter (OD) Range | 6.0 mm – 25.4 mm (¼" – 1") |
| Wall Thickness Range | 0.5 mm – 1.5 mm |
| Coil Inner Diameter (ID) | Custom (typically 100 mm – 500 mm) |
| Tube Length per Coil | 3 m – 30 m (customizable) |
| Surface Finish | No.4 Brushed / Mirror Polished / Passivated |
| Maximum Working Pressure | 1.6 MPa (16 bar) standard; 2.5 MPa available |
| Operating Temperature Range | −40°C to +200°C |
| Heat Transfer Medium | Water, Glycol-Water Mixture, Propylene Glycol |
| End Connections | Flanged, Threaded (BSPT/NPT), Welded, Compression Fitting |
| Applicable Valve System | Floating-Point Electric Thermostatic Valve (浮点式电热阀) |
| Compliance Standards | ASTM A213 / ASTM A269 / GB/T 12771 / EN 10217 |
| Surface Roughness (Ra) | ≤ 0.8 μm (polished); ≤ 1.6 μm (brushed) |
| Packaging | Wooden pallet with moisture-proof wrapping |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous multi-stage manufacturing workflow to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Material Selection & Incoming Inspection — Raw stainless steel seamless tubes or welded tubes are sourced from certified mills. Each batch undergoes spectroscopic analysis (OES) to verify chemical composition, along with mechanical testing including tensile testing and hardness verification.
- Tube Straightening & Annealing — Incoming tubes are straightened using precision rollers and subjected to solution annealing at 1050°C–1150°C followed by controlled cooling to restore full austenitic microstructure and relieve residual stresses.
- Coil Forming (Rolling) — Straightened tubes are fed through precision coiling machines equipped with hydraulic tensioning systems. The coil diameter, pitch, and number of turns are controlled programmatically to achieve exact dimensional specifications. Forming is performed at controlled speed to prevent work hardening and surface deformation.
- Welding (if applicable) — For continuous coil configurations, longitudinal or spiral welds are performed using Automatic Metal Inert Gas (AMIG) welding with argon shielding. Weld seams are inspected via ultrasonic testing (UT) or radiographic testing (RT).
- Surface Treatment & Passivation — The coil tube undergoes mechanical polishing (if mirror finish is required) followed by chemical passivation using nitric acid or citric acid solutions to remove free iron and establish a stable chromium oxide protective layer (minimum 10% Cr₂O₃ film).
- End Preparation & Fitting Installation — Tube ends are deburred, beveled, and prepared for the selected connection type (flanging, threading, or welding). End fittings are installed per application requirements.
- Pressure Testing & Hydrostatic Verification — Each coil tube assembly undergoes hydrostatic pressure testing at 1.5× the maximum working pressure for a minimum hold time of 30 minutes to verify leak-tightness and structural soundness.
- Final Inspection & Quality Control — Comprehensive dimensional measurement, visual inspection, and non-destructive testing (NDT) including eddy current testing (ECT) for wall thickness verification and surface defect detection.
Applications
The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd is designed for a wide range of thermal management and fluid conveyance applications, particularly within HVAC and building services engineering:
- Fan Coil Units (FCUs) — Primary heat exchange coil in ceiling-mounted, wall-mounted, or ducted fan coil units for commercial and residential climate control. The coil tube interfaces directly with the floating-point electric thermostatic valve for precise flow modulation and temperature regulation.
- Underfloor Radiant Heating Systems — Coiled tubing embedded in concrete slabs or screed layers for uniform radiant heat distribution in residential and commercial buildings.
- Chilled Water Distribution Systems — Coil configurations used in air handling units (AHUs) and cooling coils for sensible and latent heat removal.
- Industrial Process Heating/Cooling — Heat exchange coils in chemical processing, pharmaceutical manufacturing, and food & beverage production where sanitary-grade stainless steel is required.
- Marine & Offshore HVAC Systems — Corrosion-resistant coil tubes for marine air conditioning systems exposed to high-salinity environments (SUS316/316L grades).
- Geothermal Heat Pump Systems — Coiled ground loops for closed-loop geothermal energy extraction in heating and cooling applications.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains comprehensive quality management and product certification frameworks to ensure international compliance:
- ISO 9001:2015 — Quality Management System certification covering design, manufacturing, and service processes
- ISO 14001:2015 — Environmental Management System certification for sustainable manufacturing practices
- CE Marking — Conformity with European Union directives for product safety and performance
- EN 10204 3.1 / 3.2 — Material test certificates conforming to European standard for certification of materials
- ASTM / ASME Standards Compliance — Product specifications aligned with American Society for Testing and Materials and American Society of Mechanical Engineers standards
- GB (Guobiao) Standards — Compliance with Chinese national standards including GB/T 12771 (stainless steel seamless tubes) and GB/T 21832 (stainless steel welded tubes)
- Third-Party Inspection Available — Products available for inspection by SGS, Bureau Veritas, or TÜV upon customer request
- Mill Test Certificates (MTC) — Full chemical composition and mechanical property documentation provided with each shipment
Unique Selling Points
1. Precision Coil Geometry: Programmable coiling equipment ensures consistent coil pitch, diameter tolerance (±0.5 mm), and uniform bend radius, maximizing heat transfer surface area and minimizing pressure drop.
2. Seamless Integration with Next-Generation Thermostatic Valves: Specifically engineered for compatibility with floating-point electric thermostatic valve systems (浮点式电热阀), enabling intelligent, responsive temperature control with minimal hysteresis.
3. Multi-Grade Material Availability: Offering SUS304, SUS316, and SUS316L grades allows customers to select the optimal corrosion resistance-to-cost ratio for their specific application environment.
4. Customizable Specifications: Full customization of outer diameter, wall thickness, coil diameter, coil length, surface finish, and end connection types to meet project-specific engineering requirements.
5. Comprehensive Quality Assurance: Every production batch undergoes multi-stage inspection including spectroscopic analysis, hydrostatic pressure testing, and non-destructive testing, backed by full traceability documentation.