Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Catalog No. 1373) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous-length tubing product formed into a compact coil configuration. This product category is integral to the design and performance validation of Fan Coil Units (FCUs), where coil tubes serve as the primary heat exchange elements within air-handling systems. The coil tube geometry enables efficient thermal transfer between refrigerant or hot water media and ambient air, making it a critical component in commercial HVAC (Heating, Ventilation, and Air Conditioning) installations.
The product is engineered in accordance with rigorous performance test protocols, as documented in the research study titled "Design and Research of Performance Test Device for Fan Coil Units". This study provides the empirical foundation for evaluating coil tube thermal efficiency, pressure drop characteristics, flow distribution uniformity, and overall system COP (Coefficient of Performance).
2. Material & Properties
2.1 Base Material Composition
The coil tube is fabricated from stainless steel conforming to recognized international standards, with the following typical grades available:
- AISI 304 (UNS S30400) — Austenitic stainless steel with superior corrosion resistance and formability; the most widely specified grade for HVAC applications.
- AISI 316 (UNS S31600) — Enhanced molybdenum content provides superior resistance to chlorides and aggressive chemical environments.
- AISI 321 (UNS S32100) — Titanium-stabilized grade offering improved resistance to intergranular corrosion at elevated temperatures.
2.2 Mechanical Properties (Typical for AISI 304)
- Tensile Strength (UTS): ≥ 515 MPa
- Yield Strength (0.2% offset): ≥ 205 MPa
- Elongation at Break: ≥ 40%
- Hardness (Brinell): ≤ 201 HB
2.3 Thermal Properties
- Thermal Conductivity (at 20°C): 16.3 W/(m·K)
- Specific Heat Capacity: 0.50 J/(g·K)
- Thermal Expansion Coefficient (20–100°C): 17.3 × 10⁻⁶ /K
2.4 Corrosion Resistance
The passive chromium oxide film (Cr₂O₃) on the tube surface provides excellent resistance to atmospheric corrosion, condensation water, and dilute acids. The Pitting Resistance Equivalent Number (PREN) for AISI 304 is approximately 19, while AISI 316 achieves a PREN of approximately 24.
3. Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Product Catalog No. | 1373 | — |
| Product Name | Coil Tube (盘管) | — |
| Outer Diameter (OD) | 6.35 mm, 9.53 mm, 12.7 mm (customizable) | ASTM A269 / GB/T 12771 |
| Wall Thickness (WT) | 0.50 mm – 1.50 mm (±0.05 mm tolerance) | ASTM A269 |
| Coil Diameter | 300 mm – 800 mm (configurable) | — |
| Coil Length | Up to 50 m per continuous coil | — |
| Surface Finish | 2B (cold-rolled and annealed) / BA (Bright Annealed) | ASTM A480 |
| Operating Temperature Range | -40°C to +450°C | — |
| Maximum Operating Pressure | 1.6 MPa (standard) / 3.2 MPa (reinforced) | GB/T 12771 |
| Hydrostatic Test Pressure | 2.0 × working pressure | ASTM A269 |
| End Condition | Cut-to-length / flanged / threaded (BSP, NPT) | ASME B1.20.1 |
| Material Grade | AISI 304 / 316 / 321 | ASTM A269 / GB/T 12771 |
| Welding Method | TIG (GTAW) / Orbital Welding | ASME B31.9 |
| Packaging | Wooden pallet with moisture-proof wrapping | ISO 4180 |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Inspection — Inbound stainless steel strip or seamless tube is verified for chemical composition via Spectroscopic Analysis and mechanical properties through tensile testing.
- Slitting & Straightening — Stainless steel strip is slit to precise width tolerances (±0.1 mm) and mechanically straightened to ensure flatness.
- Coil Forming (Bending) — High-precision CNC coil forming machines bend the tube into the specified helical geometry with controlled bend radius to prevent wall thinning and ovality exceeding 2%.
- Welding — Seams are welded using Tungsten Inert Gas Welding (GTAW/TIG) with argon shielding to maintain the internal passivation layer. Orbital welding is employed for circumferential joints to ensure uniform weld bead quality.
- Post-Weld Heat Treatment — Solution annealing at 1050°C–1150°C followed by rapid water quenching to restore full austenitic microstructure and maximum corrosion resistance.
- Pickling & Passivation — Weld discoloration is removed via acid pickling (HNO₃/HF mixture), followed by passivation treatment to re-establish the protective chromium oxide film.
- Hydrostatic Pressure Testing — Each coil is subjected to hydrostatic testing at 2.0× the maximum working pressure for a minimum dwell time of 30 seconds to verify integrity.
- Dimensional & Visual Inspection — Final quality control includes dimensional verification (OD, WT, coil diameter), surface inspection, and weld radiographic testing (RT) where required.
4.2 Performance Test Validation
Based on the research documented in "Design and Research of Performance Test Device for Fan Coil Units", the coil tube performance is validated through a dedicated test rig that measures:
- Cooling Capacity (W) — per ASHRAE Standard 16
- Heating Capacity (W) — per ASHRAE Standard 16
- Air-side Pressure Drop (Pa) — across the coil face
- Water-side Pressure Drop (Pa) — through the tube circuit
- Heat Transfer Coefficient (U-value) — overall coefficient, W/(m²·K)
- Condensate Drainage Efficiency — percentage of condensate effectively removed
- Flow Distribution Uniformity — across parallel tube circuits
5. Applications
- Commercial HVAC Systems — Primary heat exchange element in fan coil units for office buildings, hotels, hospitals, and retail spaces.
- Residential Air Conditioning — Indoor units of split-system and multi-split (VRF/VAV) air conditioning systems.
- Industrial Process Cooling — Precision temperature control in electronics manufacturing, pharmaceutical production, and food processing facilities.
- Marine & Offshore Applications — AISI 316 grade coil tubes for environments with high chloride exposure.
- Refrigeration Systems — Evaporator and condenser coils in cold storage and refrigerated transport.
- Heat Recovery Systems — Energy-efficient heat exchangers in ventilation systems for thermal energy recovery.
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains the following quality assurance framework:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- ISO 45001:2018 — Occupational Health & Safety Management System
- ASME — American Society of Mechanical Engineers stamp certification for pressure-containing components
- CE Marking — Compliance with European Union directives including PED (Pressure Equipment Directive 2014/68/EU)
- EN 10204 3.1 — Material Test Certificate Type 3.1 for all shipments
- GB/T 12771 — Chinese national standard for welded stainless steel tubes
- ASTM A269/A269M — Standard specification for welded austenitic stainless steel tubes
7. Unique Selling Points
- Research-Validated Performance — Coil tube designs are backed by rigorous experimental data from dedicated FCU performance test apparatus, ensuring that thermal efficiency claims are empirically substantiated rather than purely theoretical.
- Precision Coil Geometry — CNC-controlled forming ensures uniform bend radius and minimal ovality, optimizing turbulent flow patterns within the tube for maximum heat transfer surface utilization.
- Full Material Traceability — Each coil batch is traceable to the raw material heat number, with complete mill test certificates and in-process inspection records maintained.
- Customizable Specifications — Flexible manufacturing capability allows customization of OD, wall thickness, coil diameter, coil length, and end configurations to meet project-specific engineering requirements.
- Corrosion Durability — The stainless steel construction eliminates the need for internal coatings or cathodic protection, delivering a service life exceeding 20 years in standard HVAC duty cycles without degradation of thermal performance.
- Hygienic Design — Bright Annealed (BA) surface finish with Ra ≤ 0.4 μm ensures suitability for pharmaceutical and food-grade applications where cleanability is paramount.
8. Technical Data Summary
| Property | AISI 304 | AISI 316 | AISI 321 |
|---|---|---|---|
| Carbon (C) max | 0.08% | 0.08% | 0.08% |
| Chromium (Cr) | 18.0–20.0% | 16.0–18.0% | 17.0–19.0% |
| Nickel (Ni) | 8.0–10.5% | 10.0–14.0% | 9.0–12.0% |
| Molybdenum (Mo) | — | 2.0–3.0% | — |
| Titanium (Ti) | — | — | 5×C to 0.70% |
| Density (kg/m³) | 8.00 | 8.00 | 8.00 |
| PREN (Pitting Resistance) | ≈ 19 | ≈ 24 | ≈ 21 |
Disclaimer: The specifications listed above represent typical values and may vary depending on the specific order configuration, material grade selected, and applicable project specifications. All products are manufactured and tested in accordance with the mutually agreed technical specifications between Wenzhou Jixing Metal Materials Co., Ltd. and the customer. For precise dimensional tolerances and performance guarantees, please refer to the individual Purchase Order (PO) and associated Technical Data Sheet (TDS).