Stainless Steel Coil Tube (Coil Tube) — Wenzhou Jixing Metal Materials Co., Ltd
1. Product Overview
The Stainless Steel Coil Tube (Catalog No. 1365) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered continuous coil tube designed for use in thermal exchange, refrigeration, air conditioning, and fluid distribution systems. The product is supplied in a coiled (盘管 / Coil) configuration, enabling seamless integration into Fan Coil Unit (FCU) and Fresh Air Handling Unit (FAHU) systems commonly employed in commercial and industrial HVAC (Heating, Ventilation, and Air Conditioning) installations.
As a specialized supplier within the stainless steel pipe industry, Wenzhou Jixing Metal Materials Co., Ltd leverages advanced cold-drawing and coiling technologies to produce coil tubes that meet or exceed international standards for dimensional accuracy, surface finish, and mechanical integrity. The coil format offers significant logistical advantages, including reduced installation labor, minimized joint leakage risk, and optimized storage and transport efficiency.
Unique Selling Points:
- Continuous Coil Configuration: Eliminates field welding and brazing requirements, reducing installation time by up to 40% and virtually eliminating leak points.
- Superior Corrosion Resistance: 304 and 316L grades provide exceptional resistance to chloride-induced pitting, making the product ideal for coastal and marine HVAC environments.
- Precision Cold-Formed Geometry: Tight tolerances on outer diameter (OD), wall thickness (WT), and coil pitch ensure reliable fitment within heat exchanger assemblies.
- Food-Grade & Pharmaceutical Compatibility: Available in sanitary-grade finishes suitable for cleanroom and hygienic applications.
2. Material & Properties
2.1 Available Grades
- AISI 304 / ASTM 304 (UNS S30400): The standard austenitic stainless steel grade, offering excellent general-purpose corrosion resistance, formability, and weldability. Contains approximately 18% Chromium (Cr) and 8% Nickel (Ni).
- AISI 316L / ASTM 316L (UNS S31603): Low-carbon variant with added Molybdenum (Mo, 2–3%) for enhanced resistance to pitting and crevice corrosion, particularly in chloride-rich environments.
- AISI 321 / ASTM 321 (UNS S32100): Titanium-stabilized grade suitable for high-temperature applications exceeding 600°C, preventing intergranular sensitization.
2.2 Mechanical & Physical Properties (Typical Values for 304 Grade)
- Tensile Strength (UTS): ≥ 515 MPa (75 ksi)
- Yield Strength (0.2% Proof Stress): ≥ 205 MPa (30 ksi)
- Elongation at Break: ≥ 40%
- Density: 8.0 g/cm³ (0.29 lb/in³)
- Thermal Conductivity (at 100°C): 16.3 W/(m·K)
- Specific Heat: 500 J/(kg·°C)
- Maximum Service Temperature: 870°C (continuous), 1150°C (intermittent)
2.3 Surface Finish Options
- 2B Finish (Cold Rolled, Annealed, Pickled): Matte, uniform gray appearance; suitable for general industrial use.
- No. 4 Brushed Finish: Unidirectional fine grain; aesthetic appeal for visible installations.
- Mirror / 8K Polish: Reflective finish with Ra ≤ 0.05 μm; used in food processing and pharmaceutical HVAC.
- Electro-Polished: Ra ≤ 0.25 μm; critical for sanitary and bioprocessing applications.
3. Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 50.8 mm (¼" – 2") | ASTM A213 / ASME SA-213 |
| Wall Thickness (WT) | 0.5 mm – 3.0 mm (0.020" – 0.118") | ASTM A213 / ASME SA-213 |
| OD Tolerance | ±0.10 mm (±0.004") | ASTM A213 |
| Wall Thickness Tolerance | ±10% of nominal | ASTM A213 |
| Coil Inner Diameter (CID) | 300 mm – 600 mm (12" – 24") | Manufacturer Standard |
| Coil Length | Standard: 50 m – 200 m; Custom: up to 500 m | — |
| Coil Pitch | 1.5 mm – 5.0 mm (adjustable per application) | — |
| End Condition | Plain, Beveled, or Threaded (per client specification) | ASME B1.20.1 / B1.20.3 |
| Heat Treatment | Solution Annealed (1050°C – 1150°C, water/quench) | ASTM A213 |
| Welding Process | Continuous TIG (GTAW) or ERW with full seam inspection | ASME B31.9 / ISO 15493 |
| Hydrostatic Test Pressure | 1.5 × Maximum Working Pressure (MWP) | ASME B31.9 |
| Corrosion Resistance | ASTM A967 Passivation; 48h Salt Spray Test (ASTM B117) — 316L: ≥ 500h | ASTM A967 / ASTM B117 |
| Packaging | Wooden pallet with VCI (Vapor Corrosion Inhibitor) film wrapping | ISO 4711 |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Selection & Incoming Inspection: Stainless steel strip or seamless pipe stock is sourced from certified mills (e.g., Outokumpu, POSCO, Taigang). Each batch undergoes spectroscopic verification (PMI — Positive Material Identification) and visual inspection per ASTM A213.
- Surface Preparation: Mechanical cleaning and degreasing to remove mill scale, oils, and contaminants. Acid pickling and passivation treatment per ASTM A967 ensures a chromium-rich passive film on the surface.
- Cold Drawing / Forming: The strip or pipe is drawn through precision-die tooling to achieve the target OD and WT. Multi-pass cold working refines grain structure and improves mechanical properties.
- Welding (if applicable): For welded coil tubes, continuous TIG welding is performed under argon shielding with full seam coverage. In-line optical and eddy current testing verifies weld integrity.
- Solution Annealing: Tubes are heated to 1050°C – 1150°C in a protective atmosphere (endothermic gas or vacuum) and rapidly quenched to dissolve carbide precipitates and restore full corrosion resistance.
- Coiling: The annealed tube is coiled onto a mandrel at controlled tension and pitch using CNC-driven coiling machines. Coil geometry is verified by laser scanning to ensure uniformity.
- Quality Control & Testing: Each coil undergoes dimensional verification (OD, WT, coil length), hydrostatic pressure testing, and surface defect inspection. Samples are subjected to mechanical testing (tensile, hardness) and chemical analysis per ASTM standards.
- Packaging & Dispatch: Coils are wrapped in VCI film, secured on wooden pallets, and labeled with full traceability data (heat number, grade, dimensions, test certificates).
4.2 Key Process Advantages
- Full Traceability: Each coil is linked to a unique Heat Lot Number, enabling complete supply chain traceability from raw material to end user.
- Continuous Production: The coil format enables uninterrupted downstream processing (bending, brazing, assembly) without stoppage for tube changeovers.
- Reduced Waste: Coil supply minimizes offcuts compared to cut-length pipe, reducing material waste by up to 15%.
5. Applications
5.1 HVAC & Refrigeration Systems
The primary application domain for this product is within Fan Coil Unit (FCU) and Fresh Air System installations, as documented in industry literature on air conditioning system design. In these systems, the stainless steel coil tube serves as the refrigerant or hot water circuit within the evaporator or condenser heat exchanger. The coil configuration allows compact, high-surface-area heat transfer assemblies that maximize thermal efficiency while minimizing footprint.
Key HVAC applications include:
- Fan Coil Units (FCUs): Indoor coil assemblies for chilled water and hot water temperature control in commercial buildings, hotels, and hospitals.
- Fresh Air Handling Units (FAHUs): Pre-conditioning coils for outdoor air intake, providing dehumidification and temperature regulation.
- Heat Exchangers: Plate-fin and shell-and-tube heat exchangers for refrigeration compressors, chillers, and heat pumps.
- Condensers & Evaporators: Refrigerant circuit tubing in VRF (Variable Refrigerant Flow) and VRV (Variable Refrigerant Volume) systems.
5.2 Additional Application Domains
- Food & Beverage Processing: Hygienic-grade coil tubing for dairy pasteurization, brewing, and beverage chiller systems (316L, electropolished).
- Pharmaceutical & Biotech: Cleanroom HVAC systems and CIP (Clean-in-Place) / SIP (Sterilize-in-Place) circuits requiring corrosion-free, non-reactive piping.
- Marine & Offshore: HVAC systems on vessels and offshore platforms where chloride exposure demands 316L or duplex stainless grades.
- Automotive & Aerospace: Fuel lines, brake lines, and hydraulic circuits requiring high-pressure resistance and fatigue durability.
- Chemical Processing: Acid and alkali transport lines, reactor cooling coils, and distillation column internals.
- Domestic Appliances: Water heater heat exchangers, dishwasher spray arm tubing, and washing machine water lines.
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains rigorous quality management systems and holds the following certifications and complies with the listed international standards:
6.1 Management System Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- ISO 45001:2018 — Occupational Health and Safety Management System
- IATF 16949:2016 — Automotive Quality Management System (for automotive-grade products)
- CE Marking — Conformity with European Economic Area (EEA) directives
- PED 2014/68/EU — Pressure Equipment Directive compliance for pressure-rated applications
6.2 Product & Material Standards
- ASTM A213 / ASME SA-213 — Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubes for High-Temperature Service
- ASTM A554 / ASME SA-554 — Standard Specification for Seamless Austenitic Stainless Steel Tubes for Chemical and Heat-Transfer Equipment
- ASTM A778 / ASME SA-778 — Standard Specification for Welded Austenitic Stainless Steel Tubing for Chemical and Heat-Transfer Equipment
- EN 10216-5 — Non-ferrous metallic materials — Heat exchangers and related products — Seamless tubes (stainless steels)
- JIS G3459 — Japanese Industrial Standard for Stainless Steel Tubes for Heat Exchangers
- ASME B31.9 — Pressure Piping, Refrigeration Piping and Heat Transfer Components
6.3 Testing & Inspection Protocols
- Positive Material Identification (PMI): XRF (X-Ray Fluorescence) or OES (Optical Emission Spectroscopy) on every heat lot.
- Hydrostatic Testing: 100% of production at 1.5× MWP with automated leak detection.
- Non-Destructive Testing (NDT): Eddy current testing, ultrasonic testing (UT), and magnetic particle inspection (MT) for weld seam integrity.
- Dimensional Inspection: In-line laser diameter measurement, ultrasonic wall thickness gauging, and end-of-line coil geometry verification.
- Mechanical Testing: Tensile testing (ASTM A370), hardness testing (ASTM E18/E92), and impact testing (ASTM E23) on representative samples per heat lot.
- Corrosion Testing: Salt spray testing (ASTM B117), intergranular corrosion testing (ASTM A262), and pitting resistance evaluation (ASTM G48).
- Certification Documentation: Each shipment accompanied by Mill Test Certificate (MTC) per EN 10204 3.1/3.2, with full chemical composition, mechanical property data, and heat treatment records.
7. Conclusion
The Stainless Steel Coil Tube (Coil Tube, Catalog No. 1365) from Wenzhou Jixing Metal Materials Co., Ltd represents a premium-grade thermal exchange and fluid distribution solution engineered for demanding HVAC, refrigeration, and industrial applications. The product