Stainless Steel Coil Tube (Coiltube) — Wenzhou Jixing Metal Materials Co., Ltd.
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 908) manufactures precision-engineered Stainless Steel Coil Tubes (also referred to as Coiltube or Coiled Tubing) designed for demanding thermal exchange, HVAC (Heating, Ventilation, and Air Conditioning), and industrial process applications. These coil tubes are formed from seamless or welded stainless steel tubes and wound into compact, continuous helical configurations that maximize heat transfer surface area within minimal spatial footprints. The product line is particularly suited for integration into fan coil + fresh air (FCU + OA) HVAC system architectures, where efficient heat exchange and resistance to condensation corrosion are paramount.
Material & Properties
Coil tubes are fabricated from a range of austenitic and duplex stainless steel grades, selected based on the corrosive environment and temperature regime of the intended application. Common grades include:
- SUS 304 / AISI 304 — General-purpose austenitic stainless steel with excellent formability and moderate corrosion resistance; suitable for non-aggressive HVAC and water distribution applications.
- SUS 316 / AISI 316 — Molybdenum-enhanced austenitic grade offering superior resistance to chlorides, brackish water, and chemical environments; ideal for coastal or marine HVAC installations.
- SUS 316L / AISI 316L — Low-carbon variant of 316 with enhanced weldability and resistance to intergranular corrosion after welding operations.
- SUS 321 / AISI 321 — Titanium-stabilized austenitic grade providing excellent resistance to sensitization at elevated temperatures (up to 870 °C), suitable for high-temperature process coils.
- Duplex 2205 / UNS S31803 — High-strength duplex stainless steel with a PREN (Pitting Resistance Equivalent Number) of ≥ 34, offering exceptional resistance to stress corrosion cracking (SCC) and chloride pitting.
Key material properties of the coil tube product line include:
- Thermal Conductivity: 14–16 W/(m·K) at 20 °C (austenitic grades), providing reliable heat transfer performance.
- Operating Temperature Range: −196 °C to +870 °C (grade-dependent).
- Corrosion Resistance: High resistance to atmospheric, acidic, and alkaline environments; immunity to oxidation and scaling under normal service conditions.
- Mechanical Strength: Yield strength of 205–550 MPa (grade-dependent); tensile strength of 515–800 MPa.
- Surface Finish: Available in 2B (cold-rolled and annealed), BA (Bright Annealed), No. 4 brushed, and 8K mirror finishes, with surface roughness Ra ≤ 0.4 μm for BA/8K grades.
Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Product No. | 908 |
| Tube Outer Diameter (OD) | 6.0 mm – 38.0 mm (custom sizes available) |
| Tube Wall Thickness | 0.5 mm – 2.0 mm |
| Coil Winding Diameter | 50 mm – 500 mm (adjustable per design requirement) |
| Coil Length / Unwound Length | 0.5 m – 10.0 m (per coil unit) |
| Applicable Grades | SUS 304, 304L, 316, 316L, 321, 310S, Duplex 2205 |
| Surface Treatment | 2B, BA (Bright Annealed), No. 4 Brushed, 8K Mirror |
| Winding Pattern | Continuous helical, multi-pass serpentine, or custom geometry |
| End Connection Type | Plain end, flared, grooved, threaded, or custom-fitted |
| Tolerance on OD | ±0.05 mm (precision grade) |
| Tolerance on Wall Thickness | ±0.02 mm |
| Applicable Standards | ASTM A213, ASTM A269, GB/T 12771, GB/T 13296, EN 10216-5 |
| Maximum Operating Pressure | Up to 2.5 MPa (depending on OD, wall thickness, and grade) |
| Minimum Bend Radius | 3× OD (without mandrel); 1.5× OD (with mandrel) |
| Coating / Passivation | Acid pickling and passivation (optional); PTFE coating available on request |
Manufacturing Process
The production of high-quality stainless steel coil tubes involves a precisely controlled multi-stage manufacturing sequence:
- Material Selection and Incoming Inspection: Raw stainless steel coils or seamless tubes are sourced from certified mills and subjected to spectroscopic analysis (OES), mechanical testing, and chemical composition verification to ensure compliance with the specified grade (e.g., ASTM A213 TP304 or TP316L).
- Tube Forming (Cold Drawing / Cold Drawing & Sizing): Raw material is drawn through a series of calibrated dies to achieve the target outer diameter and wall thickness with tight dimensional tolerances. This process enhances grain structure and improves surface finish.
- Intermediate Annealing: Tubes are annealed at 1050–1150 °C followed by controlled cooling to relieve cold-work hardening, restore ductility, and eliminate residual stresses. This step is critical for achieving the required bendability without cracking.
- Precision Coiling / Winding: The annealed tubes are wound onto precision-machined mandrels using CNC-controlled coiling machines. The winding process maintains uniform inter-pass spacing (typically 1.5× to 3× OD) to optimize heat transfer efficiency and minimize flow maldistribution. Multi-pass serpentine configurations are achieved through specialized bending stations with hydraulic forming and mandrel support.
- Heat Treatment and Stress Relief: Post-coiling stress relief annealing (870–900 °C for austenitic grades) is performed to stabilize the coil geometry and prevent springback or dimensional drift during subsequent welding or installation.
- Surface Finishing and Passivation: Coils undergo acid pickling (HNO₃/HF blend) and passivation to remove scale, decarburized layers, and free iron contamination. This establishes a stable chromium oxide (Cr₂O₃) passive film that maximizes corrosion resistance.
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Quality Inspection and Testing: Every coil batch undergoes:
- Dimensional inspection (OD, wall thickness, coil diameter, pitch) using laser micrometers and coordinate measuring machines (CMM).
- Hydrostatic pressure testing at 1.5× the maximum operating pressure.
- Surface quality verification (visual, magnetic particle inspection for surface defects).
- Spectroscopic re-verification of chemical composition (PMI — Positive Material Identification).
- Intergranular corrosion testing per ASTM A262 Practice E (where applicable).
- Packaging and Shipping: Coils are wrapped in moisture-proof polyethylene film, placed in wooden crates or cardboard boxes with desiccant packs, and labeled with traceability data including heat number, grade, dimensions, and test certificates.
Applications
Wenzhou Jixing's stainless steel coil tubes serve a wide range of industrial and commercial applications:
- HVAC Systems (Fan Coil Units + Fresh Air Systems): Coil tubes are integral heat exchange elements in fan coil units (FCUs), air handling units (AHUs), and fresh air pre-treatment systems. Their compact helical geometry provides high surface-area-to-volume ratios, enabling efficient sensible and latent heat exchange while resisting condensation-induced corrosion — a critical advantage in the "Fan Coil + Fresh Air" system architecture where coil tubes are continuously exposed to moisture and ambient pollutants.
- Refrigeration and Air Conditioning: Used as evaporator and condenser coils in commercial refrigeration systems, chiller units, and split-type air conditioning systems.
- Heat Exchangers: Compact heat exchanger cores for industrial process heating and cooling, including plate-and-fin, shell-and-tube, and air-to-air heat exchangers.
- Automotive and Transportation: Radiator coils, intercooler tubes, and exhaust gas recirculation (EGR) cooler elements.
- Food and Beverage Processing: Sanitary-grade coil tubes for pasteurization, sterilization, and thermal processing equipment where hygienic surface finish (Ra ≤ 0.4 μm) and corrosion resistance are mandatory.
- Pharmaceutical and Biotechnology: Bioreactor cooling coils, clean steam condensers, and CIP (Clean-In-Place) system components requiring 316L or duplex grades.
- Chemical and Petrochemical Industries: Process coils for aggressive chemical environments where 316L or 2205 duplex provides essential corrosion protection.
- Marine and Offshore Applications: Seawater coolers and condenser tubes leveraging 316L or 2205 duplex for resistance to chloride-induced pitting and crevice corrosion.
Quality Certifications and Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure product reliability and traceability:
- ISO 9001:2015 — Quality Management Systems certification covering the entire manufacturing and supply chain process.
- ISO 14001:2015 — Environmental Management Systems certification demonstrating commitment to environmentally responsible production practices.
- ISO 45001:2018 — Occupational Health and Safety Management Systems certification.
- EN 10204 3.1 — Material test certificates (MTC) issued in accordance with European standard EN 10204, Type 3.1, providing independent verification of chemical composition and mechanical properties by a qualified inspection body.
- Compliance with ASTM, ASME, and GB Standards: Products are manufactured to meet or exceed the requirements of ASTM A213/A269, ASME B31.3 (Process Piping), and relevant GB (Guobiao) national standards including GB/T 12771 and GB/T 13296.
- Third-Party Inspection: Optional third-party inspection services (SGS, BV, TUV) available for pre-shipment verification upon customer request.
Unique Selling Points
Wenzhou Jixing Metal Materials Co., Ltd. differentiates its stainless steel coil tube offering through the following competitive advantages:
- Customized Geometry and Multi-Grade Flexibility: The company provides tailored coil configurations — including continuous helical, multi-pass serpentine, and custom winding patterns — across a broad spectrum of stainless steel grades (304, 316, 316L, 321, 2205), enabling precise engineering to match specific thermal and mechanical design requirements.
- HVAC-Optimized Design for Fan Coil + Fresh Air Systems: Recognizing the specific challenges of "Fan Coil + Fresh Air" HVAC architectures — including condensation management, airflow uniformity, and long-term corrosion resistance — the coil tube designs are optimized for low pressure drop, high heat transfer coefficients, and resistance to condensate-induced degradation.
- Precision Dimensional Control: Tight tolerances (±0.05 mm on OD, ±0.02 mm on wall thickness) and uniform inter-pass spacing ensure optimal thermal performance and ease of integration into heat exchanger assemblies.
- Full Traceability and Documentation: Every product batch is accompanied by mill test certificates, heat treatment records, dimensional inspection reports, and passivation verification data, supporting regulatory compliance and lifecycle quality assurance.
- Scalable Production Capacity: The manufacturing infrastructure supports both prototype/small-batch customization and high-volume production runs, making Wenzhou Jixing a versatile partner for OEMs, system integrators, and project engineers.