Stainless Steel Coil Tube (Coiltube) — HVAC Fan Coil Unit Application Grade
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered, continuous-coiled tubular product specifically designed for integration into Fan Coil Units (FCU) and other HVAC (Heating, Ventilation, and Air Conditioning) systems. As a critical heat-exchange component, the coil tube facilitates efficient thermal transfer between circulating fluids (water or refrigerant) and ambient air, ensuring optimal climate control performance in commercial, industrial, and residential environments.
This product is engineered to meet the stringent demands of modern HVAC systems, combining superior corrosion resistance, mechanical integrity, and thermal conductivity in a single solution. The coiled configuration allows for compact installation within fan coil unit housings while maximizing heat-exchange surface area per unit volume.
Material Composition & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, weldability, and thermal performance under prolonged exposure to moisture-laden air streams.
- Primary Alloy Grades: SUS304 (AISI 304), SUS316L (AISI 316L)
- Corrosion Resistance: Superior resistance to pitting, crevice corrosion, and atmospheric oxidation; particularly suitable for humid and coastal environments
- Thermal Conductivity: Optimized for efficient heat transfer between internal fluid media and external air streams
- Mechanical Strength: High tensile strength and fatigue resistance under cyclic thermal loading conditions
- Hygienic Performance: Non-toxic, non-reactive, and resistant to biofilm formation — compliant with potable water contact standards where applicable
Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) | — |
| Material Grade | SUS304 / SUS316L (Austenitic Stainless Steel) | ASTM A213 / GB/T 12771 |
| Outer Diameter (OD) | 6.35 mm, 9.53 mm, 12.70 mm (1/4", 3/8", 1/2") | ASME B36.19M |
| Wall Thickness | 0.50 mm – 1.20 mm | — |
| Coil Pitch | 15 mm – 50 mm (adjustable per design requirement) | — |
| Coil Diameter | 50 mm – 300 mm | — |
| Surface Finish | 2B, BA (Bright Annealed), or Electropolished | ASTM A480 |
| Operating Temperature Range | -40°C to +200°C | — |
| Maximum Operating Pressure | 1.6 MPa (standard); up to 2.5 MPa (reinforced) | GB/T 12459 |
| Finish / Coating | Passivated (passivation treatment per ASTM A967) | ASTM A967 |
| Delivery Form | Continuous coil on reel or pre-cut lengths | — |
| Customization | Available per OEM drawings and specifications | — |
Manufacturing Process
The production of stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous, multi-stage manufacturing protocol to ensure dimensional accuracy, material integrity, and surface quality:
- Raw Material Selection & Inspection: Cold-rolled stainless steel strip is sourced from certified mills and subjected to spectroscopic analysis to verify alloy composition compliance with ASTM/GB standards.
- Slitting & Edge Trimming: The strip is slit to precise widths corresponding to the target tube outer diameter, with burr-free edge preparation to prevent stress concentration points.
- Rolling & Forming: The strip is fed through precision roller dies to form a seamless or helical-welded tube. For welded configurations, TIG (Tungsten Inert Gas) welding is employed with inert gas shielding to prevent oxidation at the weld seam.
- Coiling / Helical Winding: The formed tube is wound into a helical coil geometry using CNC-controlled coiling machinery, ensuring uniform pitch, consistent diameter, and minimal residual stress.
- Heat Treatment (Annealing): Where required, the coiled tube undergoes solution annealing in a controlled atmosphere to relieve internal stresses and restore full austenitic microstructure.
- Surface Treatment & Passivation: The finished coil tube receives pickling and passivation treatment per ASTM A967 to remove surface contaminants and establish a protective chromium oxide layer.
- Quality Control & Testing: Each batch undergoes dimensional verification (OD, wall thickness, coil pitch), hydrostatic pressure testing, visual inspection, and — where applicable — radiographic or eddy-current inspection of weld seams.
Applications
The stainless steel coil tube is a versatile component deployed across multiple industries, with primary applications in:
- Fan Coil Units (FCU): Serves as the primary heat-exchange element in chilled water and hot water fan coil systems, enabling efficient cooling and heating of indoor air in commercial buildings, hotels, hospitals, and office complexes.
- Chilled Water Systems: Utilized in central air-conditioning systems where corrosion-resistant heat exchangers are required for longevity and reliability.
- Industrial Process Cooling: Applied in chemical processing, pharmaceutical manufacturing, and food processing plants where hygienic and corrosion-resistant tubing is mandatory.
- Heat Recovery Units: Employed in air-to-air and air-to-water heat recovery systems for energy-efficient building climate management.
- Residential HVAC Systems: Integrated into ducted and cassette-type air conditioning units for domestic applications.
- Marine & Coastal HVAC: Ideal for HVAC installations in coastal or marine environments due to the superior chloride corrosion resistance of SUS316L grade.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure product consistency and regulatory compliance:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- CE Marking — Compliance with European Directive requirements for construction products and machinery
- GB/T 12771 — Chinese National Standard for stainless steel seamless tubes
- ASTM A213 — Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubes for High-Temperature Service
- EN 10217 — European Standard for seamless stainless steel tubes
- RoHS Compliance — Restriction of Hazardous Substances Directive compliance
Each production lot is accompanied by a Mill Test Certificate (MTC) documenting chemical composition, mechanical properties, and traceability information in accordance with EN 10204 Type 3.1 requirements.
Unique Selling Points
- Superior Corrosion Resistance: The austenitic stainless steel composition provides exceptional durability in humid, corrosive, and high-moisture HVAC environments, significantly extending service life compared to carbon steel alternatives.
- Hygienic & Food-Grade Compatible: Suitable for applications in hospitals, pharmaceutical facilities, and food processing environments where sanitary standards are enforced.
- Precision Manufacturing: CNC-controlled coiling ensures dimensional consistency, uniform coil pitch, and repeatable quality across production batches.
- Customization Capability: Full OEM (Original Equipment Manufacturer) support for custom dimensions, coil geometries, and material grades tailored to specific fan coil unit designs.
- Energy Efficiency Contribution: Optimized thermal conductivity and coil geometry design contribute to higher heat-exchange efficiency, reducing energy consumption in HVAC systems.
- Low Maintenance: The passive oxide layer on stainless steel eliminates the need for protective coatings or frequent maintenance, reducing total cost of ownership (TCO).
Note: For fan coil unit installations, correct selection of coil tube parameters — including coil pitch, tube diameter, and material grade — is critical to achieving designed thermal performance and system longevity. Wenzhou Jixing Metal Materials Co., Ltd. provides technical consultation and application engineering support to ensure optimal integration of coil tubes into HVAC system designs.