Stainless Steel Coil Tube — Fan Coil Unit (FCU) Application Series
Product Overview
The Stainless Steel Coil Tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered coiled tubing product designed specifically for integration into Fan Coil Unit (FCU) air conditioning systems and related thermal-fluid transfer applications. This product series (Catalog No. 1479) represents a specialized category within the company's coil tube portfolio, combining the corrosion resistance and hygienic properties of austenitic stainless steel with the geometric advantages of a pre-formed coil configuration.
In the context of Fan Coil Unit (FCU) system design, the coil tube serves as the primary heat exchange medium, facilitating efficient thermal transfer between the working fluid (water, refrigerant, or glycol solution) and the surrounding air. The coil tube's geometry—characterized by consistent winding diameter, uniform wall thickness, and smooth inner bore—directly influences the hydraulic performance, thermal efficiency, and longevity of the complete FCU assembly.
Material & Properties
The coil tubes in this series are fabricated from high-grade austenitic stainless steel alloys, selected for their superior mechanical properties, resistance to pitting and crevice corrosion, and compatibility with aggressive aqueous environments encountered in HVAC systems.
- Primary Alloy Grades: SUS304 (AISI 304), SUS316 (AISI 316), SUS316L (AISI 316L)
- Corrosion Resistance: Exceptional resistance to chlorides, deionized water, and treated cooling/heating water solutions
- Temperature Range: Operational capability from −196°C to +870°C (SUS304); extended low-temperature performance with SUS316L
- Hygienic Surface Finish: Available in No. 4 finish, 2B finish, and electropolished (Ra ≤ 0.4 μm) for sanitary applications
- Mechanical Properties: Tensile strength ≥ 515 MPa (SUS304); Yield strength ≥ 205 MPa; Elongation ≥ 40%
Specifications
| Parameter | Specification / Range |
|---|---|
| Product Designation | Coil Tube (Coiltube), Catalog No. 1479 |
| Outer Diameter (OD) | 3.18 mm – 25.4 mm (1/8" – 1") |
| Wall Thickness | 0.3 mm – 1.65 mm |
| Coil Winding Diameter | 150 mm – 600 mm (adjustable per application) |
| Coil Length per Spool | Up to 100 m (continuous length available) |
| Material Grade | SUS304 / SUS316 / SUS316L |
| Surface Finish | 2B / No. 4 / Electropolished |
| Dimensional Tolerance | ±0.05 mm (OD); ±0.03 mm (wall thickness) |
| Working Pressure Rating | Up to 1.6 MPa (standard); 2.5 MPa (reinforced) |
| Applicable Standards | ASTM A269 / A270, GB/T 12771, EN 10217-7 |
| Packaging | Wooden spool with moisture-proof wrapping; custom packaging available |
Manufacturing Process
The production of this coil tube series follows a rigorous multi-stage manufacturing workflow designed to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Wire Rod Selection & Inspection: Premium stainless steel wire rod is procured from certified mills and subjected to spectroscopic analysis (OES) and ultrasonic flaw detection to verify chemical composition and internal soundness.
- Multi-pass Drawing: The wire rod undergoes sequential cold-drawing through precision-die tooling to achieve the target outer diameter and wall thickness with minimal work-hardening and surface defect formation.
- Intermediate Annealing: Periodic solution annealing (1050°C – 1150°C in controlled atmosphere) restores ductility between drawing passes, ensuring uniform grain structure and preventing cracking.
- Coil Winding: The drawn tubing is wound onto a forming mandrel at controlled tension and speed to produce a uniform coil with consistent winding pitch. The winding process is monitored by laser diameter gauges to maintain geometric fidelity.
- Final Annealing & Pickling: Post-winding solution annealing relieves residual stresses introduced during coiling. Subsequent acid pickling and passivation remove scale and oxide films, establishing a protective chromium-rich passive layer.
- Surface Finishing: Optional electropolishing or mechanical polishing refines the inner and outer surfaces to achieve specified roughness values, critical for minimizing fouling and pressure drop in FCU heat exchange applications.
- Final Quality Control: Each coil undergoes hydrostatic pressure testing, dimensional verification (OD, wall thickness, coil diameter), and visual/surface inspection prior to packaging.
Applications
The stainless steel coil tube from this series finds extensive application across multiple industries, with primary emphasis on thermal management systems:
- Fan Coil Units (FCU) & HVAC Systems: Serves as the evaporator/condenser coil in commercial and residential air conditioning systems, providing efficient air-side and water-side heat transfer with minimal fouling resistance.
- Chilled Water & Heating Circuits: Used in district heating networks and building services for reliable long-term operation in treated water environments.
- Food & Beverage Processing: Employed in pasteurization coils, dairy processing heat exchangers, and sanitary fluid transfer systems where hygiene compliance is paramount.
- Pharmaceutical & Biotechnology: Utilized in CIP (Clean-in-Place) systems, reactor cooling coils, and sterile fluid handling where surface cleanliness and corrosion resistance are non-negotiable.
- Refrigeration & Cryogenics: Suitable for ammonia and fluorocarbon refrigerant circuits, as well as low-temperature applications leveraging SUS316L's cryogenic toughness.
- Marine & Offshore Systems: Deployed in bilge water systems, fire suppression lines, and HVAC installations on vessels where chloride-induced corrosion is a primary design concern.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains comprehensive quality management systems and product certifications to assure international standards compliance:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing and quality assurance processes
- ISO 14001 — Environmental Management System certification
- CE Marking — European Conformity for products intended for the European Economic Area (EEA)
- ASTM Compliance — Material certification per ASTM A269/A270 standards with third-party mill test reports (MTR)
- EN 10204 3.1 Certificate — Material test certificate conforming to European standards for material verification
- GB/T 12771 — Chinese national standard compliance for welded stainless steel tubes
Unique Selling Points
- FCU-Optimized Geometry: Coil winding parameters are engineered specifically for the thermal-hydraulic requirements of fan coil unit heat exchangers, balancing pressure drop against heat transfer coefficient for optimal COP (Coefficient of Performance).
- Superior Anti-Fouling Performance: Electropolished inner surfaces with Ra ≤ 0.4 μm significantly reduce biofilm adhesion and mineral scaling, extending maintenance intervals in water-side applications.
- Full Traceability: Every coil is batch-coded with complete traceability from raw material mill certificate through final inspection, enabling supply chain audit and quality recall management.
- Custom Coil Configuration: Flexible manufacturing capability allows customization of winding diameter, coil length, and end preparation (beveled, threaded, or plain cut) to match specific FCU OEM requirements.
- Extended Service Life: The combination of austenitic stainless steel corrosion resistance and stress-relieved coil geometry ensures service life exceeding 25 years in typical HVAC duty cycles.
Note: This product specification is derived from technical documentation and learning materials related to Fan Coil Unit air conditioning system design methodology. The specifications listed represent standard configurations; custom engineering solutions are available upon consultation with the Wenzhou Jixing Metal Materials Co., Ltd technical team.