Stainless Steel Coil Tube — Fan Coil Unit (FCU) Water System Application Grade
Product Overview
The Stainless Steel Coil Tube (盘管) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 1095) is a precision-engineered coiled stainless steel tubing specifically designed for integration into fan coil unit (FCU) water distribution systems. This product is engineered to meet the demanding hydraulic performance requirements of modern building HVAC (Heating, Ventilation, and Air Conditioning) infrastructure, where efficient fluid transport, thermal exchange, and long-term corrosion resistance are paramount.
Unlike conventional straight-length tubing, the coil tube configuration enables compact installation within tight mechanical spaces typical of commercial and residential HVAC installations. The coiled geometry minimizes spatial footprint while maintaining optimal hydraulic flow characteristics, making it an ideal solution for hydronic piping networks that require hydraulic optimization to reduce pumping energy consumption and system pressure drop.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its superior combination of mechanical strength, corrosion resistance, and thermal stability. Key material characteristics include:
- Base Alloy: Austenitic stainless steel (e.g., AISI 304 / AISI 316 grade), providing excellent resistance to chloride-induced pitting and general corrosion in water-based hydronic systems.
- Mechanical Properties: High tensile strength and elongation values ensuring dimensional stability under cyclic thermal loading and water hammer conditions inherent in FCU water loop systems.
- Thermal Conductivity: Adequate thermal conductivity to support efficient heat transfer between the hydronic fluid and the surrounding air stream in fan coil units.
- Hygienic Surface Finish: Smooth internal bore surface (Ra ≤ 0.8 μm) to minimize frictional pressure loss and prevent biofilm accumulation, directly contributing to system hydraulic efficiency.
- Temperature Range: Operational suitability from −40 °C to +200 °C, accommodating both heating and cooling modes of FCU systems.
Technical Specifications
| Parameter | Specification |
|---|---|
| Product Name | Stainless Steel Coil Tube (盘管 Coiltube) |
| Product Number | 1095 |
| Material Grade | AISI 304 / AISI 316L (Austenitic Stainless Steel) |
| Outer Diameter (OD) | 6 mm – 35 mm (customizable) |
| Wall Thickness | 0.5 mm – 2.0 mm |
| Coil Diameter | 200 mm – 1500 mm (configurable per installation requirements) |
| Coil Length | Up to 100 m per coil (continuous draw length) |
| Surface Treatment | Pickled & Passivated; optional electropolished finish |
| Internal Surface Roughness | Ra ≤ 0.8 μm |
| Maximum Operating Pressure | 1.6 MPa (16 bar) — suitable for standard FCU water loops |
| Applicable Fluids | Water, glycol-water mixtures, district heating/cooling fluids |
| Standards Compliance | ASTM A269 / ASTM A312, EN 10216-5, GB/T 14976 |
| Welding Compatibility | TIG (GTAW), orbital welding, brazing |
Manufacturing Process
The production of this coil tube follows a rigorously controlled multi-stage manufacturing sequence to ensure dimensional accuracy, metallurgical integrity, and hydraulic performance:
- Raw Material Selection: Cold-rolled stainless steel strip of certified purity is sourced from approved mills, with each lot subjected to spectroscopic analysis (PMI — Positive Material Identification) to verify alloy composition.
- Forming & Drawing: The strip is formed into a seamless tube blank via cold-rolling and subsequently drawn through precision-die tooling to achieve the target OD and wall thickness tolerances (±0.05 mm).
- Coiling: The formed tube is wound into a controlled coil geometry using CNC-guided coiling equipment, ensuring uniform coil pitch and minimal mechanical stress introduction.
- Heat Treatment (if applicable): Solution annealing at 1050–1100 °C followed by rapid water quenching to restore full austenitic microstructure and eliminate residual stresses from cold working.
- Pickling & Passivation: Immersion in nitric acid/hydrofluoric acid bath to remove mill scale and form a protective chromium oxide passive film, enhancing long-term corrosion resistance in hydronic service.
- Quality Inspection: Each coil undergoes hydrostatic pressure testing, dimensional verification (laser micrometry), and visual/surface inspection. Internal bore roughness is verified via profilometry sampling.
Applications
The primary application domain for this product is the fan coil unit (FCU) water distribution system in commercial and residential HVAC installations. Specifically:
- FCU Internal Hydronic Coils: Direct integration as the heat exchange coil element within fan coil units, where the coil tube forms the water-side channels through which chilled or heated water circulates.
- Building Water Distribution Piping: Used as supply and return piping in FCU water loop networks, where hydraulic optimization software (as referenced in the product development literature) is employed to minimize system pressure drop and reduce pumping energy consumption.
- District Heating/Cooling Connections: Suitable for connecting individual FCU terminals to central district heating or cooling mains due to its pressure rating and corrosion resistance.
- Specialty Hydronic Systems: Applicable in pharmaceutical, food processing, and laboratory HVAC systems where sanitary-grade stainless steel tubing is mandated.
Hydraulic Optimization Context: In modern FCU water system design, the coil tube geometry and internal surface finish directly influence the Darcy-Weisbach friction factor and overall system head loss. The smooth bore finish (Ra ≤ 0.8 μm) of this product reduces frictional losses by up to 20–30% compared to standard commercial-grade tubing, enabling more efficient system hydraulics and lower long-term operating costs when paired with hydraulic optimization software tools.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure product conformity:
- ISO 9001:2015 — Quality Management System certification covering design, manufacturing, and delivery processes.
- ISO 14001:2015 — Environmental Management System certification for sustainable manufacturing practices.
- Material Traceability: Full heat-number traceability from mill certificate through to finished product, enabling downstream verification of alloy composition and mechanical properties.
- Third-Party Testing: Available upon request — hydrostatic testing, chemical analysis (wet chemistry or OES), hardness testing, and intergranular corrosion testing per ASTM A269 requirements.
- Standards Reference: Products conform to ASTM A269 (Seamless and Welded Austenitic Stainless Steel Tubing), EN 10216-5 (Stainless Steel Tubes for Pressure Purposes), and GB/T 14976 (Stainless Steel Seamless Tubes for Fluid Transport).
Unique Selling Points
This product distinguishes itself through a synergistic combination of hydraulic efficiency, material durability, and system-level optimization compatibility. The precision-controlled internal surface finish directly reduces frictional pressure losses in FCU water loops, contributing to measurable energy savings in building operations. The coiled configuration offers installation flexibility and compactness unmatched by straight-length alternatives, while the austenitic stainless steel construction ensures a service life exceeding 25 years in standard hydronic environments without degradation of hydraulic or thermal performance.