Stainless Steel Coil Tube for Fan Coil Unit Systems (FCU Coiltube)

Product Overview

The Stainless Steel Coil Tube (Product No. 1512) is a precision-engineered coiled stainless steel tubing designed for integration into fan coil unit (FCU) systems, particularly within commercial and hospitality HVAC (Heating, Ventilation, and Air Conditioning) applications. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd, this coil tube serves as a critical heat exchange and fluid distribution component in fresh air treatment terminal systems. The product is engineered to meet the demanding requirements of modern building climate control, ensuring optimal thermal performance, corrosion resistance, and long-term reliability in both heating and cooling cycles.

This coil tube is specifically optimized for fresh air handling terminal state selection in hotel and commercial ventilation systems, where precise temperature and humidity control are essential for occupant comfort and energy efficiency.

Material & Properties

The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional combination of mechanical strength, thermal conductivity, and resistance to corrosion in humid and chemically aggressive environments typical of HVAC systems.

• Primary Material Grades: SUS304 (UNS S30400), SUS316 (UNS S31600) — the latter offering superior resistance to chloride-induced pitting corrosion
• Wall Thickness Range: 0.3 mm – 1.5 mm, selected based on operating pressure and thermal load requirements
• Surface Finish: Mill finish (2B), electropolished (EP), or passivated surface to maximize heat transfer efficiency and inhibit biofilm formation
• Operating Temperature Range: -40°C to +250°C (continuous service)
• Operating Pressure Rating: Up to 1.6 MPa (gauge), depending on wall thickness and outer diameter
• Corrosion Resistance: Equivalent to or exceeding ASTM A269/A270 standards; suitable for glycol-based heat transfer fluids and deionized water circuits

Technical Specifications

Parameter	Specification	Standard / Reference
Product Category	Coil Tube (盘管 / Coiltube)	Internal Classification No. 1512
Outer Diameter (OD)	6 mm – 25 mm (customizable)	ASTM A269 / EN 10217
Wall Thickness	0.3 mm – 1.5 mm	ASTM A270
Coil Pitch (Center-to-Center)	10 mm – 50 mm (adjustable per thermal load)	ASHRAE Handbook — HVAC Systems and Equipment
Coil Diameter (Overall)	100 mm – 800 mm	Project-specific
Tube Length (Uncoiled)	Up to 50 m continuous	ISO 11286
Material Grade	SUS304 / SUS316	ASTM A240 / JIS G4305
Surface Treatment	Passivated / Electropolished	ASTM A967
Tolerance on OD	±0.1 mm	ISO 6508
Roundness Tolerance	≤ 2% of OD	ISO 6508
Hydrostatic Test Pressure	1.5 × working pressure	ASME B31.9
Applicable Fluids	Water, Glycol-water mixtures, Deionized water, Refrigerant (limited)	—

Manufacturing Process

The production of the stainless steel coil tube follows a rigorously controlled multi-stage process to ensure dimensional accuracy, material integrity, and consistent thermal performance:

1. Raw Material Selection: Cold-rolled stainless steel strip (SUS304/316) conforming to ASTM A240 is inspected for chemical composition via X-ray fluorescence (XRF) and mechanical properties via tensile testing.
2. Slitting and Leveling: The coil strip is slit to precise width and cold-rolled to flatness tolerance of ≤ 0.3% to ensure uniform tube wall thickness after forming.
3. Tube Forming (Semi-Solid State): Precision roll-forming or hydraulic drawing is employed to form the strip into seamless tubing with controlled wall thickness and roundness.
4. Coil Winding: The formed tube is wound onto a precision CNC-controlled mandrel to produce the final coil geometry, with pitch and diameter controlled to within ±0.5 mm tolerance.
5. Welding (where applicable): TIG (Tungsten Inert Gas) welding per AWS D10.9 is used for header connections, with internal helium or argon gas shielding to prevent oxidation.
6. Heat Treatment: Solution annealing at 1050°C – 1150°C followed by rapid water quenching to restore full austenitic microstructure and maximize corrosion resistance.
7. Surface Passivation: Citric acid or nitric acid passivation per ASTM A967 to establish a stable chromium oxide passive film.
8. Pressure Testing: Each coil assembly undergoes hydrostatic pressure testing at 1.5× working pressure for a minimum of 30 seconds with no visible leakage or deformation.
9. Final Inspection: Dimensional verification (OD, wall thickness, coil pitch, overall diameter), visual inspection, and optional eddy current testing for wall thickness mapping.

Applications

This stainless steel coil tube is engineered for the following primary applications:

• Hotel and Hospitality HVAC Systems: Fan coil units (FCUs) for fresh air terminal treatment in hotel guest rooms, corridors, and public areas — where the coil tube operates as the heat exchange element for sensible and latent heat removal during fresh air conditioning.
• Commercial Building Ventilation: Dedicated outdoor air systems (DOAS) and air handling units (AHUs) requiring corrosion-resistant coil assemblies for high-humidity environments.
• Medical and Pharmaceutical Facilities: Cleanroom air handling systems where hygienic-grade stainless steel tubing is mandated to prevent microbial contamination.
• Food and Beverage Processing: Refrigeration and cooling systems in processing environments subject to aggressive chemical cleaning agents.
• Marine and Coastal Installations: HVAC systems in coastal or high-salinity environments where SUS316 grade provides critical chloride resistance.
• Industrial Process Cooling: Glycol-loop heat exchangers and process fluid distribution coils requiring high-temperature and high-pressure tolerance.

Quality Certifications & Compliance

Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system ensuring product traceability and conformance to international standards:

• ISO 9001:2015 — Quality Management System certification for manufacturing processes
• ISO 14001:2015 — Environmental Management System certification
• ASTM A269 / A270 — Conformance for stainless steel tube dimensions and mechanical properties
• ASME B31.9 — Compliance for refrigeration and air-conditioning piping design and fabrication
• EN 10217 — European standard for stainless steel tubes for pressure purposes
• JIS G4305 — Japanese Industrial Standard for stainless steel seamless tubes
• NSF/ANSI 61 — Drinking water system components certification (where applicable for potable water loop applications)
• Mill Test Certificates (MTC): Provided per EN 10204 Type 3.1 for every production batch, including chemical analysis and mechanical test data

Unique Selling Points

• Superior Corrosion Resistance: Austenitic stainless steel construction eliminates the risk of internal corrosion and scale buildup common in carbon steel or copper coils, extending service life beyond 20 years in aggressive environments.
• Hygienic Design: Passivated and electropolished surfaces inhibit microbial growth, making the coil tube suitable for food-grade and pharmaceutical-grade applications without additional lining or treatment.
• Thermal Performance Stability: Consistent thermal conductivity across the full operating temperature range ensures predictable heat transfer coefficients, enabling accurate fresh air terminal state calculations and energy-efficient system design.
• Customizable Geometry: CNC-controlled winding allows precise adjustment of coil pitch, diameter, and tube length to match specific thermal load calculations for each installation.
• Full Traceability: Each coil tube batch is accompanied by complete mill test documentation, enabling full material provenance tracking from raw steel mill to final installation.
• Environmental Sustainability: Stainless steel is 100% recyclable with no loss of material properties, aligning with green building certification requirements (LEED, BREEAM, WELL).

Design Considerations for Fresh Air Terminal State Selection

When integrating this coil tube into fan coil unit systems for fresh air treatment, the following engineering considerations are critical for achieving the desired terminal state (temperature and humidity) of supply air:

The selection of coil tube geometry — including tube diameter, wall thickness, and coil pitch — directly influences the air-side and water-side heat transfer coefficients (h_air and h_water), which determine the overall heat transfer rate (U-value) and the Coil Load (sensible + latent). For hotel HVAC systems operating in high-humidity climates, a reduced coil pitch (10–15 mm) with thinner wall tubes (0.3–0.5 mm) maximizes surface area and heat transfer efficiency, enabling deeper dehumidification and lower supply air temperatures required to meet the terminal state point on the psychrometric chart.

The stainless steel coil tube's low fouling factor (typically < 0.0001 m²·K/W) ensures that the designed thermal performance is maintained over the full service life, unlike copper or aluminum coils which may degrade due to oxidation and biological fouling.

Ordering Information

Customers are advised to provide the following parameters when placing an order:

• Required outer diameter (OD) and wall thickness
• Coil pitch and overall coil diameter
• Material grade (SUS304 or SUS316)
• Surface finish requirement (mill finish, electropolished, passivated)
• Operating pressure and temperature conditions
• Applicable fluid type
• Applicable standards and certifications required
• Quantity and delivery schedule

Custom engineering support and thermal performance calculations are available upon request to assist in coil tube specification for specific fan coil unit system designs.