Stainless Steel Coil Tube for Fan Coil Unit (FCU) Systems
Product Overview
The Stainless Steel Coil Tube (Product No. 1238) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered coiled tubing solution designed specifically for Fan Coil Unit (FCU) applications in modern Heating, Ventilation, and Air Conditioning (HVAC) systems. As a critical heat exchanger component, the coil tube is responsible for transferring thermal energy between the circulating fluid (water or refrigerant) and the surrounding air, thereby delivering precise temperature regulation in commercial, industrial, and residential environments.
In response to the evolving demands of China's HVAC industry—as highlighted in the technical analysis titled "Analysis of the Current Status of Fan Coil Unit Technology in China"—this product addresses key performance challenges including corrosion resistance, thermal efficiency, and long-term structural integrity under continuous operational cycles. The coil tube is manufactured to international standards, ensuring compatibility with a wide range of FCU configurations and system designs.
Material & Properties
The coil tube is fabricated from high-grade stainless steel alloys, selected for their exceptional combination of mechanical strength, corrosion resistance, and thermal conductivity. The primary material grades used include:
- SUS304 (AISI 304 / 1.4301) — The standard austenitic stainless steel grade, offering excellent general corrosion resistance and formability. Contains approximately 18% Chromium (Cr) and 8% Nickel (Ni).
- SUS316L (AISI 316L / 1.4404) — Enhanced austenitic grade with Molybdenum (Mo) addition (2–3%), providing superior resistance to pitting and crevice corrosion in aggressive chemical environments.
- SUS321 (AISI 321 / 1.4541) — Titanium-stabilized austenitic grade, offering improved resistance to intergranular corrosion at elevated temperatures (450°C–850°C).
Key Material Properties:
| Property | SUS304 | SUS316L | SUS321 |
|---|---|---|---|
| Density (g/cm³) | 7.93 | 8.00 | 8.00 |
| Thermal Conductivity (W/m·K, at 20°C) | 16.3 | 14.6 | 16.3 |
| Tensile Strength (MPa, minimum) | 520 | 485 | 520 |
| Yield Strength (MPa, minimum) | 205 | 170 | 205 |
| Elongation (% A50) | ≥40 | ≥35 | ≥40 |
| Maximum Operating Temperature (°C) | 870 | 870 | 870 |
| Corrosion Resistance Rating (ASTM A967) | Excellent | Superior | Excellent |
Specifications
The coil tube is available in a comprehensive range of dimensions to accommodate various FCU unit sizes and system designs. The following table summarizes the standard specification parameters:
| Specification Parameter | Standard Range / Options | Unit |
|---|---|---|
| Outer Diameter (OD) | 6.35 / 9.52 / 12.70 / 15.88 / 19.05 | mm |
| Wall Thickness | 0.50 – 1.20 | mm |
| Coil Inner Diameter (Diameter of the coil bundle) | 100 – 600 | mm |
| Coil Height (Number of rows × Row pitch) | 2 – 12 rows (configurable) | — |
| Row Pitch | 15 – 30 | mm |
| Tube Length per Coil | 2000 – 12000 | mm |
| Surface Finish | 2B / BA (Bright Annealed) / No. 4 Brushed | — |
| Pressure Test Rating | 1.5 × Maximum Working Pressure (MWP) | MPa |
| Maximum Working Pressure | 1.6 – 2.5 | MPa |
| Maximum Operating Temperature | -40 to +120 | °C |
| Heat Exchange Efficiency (E) | ≥ 0.75 | — |
| Design Life | ≥ 25 years | — |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous, multi-stage manufacturing workflow designed to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Inspection — Incoming stainless steel seamless or welded pipe stock is subjected to Spectroscopic Analysis (OES) to verify chemical composition, along with ultrasonic testing (UT) for internal defect detection in accordance with ASTM E165.
- Cold Drawing & Sizing — The pipe stock undergoes multi-pass cold drawing to achieve precise outer diameter and wall thickness tolerances (±0.05 mm). This process enhances surface finish and mechanical properties through work hardening.
- Solution Annealing & Pickling — Drawn tubing is annealed at 1050°C–1100°C in a protective atmosphere to relieve residual stresses and restore full austenitic ductility. Subsequent pickling and passivation remove scale and oxide layers, forming a protective chromium oxide passive film.
- Coil Forming (Bending) — Precision CNC-controlled bending machines form the tubing into the required coil geometry. Controlled bending radii (minimum 3× OD) prevent material thinning, wrinkling, or ovality exceeding 2% of OD.
- Fin Attachment — High-efficiency aluminum or copper fins are mechanically or brazed onto the coil tubes to maximize the heat transfer surface area. Fin density typically ranges from 10 to 16 fins per inch (FPI).
- Hydrostatic Pressure Testing — Each completed coil assembly is pressure-tested at 1.5× MWP for a minimum dwell time of 30 seconds to verify watertight integrity and absence of leaks.
- Final Inspection & Quality Assurance — Comprehensive dimensional inspection, surface quality assessment, and non-destructive testing (NDT) are performed. Products are serialized and documented for full traceability.
Applications
The stainless steel coil tube serves as a core component in a broad spectrum of HVAC and thermal management systems. Primary application domains include:
- Commercial Fan Coil Units — Ceiling-mounted, wall-mounted, and ducted FCUs in office buildings, hotels, hospitals, and shopping centers.
- Industrial Process Cooling & Heating — Temperature control in manufacturing facilities, clean rooms, and laboratory environments requiring high purity and corrosion resistance.
- Residential HVAC Systems — Ducted and ductless mini-split systems for individual residential climate control.
- Marine & Coastal Environments — SUS316L-grade coil tubes are specifically recommended for HVAC systems in coastal or marine environments where chloride-induced corrosion is a concern.
- Food & Pharmaceutical Processing — Sanitary-grade coil tubes meet hygienic requirements for temperature-sensitive processing environments.
- Refrigeration & Chiller Systems — Evaporator and condenser coil assemblies in commercial refrigeration equipment.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management framework and holds the following certifications and complies with international standards:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control.
- ISO 14001:2015 — Environmental Management System certification reflecting commitment to sustainable manufacturing practices.
- ISO 45001:2018 — Occupational Health and Safety Management System certification.
- CE Marking — Conformity with European health, safety, and environmental protection standards for market access within the European Economic Area.
- EN 10216-5 — Compliance with European standards for stainless steel seamless and welded tubes for pressure purposes.
- ASTM A213 / A269 — Compliance with American standards for seamless austenitic stainless steel boiler, heat exchanger, and condenser tubes.
- GB/T 14976 — Compliance with Chinese national standards for seamless stainless steel tubes for fluid transport.
- ASME B31.5 — Compliance with American Society of Mechanical Engineers standards for refrigeration piping and heat transfer components.
- NACE MR0175 / ISO 15156 — Material resistance to sulfide stress cracking (for applicable grades).
Unique Selling Points: The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd distinguishes itself through: (1) Superior corrosion resistance with design life exceeding 25 years, significantly outperforming conventional carbon steel alternatives; (2) Precision CNC coil forming ensuring geometric accuracy and optimal airflow distribution; (3) Multi-grade material availability (SUS304, SUS316L, SUS321) enabling tailored solutions for diverse environmental conditions; (4) Full traceability from raw material through final inspection; and (5) Customizable configurations to meet specific OEM and project requirements.