Stainless Steel Coil Tube — FP-51WMU Fan Coil Unit (FCU) Series
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered heat exchange component designed specifically for integration into the FP-51WMU Fan Coil Unit (Fan Coil Unit, FCU) system manufactured by Wenzhou Jixing Metal Materials Co., Ltd. As a critical thermal management element, the coil tube serves as the primary heat transfer medium within the FCU assembly, facilitating efficient cooling and heating operations in commercial and industrial HVAC (Heating, Ventilation, and Air Conditioning) environments.
Unlike conventional carbon steel or copper coil tubes, the stainless steel variant offers superior corrosion resistance, extended service life, and enhanced hygiene performance, making it particularly suitable for demanding applications in pharmaceutical manufacturing, food processing, laboratory facilities, and cleanroom environments where material integrity and fluid purity are paramount.
2. Material & Properties
2.1 Base Material
The coil tube is fabricated from high-grade Stainless Steel, typically conforming to the following material grades:
- AISI 304 (UNS S30408) — General-purpose austenitic stainless steel with excellent formability and moderate corrosion resistance.
- AISI 316 (UNS S31608) — Molybdenum-enhanced austenitic stainless steel offering superior resistance to chlorides and aggressive chemical environments.
- AISI 316L (UNS S31603) — Low-carbon variant of 316, optimized for welding applications and resistance to intergranular corrosion.
2.2 Mechanical Properties
- Tensile Strength (Ultimate Tensile Strength, UTS): ≥ 515 MPa (AISI 304); ≥ 515 MPa (AISI 316)
- Yield Strength (0.2% Offset): ≥ 205 MPa (AISI 304); ≥ 170 MPa (AISI 316)
- Elongation at Break: ≥ 40% (AISI 304); ≥ 35% (AISI 316)
- Hardness (Brinell): ≤ 217 HB (AISI 304); ≤ 217 HB (AISI 316)
- Maximum Operating Temperature: Up to 870°C (oxidizing atmosphere)
2.3 Physical Properties
- Density: 7.93 g/cm³ (AISI 304); 8.03 g/cm³ (AISI 316)
- Thermal Conductivity (at 20°C): 16.3 W/(m·K) (AISI 304); 14.6 W/(m·K) (AISI 316)
- Thermal Expansion Coefficient (20–100°C): 17.3 × 10⁻⁶ /K (AISI 304); 16.0 × 10⁻⁶ /K (AISI 316)
- Specific Heat Capacity (at 20°C): 0.50 J/(g·K)
2.4 Surface Finish
The coil tube surface is finished to a 2B (cold-rolled and annealed) or No. 4 brushed finish, achieving a surface roughness of Ra ≤ 0.8 μm. For hygienic applications, a Electropolished or Mechanical Polished finish with Ra ≤ 0.4 μm is available upon request. The interior surface may be subjected to Passivation Treatment to enhance the passive chromium oxide layer and improve long-term corrosion resistance.
3. Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Model | FP-51WMU Coil Tube | Manufacturer Specification |
| Outer Diameter (OD) | 6.35 mm (1/4"), 9.52 mm (3/8"), 12.7 mm (1/2") | ASME B36.19M |
| Wall Thickness | 0.5 mm – 1.5 mm (configurable) | — |
| Coil Pitch (Spiral Spacing) | 15 mm – 30 mm (configurable per design) | — |
| Number of Coils (Rows) | 2 – 6 rows (typical) | — |
| Tube Length (per coil circuit) | 600 mm – 3,000 mm | — |
| Material Grade | AISI 304 / 316 / 316L | ASTM A270 / ASTM A269 |
| Maximum Working Pressure | 1.6 MPa (16 bar) – 4.0 MPa (40 bar) | — |
| Maximum Operating Temperature | −40°C to +180°C (standard); up to +350°C (special order) | — |
| Heat Transfer Coefficient | ≥ 850 W/(m²·K) (water-to-air) | — |
| Dimensional Tolerance | ±0.1 mm (OD); ±10% (pitch) | ISO 286 / GB/T 14976 |
| Surface Roughness | Ra ≤ 0.8 μm (standard); Ra ≤ 0.4 μm (hygienic grade) | ISO 1302 |
| Welding Method | TIG (Tungsten Inert Gas) / Orbital Welding | ASME Section IX |
| Fin Type (if applicable) | Integral L-Fin or External Aluminium Fin | — |
| Corrosion Resistance | ASTM A96 Passivation Test; Salt Spray Test ≥ 500 hours | ASTM G102 / ASTM B117 |
| Hydrostatic Test Pressure | 1.5 × Working Pressure (minimum 2.4 MPa) | ASME B31.3 |
| Applicable Standards | ASTM A270, ASTM A269, GB/T 14976, EN 10217-7 | — |
4. Manufacturing Process
The production of the FP-51WMU Stainless Steel Coil Tube follows a rigorous, multi-stage manufacturing process to ensure dimensional accuracy, mechanical integrity, and surface quality:
- Raw Material Procurement and Inspection: Cold-rolled stainless steel strip or seamless tubing is sourced from certified mills (e.g., Outokumpu, Voestalpine, Baosteel). Each batch undergoes Spectroscopic Analysis (OES — Optical Emission Spectroscopy) and Mechanical Testing to verify chemical composition and mechanical properties against ASTM/EN standards.
- Coil Forming (Coiling): The stainless steel tube is fed through a precision Tube Coiling Machine equipped with servo-controlled forming dies. The tube is gradually bent into a helical coil geometry with controlled coil pitch, OD, and row alignment. The forming process is performed at room temperature to avoid work-hardening beyond acceptable limits.
- Dimensional Stabilization: After coiling, the tube assembly undergoes Solution Annealing (heating to 1010–1150°C followed by rapid water quenching) to relieve residual stresses, restore full ductility, and ensure uniform microstructure. This step is critical for maintaining long-term dimensional stability under thermal cycling.
- Passivation Treatment: The annealed coil tube is immersed in a Nitric Acid (HNO₃) Passivation Solution (typically 20–30% concentration) to remove free iron and enrich the surface chromium oxide layer. This treatment is verified using ASTM A96 or ASTM A380 test methods.
- Welding and Assembly: The coil tube is welded to inlet/outlet headers and connecting manifolds using Tungsten Inert Gas (TIG) Welding or Orbital Welding with argon shielding gas. Weld joints are inspected for penetration, porosity, and geometric integrity. In hygienic applications, Orbital Welding ensures consistent weld quality with minimal heat-affected zone (HAZ) distortion.
- Finning (if applicable): External fins may be mechanically attached or integrally formed. Aluminium fins are brazed or mechanically crimped onto the stainless steel tube surface to maximize the effective heat transfer area (typically increasing surface area by 4–8×).
- Hydrostatic Pressure Testing: Each completed coil tube assembly is subjected to a Hydrostatic Pressure Test at 1.5× the maximum working pressure for a minimum hold time of 30 minutes. Any leakage or deformation results in rejection and rework.
- Final Inspection and Packaging: Finished products undergo dimensional verification, surface quality inspection, and material traceability documentation. Each unit is tagged with a unique Heat Number and Batch Code for full traceability. Packaging utilizes protective foam, moisture-absorbing desiccants, and export-grade wooden crates.
5. Applications
The FP-51WMU Stainless Steel Coil Tube is engineered for a wide range of high-performance HVAC and thermal management applications:
- Commercial HVAC Systems: Fan Coil Units for office buildings, shopping malls, hotels, and hospitals where reliable temperature control and low maintenance are essential.
- Pharmaceutical and Biotechnology Facilities: Cleanroom air handling units (AHU) and laminar flow systems requiring corrosion-resistant, hygienic-grade heat exchange components compliant with GMP (Good Manufacturing Practice) standards.
- Food and Beverage Processing: Cooling and heating coils for dairy processing, beverage pasteurization, and refrigerated storage systems where fluid purity and sanitary design are critical.
- Laboratory and Research Environments: Precision temperature control systems for analytical laboratories, semiconductor fabrication cleanrooms, and scientific research facilities.
- Marine and Offshore Applications: HVAC systems for ships, offshore platforms, and marine vessels operating in high-salinity, high-humidity environments where chloride-induced corrosion is a major concern.
- Data Centers and Server Rooms: Precision cooling systems requiring high reliability, long service intervals, and resistance to condensate corrosion.
- Industrial Process Cooling: Auxiliary cooling coils for chemical processing, electronics manufacturing, and precision machining centers.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure product conformity and traceability:
- ISO 9001:2015 — Quality Management System certification ensuring consistent production quality and process control.
- ISO 14001:2015 — Environmental Management System certification for sustainable manufacturing practices.
- ISO 45001:2018 — Occupational Health and Safety Management System certification.
- CE Marking (EU) — Compliance with European Directive 2014/68/EU (Pressure Equipment Directive) for pressure-containing components.
- ASME Section IX — Welding qualification and procedure approval for pressure vessel and piping components.
- NACE MR0175 / ISO 15156 — Compliance for materials used in sour service environments (hydrogen sulfide-containing conditions).
- NSF/ANSI 61 — Drinking Water System Components certification (available for hygienic-grade variants).
- Material Certification: Each shipment is accompanied by an EN 10204 Type 3.1 Certificate of Analysis confirming chemical composition, mechanical properties, and heat treatment status.
7. Unique Selling Points
- Exceptional Corrosion Resistance: The stainless steel construction provides outstanding resistance to atmospheric corrosion, condensate-induced rust, and chemical attack — significantly outperforming carbon steel and copper alternatives in humid and aggressive environments.
- Extended Service Life: With proper installation and maintenance, the coil tube offers a design life exceeding 20–25 years, reducing total cost of ownership (TCO) and minimizing replacement frequency.
- Hygienic and Sanitary Design: Smooth interior surfaces (Ra ≤ 0.4 μm) prevent biofilm accumulation and facilitate CIP (Clean-in-Place) procedures, making the product ideal for food-grade and pharmaceutical applications.
- Thermal Stability: Consistent thermal conductivity and low thermal expansion coefficient ensure reliable heat transfer performance across a wide operating temperature range without degradation.
- Customizability: The coil tube is available in multiple material grades, dimensions, and configurations to meet specific project requirements and performance targets.
- Full Traceability: Every coil tube unit is traceable to its mill heat number, enabling complete supply chain transparency and regulatory compliance.
8. Storage and Handling Recommendations
Store the coil tube in a dry, well-ventilated indoor environment with relative humidity maintained below 65%. Avoid direct contact with carbon steel or dissimilar metals to prevent galvanic corrosion. Protect the surface finish with the original protective wrapping until installation. During installation, ensure all connections are made with compatible materials and appropriate gaskets. Perform a hydrostatic test at commissioning to verify system integrity before operational use.
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Reference: FP-51WMU Coil Tube — Stainless Steel Series
Compliance Standards: ASTM A270 / A269, GB/T 14976, EN 10217-7, ASME B31.3