Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Product No. 1507) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered continuous spiral tube designed for thermal management applications, particularly within fan coil units (FCUs) and hydronic heat exchange systems. The coil tube is formed into a continuous helical geometry from high-grade stainless steel strip or seamless tubing, offering superior thermal conductivity, corrosion resistance, and mechanical durability under a wide range of indoor operating conditions.
This product is engineered to meet the stringent requirements of heating, ventilation, and air conditioning (HVAC) systems, where accurate cooling capacity calculation under varying indoor conditions is critical. The coil tube serves as the primary heat transfer medium in fan coil units, enabling efficient heat exchange between the circulating refrigerant/water and the ambient air.
Unique Selling Points
- High Thermal Efficiency: Optimized coil geometry and material selection ensure maximum heat transfer coefficient (U-value) across diverse indoor load conditions.
- Corrosion Resistance: Stainless steel construction provides exceptional resistance to condensation corrosion, chemical degradation, and long-term oxidation.
- Continuous Spiral Design: The uninterrupted coil form eliminates weld joints, reducing potential leak points and improving structural integrity.
- Dimensional Precision: Tight manufacturing tolerances ensure consistent flow distribution and uniform thermal performance.
- Extended Service Life: Resistance to fatigue, scaling, and biofilm formation extends operational lifespan significantly compared to carbon steel alternatives.
2. Material & Properties
The coil tube is fabricated from austenitic stainless steel grades conforming to international standards, ensuring optimal combinations of mechanical strength, thermal conductivity, and corrosion resistance.
2.1 Material Grades
- AISI 304 / SUS304 (EN 1.4301): General-purpose grade with excellent corrosion resistance, suitable for most HVAC applications. Chromium (Cr) content: 18–20%, Nickel (Ni) content: 8–10.5%.
- AISI 316 / SUS316 (EN 1.4401): Enhanced corrosion resistance grade with Molybdenum (Mo) addition (2–3%), recommended for aggressive or humid environments.
- AISI 316L / SUS316L (EN 1.4404): Low-carbon variant for superior weldability and resistance to intergranular corrosion.
2.2 Key Physical and Mechanical Properties
| Property | AISI 304 | AISI 316 |
|---|---|---|
| Density (ρ) | 8.00 g/cm³ | 8.03 g/cm³ |
| Thermal Conductivity (λ) at 20°C | 16.3 W/(m·K) | 14.6 W/(m·K) |
| Specific Heat Capacity (c) | 500 J/(kg·K) | 500 J/(kg·K) |
| Tensile Strength (Rm) | ≥520 MPa | ≥520 MPa |
| Yield Strength (Rp0.2) | ≥205 MPa | ≥205 MPa |
| Elongation (A5) | ≥40% | ≥40% |
| Maximum Operating Temperature | 870°C | 870°C |
| Corrosion Resistance (pH) | Good (pH 4–10) | Excellent (pH 3–11) |
2.3 Surface Finish
- 2B Finish: Standard cold-rolled surface, smooth and uniform, suitable for general applications.
- No. 4 Brushed Finish: Satin texture with fine linear grain, enhanced aesthetic appearance and corrosion resistance.
- Pickled & Passivated: Surface treated to remove scale and form a protective chromium oxide passive layer for maximum corrosion protection.
3. Specifications
3.1 Dimensional Specifications
| Parameter | Specification | Tolerance |
|---|---|---|
| Outer Diameter (OD) | Φ6.35 mm / Φ9.52 mm / Φ12.70 mm / Φ15.88 mm | ±0.1 mm |
| Wall Thickness (t) | 0.3 mm / 0.4 mm / 0.5 mm / 0.6 mm / 0.8 mm | ±0.05 mm |
| Coil Pitch (Center-to-Center) | 15 mm – 50 mm (configurable) | ±0.5 mm |
| Coil Height (H) | 150 mm – 600 mm | ±1.0 mm |
| Coil Length (L) | 300 mm – 1200 mm | ±1.0 mm |
| Number of Rows | 1 – 6 rows | — |
| Coil Turns | 10 – 200 turns (continuous spiral) | — |
| Fin Spacing (if finned) | 1.5 mm – 3.0 mm | ±0.2 mm |
| Connection Method | Flared / Threaded / Brazed / Welded | — |
3.2 Performance Specifications
| Performance Parameter | Value / Range | Test Condition |
|---|---|---|
| Cooling Capacity (Typical) | 2.0 kW – 12.0 kW | Indoor 27°C DB / 19°C WB, Water 7°C supply |
| Heating Capacity (Typical) | 2.5 kW – 15.0 kW | Indoor 20°C DB, Water 50°C supply |
| Pressure Drop (Water Side) | 30 – 150 kPa | Flow rate 0.5 – 3.0 L/s |
| Maximum Working Pressure | 1.6 MPa (16 bar) | Hydrostatic test at 2.4 MPa |
| Heat Transfer Coefficient (U) | 150 – 350 W/(m²·K) | Air-side velocity 2.0 – 3.0 m/s |
| Operating Temperature Range | −40°C to +120°C | Continuous operation |
4. Manufacturing Process
The coil tube is produced through a multi-stage precision manufacturing process ensuring dimensional accuracy, material integrity, and thermal performance:
- Raw Material Inspection: Incoming stainless steel strip or seamless tubing is verified for chemical composition (via optical emission spectrometry), mechanical properties, and surface quality in accordance with ASTM A270 / ASTM A312 standards.
- Cutting & End Preparation: Precision laser or shear cutting to specified coil length, with deburring and end-face finishing to ensure clean connection interfaces.
- Coil Forming (Spiral Winding): Continuous spiral forming using CNC-controlled coil winding machinery. The tubing is wound around precision mandrels to achieve exact coil pitch, diameter, and height tolerances. This step is critical for ensuring uniform flow distribution and consistent thermal performance across different indoor operating conditions.
- Header Assembly: Connection of coil ends to distribution headers (manifolds) via orbital welding (TIG welding) or brazing, ensuring leak-free joints with minimum flow restriction.
- Fin Attachment (if applicable): Aluminum fins are mechanically bonded to the coil tube using specialized finning equipment, with fin-to-tube interference fit ensuring optimal thermal contact without mechanical fastening.
- Hydrostatic Pressure Testing: Each coil assembly is subjected to hydrostatic testing at 1.5 times the maximum working pressure for a minimum of 10 minutes to verify structural integrity and leak tightness.
- Surface Treatment & Passivation: Acid pickling followed by passivation treatment to remove manufacturing residues and establish a protective chromium oxide layer, enhancing long-term corrosion resistance.
- Final Quality Inspection: Dimensional verification using coordinate measuring machines (CMM), visual inspection, and performance testing under simulated operating conditions.
5. Applications
The stainless steel coil tube is specifically engineered for thermal management in fan coil units and is applicable across a broad spectrum of HVAC and industrial systems:
- Commercial HVAC Systems: Fan coil units for office buildings, hotels, hospitals, and commercial complexes where precise cooling capacity control under varying indoor loads is essential.
- Residential Climate Control: Concealed and exposed fan coil units for high-end residential applications requiring low noise, high efficiency, and long service life.
- Industrial Process Cooling: Precision temperature control in manufacturing facilities, electronics cleanrooms, and data centers.
- Food & Beverage Industry: Temperature-controlled storage, processing areas, and ventilation systems where hygiene and corrosion resistance are paramount.
- Marine & Offshore Applications: HVAC systems on vessels and offshore platforms where resistance to saltwater corrosion and humidity is critical.
- Pharmaceutical & Laboratory Environments: Cleanroom temperature regulation and controlled environment systems requiring contamination-free operation.
6. Quality Certifications & Standards Compliance
The coil tube product is manufactured under a comprehensive quality management system and complies with the following international standards and certifications:
| Standard / Certification | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification ensuring consistent product quality and continuous improvement. |
| ISO 14001:2015 | Environmental Management System certification for sustainable manufacturing practices. |
| ASTM A270 / A312 | Standard specifications for welded and seamless austenitic stainless steel tubing. |
| EN 10217-7 | European standard for heat exchanger tubes made of stainless steel. |
| GB/T 12771 | Chinese national standard for welded stainless steel tubes for general engineering. |
| EN 12039 | European standard for air-cooled heat exchangers (applicable to coil tube assemblies). |
| CE Marking | Conformity with European health, safety, and environmental protection standards. |
| RoHS Compliance | Restriction of Hazardous Substances directive compliance for environmental safety. |
Technical Note: The cooling capacity of fan coil units incorporating this stainless steel coil tube is influenced by multiple indoor operating parameters including dry-bulb temperature, wet-bulb temperature, relative humidity, air velocity, and water flow rate. Accurate capacity calculation requires consideration of the coil's effective heat transfer area, fin efficiency, air-side and water-side heat transfer coefficients, and the logarithmic mean temperature difference (LMTD) under specific operating conditions. Wenzhou Jixing Metal Materials Co., Ltd. provides engineering support for capacity verification and system optimization based on site-specific thermal load analysis.
7. Packaging & Delivery
- Individual coil assemblies are wrapped in protective plastic film and secured in export-grade wooden crates or cardboard packaging.
- Desiccant packets included to prevent moisture ingress during transit.
- Complete documentation package including material test certificates (MTC), dimensional inspection reports, and hydrostatic test records.
- Customized packaging available for bulk orders and international shipping requirements.