Stainless Steel Coil Tube (Coiltube) — Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product designed for continuous winding and coil formation. These coil tubes are primarily utilized in heat exchanger applications, particularly in Fan Coil Units (FCU), refrigeration systems, HVAC (Heating, Ventilation, and Air Conditioning) assemblies, and industrial process heat transfer systems. The coil tube configuration enables optimized thermal performance through maximized surface-area-to-volume ratios, making it an essential component in modern thermal management infrastructure.
This specification draws upon advanced model analysis of variable-structure performance characteristics in fan coil unit coil assemblies, ensuring that the coil tube geometry, material selection, and manufacturing tolerances are aligned with dynamic operational requirements under varying load conditions.
2. Material & Properties
Stainless steel coil tubes are fabricated from high-performance austenitic and duplex stainless steel grades, selected to ensure long-term corrosion resistance, mechanical integrity, and thermal conductivity in demanding service environments.
- Primary Grades: AISI 304 (UNS S30400), AISI 316 (UNS S31600), AISI 316L (UNS S31603), AISI 321 (UNS S32100), and Duplex 2205 (UNS S31803)
- Corrosion Resistance: Excellent resistance to pitting, crevice corrosion, and general corrosion in aqueous, chemical, and atmospheric environments
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20°C (grade-dependent)
- Mechanical Strength: Yield strength ≥ 205 MPa (304); ≥ 450 MPa (2205 Duplex)
- Temperature Range: −196°C to +870°C (304 grade); −196°C to +400°C (316 grade)
- Hygienic Compliance: Surface finish Ra ≤ 0.4 μm available for sanitary and pharmaceutical applications
3. Specifications
| Parameter | Specification Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.0 mm – 50.8 mm | GB/T 14976, ASTM A269 |
| Wall Thickness (WT) | 0.3 mm – 3.0 mm | GB/T 14976, EN 10216-5 |
| Coil Length (per roll) | 100 m – 2,000 m | Custom per order |
| Coil Inner Diameter (ID) | 200 mm – 600 mm | Per customer requirement |
| Surface Finish | 2B, No.4 Brushed, BA (Bright Annealed), Mirror (Ra ≤ 0.2 μm) | ASTM A480 |
| Tolerance (OD) | ±0.05 mm – ±0.15 mm | ISO 1307 |
| Tolerance (WT) | ±10% | GB/T 14976 |
| End Condition | Plain cut, Beveled, or Welded (butt joint) | Per specification |
| Winding Configuration | Spiral coil, Helical coil, Multi-pass coil | Application-specific |
| Maximum Working Pressure | Up to 2.5 MPa (grade and geometry dependent) | ASME B31.3 |
4. Manufacturing Process
The production of stainless steel coil tubes follows a rigorous multi-stage manufacturing sequence to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Procurement: Selection of certified stainless steel strip or seamless tube stock from approved mills with full material traceability (Mill Test Certificate per EN 10204 Type 3.1).
- Coil Forming / Winding: Continuous tube is wound onto precision mandrels using CNC-controlled winding machines to achieve exact coil pitch, diameter, and concentricity tolerances.
- Welding (if applicable): TIG (Tungsten Inert Gas) welding or orbital welding for butt joints, with helium leak testing at ≤ 1×10⁻⁹ Pa·m³/s to verify hermeticity.
- Pickling & Passivation: Chemical treatment to remove scale and form a protective chromium oxide layer, ensuring optimal corrosion resistance.
- Heat Treatment: Solution annealing at 1050–1150°C followed by controlled cooling for grain stabilization and residual stress relief.
- Quality Inspection: Dimensional verification via laser measurement, surface inspection (visual and eddy current), and hydrostatic pressure testing at 1.5× working pressure.
- Packaging: Protective film wrapping, VCI (Vapor Corrosion Inhibitor) treatment, and wooden pallet or steel frame crating for shipment.
5. Applications
Stainless steel coil tubes from Wenzhou Jixing Metal Materials Co., Ltd. serve a diverse range of industrial and commercial applications:
- Fan Coil Units (FCU): Core heat exchanger coils in variable-air-volume (VAV) systems, where variable-structure performance modeling ensures optimal coil geometry for dynamic load management
- HVAC Systems: Chiller coils, condenser coils, evaporator coils, and air handling unit (AHU) heat exchangers
- Refrigeration & Cryogenics: Low-temperature heat exchange in ammonia, CO₂ (transcritical), and hydrocarbon refrigerant systems
- Food & Beverage Processing: Heat exchangers for pasteurization, UHT (Ultra-High Temperature) processing, and dairy equipment
- Pharmaceutical & Biotechnology: GMP-compliant heat transfer coils in CIP (Clean-In-Place) and SIP (Sterilize-In-Place) systems
- Chemical & Petrochemical: Corrosive fluid heat exchange in acid, alkali, and halide environments
- Power Generation: Condenser tubes and economizer coils in thermal power plants
- Marine & Offshore: Seawater-cooled heat exchangers with enhanced resistance to chloride-induced stress corrosion cracking
6. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality assurance systems aligned with international standards:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- ASME (American Society of Mechanical Engineers) — Pressure vessel and piping component fabrication
- CE Marking — European Conformity for pressure equipment (PED 2014/68/EU)
- GB/T 14976 — Chinese national standard for seamless stainless steel tubes
- ASTM A269 / A270 — Standard specifications for austenitic stainless steel tube
- EN 10216-5 — European standard for welded stainless steel tubes
- 3-A Sanitary Standards — For food-grade applications
- NACE MR0175 / ISO 15156 — For sour service applications
7. Unique Selling Points
Advanced Variable-Structure Performance Optimization: Coil tube geometries are engineered based on model-driven analysis of dynamic thermal-hydraulic performance, enabling optimal heat transfer efficiency across variable operating loads in fan coil unit and heat exchanger assemblies.
- Precision Winding Technology: CNC-controlled coil forming ensures repeatable dimensional accuracy with pitch tolerance ≤ ±0.5 mm, critical for uniform flow distribution in multi-pass heat exchanger designs.
- Full Material Traceability: Every coil tube batch is accompanied by a complete Mill Test Certificate (MTC) with chemical composition, mechanical properties, and heat number identification.
- Custom Engineering Capability: Tailored coil configurations — including varying tube OD, wall thickness, pass count, and fin integration — designed to meet specific thermal performance targets.
- Extended Service Life: Superior corrosion resistance eliminates the need for frequent replacement, reducing lifecycle costs in aggressive chemical and marine environments.
- Hygienic & Food-Grade Options: Mirror-polished surfaces with Ra ≤ 0.2 μm facilitate cleaning and prevent biofilm accumulation in sanitary applications.
- Scalable Production: Capacity for both small-batch custom orders and high-volume production runs with consistent quality assurance.
8. Technical Notes
The integration of variable-structure performance modeling — as referenced in the analytical framework of fan coil unit coil design — allows engineers to predict and optimize the thermal response of coil assemblies under transient operating conditions. This includes analysis of:
- Coil pitch variation effects on air-side and fluid-side heat transfer coefficients
- Impact of tube layout (staggered vs. in-line) on pressure drop and fouling resistance
- Dynamic response characteristics during part-load operation in VAV systems
- Optimal coil tube diameter-to-pitch ratios for maximizing effectiveness-NTU (Number of Transfer Units) performance
These analytical insights directly inform the manufacturing specifications, ensuring that each coil tube produced meets the precise geometric and material requirements for peak thermal performance in its intended application.