Stainless Steel Coil Tube (Coiltube) for HVAC Fan Coil Unit Applications
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coiled piping product specifically designed for use in hydronic heating, cooling, and ventilation (HVAC) systems, with particular emphasis on four-pipe fan coil unit (FCU) applications. This product series represents a critical component in the thermal exchange infrastructure of modern commercial and residential building systems, where reliability, corrosion resistance, and thermal conductivity are paramount.
Coiltubes are formed through cold-bending processes that produce continuous spiral or helical pipe configurations, offering superior surface-area-to-volume ratios compared to straight piping arrangements. This geometric advantage enhances heat transfer efficiency, making stainless steel coil tubes ideal for chiller loops, condenser circuits, and fan coil unit coil assemblies.
Material & Properties
The coil tubes are fabricated from high-grade austenitic stainless steel, selected for their exceptional combination of mechanical strength, corrosion resistance, and thermal performance. The primary material grades include:
- SUS304 (UNS S30408): General-purpose grade offering excellent corrosion resistance in most atmospheric and chemical environments. Contains approximately 18% Chromium (Cr) and 8% Nickel (Ni).
- SUS316 (UNS S31608): Enhanced grade with 2–3% Molybdenum (Mo) addition, providing superior resistance to pitting and crevice corrosion in aggressive environments.
- SUS304L (UNS S30403): Low-carbon variant suitable for welding applications requiring reduced sensitization risk.
Key Material Properties:
- Thermal conductivity: 16.3 W/(m·K) (SUS304 at 20°C)
- Specific heat capacity: 500 J/(kg·K)
- Density: 8,000 kg/m³
- Operating temperature range: −196°C to +870°C
- Non-magnetic in the annealed condition (permeability ≤ 1.05)
- Surface finish: BA (Bright Annealed) or No. 4 brushed finish available
Technical Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 6.35 mm – 50.8 mm (¼" – 2") |
| Wall Thickness | 0.5 mm – 3.0 mm |
| Coil Inner Diameter (ID) | 100 mm – 600 mm (adjustable per application) |
| Coil Length | Up to 100 meters per continuous coil |
| Coil Pitch | 15 mm – 50 mm (configurable) |
| Material Grade | SUS304, SUS316, SUS304L, SUS321 |
| Surface Treatment | BA finish, Electropolished, or Passivated |
| Maximum Working Pressure | 1.6 MPa – 6.3 MPa (dependent on OD and wall thickness) |
| Tolerance on OD | ±0.1 mm (standard); ±0.05 mm (precision grade) |
| Tolerance on Wall Thickness | ±10% of nominal |
| Coil Straightness | ≤ 1.0 mm/m deviation |
| Helix Angle Deviation | ≤ ±1° |
| Applicable Standards | ASTM A269, ASTM A554, GB/T 12771, EN 10216-5 |
| Welding Method | TIG (GTAW) continuous seam welded or seamless |
| Packaging | Wooden crate with moisture barrier; custom packaging available |
Manufacturing Process
The production of stainless steel coil tubes follows a rigorous multi-stage manufacturing sequence ensuring dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection: Certified stainless steel strip or tube stock sourced from approved mills, verified through mill test certificates (MTC) for chemical composition and mechanical properties.
- Forming & Welding: Precision roll-forming converts flat strip into round cross-section tube. For welded configurations, continuous TIG (Tungsten Inert Gas) welding with argon shielding produces a uniform, oxide-free weld seam.
- Heat Treatment: Solution annealing at 1050°C–1150°C followed by controlled cooling eliminates residual stresses and restores full austenitic microstructure, ensuring optimal corrosion resistance.
- Cold Coiling: The straight tube is guided through precision-die coiling equipment to form the helical configuration. Computerized controls maintain consistent coil pitch, helix angle, and diameter throughout the coil length.
- Surface Finishing: Bright annealing (BA) in a controlled atmosphere furnace eliminates oxidation and produces a reflective, low-roughness surface (Ra ≤ 0.4 μm) critical for minimizing fouling and maximizing heat transfer.
- Quality Inspection: Each coil undergoes dimensional verification, visual inspection, hydrostatic pressure testing, and, where applicable, ultrasonic flaw detection (UT) and dye penetrant testing (PT).
Applications
Stainless steel coil tubes from Wenzhou Jixing Metal Materials Co., Ltd. serve diverse industrial and commercial applications:
- Four-Pipe Fan Coil Units (FCU): Primary application — coil tubes form the heat exchange coils in both heating and cooling circuits of four-pipe FCU systems, enabling simultaneous hot and cold water distribution for precise temperature control in commercial buildings, hospitals, and hotels.
- HVAC Chiller & Condenser Systems: Used in evaporator and condenser assemblies where high thermal efficiency and long service life are required.
- Refrigeration & Cold Chain: Applicable in refrigeration evaporator coils, cold storage unit piping, and cryogenic systems.
- Automotive & Aerospace Heat Exchangers: Precision coil tubes for compact heat exchanger assemblies requiring lightweight, high-strength construction.
- Food & Beverage Processing: Hygienic-grade coil tubes (electropolished) for pasteurization systems, CIP (Clean-in-Place) loops, and thermal processing equipment.
- Pharmaceutical & Bioprocessing: Sanitary coil configurations for reactor cooling, sterilization circuits, and process heat exchange.
- Chemical & Petrochemical Industry: Corrosion-resistant coil tubes for chemical heat exchangers handling aggressive media.
- Geothermal & Solar Thermal Systems: Coil tubes for ground-source heat exchangers and solar thermal collectors.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring product conformity to international standards:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- CE Marking — Conformity with European health, safety, and environmental protection standards
- EN 10204 — Type 3.1 mill test certificates provided with each shipment
- ASTM A269 / A554 — Product conformity to American Society for Testing and Materials standards
- GB/T 12771 — Compliance with Chinese national standards for stainless steel welded tubes
- PED 2014/68/EU — Pressure Equipment Directive compliance for pressure-rated applications
- NSF/ANSI 61 — Available for potable water contact applications
- 3-A Sanitary Standards — Available for food-grade applications
Unique Selling Points: Wenzhou Jixing Metal Materials Co., Ltd. distinguishes itself through (1) specialized expertise in coil tube configurations optimized for fan coil unit thermal exchange performance; (2) multi-grade material availability enabling tailored corrosion resistance solutions; (3) precision manufacturing tolerances ensuring drop-in compatibility with standard FCU coil assemblies; (4) comprehensive traceability from raw material mill to finished coil; and (5) customization capabilities for non-standard coil geometries, pitches, and surface finishes to meet specific OEM and project requirements.