Stainless Steel Coil Tube (Coiltube) for Fan Coil Unit Applications

Product Overview

The Stainless Steel Coil Tube (Coiltube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered tubular product specifically designed for use in cabinet-type fan coil units and HVAC (Heating, Ventilation, and Air Conditioning) systems. This coiltube serves as the critical heat exchange element within fan coil assemblies, where it circulates chilled or heated water to facilitate thermal transfer between the refrigerant fluid and the airstream. The product is supplied in continuous coil form, enabling efficient downstream processing into finned tube assemblies, brazed heat exchangers, and custom-configured refrigeration circuits.

A key engineering consideration in the design and manufacturing of this coiltube is noise mitigation. Research and industry experience have demonstrated that the geometric tolerances, surface finish, and dimensional consistency of the coil tube directly influence the aerodynamic and hydrodynamic performance of the finished fan coil unit. Turbulent flow within the tube, induced by surface irregularities or inconsistent wall thickness, generates pressure fluctuations that translate into audible noise. Wenzhou Jixing addresses this challenge through rigorous process controls and precision manufacturing standards.

Material & Properties

The coiltube is fabricated from high-purity austenitic stainless steel, selected for its exceptional corrosion resistance, thermal conductivity, mechanical strength, and long-term durability in HVAC environments.

Specifications

Parameter Specification Standard / Tolerance
Outer Diameter (OD) 6.35 mm, 8.00 mm, 9.53 mm, 12.70 mm, and custom sizes ±0.10 mm
Wall Thickness (WT) 0.40 mm, 0.50 mm, 0.60 mm, 0.80 mm, 1.00 mm ±0.05 mm
Coil Diameter 600 mm, 800 mm, 1000 mm (standard); custom upon request ±10 mm
Coil Length Up to 500 m per coil (continuous) ±1%
Inner Surface Roughness (Ra) ≤ 0.4 μm Per ISO 1328
Roundness ≤ 0.05 mm Per ASTM E1276
Wall Thickness Uniformity ≤ 10% deviation from nominal Per ASTM A213
Maximum Residual Stress ≤ 150 MPa (after stress-relief annealing) Per ASTM A312
Hydrostatic Test Pressure 1.5× working pressure, minimum 3.0 MPa Per EN 10217
Material Standard ASTM A269 / A270; GB/T 13296; JIS G3446 —
Manufacturing Standard ASTM A213 / A312; EN 10217-7; GB/T 14976 —

Manufacturing Process

The production of Wenzhou Jixing's stainless steel coiltube follows a multi-stage precision manufacturing process, each step engineered to ensure dimensional accuracy, surface integrity, and consistent mechanical properties:

  1. Raw Material Selection: High-purity stainless steel billets or slabs are sourced from certified suppliers and subjected to incoming chemical and mechanical property verification via spectroscopic analysis and tensile testing.
  2. Hot Rolling & Annealing: The steel is hot-rolled into seamless tube blanks, followed by solution annealing at 1050–1150°C in a controlled-atmosphere furnace to achieve a fully austenitic microstructure with uniform grain size.
  3. Cold Drawing & Sizing: The annealed tube is cold-drawn through precision-die tooling to achieve the final outer diameter and wall thickness specifications. This process ensures tight dimensional tolerances and eliminates surface scale.
  4. Inner Surface Polishing: A specialized internal polishing operation, utilizing motor-driven abrasive brushes or electrochemical polishing, achieves the required low surface roughness (Ra ≤ 0.4 μm). This is critical for reducing flow-induced noise in fan coil unit applications.
  5. Stress-Relief Annealing: A controlled low-temperature annealing cycle (650–750°C) relieves residual stresses introduced during cold working, preventing stress-corrosion cracking and ensuring dimensional stability.
  6. Coil Winding & Packaging: The finished tube is wound onto precision-machined coil reels under controlled tension to prevent deformation. Each coil is wrapped in protective film and packaged for shipment.
  7. Quality Inspection: Every coil undergoes 100% hydrostatic pressure testing, dimensional verification via ultrasonic wall thickness gauging, and surface quality assessment. Sampling for mechanical property testing and chemical composition verification is performed per applicable standards.

Applications

The stainless steel coiltube is engineered for a broad spectrum of HVAC and refrigeration applications, with particular emphasis on cabinet-type fan coil units:

Quality Certifications & Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system and holds the following certifications and complies with the following standards:

Unique Selling Points