Stainless Steel Coil Tube (Coil Tube) — HVAC & Refrigeration Grade
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered continuous tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd, specifically designed for integration into fan, air-conditioning, and heating (HVAC) systems. Unlike discrete straight-length tubes, coil tubes are produced in a continuous helical or spiral configuration, enabling efficient on-site cutting and installation while minimizing material waste and welding joints.
This product category falls within the domain of general nomenclature and terminology for coil tubes and their associated applications in mechanical ventilation and thermal exchange systems. The coil tube serves as a critical structural and functional component in heat exchangers, condensate drain lines, refrigerant piping, and air distribution ductwork within commercial and industrial HVAC installations.
Material & Properties
Stainless steel coil tubes are fabricated from austenitic or duplex stainless steel grades, selected for their superior corrosion resistance, mechanical strength, and thermal stability across a wide operating temperature range.
- Common Grades: AISI 304 (UNS S30400), AISI 316 (UNS S31600), AISI 321 (UNS S32100), and Duplex 2205 (UNS S31803)
- Corrosion Resistance: Excellent resistance to atmospheric corrosion, chlorides, and acidic environments — particularly critical for HVAC condensate systems and marine-coastal installations
- Mechanical Properties: Tensile strength of 515–720 MPa; Yield strength of 205–450 MPa; Elongation ≥ 40% (304 grade, annealed condition)
- Thermal Conductivity: 14–16 W/(m·K) at 20°C, suitable for thermal exchange applications
- Operating Temperature Range: −196°C to +870°C (304 grade); −270°C to +350°C (316 grade, limited by pitting risk at elevated temperatures)
- Hygienic Surface: Ra ≤ 0.5 μm achievable for sanitary-grade applications in food-service HVAC systems
Technical Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 108.0 mm | ASTM A213 / EN 10216-5 |
| Wall Thickness | 0.5 mm – 6.0 mm | ASTM A269 / ISO 3506 |
| Coil Inner Diameter (CID) | 300 mm – 1,200 mm | Manufacturer specification |
| Coil Length (per coil) | 30 m – 300 m (continuous) | — |
| Surface Finish | No. 1 (Annealed & Pickled), 2B, BA (Bright Annealed), Electropolished | ASTM A480 |
| Tolerance (OD) | ±0.05 mm – ±0.15 mm | EN 10217-7 |
| Tolerance (Wall Thickness) | ±10% of nominal | ASTM A213 |
| End Condition | Plain cut, Beveled, Flared, or Threaded (as requested) | — |
| Helix Pitch | 25 mm – 100 mm (adjustable) | — |
| Helix Diameter | 300 mm – 1,500 mm | — |
Manufacturing Process
The production of stainless steel coil tubes involves a multi-stage manufacturing sequence ensuring dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Procurement: Cold-rolled stainless steel strip is sourced from certified mills, with mill test certificates (MTC) verifying chemical composition and mechanical properties in accordance with ASTM A240 or EN 10088.
- Coiling (Tube Forming): The strip is fed through a series of progressive roll-forming dies, gradually transforming the flat profile into a seamless circular cross-section. This process maintains material continuity without weld seams.
- Welding (where applicable): For welded coil tubes, the formed strip is longitudinally welded using Automatic Submerged Arc Welding (ASAW) or Gas Metal Arc Welding (GMAW), followed by post-weld heat treatment to restore austenitic microstructure.
- Heat Treatment: Solution annealing at 1,050–1,150°C with rapid water quenching ensures a fully austenitic grain structure, maximizing corrosion resistance and ductility.
- Pickling & Passivation: Acid pickling removes oxide scale; passivation (nitric acid or citric acid) establishes a protective chromium oxide layer on the surface.
- Helical Coiling: The straight tube is wound onto a coiling mandrel to produce the helical coil configuration. Tension control ensures uniform helix geometry without cold-work hardening or deformation.
- Quality Inspection: Each coil undergoes dimensional verification (laser gauging), visual inspection, eddy current testing (ECT) for wall-thickness consistency, and hydrostatic pressure testing.
Applications
HVAC Systems
- Heat Exchanger Coils: Helical coil tubes serve as the primary medium-carrying elements in air-cooled and water-cooled heat exchangers for chillers, condensers, and evaporators.
- Condensate Drain Lines: Continuous coil configuration allows flexible routing in tight mechanical rooms, reducing the number of fittings and potential leak points.
- Refrigerant Piping: Used in commercial refrigeration systems where the coil tube is expanded into microchannel or fin-and-tube heat exchanger configurations.
Additional Industrial Applications
- Boiler tube systems and superheater coils
- Industrial process piping requiring corrosion resistance
- Automotive exhaust system components (flexible coil sections)
- Food and beverage processing (sanitary-grade BA finish)
- Pharmaceutical and biotech facility HVAC systems
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd adheres to internationally recognized quality management and product standards:
- ISO 9001:2015 — Quality Management System certification ensuring consistent production quality and traceability
- ISO 14001:2015 — Environmental Management System, governing sustainable manufacturing practices
- ASTM A213 / A269 — Standard specifications for seamless and welded austenitic stainless steel tubing
- EN 10216-5 — European standard for welded stainless steel tubes for general applications
- EN 10217-7 — European standard for seamless stainless steel tubes for high-pressure applications
- ASME B31.5 — Code for power boiler and heating systems (where applicable)
- Mill Test Certificate (MTC / EN 10204 3.1) — Provided with each shipment, documenting chemical analysis, mechanical test results, and heat number traceability
Unique Selling Points
Continuous Coil Advantage: The helical coil configuration eliminates the need for field welding of short tube segments, significantly reducing installation labor, installation time, and long-term maintenance costs associated with weld-joint degradation.
- Seamless & Welded Options: Available in both seamless (for high-pressure and critical-service applications) and longitudinally welded (for cost-efficient general applications) configurations.
- Custom Coil Geometry: Helix diameter, pitch, and total coil length are customizable to match specific OEM heat exchanger designs and installation constraints.
- Superior Corrosion Performance: Austenitic stainless steel grades provide decades of service life in aggressive HVAC condensate environments without degradation.
- Full Traceability: Each coil is heat-number traced from raw material to finished product, ensuring complete supply chain transparency.
- Minimal Material Waste: Continuous coil production generates less off-cut waste compared to discrete tube fabrication, offering both economic and environmental benefits.