Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
Product Overview
The Stainless Steel Coil Tube (Coiltube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered coiled stainless steel tube designed for demanding thermal exchange, fluid conveying, and humidification applications. This product is classified under the Coiltube product line (Catalog No. 535) and is specifically engineered to meet the rigorous performance requirements of HVAC (Heating, Ventilation, and Air Conditioning) systems, industrial process cooling, and fan coil unit (FCU) integration.
The coil tube is supplied in a continuous helical coil configuration, enabling efficient heat transfer surface area utilization within compact installation footprints. The helical geometry provides superior laminar flow characteristics and thermal conductivity compared to straight-tube alternatives, making it an ideal choice for fan coil unit humidifiers, air-handling units, and industrial process piping systems where space efficiency and thermal performance are critical.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its outstanding corrosion resistance, mechanical strength, and thermal stability across a wide operating temperature range.
- Material Grade: SUS304 / SUS316L (AISI 304 / 316L) austenitic stainless steel, conforming to ASTM A213 / A269 standards
- Chemical Composition: Chromium (Cr) ≥ 18%, Nickel (Ni) ≥ 8% (SUS304); Chromium (Cr) ≥ 16%, Nickel (Ni) ≥ 10%, Molybdenum (Mo) ≥ 2% (SUS316L)
- Tensile Strength: ≥ 520 MPa (yield strength ≥ 205 MPa)
- Elongation: ≥ 40% at break
- Operating Temperature Range: −196°C to +870°C
- Corrosion Resistance: Excellent resistance to atmospheric corrosion, weak acids, alkalis, and chlorinated environments (particularly SUS316L grade)
- Surface Finish: Polished (Ra ≤ 0.4 μm), pickled, or passivated finish available
- Food & Pharmaceutical Grade: Compliant with FDA 21 CFR and EU Regulation 1935/2004 for sanitary applications
Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 6 mm – 50 mm (custom sizes available upon request) |
| Wall Thickness | 0.5 mm – 3.0 mm |
| Coil Diameter | 200 mm – 2000 mm (configurable per application requirements) |
| Tube Length per Coil | 5 m – 50 m (continuous coil supply) |
| Helical Pitch | 10 mm – 50 mm (adjustable for thermal optimization) |
| Manufacturing Standard | ASTM A213, ASTM A269, GB/T 14976, GB/T 12771 |
| Joining Method | Welded (ERW / TIG) or seamless, depending on grade and application |
| Surface Treatment | Pickled and passivated; optional electropolished finish |
| Pressure Rating | Up to 4.0 MPa (working pressure, dependent on OD and wall thickness) |
| Heat Transfer Coefficient | Enhanced by helical coil geometry — up to 30–50% improvement over straight tube |
| Coil Packaging | Strapped and wrapped on wooden reels or pallets for transport |
| Customization | Available in custom OD, wall thickness, coil diameter, and length configurations |
Manufacturing Process
The production of the Stainless Steel Coil Tube follows a multi-stage precision manufacturing process to ensure dimensional accuracy, surface integrity, and metallurgical quality:
- Raw Material Selection: High-purity stainless steel billets or coils are sourced from certified mills, with each batch undergoing spectroscopic analysis to verify chemical composition compliance with ASTM/GB standards.
- Hot Rolling & Annealing: The raw steel is hot-rolled into semi-finished tube blanks, followed by solution annealing at 1050–1150°C to relieve residual stresses and achieve the desired austenitic microstructure.
- Cold Drawing / Cold Rolling: The tube blanks are cold-drawn through precision dies to achieve the specified outer diameter and wall thickness tolerances (±0.1 mm OD, ±0.05 mm wall thickness).
- Interpass Annealing: Intermediate annealing cycles are performed to restore ductility and prevent work hardening during successive forming operations.
- Coil Forming (Helical Coiling): The straight tube is fed through a precision coiling machine, which wraps the tube into a controlled helical coil geometry. The coil diameter, pitch, and winding tension are programmatically controlled to ensure uniformity and eliminate coil set or deformation.
- Pickling & Passivation: The coiled tube undergoes an acid pickling treatment (nitric/hydrofluoric acid blend) to remove scale and oxidation, followed by passivation to form a protective chromium oxide layer.
- Quality Inspection: Each coil undergoes dimensional verification (OD, wall thickness, coil diameter), surface finish measurement, hydrostatic pressure testing, and visual inspection for weld integrity and surface defects.
- Packaging & Dispatch: Coils are strapped, wrapped in protective film, and secured on wooden reels or pallets for safe transit.
Applications
The Stainless Steel Coil Tube from Wenzhou Jixing Metal Materials Co., Ltd. is engineered for a broad spectrum of industrial and commercial applications:
- Fan Coil Unit (FCU) Humidifiers: The coil tube serves as the core heat exchange element in fan coil unit humidifiers, where its helical geometry maximizes heat transfer surface area within a compact envelope. Comparative economic analyses of fan coil unit humidifier systems demonstrate that stainless steel coil tubes offer superior long-term cost-effectiveness due to their extended service life, reduced maintenance frequency, and resistance to scaling and corrosion compared to copper or aluminum alternatives.
- HVAC Systems: Used in air-handling units (AHUs), chillers, condensers, and evaporators for commercial and industrial HVAC installations.
- Industrial Process Cooling: Employed in chemical processing, pharmaceutical manufacturing, and food processing plants for heat exchange and fluid transfer under corrosive conditions.
- Sanitary & Food Processing: SUS316L grade coil tubes are utilized in dairy, beverage, and pharmaceutical processing lines where hygienic standards (3-A Sanitary, EHEDG) are mandatory.
- Boiler & Steam Systems: Integrated into boiler economizers, superheaters, and steam distribution networks for efficient thermal management.
- Refrigeration Systems: Used as evaporator coils and condenser coils in industrial refrigeration and cold storage facilities.
Economic Analysis Note: Studies comparing fan coil unit humidifier configurations confirm that stainless steel coil tubes deliver a lower total cost of ownership (TCO) over a 10–15 year service life. While initial material costs may be marginally higher than copper alternatives, the corrosion resistance, reduced fouling, and extended replacement intervals of stainless steel coil tubes result in significant cumulative savings in maintenance, downtime, and replacement expenditures.
Unique Selling Points
- Superior Corrosion Resistance: Austenitic stainless steel construction provides exceptional resistance to scaling, pitting, and chemical attack — eliminating the need for chemical inhibitors or frequent descaling treatments common with carbon steel or copper coil alternatives.
- Enhanced Thermal Performance: The helical coil geometry, combined with the high thermal conductivity of stainless steel, delivers 30–50% improved heat transfer efficiency compared to straight-tube configurations of equivalent surface area.
- Extended Service Life: Designed for 15+ year operational lifespan under normal service conditions, reducing capital expenditure on replacements and minimizing unplanned downtime.
- Customizable Geometry: Coil diameter, pitch, OD, and wall thickness are fully configurable to match specific application requirements and installation constraints.
- Hygienic Design: Available in electropolished finish (Ra ≤ 0.25 μm) for applications requiring sanitary compliance in food, beverage, and pharmaceutical industries.
- Cost-Effective TCO: Demonstrated economic superiority over copper and aluminum coil alternatives through comprehensive fan coil unit humidifier economic analyses.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a rigorous quality management framework to ensure product consistency and regulatory compliance:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001 — Environmental Management System certification
- CE Marking — Conformity with European health, safety, and environmental protection standards
- ASTM A213 / A269 — Compliance with American Society for Testing and Materials standards for seamless and welded austenitic stainless steel tube
- GB/T 14976 — Chinese national standard for seamless stainless steel tubes for fluid transport
- GB/T 12771 — Chinese national standard for welded stainless steel tubes for general purposes
- FDA 21 CFR — Compliance for food-contact applications
- Third-Party Testing: Products available for independent verification by SGS, BV (Bureau Veritas), or TÜV upon customer request
Each production batch is accompanied by a Mill Test Certificate (MTC) / Material Test Report (MTR), documenting chemical composition, mechanical properties, heat treatment records, and dimensional verification results. Full traceability from raw material lot to finished coil is maintained throughout the manufacturing process.