Stainless Steel Coil Tube (盘管 Coiltube) — HVAC & Medical Air Purification Grade
Product Overview
The Stainless Steel Coil Tube (盘管 Coiltube) is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd., designed specifically for integration into Fan Coil Units (FCUs) and HVAC (Heating, Ventilation, and Air Conditioning) systems. This coil tube serves as a critical heat exchange and air distribution component, particularly in hospital-grade cleanroom and isolation environments where stringent air purification standards must be maintained in accordance with national standards such as the Technical Standard for Hospital Clean Nursing and Isolation Units (GB/T 医院洁净护理与隔离单元技术标准).
Unlike conventional carbon steel coil tubes, the stainless steel variant offers superior corrosion resistance, hygienic surface properties, and extended service life, making it indispensable in applications demanding high sanitary standards — including operating theatres, intensive care units (ICUs), laminar flow cleanrooms, and pharmaceutical manufacturing facilities.
Material & Properties
The coil tube is fabricated from high-purity austenitic stainless steel, selected for its exceptional combination of mechanical strength, weldability, and resistance to pitting and crevice corrosion in humid, chemically aggressive environments.
- Base Material: Austenitic Stainless Steel conforming to AISI 304 (UNS S30400) or AISI 316L (UNS S31603) specifications
- Chromium (Cr) Content: ≥ 18.0% (304 grade) / ≥ 16.5% (316L grade)
- Nickel (Ni) Content: ≥ 8.0% (304 grade) / ≥ 10.0% (316L grade)
- Molybdenum (Mo) Content: ≤ 0.03% (304) / 2.0–3.0% (316L) — provides enhanced resistance to chloride-induced corrosion
- Surface Finish: Electropolished or passivated to achieve a Ra (Surface Roughness Average) ≤ 0.4 μm, ensuring minimal bacterial adhesion and ease of sterilization
- Tensile Strength: ≥ 520 MPa (304) / ≥ 485 MPa (316L)
- Yield Strength: ≥ 205 MPa
- Elongation at Break: ≥ 40%
- Operating Temperature Range: −196°C to +870°C
- Corrosion Resistance: Excellent resistance to condensation water, cleaning agents (hypochlorite, hydrogen peroxide), and hospital-grade disinfectants
Technical Specifications
| Parameter | Specification | Tolerance | Test Standard |
|---|---|---|---|
| Outer Diameter (OD) | 6.0 mm / 8.0 mm / 10.0 mm / 12.0 mm | ±0.05 mm | ASTM A213 / GB/T 12771 |
| Wall Thickness (WT) | 0.5 mm / 0.6 mm / 0.8 mm / 1.0 mm | ±0.03 mm | ASTM A269 |
| Coil Pitch | 15 mm – 40 mm (configurable) | ±0.5 mm | Internal Standard |
| Coil Diameter | Ø 100 mm – Ø 300 mm | ±1.0 mm | ISO 80359 |
| Tube Length (per coil) | 2 m – 12 m (customizable) | ±10 mm | Client Specification |
| Surface Roughness (Ra) | ≤ 0.4 μm (electropolished) | — | ASTM A967 |
| Pressure Test | 1.5× Working Pressure (hydrostatic) | 30 min hold, no leakage | EN 10216-5 |
| Helium Leak Test | ≤ 1×10⁻⁷ Pa·m³/s | — | ISO 14644-1 |
| Weld Seam | Double-sided TIG (GTAW), fully radiographic inspection | Acceptance per ASME V | ASTM A240 |
| Heat Treatment | Solution Annealing at 1050–1100°C, water quench | — | ASTM A473 |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous, multi-stage process designed to ensure dimensional accuracy, metallurgical integrity, and hygienic surface quality:
- Material Selection & Incoming Inspection: Stainless steel strip or seamless tube blanks are sourced from certified mills and subjected to spectroscopic analysis (OES) to verify chemical composition compliance.
- Cold Forming / Coil Winding: Precision CNC-controlled winding machines form the tube into the specified helical coil geometry with exact pitch and diameter control. Cold forming ensures work-hardened surface integrity without grain distortion.
- Welding (if applicable): Longitudinal and circumferential joints are welded using Tungsten Inert Gas Welding (TIG / GTAW) with argon shielding on both sides to prevent oxidation. Weld parameters are monitored in real time via automated control systems.
- Solution Annealing & Pickling: The formed coil is annealed at 1050–1100°C to relieve residual stresses, followed by acid pickling to remove surface oxides and restore the passive chromium oxide layer.
- Electropolishing / Passivation: Electrochemical polishing reduces surface roughness to ≤ 0.4 μm and removes free iron contamination, achieving a corrosion-resistant, hygienic surface suitable for medical environments.
- Quality Control & Testing: Each coil undergoes hydrostatic pressure testing, dimensional verification (CMM or laser measurement), radiographic inspection of welds, and surface finish measurement.
- Protective Packaging: Finished coils are wrapped in food-grade polyethylene film, placed in protective wooden crates, and labeled with material certification documentation (Mill Test Certificate / MTC).
Applications
Primary Application Domains
- Hospital Fan Coil Units (FCUs): Integration into HVAC terminal units for hospital wards, operating rooms, ICUs, and isolation rooms — directly supporting compliance with the Technical Standard for Hospital Clean Nursing and Isolation Units. The coil tube serves as the heat exchanger core, enabling precise temperature and humidity control while maintaining air cleanliness levels (ISO Class 5–8).
- Medical Air Purification Systems: Used in conjunction with High Efficiency Particulate Air (HEPA) and Ultra Low Penetration (ULPA) filters to achieve multi-stage air purification. Research has demonstrated that stainless steel coil tubes with electropolished surfaces contribute to reduced microbial colonization and improved overall air quality in hospital settings.
- Pharmaceutical & Biotechnology Cleanrooms: Compliant with GMP (Good Manufacturing Practice) requirements for cleanroom HVAC systems in pharmaceutical production, biotech laboratories, and vaccine manufacturing facilities.
- Food & Beverage Processing: Heat exchangers in food-grade refrigeration, pasteurization, and cooling systems where sanitary design is mandatory.
- Commercial & Institutional HVAC: General-purpose fan coil units in laboratories, data centers, and high-end commercial buildings requiring corrosion-resistant, long-life components.
Performance Enhancement in Hospital Environments
Experimental research conducted under the auspices of the national standards committee for hospital clean nursing and isolation units has demonstrated that the addition of filtration systems to existing fan coil units — utilizing stainless steel coil tubes as the heat exchange core — significantly improves air purification effectiveness in hospital wards. The non-porous, smooth-surface characteristics of electropolished stainless steel coil tubes minimize particulate and microbial accumulation, reducing the risk of Hospital-Acquired Infections (HAIs) and supporting the achievement of target air cleanliness grades without requiring full system replacement.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring that all coil tube products meet international and national standards:
- ISO 9001:2015 — Quality Management System certification covering design, manufacturing, and delivery processes
- ISO 14644-1 — Compliance with cleanroom classification standards for particulate control
- ISO 14644-7 — Cleanroom design and operation guidelines
- EN 10216-5 — European standard for pressure equipment — welded austenitic stainless steel tubes
- ASTM A213 / A269 — American standards for seamless and welded austenitic stainless steel tubes
- GB/T 12771 — Chinese national standard for stainless steel seamless tubes
- GB/T 医院洁净护理与隔离单元技术标准 — National standard for hospital clean nursing and isolation units (supporting compliance)
- CE Marking — European conformity for pressure equipment (PED 2014/68/EU)
- Mill Test Certificate (MTC / EN 10204 3.1) — Provided with every shipment, documenting chemical composition, mechanical properties, and heat treatment records
- 3-A Sanitary Standards — Applicable for food-grade applications (available upon request)
Unique Selling Points
- Medical-Grade Surface Finish: Electropolished surface with Ra ≤ 0.4 μm — 50% smoother than standard commercial finish — minimizing bacterial biofilm formation and enabling effective disinfection with hospital-grade agents (quaternary ammonium compounds, hydrogen peroxide vapor, UV-C).
- Hospital Standards Compliance: Specifically engineered to support compliance with the national standard for hospital clean nursing and isolation units, validated through experimental research on air purification effectiveness in hospital ward environments.
- Superior Corrosion Resistance: 316L grade option with molybdenum alloying provides outstanding resistance to chloride-induced pitting in humid hospital environments where chlorine-based disinfectants are routinely used.
- Full Traceability: Each coil tube is traceable from raw material mill to final delivery through a complete digital quality record, including OES chemical analysis, ultrasonic flaw detection, and pressure test data.
- Custom Configurable: Coil pitch, diameter, tube dimensions, and surface finish are all customizable to match specific FCU designs and HVAC system requirements, reducing integration engineering effort.
- Extended Service Life: Austenitic stainless steel construction provides a design life exceeding 25 years under normal HVAC operating conditions — significantly outperforming copper or carbon steel alternatives in corrosive environments.
Technical Support & Documentation
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive technical support including:
- Detailed Material Test Reports (MTR) and Mill Test Certificates (MTC) per EN 10204 Type 3.1
- Dimensional drawings and 3D CAD models for FCU integration
- Weld procedure qualifications (WPQ) and welder certifications
- Corrosion testing reports (salt spray per ASTM B117, pitting resistance per ASTM G48)
- Application engineering consultation for hospital HVAC system design and compliance validation
Wenzhou Jixing Metal Materials Co., Ltd. — Delivering precision-engineered stainless steel coil tube solutions that meet the highest standards of hygiene, durability, and performance for critical healthcare and industrial applications.