Stainless Steel Coil Tube — Air-Conditioning Coil Tube for Painting Booth Applications
Product Overview
The Stainless Steel Coil Tube (also designated as Coiltube, Product No. 926) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular component specifically designed for air-conditioning (HVAC) coil assemblies in industrial painting booth environments. These coil tubes serve as the primary heat-exchange conduits within evaporator and condenser coils, facilitating efficient thermal transfer between the refrigerant and the ambient air stream in paint-spray rooms. The product has been extensively studied and validated through the technical review documented in "Protection and Renovation of Air-Conditioning Coil Tubes in Painting Rooms", which provides critical insights into the corrosion resistance, thermal performance, and long-term service durability of stainless steel coil tubes under aggressive atmospheric conditions.
Painting booths present uniquely harsh operating environments characterized by elevated humidity, volatile organic compound (VOC) exposure, acidic aerosol deposition, and frequent chemical cleaning cycles. The stainless steel coil tube addresses these challenges by offering superior corrosion resistance compared to conventional carbon steel or copper-tube alternatives, thereby reducing maintenance frequency, extending service life, and ensuring consistent thermal performance over extended operational periods.
Material Composition and Properties
The coil tube is fabricated from austenitic stainless steel grades, with the primary material specification being AISI 304 (UNS S30400) and AISI 316 (UNS S31600), depending on the severity of the corrosive environment.
- Grade 304 (UNS S30400): Contains a minimum of 18% Chromium (Cr) and 8% Nickel (Ni), providing excellent general corrosion resistance suitable for standard painting booth conditions.
- Grade 316 (UNS S31600): Incorporates an additional 2–3% Molybdenum (Mo), delivering enhanced resistance to chloride-induced pitting and crevice corrosion, making it the preferred grade for high-humidity or salt-laden environments.
Key Mechanical and Physical Properties
| Property | Grade 304 (UNS S30400) | Grade 316 (UNS S31600) |
|---|---|---|
| Tensile Strength (MPa) | ≥ 515 | ≥ 485 |
| Yield Strength (0.2% Offset, MPa) | ≥ 205 | ≥ 170 |
| Elongation at Break (%) | ≥ 40 | ≥ 40 |
| Thermal Conductivity (W/m·K, at 100°C) | 16.3 | 14.6 |
| Linear Thermal Expansion (×10⁻⁶/°C, 20–100°C) | 17.2 | 16.8 |
| Density (g/cm³) | 7.93 | 8.03 |
| Maximum Service Temperature (°C) | 870 | 870 |
| Pitting Resistance (PREN) | ~18–20 | ~24–26 |
Technical Specifications
| Parameter | Specification |
|---|---|
| Product Designation | Stainless Steel Coil Tube (Coiltube), Catalogue No. 926 |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd. |
| Material Grade | AISI 304 / AISI 316 (Austenitic Stainless Steel) |
| Tube Outer Diameter (OD) | 6.35 mm (¼") – 12.7 mm (½") [custom sizes available] |
| Wall Thickness | 0.5 mm – 1.5 mm |
| Coil Diameter (CD) | 100 mm – 400 mm (configurable per HVAC design) |
| Coil Length | Up to 50 m per continuous coil (standard); custom lengths available |
| Surface Finish | 2B (Cold-Rolled and Annealed) / No. 4 Brushed / Polished (Ra ≤ 0.4 μm) |
| Pressure Rating | Up to 2.5 MPa (362.6 psi) at 20°C |
| Refrigerant Compatibility | R-134a, R-410A, R-407C, R-22, Water/Glycol Mixtures |
| Welding Process | Orbital TIG (GTAW) / Laser Welding — Argon Shielded |
| Compliance Standards | ASTM A213 / ASTM A269 / EN 10216-5 / GB/T 12771 |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorous, multi-stage manufacturing sequence designed to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Procurement and Inspection: Cold-rolled stainless steel strip is sourced from certified mills and subjected to spectrographic analysis (OES — Optical Emission Spectroscopy) to verify chemical composition compliance with the specified grade.
- Precision Coil Forming: The strip is fed through a progressive die coil-forming system that produces uniform helical tubes with consistent OD, wall thickness, and pitch. CNC-controlled forming equipment ensures repeatability across production batches.
- Orbital TIG Welding: Seams are welded using orbital Gas Tungsten Arc Welding (GTAW) with high-purity Argon (Ar, ≥ 99.99%) shielding gas on both the internal and external surfaces. This technique produces clean, penetration-consistent welds free from oxidation and porosity.
- Post-Weld Heat Treatment: Welded tubes undergo solution annealing at 1050–1100°C followed by rapid water quenching to restore full austenitic microstructure, eliminate residual stresses, and maximize corrosion resistance.
- Pickling and Passivation: The tubes are immersed in a citric acid or dilute nitric acid solution to remove welding scale and chromium-depleted zones, followed by passivation to re-establish a stable chromium oxide (Cr₂O₃) passive film on the surface.
- Dimensional and Non-Destructive Testing (NDT): Each coil is inspected for dimensional conformance using laser micrometers and ultrasonic thickness gauges. Weld integrity is verified through visual inspection (VT) and, where required, dye penetrant testing (PT) or eddy current testing (ET).
- Surface Finishing: Final surface treatment (2B, brushed, or polished finish) is applied per customer specification to meet aesthetic and functional requirements of the target application.
- Coil Packaging and Shipping: Completed coils are wrapped in protective film, placed on wooden reels or steel crates, and shipped with accompanying mill test certificates (MTC) and traceability documentation.
Applications
The stainless steel coil tube is specifically engineered for the following industrial and commercial applications:
- Industrial Painting Booth HVAC Systems: Primary application — coil tubes serve as heat-exchange elements in evaporator and condenser units within paint-spray rooms, where resistance to solvent vapors, acidic condensates, and high humidity is critical.
- Automotive and Aerospace Paint Shops: High-volume coating facilities requiring reliable, low-maintenance thermal management systems with long service intervals.
- Food and Beverage Processing HVAC: Sanitary-grade air conditioning systems in processing plants where hygienic and corrosion-resistant materials are mandated.
- Pharmaceutical and Cleanroom Environments: Temperature and humidity control systems in facilities subject to frequent chemical decontamination cycles.
- Marine and Coastal HVAC Systems: Air conditioning installations in marine vessels and coastal facilities where chloride-rich atmospheres accelerate corrosion of conventional materials.
- Retrofit and Renovation Projects: Replacement of deteriorated carbon steel or copper coil tubes in existing painting booth systems, as documented in the technical study "Protection and Renovation of Air-Conditioning Coil Tubes in Painting Rooms."
Quality Certifications and Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring product conformity and traceability:
- ISO 9001:2015 — Quality Management System certification, demonstrating adherence to internationally recognized quality assurance practices.
- ISO 14001:2015 — Environmental Management System certification, reflecting commitment to environmentally responsible manufacturing processes.
- Mill Test Certificates (MTC) / EN 10204 3.1: Each production batch is accompanied by a third-party certified material test report documenting chemical composition, mechanical properties, and heat treatment records.
- Compliance with ASTM A213 / A269: Seamless and welded austenitic stainless steel tubes conform to American Society for Testing and Materials (ASTM) specifications for chemical composition, dimensions, and mechanical requirements.
- Compliance with EN 10216-5: European standard for welded austenitic stainless steel tubes for heat exchangers and heat transfer applications.
- Compliance with GB/T 12771: Chinese national standard for welded austenitic stainless steel tubes used in heat exchangers and heat-transfer equipment.
Unique Selling Points
The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd. distinguishes itself through the following competitive advantages:
- Superior Corrosion Resistance in Aggressive Environments: The austenitic stainless steel construction provides exceptional resistance to the corrosive cocktail of solvent vapors, acidic condensates, and high humidity inherent to painting booth applications — significantly outperforming copper and carbon steel alternatives.
- Extended Service Life and Reduced Maintenance: The validated corrosion resistance translates to service lives exceeding 15–20 years under normal operating conditions, reducing total cost of ownership (TCO) and minimizing unplanned downtime for coil replacement.
- Technical Validation Through Applied Research: The product's performance characteristics have been documented and peer-reviewed through the study "Protection and Renovation of Air-Conditioning Coil Tubes in Painting Rooms," providing empirical evidence of field performance and reliability.
- Customizable Configurations: Flexible manufacturing capabilities allow for tailored coil diameters, tube dimensions, surface finishes, and lengths to match specific HVAC system design requirements.
- Full Traceability and Certification: Every coil is traceable to its raw material mill heat number, with complete documentation of manufacturing parameters, test results, and quality certifications — ensuring regulatory compliance and customer confidence.
- Refrigerant Compatibility: Compatible with all major HFC and HCFC refrigerants currently in use, including environmentally preferred alternatives such as R-134a and R-410A, supporting transition to lower-global-warming-potential (GWP) refrigerants.
Summary
The Stainless Steel Coil Tube (Product No. 926) represents a purpose-engineered solution for the demanding thermal management requirements of industrial painting booth air-conditioning systems. By combining the inherent corrosion resistance of austenitic stainless steel with precision manufacturing, rigorous quality control, and validated field performance, Wenzhou Jixing Metal Materials Co., Ltd. delivers a product that maximizes operational reliability, minimizes lifecycle costs, and ensures long-term thermal efficiency in the most challenging industrial HVAC environments.