Stainless Steel Coil Tube for VRV/VRF Multi-Split Refrigerant Lines
1. Product Overview
Wenzhou Jixing Metal Materials Co., Ltd presents a high-performance stainless steel coil tube (Coiltube) engineered specifically for Variable Refrigerant Volume (VRV) / Variable Refrigerant Flow (VRF) multi-split commercial air conditioning systems. This product is designed to operate under high-pressure refrigerant conditions of 4–5 MPa, compatible with next-generation refrigerants R410A and R32. As a direct replacement for traditional copper refrigerant piping, this stainless steel solution offers superior mechanical strength, exceptional corrosion resistance, and extended service life, addressing critical challenges in modern commercial HVAC installations.
The coil tube is supplied in coiled form for maximum installation flexibility, enabling efficient field bending and routing without the need for extensive joint fittings. This significantly reduces installation time, leak risk points, and overall system cost.
2. Material & Properties
2.1 Material Grade
- Base Material: Austenitic Stainless Steel, Grade 304 (UNS S30400 / AISI 304)
- Surface Finish: BA (Bright Annealed) — a high-purity, low-carbon surface treatment providing excellent internal cleanliness and smoothness critical for refrigerant flow efficiency
- Tube Type: Welded (seam-welded) stainless steel coil tube
2.2 Mechanical Properties
- Tensile Strength: ≥ 520 MPa
- Yield Strength: ≥ 205 MPa
- Elongation: ≥ 40%
- Corrosion Resistance: Excellent resistance to chloride-induced pitting, acid rain, and humid coastal environments — far surpassing copper tube performance in aggressive atmospheric conditions
- Operating Temperature Range: −40°C to +200°C
2.3 Refrigerant Compatibility
- R410A: HFC-410A (blend of R32 and R125), high-pressure refrigerant with operating pressures up to 4.0 MPa (high side)
- R32: HFC-32, single-component refrigerant with lower Global Warming Potential (GWP = 675 vs. 2088 for R410A), operating pressures up to 5.0 MPa (high side)
- Both refrigerants impose significantly higher pressure loads compared to legacy R22 systems, necessitating enhanced tube wall strength
3. Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Material Grade | Stainless Steel 304 (AISI 304 / SUS304) | ASTM A778 / EN 10217-7 |
| Surface Finish | BA (Bright Annealed) | ASTM A269 |
| Tube Construction | Welded (Seam-Welded) | — |
| Refrigerant Compatibility | R410A / R32 | ASHRAE 34 |
| Maximum Operating Pressure | 4.0 – 5.0 MPa (High Side) | — |
| Supply Form | Coiled (Coiltube) | — |
| Typical Outer Diameter Range | 6.35 mm (1/4") to 28.58 mm (1-1/8") | ASHRAE Standard 36 |
| Wall Thickness | 0.5 mm – 1.0 mm (customizable) | — |
| Minimum Bending Radius | ≥ 3D (3× outer diameter) — clearly marked on product documentation | — |
| Flaring Performance | Verified — meets flaring and brazing requirements for field installation | — |
| Weld Seam Quality | 100% inspected; full penetration weld with ground-flat internal surface | ASTM A778 |
| Hydrostatic Test Pressure | ≥ 10.0 MPa (minimum) | — |
| Coil Length per Spool | 50 m – 100 m (customizable) | — |
| Operating Temperature | −40°C to +200°C | — |
4. Manufacturing Process
The production of this stainless steel coil tube follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, structural integrity, and surface quality:
- Hot Rolling: 304 stainless steel strip is produced via continuous hot rolling, establishing initial geometry and metallurgical homogeneity.
- Cold Rolling & Annealing: The strip undergoes cold reduction to achieve precise thickness tolerances, followed by controlled annealing to relieve residual stresses and optimize the austenitic microstructure.
- Coil Winding & Forming: The precision strip is wound onto a forming mandrel and cold-formed into the target outer diameter using high-precision roll-forming equipment.
- Resistance Seam Welding: A high-frequency induction resistance welding process creates a full-penetration longitudinal weld seam. The weld zone is subsequently ground flush on both the internal and external surfaces to ensure smooth refrigerant flow and eliminate stress concentrations.
- Bright Annealing (BA): The welded coil tube is subjected to a controlled atmosphere bright annealing process (typically in a reducing or protective atmosphere at 1050–1150°C), producing a clean, oxide-free, bright surface finish with low internal contamination — critical for refrigerant system reliability.
- Coil Winding: The finished tube is wound into coiled spools of specified length, protected with anti-corrosion packaging materials.
- Quality Inspection: Every production batch undergoes comprehensive testing including hydrostatic pressure testing, dimensional measurement, weld seam inspection (visual and/or radiographic), and mechanical property verification.
5. Applications
5.1 Primary Application: Commercial HVAC Systems
- VRV/VRF Multi-Split Systems: Used as liquid line and suction/discharge lines connecting outdoor condensing units to multiple indoor fan coil units in commercial buildings, hotels, hospitals, shopping centers, and office complexes.
- High-Pressure Refrigerant Lines: Specifically engineered for R410A and R32 refrigerant circuits operating at 4–5 MPa, where copper tube alternatives may face durability limitations under repeated thermal cycling and elevated pressure.
- Outdoor & Harsh Environment Installations: The superior corrosion resistance of 304 stainless steel makes this coil tube ideal for coastal installations, industrial environments, and regions with high humidity or acid rain exposure.
5.2 Secondary Applications
- Industrial process refrigeration piping
- Cold storage and cold chain logistics infrastructure
- Heat recovery systems and chiller connections
- Any application requiring high-pressure, corrosion-resistant, flexible refrigerant or fluid transport lines
6. Quality Certifications & Testing
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system and adheres to internationally recognized standards for stainless steel tube production:
- ISO 9001: Quality Management System certification ensuring consistent product quality and process control
- ISO 14001: Environmental Management System certification
- Product Standards: Manufactured in compliance with ASTM A778 (welded austenitic stainless steel tube), ASTM A269 (stainless steel tube for general applications), and EN 10217-7 (stainless steel tubes for pressure purposes)
- Hydrostatic Testing: 100% of production batches undergo hydrostatic pressure testing at ≥ 10.0 MPa to verify structural integrity and weld seam soundness
- Flaring Performance Verification: Each batch is subjected to flaring and bending qualification tests to confirm that the tube maintains dimensional accuracy, mechanical integrity, and leak-tightness after field flaring operations — a critical requirement for reliable refrigerant line installation
- Minimum Bending Radius Documentation: The minimum recommended bending radius (≥ 3D) is clearly specified and marked on product documentation to prevent tube deformation, wall thinning, or kinking during field installation
- Material Traceability: Full heat number traceability from raw material mill certificates through to finished product delivery
7. Unique Selling Points
Why Choose Stainless Steel Coil Tube Over Traditional Copper Piping for VRV/VRF Systems?
- Superior Corrosion Resistance: 304 BA stainless steel offers dramatically improved resistance to atmospheric corrosion, chloride pitting, and chemical attack compared to copper — extending service life by 3–5× in aggressive environments and eliminating copper oxide contamination risks.
- High Pressure Capability: Engineered and verified for R410A/R32 operating pressures of 4–5 MPa, providing a safety margin well above the requirements of modern high-efficiency refrigerant systems.
- Flaring Performance Guaranteed: Unlike some stainless steel tubes that are difficult to flare, this product has undergone rigorous flaring performance verification, ensuring reliable field installation with standard HVAC tools and techniques.
- Coiled Supply for Installation Efficiency: The coil form enables continuous bending and routing in the field, minimizing the number of joints and fittings — reducing potential leak points and installation labor costs.
- Bright Annealed Surface Quality: The BA finish ensures an ultra-clean internal surface free of scale and oxide contamination, preventing debris-induced blockages or degradation of refrigerant system performance over time.
- Environmental Advantage: Stainless steel is 100% recyclable and has a lower lifecycle environmental impact compared to copper, aligning with global sustainability and green building initiatives.
- Cost-Effective Lifecycle: While the initial material cost may be comparable or slightly higher than copper, the extended service life, reduced maintenance, and lower failure rate result in a significantly lower total cost of ownership (TCO) over the system's operational lifetime.
Wenzhou Jixing Metal Materials Co., Ltd — A trusted manufacturer of premium stainless steel tube products for the global HVAC, industrial, and specialty applications markets, committed to delivering engineering excellence and consistent quality.