304 BA Stainless Steel Coiltube for VRV/VRF Multi-Split Refrigerant Systems
Product Overview
The 304 BA (Bright Annealed) Stainless Steel Coiltube is a precision-engineered refrigerant piping solution specifically designed for Variable Refrigerant Volume (VRV) and Variable Refrigerant Flow (VRF) multi-split air conditioning systems operating with high-pressure refrigerants such as HFC-410A (R410A) and HFC-32 (R32). This product represents a significant advancement in commercial HVAC (Heating, Ventilation, and Air Conditioning) refrigerant distribution technology, offering a robust and durable alternative to traditional copper refrigerant tubing.
Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this coiltube product is engineered to withstand operating pressures ranging from 4 to 5 MPa (580–725 psi), ensuring reliable performance under the demanding conditions of modern high-efficiency refrigerant systems. The coiltube form factor enables efficient material utilization, reduced storage and transportation costs, and superior handling characteristics during field installation.
Material Composition & Properties
Base Alloy Specification
- Grade: AISI 304 / SUS 304 / UNS S30400
- Surface Finish: BA (Bright Annealed) — providing a clean, oxide-free inner and outer surface essential for refrigerant flow integrity
- Carbon (C): ≤ 0.08%
- Chromium (Cr): 18.0–20.0%
- Nickel (Ni): 8.0–10.5%
- Manganese (Mn): ≤ 2.0%
- Silicon (Si): ≤ 1.0%
- Sulfur (S): ≤ 0.03%
- Phosphorus (P): ≤ 0.045%
Mechanical Properties
- Tensile Strength (UTS): ≥ 520 MPa (75,400 psi)
- Yield Strength (0.2% offset): ≥ 205 MPa (29,700 psi)
- Elongation (A50): ≥ 40%
- Hardness (HRB): 70–95
- Operating Pressure Rating: 4–5 MPa (580–725 psi)
- Operating Temperature Range: −40°C to +200°C (−40°F to +392°F)
Key Performance Characteristics
- Corrosion Resistance: Superior resistance to atmospheric corrosion, refrigerant-oil contamination, and condensation-induced degradation compared to copper alternatives
- Thermal Conductivity: 16.3 W/(m·K) — while lower than copper, the inherent advantages of stainless steel offset this through design optimization
- Flaring Performance: Verified and certified for reliable flare joint formation, ensuring leak-free connections critical to refrigerant system integrity
- Creep Resistance: Excellent long-term dimensional stability under sustained pressure loads
- Fatigue Life: Significantly extended service life under cyclic pressure loading conditions inherent in compressor-driven systems
Technical Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Type | Seamless / Welded Coiltube (盘管) | ISO 11431 / EN 10217 |
| Material Grade | 304 BA (Bright Annealed) | AISI 304 / SUS 304 |
| Tube Form | Coil (continuous length on spool) | — |
| Refrigerant Compatibility | R410A (HFC-410A), R32 (HFC-32) | ASHRAE Standard 34 |
| Maximum Operating Pressure | 4–5 MPa (580–725 psi) | EN 12828 / ISO 2289 |
| Hydrostatic Test Pressure | ≥ 6 MPa (870 psi) — 1.5× working pressure | ISO 11431 |
| Typical Outer Diameters (OD) | 6.35 mm, 9.52 mm, 12.70 mm, 15.88 mm, 19.05 mm | ASME B36.19M |
| Wall Thickness Range | 0.50 mm – 1.50 mm | — |
| Minimum Bending Radius | ≥ 3D (three times outer diameter) — clearly marked | Manufacturer specification |
| Surface Roughness (Ra) | ≤ 0.4 μm (inner surface) | ISO 1302 |
| Coil Weight Range | 100 kg – 500 kg (typical) | — |
| Coil Inner Diameter | 500 mm – 1000 mm (typical) | — |
| End Condition | Deburred, clean-cut ends; flare-ready | — |
| Packaging | Wooden pallet / steel drum with moisture barrier | — |
Manufacturing Process
1. Steel Mill Sourcing & Certification
The base material is sourced from certified stainless steel mills producing 304 grade strip or rod stock meeting ASTM A240 / EN 10088-2 chemical composition requirements. Each heat lot is accompanied by a Mill Test Certificate (MTC) verifying chemical analysis and mechanical properties.
2. Coil Forming & Welding
For welded coiltube configurations, precision cold-rolled strip is formed into a circular cross-section and joined via a TIG (Tungsten Inert Gas) welding process using argon shielding gas. The weld seam undergoes precision grinding and polishing to achieve surface continuity equivalent to the base tube material, eliminating stress concentration points and ensuring uniform wall thickness.
3. Bright Annealing (BA) Treatment
The formed tube undergoes a controlled bright annealing process in a reducing atmosphere (endothermic gas or vacuum). This process:
- Relieves cold-work stresses to restore full ductility
- Eliminates surface scale and oxide contamination
- Produces a smooth, bright, oxide-free surface finish critical for refrigerant system cleanliness
- Ensures minimum elongation values required for reliable flaring operations
4. Precision Sizing & Dimensional Control
Post-annealing, the tube passes through a series of cold drawing or rolling stations to achieve precise outer diameter (OD) and wall thickness tolerances. Final dimensional inspection ensures conformance to ±0.05 mm OD tolerance and ±0.02 mm wall thickness tolerance.
5. Flaring Performance Verification
Each production batch undergoes rigorous flaring performance testing. Representative samples are subjected to flaring operations using standard HVAC flare tools to verify:
- Uniform material flow during flare formation
- Absence of cracking, splitting, or excessive thinning at the flare base
- Adequate flare wall thickness for gasket sealing integrity
- Repeatable flare geometry suitable for reliable joint assembly
6. Hydrostatic Pressure Testing
Every coil undergoes 100% hydrostatic pressure testing at a minimum of 6 MPa (1.5× maximum operating pressure) for a sustained dwell time of not less than 10 seconds per meter of tube length. This ensures freedom from porosity, weld defects, and wall thinning.
7. Coiling & Packaging
Upon passing all quality inspections, the tube is coiled onto precision-machined reels at controlled bending speeds to avoid work-hardening or surface damage. Minimum bending radius is maintained at ≥ 3D throughout the coiling process. Coils are wrapped in moisture-barrier film, secured with steel strapping, and packaged on wooden pallets or within steel drums for shipping.
8. Minimum Bending Radius Marking
Each coil is clearly marked with the minimum permissible bending radius (≥ 3D) to guide field installers in proper tube handling and routing. This marking prevents field damage from over-bending, which could compromise structural integrity and refrigerant flow characteristics.
Applications
Primary Application: VRV/VRF Multi-Split Systems
This product is specifically engineered for the refrigerant distribution piping of Variable Refrigerant Volume (VRV) and Variable Refrigerant Flow (VRF) multi-split air conditioning systems in commercial and institutional buildings. These systems utilize high-pressure refrigerants (R410A at pressures up to 4.0 MPa; R32 at pressures up to 5.0 MPa) and require piping materials capable of maintaining structural integrity over extended service lives.
Specific Use Cases
- Commercial Office Buildings: Multi-zone temperature control systems with extensive refrigerant piping networks connecting outdoor condensing units to indoor air-handling units
- Hospital & Healthcare Facilities: Critical environments requiring reliable, maintenance-free refrigerant distribution with minimal risk of leakage or contamination
- Hotel & Hospitality Industry: Large-scale HVAC systems with distributed indoor units requiring long pipe runs and complex routing
- Shopping Malls & Retail Complexes: High-capacity systems serving multiple zones with diverse thermal loads
- Industrial & Data Center Cooling: Precision temperature control applications requiring reliable refrigerant piping under continuous operation
- Residential High-Rise Buildings: Multi-apartment VRF systems with shared outdoor units and individual indoor terminals
Refrigerant System Components Served
- Outdoor unit to indoor unit liquid line piping
- Outdoor unit to indoor unit suction line piping
- Multi-way valve (4-way valve) connection piping
- Expansion valve inlet/outlet piping
- Accumulator and receiver connections
- Service port and manifold connections
Quality Certifications & Compliance
Product Standards
- ISO 11431: Metallic tubes for general purposes — Technical delivery conditions
- EN 10217-7: Heat-resistant seamless and welded tubes for pressure purposes — Stainless steels
- ASME B36.19M: Welded and seamless wrought stainless steel pipe
- JIS G 3459: Stainless steel tubes for pressure purposes
Material Certifications
- EN 10204 3.1: Material test certificate — Chemical analysis and mechanical property verification per heat lot
- EN 10204 3.2: Inspection report — Independent third-party verification available upon request
- Mill Test Certificate (MTC): Provided with each shipment, traceable to specific production heat numbers
Performance Verification
- Flaring Test Report: Documented verification of flare joint integrity per batch
- Hydrostatic Test Records: 100% test coverage with documented test pressures and dwell times
- Dimensional Inspection Report: OD, wall thickness, roundness, and straightness verification
- Surface Quality Assessment: Visual and microscopic inspection confirming BA surface integrity
- Refrigerant Compatibility Test: Verified compatibility with R410A and R32 refrigerant-oil systems
System-Level Certifications
- ISO 9001:2015: Quality Management System certification covering full manufacturing and quality assurance processes
- ISO 14001:2015: Environmental Management System certification
- CE Marking: Conformity with European pressure equipment directive requirements
- UL Listed: Available for North American market applications
Unique Selling Points
1. Proven Copper Tube Alternative
While traditional copper refrigerant tubing remains widely used, 304 BA stainless steel coiltube offers distinct advantages in durability, corrosion resistance, and long-term system reliability. The inherent corrosion resistance of austenitic stainless steel eliminates the risk of copper contamination in refrigerant systems, which can lead to compressor degradation and reduced system efficiency over time.
2. High-Pressure Capability for Modern Refrigerants
Engineered specifically for the elevated operating pressures of R410A (4.0 MPa) and R32 (5.0 MPa) refrigerants, this product provides a 1.5× safety margin through hydrostatic testing at 6 MPa minimum, exceeding industry standard requirements for pressure vessel applications.
3. Verified Flaring Performance
A critical differentiator for field-installable refrigerant piping, the flaring performance of this product is verified through systematic testing protocols. This ensures that HVAC technicians can achieve reliable, leak-free connections using standard flare tools without requiring specialized brazing equipment or filler metal.
4. Coiltube Form Factor Advantages
- Reduced material waste compared to straight-length tubing
- Lower transportation and storage costs per unit length
- Flexible field cutting to exact required lengths