Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd, designed primarily for HVAC (Heating, Ventilation, and Air Conditioning) systems, particularly in fan coil unit (FCU) condensate water drainage applications. The Coiltube is supplied in a continuous coiled configuration, enabling efficient installation in horizontal main pipe runs for condensate water transport within building mechanical systems.
Based on extensive hydraulic calculation methodology research — specifically the hydraulic calculation method for condensate water horizontal main pipes in fan coil units — the Coiltube product line is engineered to meet stringent flow dynamics requirements. The product ensures reliable condensate drainage performance under varying system pressures, flow velocities, and pipe diameters, minimizing the risk of water hammer, sedimentation, and blockage in horizontal condensate lines.
Key design considerations derived from hydraulic analysis include:
- Optimized internal surface roughness to reduce friction loss in horizontal runs
- Controlled dimensional tolerances to maintain consistent flow cross-section
- Corrosion-resistant material selection for long-term condensate water service
- Appropriate wall thickness to withstand static and dynamic pressure loads
2. Material & Properties
2.1 Base Material
The Coiltube is fabricated from austenitic stainless steel grades conforming to international standards, with the primary grade being AISI 304 (UNS S30408) and AISI 316L (UNS S31603), selected for their superior corrosion resistance, mechanical integrity, and compatibility with condensate water environments containing trace acidic compounds (pH 4.5–7.0).
2.2 Chemical Composition (Typical)
| Element | 304 (wt%) | 316L (wt%) |
|---|---|---|
| C (Carbon) | ≤ 0.08 | ≤ 0.03 |
| Si (Silicon) | ≤ 0.80 | ≤ 0.80 |
| Mn (Manganese) | ≤ 2.00 | ≤ 2.00 |
| P (Phosphorus) | ≤ 0.045 | ≤ 0.045 |
| S (Sulfur) | ≤ 0.030 | ≤ 0.030 |
| Cr (Chromium) | 18.00–20.00 | 16.00–18.00 |
| Ni (Nickel) | 8.00–10.50 | 10.00–14.00 |
| Mo (Molybdenum) | — | 2.00–3.00 |
2.3 Mechanical Properties
| Property | Specification | Test Standard |
|---|---|---|
| Tensile Strength (Rm) | ≥ 520 MPa (75,000 psi) | ASTM A213 / EN 10216-5 |
| Yield Strength (Rp0.2) | ≥ 205 MPa (29,700 psi) | ASTM A213 / EN 10216-5 |
| Elongation (A50) | ≥ 40% | ASTM A213 |
| Hardness (HV10) | ≤ 230 HV | ISO 6507 |
2.4 Physical Properties
- Density: 8.00 g/cm³ (304) / 8.03 g/cm³ (316L)
- Thermal Conductivity: 16.3 W/(m·K) at 300 K
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /K (10–100°C)
- Maximum Service Temperature: 870°C (oxidation limit)
- Surface Roughness (Ra): ≤ 0.4 μm (electropolished finish available)
3. Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | Φ12.7 mm – Φ50.8 mm (1/2" – 2" NPS) | ASTM A554 / ISO 14399 |
| Wall Thickness (WT) | 0.50 mm – 2.00 mm | EN 10216-5 |
| Coil Diameter (CD) | Φ500 mm – Φ1200 mm | Manufacturer Specification |
| Coil Length per Spool | 10 m – 50 m (adjustable) | — |
| OD Tolerance | ± 0.05 mm (± 0.10 mm for OD > 25 mm) | ASTM A554 |
| Wall Thickness Tolerance | ± 10% of nominal | EN 10216-5 |
| Surface Finish | Bright Annealed (BA), Pickled & Passivated (PP), or Electropolished (EP) | ASTM A473 / ASTM A967 |
| Hydrostatic Test Pressure | 2 × working pressure (minimum 6.0 MPa) | ISO 443 |
| Maximum Working Pressure | 1.6 MPa (16 bar) at 20°C | EN 10216-5 |
| Recommended Flow Velocity | 0.3 – 0.5 m/s (condensate service) | ASHRAE Handbook — HVAC Applications |
| Recommended Pipe Slope | 1:100 – 1:200 (for condensate horizontal runs) | ASHRAE / Manufacturer Hydraulic Guidelines |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Procurement: High-purity stainless steel strip (cold-rolled coil) sourced from certified mills, verified via mill test certificates (MTC) conforming to ASTM A240 / EN 10204 Type 3.1.
- Slitting: Precision slitting of cold-rolled coil to specified width using CNC-controlled slitting lines, achieving edge quality ≤ Ra 1.6 μm.
- Forming (Roll Forming): Multi-stage roll forming process with progressive die sets to achieve seamless tube geometry. Roll forming minimizes work hardening and maintains uniform wall thickness throughout the coil length.
- Welding (if applicable for welded coil tube): TIG (Tungsten Inert Gas) welding with argon shielding (99.99% Ar), achieving weld penetration ≥ 95% of wall thickness. Weld root passivation is performed post-weld.
- Coiling: Continuous coiling onto precision-mandrel coils at controlled tension to prevent ovality and flat spots. Coil tension is monitored via load cells with ± 5% accuracy.
- Heat Treatment (Annealing): Solution annealing at 1050°C ± 25°C in a protective atmosphere (endothermic gas or vacuum) to relieve residual stresses, restore full austenitic structure, and achieve maximum corrosion resistance.
- Pickling & Passivation: Acid pickling (HNO₃/HF blend) followed by water rinse and passivation treatment per ASTM A967 Method A or C to establish a chromium oxide passive film thickness of 2–5 nm.
- Hydrostatic Testing: 100% inline hydrostatic testing at 6.0 MPa minimum, with pneumatic pressure decay testing as an alternative for leak detection.
- Dimensional Inspection: Laser-based OD and wall thickness gauging at 100% coverage; ultrasonic thickness measurement for spot verification.
- Packaging & Shipping: Coils wrapped in VCI (Vapor Corrosion Inhibitor) film, secured on wooden pallets with steel strapping, and labeled with product identification, heat number, and test data.
4.2 Process Quality Controls
- In-line Process Monitoring: Real-time monitoring of forming forces, coil tension, and dimensional parameters via SCADA systems
- Spectroscopic Verification: PMI (Positive Material Identification) via XRF (X-Ray Fluorescence) spectrometry at each heat transition
- Weld Quality: Radiographic testing (RT) per ASTM E94 for minimum 1% of weld length per shift
- Passivation Verification: Ferrite probe testing (≤ 50 FN) and salt spray test (ASTM B117, ≥ 1000 hours without red rust)
5. Applications
5.1 Primary Application: HVAC Condensate Drainage
The Coiltube is specifically engineered for fan coil unit (FCU) condensate water horizontal main pipe systems in commercial and industrial buildings. The hydraulic calculation methodology underlying the product design ensures:
- Self-draining capability with minimum slope of 1:200
- Resistance to biofilm formation due to smooth internal surface (Ra ≤ 0.4 μm)
- Long service life exceeding 25 years in condensate water environments
- Compatibility with condensate water pH range of 4.5–7.0 (including acidic condensate from aluminum heat exchangers)
5.2 Additional Applications
- Medical Gas Systems: Compressed air and medical gas distribution (316L grade, electropolished)
- Food & Beverage Processing: CIP (Clean-In-Place) compatible piping for beverage and dairy processing
- Pharmaceutical Systems: Water for Injection (WFI) and Purified Water (PW) distribution
- Chemical Processing: Corrosive fluid transfer in mild acid environments
- Automotive Fuel Systems: Hydrogen piping for fuel cell vehicles
- Heat Exchanger Tubes: Condenser and evaporator tube applications
6. Quality Certifications & Compliance
6.1 Product Certifications
| Certification | Standard | Scope |
|---|---|---|
| ISO 9001:2015 | Quality Management System | Full manufacturing operations |
| ISO 3834-2 | Quality Requirements for Fusion Welding | Welding operations |
| EN 10204 3.1 | Inspection Document | Mill Test Certificate per heat |
| CE Marking | EU Construction Products Regulation | Pressure piping applications |
| NSF/ANSI 61 | Drinking Water System Components | Potable water contact (304/316L) |
| 3-A Sanitary Standards | Sanitary Equipment | Food-grade applications (EP finish) |
6.2 Material Standards Compliance
- ASTM A213: Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for High-temperature Service
- ASTM A554: Standard Specification for Seamless and Welded Stainless Steel Tubing for General Applications
- EN 10216-5: Seamless and welded austenitic stainless steel tubes for mechanical and technological uses
- ISO 14399: Stainless steel tubes — Dimensions and tolerances
- JIS G3459: Seamless austenitic stainless steel tubes for general service
6.3 Testing & Inspection Protocols
- Chemical Analysis: Spark-OES (Optical Emission Spectroscopy) per ASTM E415
- Mechanical Testing: Tensile testing per ASTM E8/E8M; hardness testing per ASTM E10
- Hydrostatic Testing: 100% inline per ISO 443, minimum 6.0 MPa
- Dimensional Inspection: 100% laser gauging; ultrasonic spot verification
- Visual Inspection: 100% inline visual inspection for surface defects, weld quality, and dimensional conformity
- Corrosion Testing: Salt spray test per ASTM B117 (≥ 1000 hours); intergranular corrosion test per ASTM A240 (Section 13)
- Passivation Verification: Ferrite probe testing (≤ 50 FN); passivity check per ASTM A967
7. Unique Selling Points
Hydraulically Optimized Design: The Coiltube product line is uniquely informed by rigorous hydraulic calculation methodology for fan coil unit condensate water horizontal main pipe systems. This engineering foundation ensures that pipe diameter selection, wall thickness, and surface finish are optimized for minimum pressure drop, maximum self-draining capability, and resistance to sediment accumulation — resulting in superior system performance and reduced maintenance requirements.
- Superior Surface Quality: Electropolished finish (Ra ≤ 0.4 μm) reduces biofilm adhesion by 90% compared to standard passivated surfaces,