Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube), catalogued under reference number 1406 by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered coiled tubular product designed for thermal-fluid management applications. Manufactured from high-grade austenitic and duplex stainless steel grades, this product is supplied in continuous coil form to facilitate downstream processing, forming, and integration into complex systems such as heat exchangers, HVAC fan coil units, refrigeration circuits, and industrial fluid conveyance lines.
Unlike discrete tube lengths, the coil configuration offers significant advantages in material utilization, handling efficiency, and seamless integration into automated manufacturing lines. The product is engineered to address critical performance challenges observed in fan coil unit (FCU) systems, including water leakage, corrosion resistance, and long-term structural integrity under cyclic thermal loading conditions.
2. Material & Properties
2.1 Available Grades
- Austenitic Grades: SUS304 (ASTM 304), SUS304L (ASTM 304L), SUS316 (ASTM 316), SUS316L (ASTM 316L)
- Super-Austenitic Grades: SUS317L (ASTM 317L), 904L (ASTM N08904)
- Duplex Grades: 2205 (UNS S31803), 2507 (UNS S32750)
2.2 Key Material Properties
| Property | SUS304 | SUS316L | 2205 Duplex |
|---|---|---|---|
| Chemical Composition (Cr) | 18.0–20.0% | 16.5–18.5% | 22.0–23.0% |
| Chemical Composition (Ni) | 8.0–10.5% | 10.0–14.0% | 4.5–6.5% |
| Chemical Composition (Mo) | — | 2.0–3.0% | 3.0–3.5% |
| Tensile Strength (MPa) | ≥520 | ≥485 | ≥550 |
| Yield Strength (MPa) | ≥205 | ≥170 | ≥450 |
| Elongation (%) | ≥40 | ≥40 | ≥25 |
| Maximum Service Temperature (°C) | 870 | 870 | 300 (continuous) |
| PREN (Pitting Resistance Equivalent Number) | 19–20 | 24–26 | 34–36 |
2.3 Mechanical & Physical Characteristics
- Corrosion Resistance: Superior resistance to atmospheric corrosion, chemical media, and chloride-induced pitting and crevice corrosion, particularly in grades 316L and duplex variants.
- Cryogenic Performance: Maintains ductility and toughness at temperatures as low as −196°C (liquid nitrogen temperature), making it suitable for cryogenic applications.
- Non-Magnetic: Austenitic grades exhibit essentially non-magnetic properties, advantageous in electromagnetic-sensitive environments.
- Hygienic Surface: Available with electropolished or passivated inner surfaces (Ra ≤ 0.4 μm) for pharmaceutical and food-grade applications.
3. Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 3.0 mm – 108.0 mm |
| Wall Thickness | 0.3 mm – 8.0 mm |
| Coil Inner Diameter (ID) | 100 mm – 500 mm (customizable) |
| Coil Length (per coil) | Up to 1000 m (continuous) |
| Coil Weight | Up to 2,500 kg per coil |
| OD Tolerance | ±0.1 mm or ±2% (whichever is greater) |
| Wall Thickness Tolerance | ±10% (per ASTM A778) |
| Surface Finish | Bright annealed, passivated, electropolished, or hairline finished |
| Forming Condition | Annealed (soft), half-hard, or full-hard |
| Applicable Standards | ASTM A778, ASTM A269, EN 10217-7, GB/T 14976, JIS G3459 |
| End Condition | Open end, closed end, or custom formed (bellows, corrugated, etc.) |
| Packaging | Wooden pallet with moisture-proof wrapping and steel banding |
4. Manufacturing Process
4.1 Production Workflow
- Raw Material Selection: Ingot or strip material sourced from certified mills, subjected to incoming chemical composition analysis (OES — Optical Emission Spectroscopy) and mechanical property verification.
- Strip Rolling & Annealing: Cold-rolled stainless steel strip is annealed to achieve the desired grain structure and mechanical properties prior to tube forming.
- Tube Forming & Welding: Strip is formed into tubular geometry and joined via automatic argon arc welding (TIG — Tungsten Inert Gas welding) or resistance welding, ensuring uniform weld bead quality and minimal heat-affected zone (HAZ).
- Weld Heat Treatment: Post-weld annealing and pickling to restore corrosion resistance in the weld zone, particularly critical for grades susceptible to chromium depletion.
- Precision Sizing: Multi-stand cold-drawing or cold-rolling to achieve exact OD and wall thickness tolerances per customer specification.
- Surface Treatment: Passivation (nitric acid or citric acid treatment), electropolishing, or mechanical polishing to achieve required surface finish and corrosion resistance.
- Coiling & Inspection: Continuous tube is coiled onto precision-wound coils with controlled tension to prevent deformation. Each coil undergoes 100% visual inspection and periodic dimensional/mechanical testing.
- Quality Assurance & Packaging: Final inspection per applicable standards, mill test certificate (MTC) documentation, and protective packaging for shipment.
4.2 Process Controls for Fan Coil Unit Applications
Given the known susceptibility of fan coil unit (FCU) systems to water leakage — often attributed to corrosion-driven wall thinning, thermal fatigue cracking, or inadequate weld integrity — the manufacturing process incorporates the following enhanced controls:
- Ultrasonic Testing (UT): 100% inline ultrasonic inspection of weld seams to detect internal porosity, lack of fusion, or cracks.
- Pressure Testing: Hydrostatic or pneumatic pressure testing at 1.5× working pressure to verify leak-tightness.
- Corrosion Testing: Salt spray testing (ASTM B117) for a minimum of 48 hours, with duplex and 316L grades achieving over 500 hours without pitting.
- Cyclic Thermal Fatigue Simulation: Accelerated aging tests to validate long-term performance under repeated heating/cooling cycles typical of HVAC operation.
5. Applications
5.1 Primary Application Domains
- HVAC & Fan Coil Units: Refrigerant tubes and condensate drain lines in commercial and residential air conditioning systems, where corrosion resistance and thermal efficiency are paramount.
- Heat Exchangers: Shell-and-tube heat exchangers, plate-fin heat exchangers, and evaporators/condensers in industrial process cooling and refrigeration.
- Refrigeration & Cryogenics: Liquid ammonia, R-134a, R-410A, and other refrigerant lines requiring high purity and leak-free integrity.
- Food & Beverage Processing: Hygienic fluid transfer lines, CIP (Clean-in-Place) compatible piping for dairy, brewery, and pharmaceutical manufacturing.
- Chemical & Petrochemical: Corrosive medium conveyance lines, reactor internals, and heat transfer coils in aggressive chemical environments.
- Automotive & Transportation: Exhaust system components, turbocharger intercooler lines, and fuel delivery systems.
- Water Treatment & Desalination: Seawater intake piping, brine handling lines, and RO (Reverse Osmosis) system components.
5.2 Addressing Fan Coil Unit Leakage Issues
Field investigations into fan coil unit water leakage have identified root causes including: (1) galvanic corrosion between dissimilar metals, (2) condensate accumulation leading to internal corrosion and wall thinning, (3) thermal stress cracking at weld joints, and (4) vibration-induced fatigue failure. The use of high-grade stainless steel coil tubes — particularly SUS316L and 2205 duplex — with controlled manufacturing tolerances and verified weld integrity directly mitigates these failure modes, significantly extending service life and reducing maintenance-related downtime.
6. Quality Certifications & Standards Compliance
6.1 Certifications
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health & Safety Management System Certification
- EN 10204 — Certificate Type 3.1 (Mill Test Certificate per inspection lot)
- PED (Pressure Equipment Directive) 2014/68/EU — Compliance for pressure-containing applications
- ASME BPV Code — Section VIII compliance for pressure vessel and piping applications
- NSF/ANSI 61 — Drinking water system component certification (for food-grade applications)
6.2 Inspection & Testing Protocols
| Test Method | Standard Reference | Frequency |
|---|---|---|
| Chemical Composition Analysis | ASTM E415 (OES) | Per heat lot |
| Tensile Testing | ASTM A370 / EN 10002 | Per heat lot |
| Hardness Testing | ASTM E10 / EN ISO 6507 | Per production lot |
| Hydrostatic Pressure Testing | ASTM A778 | 100% of product |
| Ultrasonic Flaw Detection | ASTM E1274 | 100% inline |
| Visual Weld Inspection | ASTM E165 | 100% of product |
| Salt Spray Testing | ASTM B117 | Per material grade qualification |
| Dimensional Verification | ASTM A778 / EN 10217-7 | Per production lot |
7. Unique Selling Points
- Integrated Coil Supply Advantage: Continuous coil format eliminates butt-weld joints in downstream fabrication, reducing leak points and improving system reliability — a direct response to the water leakage challenges documented in fan coil unit systems.
- Grade Diversity & Customization: Comprehensive range of austenitic, super-austenitic, and duplex stainless steel grades enables precise material selection for specific service environments, from mild atmospheric exposure to highly aggressive chloride-containing media.
- Enhanced Weld Integrity: Post-weld heat treatment and 100% ultrasonic inspection ensure weld seam quality comparable to seamless tube, mitigating the primary failure mode in welded coil tube systems.
- Thermal Cycling Durability: Engineered for extended service life under repeated thermal expansion/contraction cycles, validated through accelerated fatigue testing protocols.
- Traceability & Documentation: Full lot traceability with EN 10204 Type 3.1 mill test certificates, ensuring regulatory compliance and quality assurance for critical infrastructure applications.
- Cost Efficiency: Coil supply reduces material waste by up to 15–20% compared to discrete tube lengths, while minimizing downstream handling and installation labor costs.
8. Ordering Information & Technical Support
Wenzhou Jixing Metal Materials Co., Ltd. provides comprehensive pre-sale technical consultation, material selection guidance, and post-sale quality assurance support. Custom specifications — including non-standard OD, wall thickness, coil dimensions, surface finish, and forming configurations — are available upon request. Minimum order quantities (MOQ) and lead times are negotiable based on grade, specification, and quantity requirements.
For detailed material selection, application engineering, or compliance documentation, customers are encouraged to submit technical inquiries specifying operating conditions (temperature, pressure, fluid media, environmental exposure) to receive a tailored product recommendation with full specification and certification documentation.