Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 1229), is a precision-engineered continuous-length tubular product supplied in coiled form. This product category encompasses a wide range of stainless steel coil tubes designed for hydraulic, pneumatic, thermal, and structural applications. The coiled delivery format offers logistical advantages including reduced handling damage, continuous welding without butt joints, and compatibility with automated tube-cutting and forming machinery.
The product line is particularly recognized for its integration with Fan Coil Unit (FCU) Metal Flexible Joints — a specialized application where stainless steel coil tubes serve as vibration-isolating, thermally conductive interconnections between HVAC (Heating, Ventilation, and Air Conditioning) fan coil units and building piping infrastructure. The coil tube's inherent flexibility, combined with the corrosion resistance of stainless steel, provides superior performance over traditional rubber or fabric flexible connectors in demanding industrial and commercial environments.
2. Material & Properties
2.1 Material Grades
The coil tubes are manufactured from high-quality austenitic and duplex stainless steel grades conforming to international standards. The primary material specifications include:
- AISI 304 (ASTM A269 TP304 / EN 1.4301): The standard austenitic stainless steel offering excellent corrosion resistance in most atmospheric and chemical environments, with a maximum service temperature of 870 °C.
- AISI 316 (ASTM A269 TP316 / EN 1.4401): Enhanced pitting and crevice corrosion resistance due to 2–3% Molybdenum (Mo) addition; suitable for marine, chemical, and pharmaceutical applications.
- AISI 316L (ASTM A269 TP316L / EN 1.4404): Low-carbon variant (C ≤ 0.03%) of 316, optimized for welding applications to prevent intergranular corrosion.
- AISI 321 (ASTM A269 TP321 / EN 1.4541): Titanium-stabilized grade providing exceptional resistance to intergranular corrosion at elevated temperatures (up to 870 °C).
- AISI 304L (ASTM A269 TP304L / EN 1.4307): Low-carbon variant of 304 for enhanced weldability and post-weld corrosion resistance.
2.2 Mechanical Properties (AISI 304, Annealed Condition)
- Tensile Strength (Rm): ≥ 520 MPa (75,400 psi)
- Yield Strength (Rp0.2): ≥ 205 MPa (29,730 psi)
- Elongation (A50): ≥ 40%
- Hardness (HV): ≤ 200 HV
- Density: 7.93 g/cm³
- Thermal Conductivity (at 20 °C): 16.3 W/(m·K)
- Modulus of Elasticity: 193 GPa
2.3 Physical & Corrosion Resistance Properties
- Corrosion Resistance: Superior resistance to atmospheric corrosion, dilute acids, organic acids, and alkaline solutions. 316/316L grades exhibit outstanding resistance to chlorides and marine atmospheres.
- Cryogenic Performance: Maintains mechanical integrity at temperatures as low as −196 °C (liquid nitrogen temperature) without brittle fracture.
- Magnetic Properties: Essentially non-magnetic in annealed condition (μr ≈ 1.02–1.05).
- Hygienic Surface: Surface finish Ra ≤ 0.5 μm available for food-grade and pharmaceutical applications.
3. Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) Range | 3.0 mm – 159.0 mm (0.118 in – 6.260 in) |
| Wall Thickness Range | 0.3 mm – 6.0 mm (0.012 in – 0.236 in) |
| OD Tolerance | ±0.1 mm (≤ 25 mm OD); ±0.15% (＞ 25 mm OD) |
| Wall Thickness Tolerance | ±10% (standard); ±5% (precision grade) |
| Coil Weight | 200 kg – 2,000 kg (441 lb – 4,409 lb) |
| Coil Inner Diameter | 150 mm – 400 mm (5.9 in – 15.7 in) |
| Surface Finish | 2B (Bright Annealed), BA (Bright Annealed & Pickled), No. 4 Brushed, Electropolished (Ra ≤ 0.25 μm) |
| Heat Treatment Condition | Annealed (Solution Annealed at 1050–1100 °C, followed by rapid cooling) |
| End Condition | Plain end, Beveled end (45°), Flanged, Threaded |
| Standard References | ASTM A269 / A213, EN 10216-5, ISO 3506, GB/T 12771, JIS G3459 |
| Maximum Operating Temperature | 870 °C (1598 °F) — AISI 304/316; 1093 °C — AISI 321 |
| Minimum Operating Temperature | −196 °C (−321 °F) |
| Maximum Operating Pressure | Up to 40 MPa (5,800 psi) — dependent on OD, wall thickness, and grade |
4. Manufacturing Process
The production of stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous, multi-stage manufacturing process ensuring dimensional accuracy, metallurgical integrity, and surface quality:
4.1 Process Flow
- Raw Material Selection & Inspection: Hot-rolled stainless steel strips (band) are sourced from certified mills. Incoming material undergoes spectroscopic analysis (OES — Optical Emission Spectroscopy) to verify chemical composition compliance with ASTM/EN standards.
- Strip Cleaning & Surface Preparation: Hot-rolled scale is removed through acid pickling and electrolytic cleaning to achieve a uniform, oxide-free surface suitable for cold forming.
- Slitting & Edge Trimming: Wide coils are precision-slitted to required strip widths using high-precision slitting lines. Edge quality is maintained to prevent defect initiation during tube forming.
- Tube Forming (Coil-to-Tube Conversion): The strip is formed into a tubular cross-section using a progressive die roll-forming system. This involves sequential roll stations that gradually deform the flat strip into a closed or nearly-closed tube shape.
- Continuous Welding: The formed tube is welded using one of the following methods:
- Continuous Welded (CW): Resistance seam welding (RSW) for standard applications.
- Laser Welded (LW): High-speed fiber laser welding for superior weld quality, minimal heat-affected zone (HAZ), and superior mechanical properties at the weld seam.
- Orbital TIG Welded (OTW): For high-purity, high-pressure applications requiring weld seam integrity comparable to seamless tubes.
- In-line Annealing & Pickling: Post-welding, the tube passes through a continuous annealing furnace (1050–1100 °C) followed by pickling and passivation to restore full metallurgical properties and remove weld-induced oxide scale.
- Hydrostatic Testing: Every coil undergoes 100% hydrostatic pressure testing at 1.5× the maximum design pressure to verify weld seam integrity and wall thickness uniformity.
- Dimensional Inspection: Automated optical gauging systems measure OD, wall thickness, and ovality along the tube length at speeds of up to 60 m/min. Data is recorded for traceability.
- Coiling & Packaging: The finished tube is wound onto a coil core with appropriate strapping and protective wrapping. Each coil is labeled with a unique batch/heat number for full traceability.
5. Applications
The stainless steel coil tube product line finds extensive application across multiple industrial sectors:
5.1 HVAC & Fan Coil Units (FCU)
In fan coil unit metal flexible joint applications, the coil tube serves as a vibration-isolating interconnect between the FCU and the building's hydronic piping system. The inherent spring-back properties of the stainless steel coil tube provide:
- Vibration attenuation between fan motors and rigid piping
- Thermal expansion accommodation
- Corrosion resistance in humid HVAC environments
- Long service life exceeding 20 years without degradation (compared to rubber joints limited to 3–5 years)
5.2 Additional Application Domains
- Food & Beverage Industry: Hygienic process piping, CIP (Clean-In-Place) systems, dairy and brewing equipment.
- Pharmaceutical & Biotechnology: GMP-compliant process lines, steam distribution, condensate return systems.
- Chemical & Petrochemical: Reactor feed lines, distillation columns, chemical transfer piping (316/316L grades).
- Power Generation: Superheater tubes, economizer tubes, boiler feedwater systems (321 grade).
- Automotive & Aerospace: Exhaust systems, fuel lines, hydraulic lines, heat exchanger tubes.
- Construction & Architectural: Structural bracing, handrails, decorative elements, curtain wall systems.
- Water Treatment & Desalination: RO (Reverse Osmosis) feed piping, seawater intake systems.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality management and product certification systems ensuring global market compliance:
| Certification / Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ISO 14001:2015 | Environmental Management System |
| ISO 45001:2018 | Occupational Health & Safety Management |
| EN 10204 3.1 | Material Test Certificate (MTC) — Full third-party inspection |
| CE Marking | Compliance with EU Pressure Equipment Directive (PED 2014/68/EU) |
| ASME B31.3 / B31.5 | Piping Design Code Compliance (Process Piping / Building Services) |
| 3-A Sanitary Standards | Food and Dairy Equipment Sanitary Design |
| NSF/ANSI 61 | Drinking Water System Components — Health Effects |
| TÜV / SGS Inspection | Independent Third-Party Product Verification |
| Mill Test Reports (MTR) | Chemical Analysis, Mechanical Properties, Weld Inspection for every batch |
7. Unique Selling Points
Continuous Production Advantage: Unlike discrete-length seamless tubes, coil tubes are produced continuously, resulting in superior dimensional consistency, reduced material waste (up to 15% less compared to cut-length seamless), and elimination of butt-weld joints in downstream fabrication.
- Full Traceability: Every coil is linked to its mill heat number, production batch, and complete test data through a digital traceability system.
- Custom Configurations: Flexible customization of OD, wall thickness, surface finish, and coil weight to match specific project requirements.
- Superior Weld Quality: Laser-welded variants achieve weld seam strength exceeding 95% of the base metal, with weld penetration verified by 100% ultrasonic testing (UT).
- Cost Efficiency: Coil tube pricing is typically 10–20% lower than equivalent seamless tube, while offering comparable performance in most applications.
- Environmental Sustainability: The continuous manufacturing process reduces energy consumption per ton by approximately 25% compared to conventional seamless tube production methods.
- Global Compliance: Product certifications covering EU, US, Asian, and Middle Eastern regulatory frameworks enable seamless integration into international supply chains.
8. Technical Notes
For Fan Coil Unit (FCU) metal flexible joint applications, the coil tube should be formed into a bellows or expansion loop configuration. The recommended minimum number of loops is determined by the required axial expansion capacity and the maximum system vibration amplitude. Material selection for FCU applications typically defaults to AISI 304 for standard indoor environments, with AISI 316L recommended for coastal or high-humidity installations where chloride-induced pitting corrosion is a concern.
All products are supplied with a comprehensive Mill Test Certificate (MTC) in accordance with EN 10204 Type 3.1, providing full documentation of chemical composition, mechanical properties, dimensional verification, and non-destructive testing (NDT) results for complete quality assurance traceability.