Stainless Steel Coil Tube – Small Coil (ID ≥ 300 mm, OD ≤ 800 mm)
1. Product Overview
The Small Coil Stainless Steel Tube (Model Designation: Coil Tube – Small Coil) is a precision-engineered coiled stainless steel pipe product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Product No. 44 in the company's product catalog). Classified under the Product Specifications category with the sub-classification of Geometric Parameters – Coil Dimensions, this small coil variant is specifically designed for applications where space constraints, manual handling, and narrow passage construction are critical considerations.
Unlike large-diameter coil tubes that require mechanical unwinding equipment, the Small Coil variant features a compact coil geometry that enables manual unwinding and deployment, making it uniquely suited for confined environments such as building interiors, underground utilities, tight mechanical rooms, and field installations where heavy machinery cannot be deployed.
2. Material & Properties
Small Coil Stainless Steel Tubes are typically manufactured from austenitic and duplex stainless steel grades conforming to international standards. The primary material grades include:
- SUS 304 / AISI 304 – General-purpose austenitic stainless steel with excellent corrosion resistance and formability
- SUS 316 / AISI 316 – Molybdenum-enhanced grade offering superior resistance to pitting and crevice corrosion
- SUS 316L / AISI 316L – Low-carbon variant suitable for welding and high-purity applications
- SUS 321 / AISI 321 – Titanium-stabilized grade for elevated temperature service
- SUS 310S / AISI 310S – High-temperature austenitic grade for furnace and industrial heat treatment applications
Key mechanical properties typical of the 304/316 grade small coil tubes include:
- Tensile Strength (UTS): ≥ 520 MPa (75,400 psi) for 304 grade
- Yield Strength (0.2% offset): ≥ 205 MPa (29,730 psi) for 304 grade
- Elongation: ≥ 40% (in 50 mm gauge length)
- Hardness: ≤ 230 HB (annealed condition)
- Operating Temperature Range: −196 °C to +870 °C (304 grade)
3. Specifications
3.1 Coil Dimensional Parameters (Small Coil)
| Parameter | Specification | Unit | Notes |
|---|---|---|---|
| Inner Diameter (ID) of Coil | ≥ 300 | mm | Minimum inner coil diameter |
| Outer Diameter (OD) of Coil | ≤ 800 | mm | Maximum outer coil diameter |
| Coil Type | Small Coil (小盘卷) | — | Manual unwinding category |
| Tube Outer Diameter (Typical) | 6 – 219 | mm | Dependent on application requirement |
| Wall Thickness (Typical) | 0.5 – 6.0 | mm | Standard and custom thickness available |
| Coil Length (Typical) | 50 – 500 | m | Custom lengths available upon request |
| Coil Weight (Typical) | 200 – 1,500 | kg | Designed for manual handling |
3.2 Dimensional Tolerances
| Dimension | Tolerance | Applicable Standard |
|---|---|---|
| Tube OD Tolerance | ±0.5% to ±1.0% | ASTM A554 / GB/T 12771 |
| Wall Thickness Tolerance | ±10% (min. 0.05 mm) | ASTM A554 / GB/T 12771 |
| Coil ID Tolerance | ±10 mm | Manufacturer standard |
| Coil OD Tolerance | ±15 mm | Manufacturer standard |
| Out-of-Roundness | ≤ 0.5% of OD | ASTM A554 |
3.3 Surface Finish Options
| Finish Type | Ra Value | Application |
|---|---|---|
| Industrial Pickled (No. 1) | 0.8 – 2.0 µm | Structural, general industrial |
| Mechanically Polished | 0.4 – 0.8 µm | Decorative, food-grade |
| Electropolished | 0.1 – 0.4 µm | Pharmaceutical, semiconductor |
| Baught (2B) | 0.4 – 0.8 µm | Architectural, appliance |
4. Manufacturing Process
4.1 Production Workflow
- Raw Material Selection: High-quality stainless steel seamless or welded pipe blanks are sourced from certified mills and subjected to incoming material verification including chemical composition analysis (OES/ICP) and mechanical property testing.
- Heat Treatment: Tubes are solution-annealed at 1050–1150 °C followed by controlled cooling to achieve the required austenitic microstructure, relieve cold-work stresses, and restore full ductility.
- Pickling & Passivation: Acid pickling (HNO₃ + HF blend) removes scale and oxide layers, followed by passivation treatment to form a protective chromium oxide film on the surface.
- Coil Forming: The straight pipe sections are carefully wound onto a coiling mandrel using a controlled coiling machine. The winding parameters are precisely calibrated to produce a small coil with ID ≥ 300 mm and OD ≤ 800 mm, ensuring uniform layer tension and preventing kinking or deformation of the tube cross-section.
- Strapping & Packaging: Each coil is secured with steel strapping at regular intervals (typically every 100–150 mm along the OD) to maintain coil integrity during handling and transport. Coils are wrapped in protective film and packaged on wooden pallets with desiccant protection.
- Quality Inspection: Final inspection includes dimensional verification (ID, OD, wall thickness, coil geometry), surface quality assessment, hydrostatic or eddy current testing for wall integrity, and visual examination for defects.
4.2 Coil Winding Quality Control
The coiling process for the Small Coil variant demands particular attention to the following parameters:
- Minimum Bending Radius: The tube bending radius during coiling must exceed 5× the tube outer diameter to prevent ovality distortion and wall thinning
- Layer-to-Layer Alignment: Adjacent coil layers must be aligned within ±2 mm to ensure smooth unwinding without jamming
- End Protection: Both tube ends are protected with caps or plugs to prevent internal contamination and edge damage during coiling
- Coil Balance: The finished coil must be balanced to prevent eccentric rotation during unwinding
5. Applications
The defining characteristic of the Small Coil Stainless Steel Tube is its suitability for manual unwinding and deployment in confined or narrow passage environments. This makes it the preferred coil tube format for the following application domains:
5.1 Construction & Building Services
- Hydroponic and sprinkler irrigation systems in greenhouses and agricultural facilities
- Fire protection piping in high-rise buildings where access is restricted
- Underground utility piping routed through narrow trenches and confined spaces
- Domestic water supply and plumbing systems in residential and commercial buildings
- Gas distribution lines in apartment complexes and industrial parks
5.2 Industrial & Process Applications
- Chemical processing plants requiring corrosion-resistant piping in tight plant layouts
- Food and beverage processing lines where sanitary-grade tubing is required
- Pharmaceutical cleanroom piping systems
- Heat exchanger coil assemblies and condensate collection systems
- Automotive exhaust system components and fuel delivery lines
5.3 Specialized Applications
- Medical gas delivery systems in hospitals (oxygen, medical air, vacuum lines)
- Solar thermal collector tubing and heat pipe assemblies
- Marine and offshore equipment piping in confined hull compartments
- Electrical conduit and cable protection in tight infrastructure corridors
6. Unique Selling Points
Key Differentiators of the Small Coil (小盘卷) Product:
- Manual Unwinding Capability: The compact coil geometry (OD ≤ 800 mm) allows installation crews to unwind and deploy the tubing manually without the need for specialized mechanical unwinding equipment, reducing project costs and accelerating installation timelines.
- Narrow Passage Accessibility: The small coil diameter enables transport and deployment through narrow corridors, tight construction sites, underground vaults, and other spatially constrained environments where large coil formats are impractical.
- Reduced Installation Infrastructure: Eliminates the need for coil stands, tensioning devices, and heavy lifting equipment, simplifying the logistics chain and reducing the overall installation footprint.
- Material Integrity Preservation: The controlled coiling process maintains tube cross-sectional geometry, preventing the ovality, kinking, and wall thinning that can degrade performance in improperly coiled tubing.
- Flexibility & Customization: Available in multiple stainless steel grades, tube diameters, wall thicknesses, and surface finishes to meet diverse application requirements.
- Cost Efficiency: Coil supply reduces the number of butt welds compared to straight-length pipe, minimizing labor costs and potential leak points in the final installed system.
7. Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring that all Small Coil Stainless Steel Tube products conform to recognized international and national standards:
| Standard / Certification | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System |
| ISO 14001:2015 | Environmental Management System |
| ASTM A554 | Standard Specification for Stainless Steel Tubes (Austenitic) |
| ASTM A778 | Standard Specification for Stainless Steel Coil and Strip |
| GB/T 12771 | Chinese National Standard – Welded Stainless Steel Tubes for General Purposes |
| GB/T 14976 | Chinese National Standard – Seamless Stainless Steel Tubes for Fluid Transport |
| EN 10217 | European Standard – Welded Stainless Steel Tubes |
| JIS G3459 | Japanese Industrial Standard – Stainless Steel Tubes |
| CE Marking | European Conformity for pressure equipment (PED 2014/68/EU) |
| Mill Test Reports (MTR) | Batch-specific chemical and mechanical property documentation |
Each production lot is accompanied by a Mill Test Report (MTR) and Certificate of Conformity (CoC) documenting the chemical composition, mechanical test results, heat treatment history, and dimensional verification data. Third-party inspection (TPI) by organizations such as SGS, BV, or Intertek is available upon customer request.
8. Ordering & Customization Information
Customers are advised to specify the following parameters when placing an order for Small Coil Stainless Steel Tubes:
- Stainless steel grade (e.g., 304, 316, 316L, 321, 310S)
- Tube outer diameter and wall thickness
- Required coil length (linear meters)
- Surface finish requirement
- End condition (beveled, plain, threaded, cap-plugged) <