Stainless Steel Coil Tube (Coiltube) — Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (盘管 / Coiltube), manufactured by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-formed tubular product designed for applications requiring continuous helical or spiral winding geometry. Unlike conventional straight pipe sections, coil tubes are supplied in pre-formed coil configurations, offering significant advantages in terms of installation efficiency, spatial adaptability, and thermal-hydraulic performance.
This product category encompasses a range of stainless steel coil tubes engineered for heat exchanger applications, cooling systems, pump station technical water supply systems, and industrial process piping. The coil geometry provides a high surface-area-to-volume ratio, making these products particularly effective in heat transfer scenarios where compact footprint and efficient thermal exchange are paramount.
A notable case study demonstrating the practical application of coil tube technology is documented in the technical literature: "Application of Self-Made Coil Coolers in the Technical Water Supply System Renovation of Songzhuang Pumping Station" (《自制盘管冷却器在宋庄泵站技术供水系统改造中的应用》). This reference case validates the engineering reliability and operational effectiveness of stainless steel coil tubes in demanding hydraulic infrastructure environments.
2. Material & Properties
2.1 Base Material Grades
Stainless steel coil tubes are predominantly fabricated from austenitic stainless steel grades, selected for their superior corrosion resistance, mechanical ductility, and thermal stability. The primary grades utilized include:
- SUS 304 / AISI 304 — General-purpose austenitic grade with excellent corrosion resistance and formability
- SUS 316 / AISI 316 — Molybdenum-enhanced grade offering superior resistance to pitting and crevice corrosion in aggressive environments
- SUS 316L / AISI 316L — Low-carbon variant of 316, ideal for welding applications requiring high resistance to intergranular corrosion
- SUS 321 / AISI 321 — Titanium-stabilized grade for elevated temperature service (up to 870°C)
- SUS 304L / AISI 304L — Low-carbon variant for enhanced weldability and resistance to sensitization
2.2 Key Mechanical Properties
- Tensile Strength (抗拉强度): ≥ 520 MPa (for 304 grade)
- Yield Strength (屈服强度): ≥ 205 MPa
- Elongation (延伸率): ≥ 40%
- Hardness (硬度): ≤ 217 HB (annealed condition)
- Operating Temperature Range: −196°C to +870°C
2.3 Corrosion Resistance Characteristics
- Excellent resistance to atmospheric corrosion and mild chemical environments
- High resistance to pitting and crevice corrosion (particularly 316/316L grades)
- Non-magnetic in annealed condition (residual magnetism < 0.5 GS)
- Passivation film self-healing capability in oxidizing environments
3. Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 50.8 mm (¼" – 2") | ASTM A269 / GB/T 12771 |
| Wall Thickness | 0.5 mm – 3.0 mm | ASTM A269 / GB/T 12771 |
| Coil Inner Diameter (Coil ID) | 200 mm – 1,200 mm | Manufacturer Specification |
| Coil Length (per coil) | 5 m – 100 m (customizable) | Manufacturer Specification |
| Material Grade | SUS 304, 304L, 316, 316L, 321 | ASTM A270 / JIS G4305 |
| Surface Finish | Bright Annealed (BA), No. 4 Hairline, Mirror Polish, Matte | ASTM A240 |
| End Condition | Plain Cut, Beveled, Threaded, Flanged | ASME B1.20.1 / GB/T 7306 |
| Tolerance — OD | ±0.1 mm (standard), ±0.05 mm (precision) | GB/T 12771 |
| Tolerance — Wall Thickness | ±10% (standard), ±5% (precision) | GB/T 12771 |
| Winding Tolerance | ±2% of nominal coil diameter | Manufacturer Specification |
| Maximum Working Pressure | Up to 4.0 MPa (grade-dependent) | ASME B31.3 |
| Welding Compatibility | TIG (GTAW), MIG (GMAW), Orbital | ASME IX / ISO 14732 |
| Packaging | Wooden crate / Steel banding / VCI wrap | ISO 4180 |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Procurement: Hot-rolled stainless steel strip or seamless tube blanks are sourced from certified mills with full mill test certificates (MTC) per EN 10204 Type 3.1.
- Strip Preparation: Incoming coil stock undergoes inspection for dimensional accuracy, surface quality, and chemical composition verification via optical emission spectroscopy (OES).
- Coil Winding (卷管成型): Precision winding machinery forms the tube into the specified helical geometry. The winding process employs controlled tension and diameter tooling to ensure uniformity of coil diameter and pitch throughout the length. For seamless coil tubes, the forming process involves cold winding of pre-drawn tube stock; for welded coil tubes, strip is formed into tube and continuously welded during the winding operation.
- Heat Treatment (热处理): Bright annealing in a protective atmosphere (H₂/N₂ mixture) is performed to relieve residual stresses introduced during cold forming, restore full ductility, and establish a clean, oxide-free surface suitable for passivation. Annealing temperature: 1050°C – 1150°C, followed by controlled cooling.
- Pickling & Passivation (酸洗钝化): The annealed product undergoes pickling to remove any scale or discoloration, followed by passivation treatment using nitric acid or citric acid solutions to establish a protective chromium oxide passive film on the surface.
- Dimensional Inspection: Final products are inspected for outer diameter, wall thickness, coil diameter uniformity, and overall length using ultrasonic thickness gauges and laser measurement systems.
- Non-Destructive Testing (NDT): Electromagnetic testing (ET) or ultrasonic testing (UT) is applied to verify weld integrity and detect subsurface defects in welded coil tubes.
- Surface Treatment (Optional): Additional surface finishing (polishing, brushing, or coating) may be applied per customer specification.
- Final Packaging & Dispatch: Coils are secured with steel banding, wrapped with VCI (Volatile Corrosion Inhibitor) paper, and packed in export-grade wooden crates with appropriate moisture protection.
4.2 Key Process Controls
- Winding tension control to prevent ovality and dimensional deviation
- Atmosphere monitoring during annealing (dew point < −60°C, O₂ < 10 ppm)
- Passivation verification via ferri-cope test (ASTM A967) or redox potential measurement
- Batch traceability through heat number tracking from mill to finished product
5. Applications
5.1 Primary Application Domains
- Heat Exchangers & Coolers (换热器与冷却器): Coil tubes serve as the core heat transfer element in shell-and-coil heat exchangers, providing high thermal exchange efficiency within a compact envelope. The helical geometry enhances turbulent flow characteristics, improving the overall heat transfer coefficient (U-value).
- Pump Station Technical Water Supply Systems (泵站技术供水系统): As demonstrated in the Songzhuang Pumping Station renovation project, self-fabricated coil coolers utilizing stainless steel coil tubes provide reliable thermal management for pump station auxiliary systems, including bearing cooling loops, lubrication oil cooling, and technical water temperature regulation.
- Chemical Processing Industry: Resistant to aggressive chemical media, coil tubes are employed in chemical reactors, distillation columns, and process cooling loops where corrosion resistance is critical.
- Food & Pharmaceutical Industry: Hygienic-grade coil tubes (316L, electropolished finish) are used in pasteurization systems, CIP (Clean-in-Place) circuits, and pharmaceutical process cooling.
- Petrochemical & Oil & Gas: 316/316L coil tubes are utilized in offshore platform cooling systems, heat recovery units, and sour service environments.
- Cryogenic Applications: 304L and 316L coil tubes maintain ductility at cryogenic temperatures (down to −196°C), making them suitable for LNG (Liquefied Natural Gas) processing and cryogenic heat exchangers.
- Power Generation: Used in condenser tube bundles, feedwater preheaters, and auxiliary cooling systems in thermal and nuclear power plants.
- Marine & Offshore: Seawater cooling systems and ballast water treatment circuits benefit from the corrosion resistance of 316L coil tubes in marine environments.
5.2 Engineering Advantages of Coil Geometry
- Enhanced Heat Transfer: The helical configuration induces secondary flow patterns (Dean vortices), increasing the convective heat transfer coefficient by 20%–40% compared to equivalent straight tubes.
- Compact Footprint: Significant space savings compared to straight-tube bank configurations, critical for retrofit applications in existing infrastructure.
- Reduced Installation Labor: Pre-formed coils can be installed as complete units, reducing field welding and assembly time.
- Thermal Stress Relief: The inherent flexibility of coil geometry accommodates thermal expansion and contraction without requiring expansion joints.
6. Quality Certifications & Standards Compliance
6.1 Applicable Standards
- ASTM A269: Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubes for Chemical and Heat-Transfer Applications
- ASTM A270: Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing
- ASTM A312: Standard Specification for Seamless and Welded Austenitic Chromium-Chromium-Nickel Stainless Steel Tubes for High-Temperature Service
- GB/T 12771: Stainless Steel Tubes for General Purposes (Chinese National Standard)
- GB/T 14976: Seamless Stainless Steel Tubes for Fluid Transport
- JIS G4305: Seamless and Welded Stainless Steel Tubes for General Use (Japanese Industrial Standard)
- EN 10216-5: Heat Exchanger and Heat Transfer Component Tubes — Part 5: Non-Ferrous Tubes
- ISO 1149: General Purpose Tubes for Fluid Transfer
6.2 Quality Assurance Certifications
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001:2015 — Environmental Management System Certification
- ISO 45001:2018 — Occupational Health and Safety Management System
- Mill Test Certificates (MTC): Provided per EN 10204 Type 3.1 for each production batch
- Third-Party Inspection: Available upon request (SGS, Bureau Veritas, TÜV, Lloyd's Register)
- PED (Pressure Equipment Directive) Compliance: Available for EU market applications (Category I and II)
- NACE MR0175 / ISO 15156: Compliance for sour service applications (316/316L grades)
6.3 Testing & Inspection Protocols
- Chemical composition analysis per ASTM E195 (OES) — verified per batch
- Hydrostatic testing at 1.5× working pressure — 100% inspection
- Dimensional inspection per ASTM A751 — 100% for critical dimensions
- Surface inspection — visual and magnetic particle testing (MT) where applicable
- Hardness testing per ASTM E10 (Rockwell B scale)
- Tensile testing per ASTM E8 — witness samples retained per heat
7. Unique Selling Points
Wenzhou Jixing Metal Materials Co., Ltd. differentiates its stainless steel coil tube product line through the following value propositions:
- Custom Coil Geometry: Flexible coil diameter, pitch, and length configurations tailored to specific heat exchanger designs and installation constraints
- Demonstrated Field Performance: Validated application in critical infrastructure projects, including pump station technical water supply system retrofits
- Multi-Grade Capability: Full range from standard 304 to specialty grades (316L, 321, duplex) to address diverse environmental and service requirements
- End-to-End Traceability: Complete heat number tracking from raw material mill through final product dispatch, ensuring full supply chain transparency
- Engineering Support: Technical consultation on coil tube selection, thermal performance optimization, and system integration
- Cost-Effective Solution: Pre-formed coil configurations reduce total system cost by minimizing field fabrication, welding, and assembly labor
8. Conclusion
The stainless steel coil tube product from Wenzhou Jixing Metal Materials Co., Ltd. represents a mature, standards-compliant engineered solution for heat transfer and fluid handling applications across multiple industrial sectors. The combination of austenitic stainless steel's inherent corrosion resistance, the thermal-hydraulic advantages of helical coil geometry, and rigorous manufacturing quality controls positions this product as a reliable choice for both new installations and retrofit applications in demanding industrial environments. The documented success in the Songzhuang Pumping Station technical water supply system renovation