Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered tubular product manufactured by Wenzhou Jixing Metal Materials Co., Ltd (Product No. 1448). This coil tube is designed for use in thermal exchange systems, process piping, and industrial heat transfer applications. The product has successfully passed technical appraisal as part of the Coil Tube and Shell-and-Tube Glass Heat Exchanger Technical Appraisal Program, demonstrating its compliance with rigorous performance and reliability standards.
Coil tubes are formed by cold-rolling or hot-rolling stainless steel strip into a continuous helical configuration, providing a high surface-area-to-volume ratio that maximizes heat transfer efficiency. This product line is classified under the Literature & Learning Reference (文献学习) category, serving as both a production standard and a technical knowledge benchmark for the stainless steel pipe industry.
Unique Selling Points
- Superior Corrosion Resistance: Utilizes high-grade austenitic stainless steel (e.g., 304, 316, 321) providing excellent resistance to pitting, crevice, and intergranular corrosion.
- Technical Appraisal Certified: Passed formal technical appraisal for use in coil-type and shell-and-tube heat exchanger assemblies, ensuring validated thermal performance.
- Continuous Helical Geometry: Seamless coil construction eliminates longitudinal weld seams, reducing stress concentration points and improving fatigue life.
- High Surface Efficiency: The helical coiling configuration achieves up to 3× greater heat transfer surface area compared to straight tube equivalents of the same length.
- Dimensional Consistency: Precision manufacturing tolerances ensure uniform wall thickness and diameter throughout the coil length.
2. Material & Properties
The coil tube is manufactured from premium-grade austenitic stainless steel, selected for optimal combinations of thermal conductivity, corrosion resistance, and mechanical integrity under elevated temperature and pressure conditions.
2.1 Available Grades
- SUS 304 / AISI 304: General-purpose grade with excellent formability and corrosion resistance; suitable for moderate chemical environments.
- SUS 316 / AISI 316: Molybdenum-enhanced grade offering superior resistance to chlorides, acids, and marine environments.
- SUS 316L / AISI 316L: Low-carbon variant of 316 for enhanced weldability and resistance to intergranular corrosion (IGC).
- SUS 321 / AISI 321: Titanium-stabilized grade providing excellent resistance to intergranular corrosion at elevated temperatures (up to 870°C).
- SUS 310S / AISI 310S: High-temperature grade suitable for sustained service up to 1150°C.
2.2 Mechanical Properties (Typical — Annealed Condition)
| Property | SUS 304 | SUS 316 | SUS 321 | Test Standard |
|---|---|---|---|---|
| Tensile Strength (Rm) | ≥ 520 MPa | ≥ 515 MPa | ≥ 515 MPa | ASTM A240 / EN 10204 |
| Yield Strength (Rp0.2) | ≥ 205 MPa | ≥ 170 MPa | ≥ 170 MPa | ASTM A240 |
| Elongation (A) | ≥ 40% | ≥ 40% | ≥ 40% | ASTM A240 |
| Thermal Conductivity (λ) at 100°C | 16.3 W/(m·K) | 16.3 W/(m·K) | 14.2 W/(m·K) | ASTM A240 |
| Maximum Service Temperature | 870°C | 870°C | 870°C | ASTM A240 |
2.3 Chemical Composition (Typical, wt%)
| Element | Cr | Ni | Mo | C | Ti | Si | Mn |
|---|---|---|---|---|---|---|---|
| SUS 304 | 18.0–20.0 | 8.0–10.5 | — | ≤ 0.08 | — | ≤ 1.0 | ≤ 2.0 |
| SUS 316 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 | ≤ 0.08 | — | ≤ 1.0 | ≤ 2.0 |
| SUS 321 | 17.0–19.0 | 9.0–12.0 | — | ≤ 0.08 | 5×C to 0.70 | ≤ 1.0 | ≤ 2.0 |
3. Specifications
3.1 Dimensional Specifications
| Parameter | Specification Range | Tolerance | Standard Reference |
|---|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 108 mm | ±0.1 mm (OD ≤ 50 mm); ±0.2% (OD > 50 mm) | ASTM A269 / EN 10217 |
| Wall Thickness (t) | 0.3 mm – 6.0 mm | ±10% of nominal | ASTM A269 |
| Coil Inner Diameter (CID) | 150 mm – 600 mm | ±5 mm | Manufacturer Specification |
| Coil Length (per roll) | 50 m – 500 m | As specified | — |
| Coil Weight | Up to 2,500 kg per coil | — | — |
| End Condition | Plain, beveled, or formed (U-bend ready) | — | ASME B31.3 |
| Surface Finish | No. 4 Brushed, 2B Annealed, Mirror (Ra ≤ 0.4 μm) | — | ASTM A480 |
3.2 Heat Exchanger Assembly Specifications (Coil & Shell-and-Tube Glass Heat Exchanger)
| Parameter | Specification |
|---|---|
| Maximum Operating Pressure | 1.6 MPa (design); up to 2.5 MPa (special order) |
| Maximum Operating Temperature | 350°C (standard); 500°C (310S grade) |
| Pressure Test | 1.5× design pressure, 30-minute hold, no leakage |
| Heat Transfer Efficiency | ≥ 90% of theoretical (validated per technical appraisal) |
| Shell Material | Borosilicate glass (heat exchanger variant) or SS304/316 |
| Connection Type | Flanged (ASME B16.5), threaded (NPT/BSP), or socket-weld |
4. Manufacturing Process
The production of stainless steel coil tubes follows a rigorous multi-stage process ensuring dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Procurement: Cold-rolled stainless steel strip or seamless tube blanks are sourced from certified mills with full chemical and mechanical traceability (Mill Test Certificate — MTC per EN 10204 Type 3.1).
- Coil Forming:
- For seamless coil tube: Tube blanks are fed through precision roller dies that progressively bend the tube into a helical coil shape without deformation of cross-section.
- For welded coil tube: Stainless steel strip is cold-rolled into a helical coil with continuous longitudinal welding (TIG/GTAW or laser welding), followed by stress relief annealing.
- Heat Treatment (Annealing): Coiled tubes are subjected to solution annealing at 1050°C – 1150°C followed by controlled air or water quenching to restore full austenitic microstructure, relieve residual stresses, and maximize corrosion resistance.
- Pickling & Passivation: The surface is treated with a mixed acid pickling solution (HNO3/H2SO4) to remove scale and oxide, followed by nitric acid passivation to establish a protective chromium oxide (Cr2O3) layer.
- Surface Finishing: Depending on application requirements, tubes may undergo mechanical polishing, electropolishing, or chemical polishing to achieve specified surface roughness (Ra values).
- Quality Inspection:
- Visual inspection (VT) for surface defects
- Eddy current testing (ET) for internal and external flaw detection
- Hydrostatic pressure testing per ASTM A269
- Dimensional verification (OD, wall thickness, coil diameter) using ultrasonic thickness gauging and optical measurement
- Spectroscopic analysis (PMI) for chemical composition verification
- Packaging & Dispatch: Coils are wrapped in moisture-proof kraft paper, strapped with steel bands, and shipped on wooden pallets or in protective containers to prevent mechanical damage and moisture exposure.
5. Applications
The Stainless Steel Coil Tube is engineered for demanding industrial applications where corrosion resistance, thermal performance, and mechanical reliability are critical:
- Heat Exchangers: Primary application in coil-type heat exchangers, shell-and-tube glass heat exchangers, and double-pipe heat exchangers for liquid-liquid and liquid-gas heat transfer.
- Chemical Processing: Transfer of aggressive chemicals, acids, and solvents in chemical manufacturing plants where 316L grade provides chloride resistance.
- Pharmaceutical & Food Processing: Sanitary-grade coil tubes for CIP (Clean-in-Place) systems, pasteurization, sterilization, and product transfer in pharmaceutical and food/beverage industries.
- Power Generation: Condenser tubes, economizer coils, and feedwater heaters in thermal power plants and cogeneration systems.
- Oil & Gas: Subsea production lines, heat tracing systems, and offshore platform piping where corrosion and fatigue resistance are paramount.
- Automotive & Aerospace: Exhaust system components, turbocharger manifolds, and hydraulic fluid transfer lines.
- Marine & Offshore: Seawater cooling systems, ballast water systems, and desalination plant heat recovery units.
6. Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains rigorous quality management systems and holds the following certifications and compliances:
| Certification / Standard | Scope |
|---|---|
| ISO 9001:2015 | Quality Management System (QMS) |
| ISO 14001:2015 | Environmental Management System (EMS) |
| ISO 45001:2018 | Occupational Health & Safety Management System (OHSMS) |
| CE Marking (EU) | Compliance with European Pressure Equipment Directive (PED 2014/68/EU) |
| ASME Stamp (where applicable) | Construction of pressure vessels and heat exchangers per ASME Section VIII |
| EN 10204 3.1 MTC | Material Test Certificate with specific inspection results |
| Technical Appraisal Certification | Coil Tube & Shell-and-Tube Glass Heat Exchanger — Passed Technical Appraisal (技术鉴定) |
6.1 Applicable Standards
- ASTM A269: Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for Chemical and Gas-Industry Service
- ASTM A213: Standard Specification for Seamless Austenitic Chromium-Nickel Stainless Steel Tubing for Heat-Transfer Applications
- EN 10217-7: Heat-resistant steels and stainless steels — Tubes for heat exchangers and similar items
- ASME B31.3: Process Piping Code
- GB/T 12771: Chinese National Standard for Stainless Steel Seamless Tubes for General Purposes
- GB/T 21830: Chinese National Standard for Stainless Steel Seamless Tubes for Heat Exchangers
6.2 Traceability & Inspection Protocol
Every coil tube production batch is assigned a unique heat number and production lot identifier. Full traceability from raw material mill certificate through final dispatch inspection is maintained. Non-destructive testing (NDT) records, dimensional measurement reports, and surface finish certifications are provided with each shipment upon request.
7. Conclusion
The Stainless Steel Coil Tube (Product No. 1448) from Wenzhou Jixing Metal Materials Co., Ltd represents a technically validated, high-performance solution for thermal exchange and process piping applications. Its successful passage through the Coil Tube and Shell-and-Tube Glass Heat