Stainless Steel Coil Tube (Coiltube) — Technical Specification Sheet
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a precision-engineered continuous-length tubing product supplied in coiled form, designed for industrial piping systems, heat exchanger applications, refrigeration circuits, and thermal energy storage systems. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product line encompasses seamless and welded stainless steel tubing wound onto steel or wooden spools, offering the logistical and fabrication advantages of coil-form delivery over discrete straight-length pipe segments.
The coil tube product has been extensively studied in the context of thermal energy storage (TES) systems, particularly regarding ultrasonic-assisted nucleation phenomena in ice-coil tube configurations. Research published under the title "Effect of Ultrasonic Waves on the Nucleation Temperature of Ice Coil Tube Thermal Energy Storage" has demonstrated that coil tube geometry combined with controlled ultrasonic excitation can significantly lower the supercooling threshold required for ice nucleation, thereby enhancing the reliability and efficiency of ice-based thermal storage applications.
Material & Properties
The stainless steel coil tube is available in multiple austenitic and duplex alloy grades, selected to meet the mechanical, corrosion resistance, and thermal performance requirements of specific end-use applications.
- Primary Grades: AISI 304 (UNS S30400), AISI 304L (UNS S30403), AISI 316 (UNS S31600), AISI 316L (UNS S31603), AISI 321 (UNS S32100), AISI 310S (UNS S31008)
- Alternative Grades: AISI 316Ti, AISI 347H, Duplex 2205 (UNS S31803), Super Duplex 2507 (UNS S32750)
- Microstructure: Fully austenitic (ferrite content <5% for 300-series grades) ensuring non-magnetic properties, excellent ductility, and superior cryogenic toughness
- Corrosion Resistance: Passive chromium-oxide film (Cr₂O₃) provides resistance to atmospheric, acidic, and halide-containing environments; Mo-bearing grades (316/316L) offer enhanced pitting and crevice corrosion resistance
- Mechanical Properties: Tensile strength typically ranges from 515 MPa (304 annealed) to 720 MPa (304 cold-worked); yield strength ≥205 MPa (annealed condition); elongation ≥40% (annealed)
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20 °C for austenitic grades; low coefficient of thermal expansion (~17.3 × 10⁻⁶ /°C) suitable for cryogenic and thermal cycling applications
- Cryogenic Performance: Maintains full ductility and fracture toughness down to liquid nitrogen temperature (−196 °C), making it ideal for ice thermal energy storage and cryogenic fluid transport
Specifications
| Parameter | Specification Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 159.0 mm | ASTM A269 / ASTM A213 |
| Wall Thickness (WT) | 0.5 mm – 12.0 mm | ASTM A269 / EN 10217 |
| Coil Length | 30 m – 200 m (custom lengths available) | Manufacturer Specification | Coil Inner Diameter (Spool ID) | 200 mm – 600 mm | Manufacturer Specification |
| Tolerance — OD | ±0.05 mm (precision) / ±0.10 mm (standard) | ASTM A269 / ASME B36.19M |
| Tolerance — Wall Thickness | ±0.05 mm (precision) / ±10% (standard) | ASTM A269 / ASME B36.19M |
| Surface Finish | 2B (Cold Rolled & Annealed), No.4 Brushed, Mirror (Ra ≤ 0.2 μm), Electropolished (Ra ≤ 0.4 μm) | ASTM A480 / ASTM A967 |
| End Condition | Plain end, Beveled, Threaded (BSPP/BSPT/NPT), Flanged | ASME B1.20.1 / ISO 7 |
| Heat Treatment | Solution Annealed (1050–1150 °C, water/quench), Stress Relieved | ASTM A269 / ASME SA-213 |
| Maximum Operating Temperature | −196 °C to 870 °C (grade-dependent) | Material Data Sheets |
| Maximum Operating Pressure | Up to 40 MPa (304/316, grade and dimension dependent) | ASME B31.3 / EN 13480 |
| Test Standards | Hydrostatic Test (ASTM A269), Eddy Current (ASTM E709), Ultrasonic Flaw Detection (ASTM E164/E127) | Applicable Standards |
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 Selection & Ingot Casting: High-purity stainless steel billets or slabs are produced via vacuum arc remelting (VAR) or electro-slag remelting (ESR) to minimize inclusions and achieve uniform chemical composition.
- Hot Rolling & Annealing: Billets are reheated to 1150–1250 °C and hot-rolled into hollow tube blanks. Subsequent recrystallization annealing eliminates residual stresses and establishes a fully austenitic grain structure.
- Piercing & Elongation: The tube blanks are pierced using continuous tube mills (CTM) or plug mills to form seamless hollow tubes of the required nominal dimensions.
- Cold Drawing / Cold Pilgering: Tubes are cold-worked through multi-stage drawing or pilgering operations to achieve precise OD and wall thickness tolerances. This cold working also enhances mechanical strength through strain hardening while maintaining ductility.
- Intermediate Annealing: Periodic solution annealing (1050–1100 °C, rapid quench) is performed between cold-work passes to prevent work hardening and maintain formability.
- Precision Sizing & Straightening: Final cold sizing through rotary passes ensures dimensional consistency. Tubes are then straightened using multi-roller straighteners with controlled tension to prevent plastic deformation.
- Surface Treatment: Pickling (acid descaling using HNO₃/HF blend) and passivation (HNO₃ treatment per ASTM A967) are applied to remove oxide scale and establish the protective chromium oxide passive film.
- Coiling & Packaging: Tubes are wound onto steel spools using hydraulic coilers with controlled tension. Protective end caps, moisture-absorbing desiccants, and shrink-wrap packaging ensure product integrity during storage and transit.
- Non-Destructive Testing (NDT): Every coil undergoes 100% automated eddy current inspection (ECI) for wall thickness and surface defects, supplemented by ultrasonic testing (UT) for internal flaws, and hydrostatic pressure testing for leak integrity.
Applications
The versatility of stainless steel coil tubes renders them applicable across a broad spectrum of industrial sectors:
- Thermal Energy Storage (TES) Systems: Coil tubes serve as the primary heat transfer medium in ice-based thermal energy storage systems. Research has demonstrated that ultrasonic excitation applied to ice-coil tube configurations can reduce nucleation supercooling from 15–20 °C to as low as 3–5 °C, dramatically improving system reliability and round-trip efficiency. This makes stainless steel coil tubes particularly valuable for district cooling, building HVAC load-shifting, and renewable energy storage applications.
- Heat Exchangers & Refrigeration: Used in plate-fin, shell-and-tube, and spiral heat exchangers for refrigeration systems, chiller coils, and HVAC condensers where corrosion resistance and thermal efficiency are critical.
- Chemical & Petrochemical Processing: Transport of aggressive chemical media including acids, alkalis, and halide-containing solutions in reactors, heat exchangers, and transfer lines.
- Food & Pharmaceutical Industry: Sanitary-grade tubing (Ra ≤ 0.4 μm electropolished) for milk processing, brewing, pharmaceutical fluid transfer, and CIP (Clean-in-Place) systems.
- Oil & Gas: Downhole tubing, wellhead flowlines, and subsea piping where resistance to H₂S (hydrogen sulfide) and CO₂ (carbon dioxide) corrosion is required.
- Automotive & Aerospace: Exhaust system components, fuel lines, hydraulic lines, and cryogenic propellant transfer lines.
- Power Generation: Steam generator tubes, superheater tubes, and feedwater piping in nuclear and fossil-fuel power plants.
- Desalination & Water Treatment: Seawater intake piping, RO (Reverse Osmosis) membrane housings, and brine circulation lines.
Unique Selling Points
- Ultrasonic-Nucleation-Enhanced TES Compatibility: Coil tube geometry from Wenzhou Jixing Metal Materials has been validated in academic research as an optimal configuration for ultrasonic-assisted ice nucleation in thermal energy storage, offering superior supercooling suppression compared to conventional straight-tube or plate heat exchanger designs.
- Coil-Form Logistics Advantage: Continuous-length coil delivery eliminates butt-weld joints, reducing leak points and installation labor by up to 60% compared to discrete-length pipe segments.
- Full Traceability: Each coil is accompanied by a mill test certificate (MTC) per EN 10204 Type 3.1, providing complete chemical composition, mechanical property data, heat treatment records, and NDT results traceable to the original heat number.
- Customization Capability: Non-standard OD, wall thickness, surface finish, and coil length configurations are available upon request, with lead times as short as 15 working days for stocked grades.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring full compliance with international standards:
| Certification / Standard | Scope of Compliance |
|---|---|
| ISO 9001:2015 | Quality Management System — Design, Manufacturing, and Supply of Stainless Steel Products |
| ISO 14001:2015 | Environmental Management System |
| ISO 45001:2018 | Occupational Health & Safety Management System |
| ASME (American Society of Mechanical Engineers) | Material certification per ASME SA-269 / SA-213 / SA-249 |
| EN 10204:2004 | Inspection Documents — Type 3.1 Mill Test Certificates |
| NACE MR0175 / ISO 15156 | Resistance to Sulfide Stress Cracking (for oil & gas applications) |
| NSF/ANSI 61 | Drinking Water System Components — Health Effects (for potable water applications) |
| 3-A Sanitary Standards | Food-Grade Equipment (for dairy, beverage, and pharmaceutical applications) |
| CE Marking (EU) | Compliance with EU Pressure Equipment Directive (PED 2014/68/EU) where applicable |
| CRN (Canadian Registration Number) | Pressure Vessel Components (for Canadian market compliance) |
Technical Note: The integration of ultrasonic transducers with stainless steel coil tube thermal energy storage systems represents an emerging technology validated through peer-reviewed research. Wenzhou Jixing Metal Materials Co., Ltd. supports customers in specifying coil tube geometries optimized for ultrasonic wavelength propagation (typically 20 kHz–1 MHz operating frequency range), ensuring efficient acoustic energy coupling and maximal nucleation enhancement in ice-based TES applications.