Stainless Steel Coil Tube (Coiltube) — Technical Product Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered continuous-length tubular product formed through advanced coiling and cold-forming processes. Designed for demanding industrial applications requiring superior heat transfer efficiency, corrosion resistance, and mechanical durability, this product represents the culmination of decades of metallurgical expertise in seamless and welded stainless steel tubing technology.
Coiltube products are distinguished by their continuous, spiral-wound geometry, which enables exceptional thermal performance in heat exchanger applications. The helical configuration maximizes surface area-to-volume ratio, promotes turbulent flow within the tube bore, and significantly enhances convective heat transfer coefficients compared to conventional straight-tube designs. This product line encompasses a comprehensive range of diameters, wall thicknesses, and grades suitable for applications spanning from chemical processing to petrochemical refining and marine engineering.
2. Material & Properties
2.1 Available Grades
- Austenitic Grades: 304 (UNS S30400), 304L (UNS S30403), 316 (UNS S31600), 316L (UNS S31603), 321 (UNS S32100), 347 (UNS S34700)
- Super-Austenitic Grades: 904L (UNS N08904), 254 SMO (UNS S31254)
- Duplex Grades: 2205 (UNS S32205), 2507 (UNS S32750)
- Superalloy Grades: Inconel 625 (UNS N06625), Hastelloy C-276 (UNS N10276)
2.2 Mechanical Properties (Typical for Grade 316L, Annealed Condition)
- Tensile Strength (UTS): 485–620 MPa (70,000–90,000 psi)
- Yield Strength (0.2% Offset): ≥205 MPa (≥29,700 psi)
- Elongation (A50): ≥40%
- Hardness: ≤230 HB (Brinell)
- Density: 8.0 g/cm³
- Thermal Conductivity (20°C): 14.6 W/(m·K)
- Thermal Expansion Coefficient (20–100°C): 17.3 × 10⁻⁶ /°C
2.3 Corrosion Resistance
The chromium (Cr ≥16%), nickel (Ni ≥10%), and molybdenum (Mo ≥2%) alloying system provides outstanding resistance to pitting, crevice corrosion, and intergranular corrosion (IGC). The low-carbon variants (304L, 316L) exhibit carbon content ≤0.03% to prevent chromium carbide precipitation at welding and heat treatment temperatures, ensuring sustained corrosion resistance in sensitized zones.
3. Specifications
| Parameter | Specification Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 3.18 mm – 159.0 mm (1/8" – 6") | ASTM A213 / ASME SA-213 |
| Wall Thickness (WT) | 0.25 mm – 6.35 mm (0.010" – 0.250") | ASTM A269 / ASME SA-269 |
| Coil Length (per coil) | 50 m – 3,000 m (configurable) | Manufacturer Specification |
| Coil Inner Diameter (ID) | 150 mm – 600 mm (6" – 24") | ISO 1155 |
| Coil Outer Diameter (OD) | 400 mm – 1,500 mm (16" – 60") | ISO 1155 |
| Spiral Pitch | 15 mm – 50 mm (adjustable) | Design-Specific |
| Surface Finish | 2B, BA (Bright Annealed), No. 4, No. 8, Mirror (Ra ≤0.1 μm) | ASTM A478 |
| Dimensional Tolerance (OD) | ±0.05 mm to ±0.50 mm (per grade) | ASTM A213, Table 1 |
| Dimensional Tolerance (WT) | ±10% of nominal | ASTM A213 |
| Heat Treatment Condition | Solution Annealed (1010–1150°C), Pickled & Passivated | ASTM A213 |
| Maximum Operating Temperature | 870°C – 1100°C (grade-dependent) | ASME BPVC Section I |
| Minimum Operating Temperature | −196°C (Cryogenic) | ASME BPVC Section VIII |
| Maximum Working Pressure | Up to 320 bar (design-dependent) | ASME BPVC Section VIII Div. 1 |
| Welding Suitability | Gas Tungsten Arc (GTAW), Metal Arc (MAW), Orbital TIG | ASME Section IX |
| Weight per Meter (316L, 19.05 mm OD × 1.65 mm WT) | 0.907 kg/m | Calculated per ASTM |
4. Manufacturing Process
4.1 Raw Material Procurement & Inspection
High-purity stainless steel strip or wire rod is sourced from certified mill suppliers with full traceability documentation. Incoming material undergoes rigorous inspection including chemical composition verification (spectrometric analysis), mechanical testing, and visual surface quality assessment in compliance with ASTM A240 and ASTM A666 specifications.
4.2 Coil Forming & Cold Work
The stainless steel strip or drawn tubing is fed through precision CNC-controlled coiling machinery that imparts the characteristic spiral/helical geometry. The forming process maintains controlled strain rates to prevent work hardening beyond acceptable limits while achieving the required dimensional accuracy. Multi-roller forming stations ensure uniform curvature throughout the coil length.
4.3 Welding (for Welded Coiltube)
Where welded construction is specified, longitudinal seams are formed using high-frequency induction welding (HF) or continuous gas tungsten arc welding (GTAW). Weld parameters are precisely controlled to minimize heat-affected zone (HAZ) width and prevent sensitization. Post-weld solution annealing (1010–1150°C) restores full corrosion resistance.
4.4 Heat Treatment & Solution Annealing
Coiltube products undergo full solution annealing in inert atmosphere (argon or vacuum) furnaces at temperatures between 1010°C and 1150°C, followed by rapid controlled cooling. This process dissolves all precipitated chromium carbides, homogenizes the microstructure, and achieves optimal ductility and corrosion resistance. The austenitic microstructure is fully stabilized in the single-phase condition.
4.5 Surface Treatment
- Pickling: Immersion in mixed acid baths (HNO₃/HF or H₂SO₄/HNO₃) to remove oxide scale and surface contaminants.
- Passivation: Nitric acid (HNO₃) or citric acid treatment to establish a protective chromium oxide (Cr₂O₃) passive film on the surface.
- Surface Polishing: Mechanical polishing, electrolytic polishing, or electropolishing to achieve specified surface roughness (Ra) values.
4.6 Final Inspection & Coiling
Finished coiltube undergoes comprehensive quality assurance including dimensional verification (OD, WT, coil diameter), hydrostatic pressure testing (1.5× design pressure), visual inspection, and non-destructive testing (EDDY CURRENT, electromagnetic detection). Product is then packaged on protective coil carriers with moisture-absorbent desiccants and protective wrapping for shipment.
5. Applications
5.1 Heat Exchangers & Thermal Management
The spiral geometry of coiltube is particularly advantageous in shell-and-coil heat exchangers, air-cooled condensers, and plate-and-coil assemblies. The helical configuration induces secondary Dean flow vortices that enhance turbulent mixing, increasing the Nusselt number (Nu) and overall heat transfer coefficient (U) by 20–40% compared to straight-tube equivalents. Applications include:
- Crude oil preheating and fractionation systems
- Refinery distillation column reboilers
- Chemical reactor cooling jackets
- Process heat recovery systems
- Cryogenic air separation units
5.2 Petrochemical & Oil & Gas
Stainless steel coiltube products serve critical functions in upstream and downstream petrochemical processing, including wellhead flow lines, separator internals, gas-liquid exchangers, and flare cooling systems. The combination of corrosion resistance and mechanical strength ensures long service life in aggressive hydrocarbon environments.
5.3 Marine & Offshore Engineering
Marine-grade duplex and super-austenitic coiltube products are employed in ballast water treatment systems, seawater cooling circuits, desalination plants, and subsea production manifolds. Resistance to chloride-induced pitting and stress corrosion cracking (SCC) makes these products ideal for marine environments.
5.4 Food & Pharmaceutical Processing
Hygienic-grade (No. 4 or Mirror finish) coiltube products conform to FDA 21 CFR and EHEDG guidelines for use in dairy processing, beverage pasteurization, pharmaceutical CIP (Clean-In-Place) systems, and sanitary heat exchangers where product contact surfaces must resist microbial adhesion and facilitate thorough cleaning.
5.5 Power Generation
Coiltube products are utilized in supercritical and ultra-supercritical (USC) boiler economizers, steam generators in nuclear power plants (NPP), and condenser tube bundles where high-temperature steam-water interactions demand exceptional metallurgical stability and fatigue resistance.
6. Quality Certifications & Standards Compliance
6.1 International Standards
- ASTM A213 / ASME SA-213: Seamless and welded austenitic stainless steel tube for heat exchangers
- ASTM A269 / ASME SA-269: Seamless, cold-drawn austenitic stainless steel tubing
- ASTM A312 / ASME SA-312: Seamless, welded, and heavily cold-worked austenitic stainless steel tubing
- EN 10216-5: Non-ferrous metallic tubes and fittings — stainless steel tubes for pressure purposes
- ISO 1155: Tubes and pipes — steel tube coils
- JIS G3459: Cold-drawn stainless steel tubes for general purposes
6.2 Quality Management Certifications
- ISO 9001:2015 — Quality Management Systems
- ISO 14001:2015 — Environmental Management Systems
- ISO 45001:2018 — Occupational Health & Safety Management Systems
- NADCAP — National Aerospace and Defense Contractors Accreditation Program (for aerospace applications)
6.3 Industry-Specific Certifications
- ASME "U" Stamp — Authorized Manufacturer for Pressure Vessel Components
- ASME "S" Stamp — Authorized Manufacturer for Steam Generators
- NB (National Board) Registration — Pressure Equipment Manufacturer
- API Q1 (Q94) — Quality Management System for Petroleum/Natural Gas
- DNV-GL Type Approval — Marine Equipment Certification
- CE Marking — European Conformity per PED 2014/68/EU
- EAC Marking — Eurasian Conformity
6.4 Testing & Documentation
Each production lot is accompanied by a comprehensive Material Test Certificate (MTC / EN 10204 3.1) documenting chemical composition, mechanical properties, heat treatment records, and dimensional inspection results. Optional third-party inspection (TPI) by organizations such as Lloyd's Register (LR), Bureau Veritas (BV), DNV, or SGS is available upon customer request. Full traceability from mill heat number through final product identification is maintained throughout the manufacturing chain.
7. Unique Selling Points
- Enhanced Heat Transfer Performance: Spiral geometry achieves 20–40% improvement in overall heat transfer coefficient (U-value) over conventional straight-tube designs, reducing equipment footprint and capital expenditure.
- Continuous Length Advantage: Elimination of longitudinal welds and joints reduces leak paths, pressure drop, and potential failure points in high-pressure applications.
- Comprehensive Grade Range: Availability in austenitic, duplex, and superalloy grades accommodates the full spectrum of corrosive environments from mild industrial to extreme chemical exposure.
- Precision Dimensional Control: CNC-manufactured coil geometry with tolerances as tight as ±0.05 mm ensures reliable installation in precision-engineered heat exchanger assemblies.
- Full Traceability: Complete metallurgical documentation and heat number traceability from raw material to finished product supports regulatory compliance and quality assurance requirements.
- Custom Configuration Capability: Flexible manufacturing parameters (pitch, OD, WT, coil diameter, surface finish) enable tailoring to specific application requirements and design specifications.
Note: All specifications listed herein represent typical values and ranges. Actual product specifications shall be determined by the applicable purchase order, design drawings, and governing standards. Wenzhou Jixing Metal Materials Co., Ltd reserves the right to modify specifications upon mutual agreement with the customer, subject to compliance with applicable regulatory and safety standards.