Stainless Steel Coil Tube (Coiltube) — Technical Product Specification
Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product formed into a continuous helical or serpentine coil configuration. These coil tubes are integral components in thermal exchange systems, chemical processing reactors, and continuous stirred tank reactor (CSTR) assemblies, where their coiled geometry maximizes heat transfer surface area within a compact volumetric footprint. The product is designed to deliver superior thermal performance, mechanical durability, and corrosion resistance under demanding industrial operating conditions.
Coil tubes serve as critical internal elements in process equipment, facilitating efficient heat transfer between process fluids and cooling/heating media. Their application in Continuous Stirred Tank Reactors (CSTRs) has been extensively studied, particularly regarding the influence of coil geometry on Residence Time Distribution (RTD) under varying impeller configurations, confirming their role in enhancing mixing efficiency and thermal uniformity within reactor systems.
Material & Properties
Base Material Grades
- ASTM A213 TP304 / TP304L — General-purpose austenitic stainless steel with excellent corrosion resistance and formability
- ASTM A213 TP316 / TP316L — Molybdenum-enhanced grade offering superior resistance to pitting and crevice corrosion
- ASTM A213 TP321 — Stabilized with titanium for elevated-temperature applications
- ASTM A213 TP347 — Stabilized with niobium for high-temperature service
- ASTM A213 TP310S — High-chromium grade for extreme oxidation environments
- ASTM A213 TP904L — Ultra-low carbon high-alloy grade for aggressive chemical environments
Mechanical Properties
- Tensile Strength: 515–750 MPa (depending on grade and condition)
- Yield Strength: 205–310 MPa (0.2% offset)
- Elongation: ≥ 35% (minimum)
- Operating Temperature Range: −196 °C to 870 °C (grade-dependent)
Thermal Properties
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20 °C
- Specific Heat Capacity: 0.50 J/(g·K) at 20 °C
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (20–100 °C)
Corrosion Resistance
- Excellent resistance to atmospheric corrosion, weak organic acids, and dilute inorganic acids
- Superior resistance to pitting, crevice corrosion, and intergranular corrosion (in low-carbon/L-grade variants)
- Resistance to stress corrosion cracking (SCC) in chloride-containing environments (316L/904L grades)
Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | Φ6.0 mm – Φ114.3 mm (customizable) | ASTM A213 / ASTM A511 |
| Wall Thickness | 0.5 mm – 8.0 mm (customizable) | ASTM A213 / EN 10216-5 |
| Coil Pitch | 10 mm – 100 mm (configurable per application) | Customer-specific design |
| Coil Diameter | Φ50 mm – Φ2000 mm (customizable) | Customer-specific design |
| Tube Length (per coil) | 1 m – 500 m (continuous coil) | ASTM A213 |
| Surface Finish | BA (Bright Annealed), Pickled & Passivated, Polished (Ra ≤ 0.4 μm) | ASTM A473 / ASTM A269 |
| Tolerance on OD | ±0.05 mm (precision grade); ±0.10 mm (standard grade) | ASTM A213 |
| Tolerance on Wall Thickness | ±10% of nominal | ASTM A213 |
| Pressure Rating | Up to 40 MPa (depending on OD, wall thickness, and grade) | ASME B31.3 |
| Connection Type | Flanged, Threaded, Welded (butt/weld), Socket Weld, Custom | ASME B16.5 / ASME B16.11 |
| Coil Form | Helical, Serpentine, Spiral, Multi-pass, Layered | Customer-specific design |
Manufacturing Process
Process Flow
- Material Selection & Procurement: High-purity stainless steel billets or wire rod are sourced from certified suppliers, with incoming inspection for chemical composition (spectroscopic analysis) and mechanical properties.
- Hot Rolling / Extrusion: Raw stock is processed into seamless tube blanks via hot rolling or extrusion methods, ensuring homogeneity and dimensional consistency.
- Piercing & Hot Finishing: Tubes are pierced and hot-finished to approximate dimensions, followed by controlled cooling to achieve desired microstructure.
- Cold Drawing: Tubes undergo multi-pass cold drawing through precision dies to achieve final OD and wall thickness tolerances. Drawing lubricants are carefully selected to prevent contamination.
- Intermediate Annealing: Periodic annealing is performed between cold working passes to relieve residual stresses and restore ductility for further deformation.
- Coil Forming (Cold Bending): Precision coil forming machines cold-bend the straight tube into the specified helical or serpentine geometry. The bending process employs controlled curvature rates to prevent ovalization, buckling, or cracking. Bending fixtures are designed to maintain uniform coil pitch and diameter.
- Final Annealing & Pickling: The formed coil tube undergoes solution annealing (typically 1050–1150 °C, grade-dependent) followed by rapid water quenching. The tube is then acid pickled (hydrochloric + nitric acid mixture) to remove oxide scale and surface contaminants.
- Passivation: A final passivation treatment using dilute nitric or citric acid solution establishes a stable chromium oxide passive film on the surface, enhancing corrosion resistance.
- Surface Finishing: Optional electropolishing or mechanical polishing is applied for sanitary or high-purity applications requiring low surface roughness (Ra ≤ 0.4 μm).
- Quality Inspection & Testing: Comprehensive inspection including dimensional verification, hydrostatic pressure testing, eddy current testing, radiographic testing (RT), and chemical analysis.
- Packaging & Dispatch: Coiled tubes are carefully packaged with protective end caps, moisture-absorbing desiccants, and appropriate labeling for traceability.
Applications
Chemical Processing & Reactors
- Continuous Stirred Tank Reactors (CSTR): Coil tubes serve as internal heat exchange elements within CSTRs, managing exothermic/endothermic reaction temperatures. Research on Residence Time Distribution (RTD) in CSTRs with internal coils demonstrates that coil geometry significantly influences mixing patterns and thermal uniformity under various impeller types (Rushton turbine, marine propeller, paddle), directly impacting reaction selectivity and yield.
- Reactor Jackets & Internal Coils: Used in polymerization reactors, hydrogenation reactors, and distillation column reboilers.
- Heat Exchangers: Double-pipe heat exchangers, spiral heat exchangers, and plate-and-frame heat exchanger internals.
Pharmaceutical & Biotechnology
- Bioreactor cooling/heating coils for precise temperature control of biological cultures
- Clean-in-place (CIP) and sterilize-in-place (SIP) compatible coil assemblies
- Pharmaceutical process equipment requiring sanitary-grade (Ra ≤ 0.4 μm) surfaces
Food & Beverage Industry
- Pasteurization and sterilization equipment heat exchange coils
- UHT (Ultra-High Temperature) processing systems
- Dairy, brewing, and beverage processing thermal management
Oil & Gas / Petrochemical
- Refinery process heat exchangers
- Upstream/downstream processing equipment
- Offshore platform thermal systems
Power Generation
- Boiler economizers and superheaters
- Nuclear reactor cooling circuits (specialized grades)
- Waste heat recovery systems
Automotive & Aerospace
- Brake-by-wire cooling systems
- Fuel system heat management
- Aviation hydraulic system heat exchangers
Quality Certifications & Standards Compliance
International Standards
- ASTM A213 — Standard Specification for Seamless Ferritic, Austenitic, and Ferritic-Austenitic Alloy Steel Tubing for Heat-Transfer and Similar Applications
- ASTM A511 — Standard Specification for Seamless and Welded Austenitic Chromium-Nickel Stainless Steel Tubing for Boilers, Heaters, and Similar Applications
- EN 10216-5 — Seamless Stainless Steel Tubes for Technical Uses
- ISO 3506 — Corrosion-Resistant Stainless Steel Tubes
- ASME B31.3 — Process Piping
- ASME B31.1 — Power Piping
- ASME B31.5 — Hydraulic Power Transmission Piping
- ASME BPE — Bioprocessing Equipment (for pharmaceutical applications)
- 3-A Sanitary Standards — For food and dairy processing applications
Quality Management Certifications
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001 — Environmental Management System Certification
- ISO 45001 — Occupational Health and Safety Management System
- CE Marking — European Conformity (for pressure equipment under PED 2014/68/EU)
- PED 2014/68/EU — Pressure Equipment Directive compliance (Category I–IV as applicable)
Testing & Inspection Protocols
- Hydrostatic Pressure Testing: Performed at 1.5× working pressure with minimum dwell time of 30 seconds
- Eddy Current Testing (ECT): 100% inline detection of surface and near-surface defects
- Radiographic Testing (RT): Welded coil joints inspected per ASTM E94 / ISO 17636
- Positive Material Identification (PMI): XRF or OES verification of chemical composition
- Dimensional Inspection: 100% OD and wall thickness verification via ultrasonic measurement
- Surface Roughness Measurement: Verified per ISO 4287 / ASTM E138 for sanitary applications
- Intergranular Corrosion Testing: ASTM A262 Practice A/E for stabilized grades
- Pitting Corrosion Testing: ASTM G48 for 316L and higher-alloy grades
Unique Selling Points
1. Precision Coil Forming Technology: Wenzhou Jixing Metal Materials employs advanced cold-bending technology with computerized control systems to achieve uniform coil pitch, consistent curvature, and minimal ovalization (< 2% of nominal OD), ensuring optimal heat transfer performance and installation compatibility.
2. Enhanced Thermal Performance: The helical coil geometry provides a surface-area-to-volume ratio up to 10× greater than straight-tube equivalents, enabling compact heat exchanger designs with superior thermal efficiency. This is particularly advantageous in CSTR applications where internal coils manage reaction temperatures while maintaining favorable RTD characteristics.
3. Full Traceability & Documentation: Every coil tube lot is accompanied by a comprehensive material test certificate (MTC) per EN 10204 3.1/3.2, including chemical analysis, mechanical test results, heat treatment records, and traceable mill certificates from raw material suppliers.
4. Custom Engineering Capability: The company offers full design-to-delivery customization, including non-standard OD/wall combinations, special alloy grades, custom coil geometries (multi-pass, layered, spiral), and application-specific surface finishes tailored to end-use requirements.
5. Research-Validated Performance: Coil tube performance in CSTR environments has been validated through academic research examining the interaction between coil geometry and impeller type on RTD, providing engineering confidence in thermal management and mixing performance for chemical process applications.
6. Wide Grade Availability: From standard