Stainless Steel Coil Tube (Coiltube) — Intermittent Working Coil Heat Exchanger Series
Manufactured by Wenzhou Jixing Metal Materials Co., Ltd. (Product Ref. No. 1329), this stainless steel coil tube is specifically engineered for intermittent-duty coil-type heat exchanger applications. The product integrates precision cold-formed coiling technology with high-grade austenitic stainless steel materials to deliver superior thermal transfer efficiency, mechanical durability, and long-term corrosion resistance in cyclic thermal environments.
Product Overview
The Stainless Steel Coil Tube (Coiltube) is a continuous spiral-wound tubular component designed for use in intermittent operating heat exchangers. Unlike continuous-duty systems, intermittent heat exchangers experience repeated cycles of heating, cooling, and thermal standstill, imposing significant thermal fatigue stress on the coil structure. This product addresses these demanding conditions through optimized geometric parameters, material selection, and manufacturing tolerances that ensure reliable performance over extended service lifetimes.
The coil tube serves as the primary heat transfer element within shell-and-coil or double-pipe configurations, facilitating efficient thermal exchange between working fluids under non-steady-state conditions. Its helical geometry maximizes surface area within a compact envelope while promoting turbulent flow characteristics that enhance convective heat transfer coefficients.
Material & Properties
The coil tube is fabricated from premium-grade austenitic stainless steel, selected for its exceptional combination of corrosion resistance, thermal stability, and mechanical integrity under cyclic loading conditions.
- Base Alloy Grades: AISI 304 (UNS S30400), AISI 316 (UNS S31600), AISI 321 (UNS S32100), and AISI 316L (UNS S31603) — available upon specification.
- Corrosion Resistance: Chromium (Cr) content of 18–22% provides a passive oxide layer that resists pitting, crevice corrosion, and general chemical attack. Molybdenum (Mo) additions in 316/316L grades enhance resistance to chlorides and acidic media.
- Thermal Stability: Maintains mechanical properties across operating temperatures ranging from −196°C (−320°F) to +870°C (+1600°F), with no risk of embrittlement during thermal cycling.
- Mechanical Properties: Yield strength of 205–310 MPa (30–45 ksi) with elongation of 40–60%, providing adequate ductility to absorb thermal expansion stresses without fatigue failure.
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20°C, balancing thermal transfer capability with the inherent insulating properties of austenitic structures.
- Hygienic Surface Finish: Available in 2B, No. 4 brushed, or electropolished (Ra ≤ 0.5 μm) finishes to minimize fouling and facilitate CIP (Clean-In-Place) procedures.
Specifications
| Parameter | Specification Range | Unit | Notes |
|---|---|---|---|
| Outer Diameter (OD) | 6.0 – 50.8 | mm | Standard increments of 0.5 mm |
| Wall Thickness (WT) | 0.5 – 3.0 | mm | Tolerance ±10% per ASME B31.3 |
| Coil Pitch | 10 – 150 | mm | Optimized for flow velocity & ΔP |
| Coil Diameter (Center-to-Center) | 100 – 2000 | mm | Custom configurations available |
| Number of Turns | 5 – 500+ | turns | Determined by heat duty requirement |
| Total Tube Length | 10 – 500 | m | Continuous coil, no welded joints |
| Operating Pressure | 0.1 – 6.0 | MPa | Hydrostatic test at 1.5× working pressure |
| Operating Temperature | -196 to +870 | °C | Material-dependent range |
| Thermal Cycling Endurance | ≥ 50,000 | cycles | Intermittent duty fatigue life |
| End Connections | Welded, Flanged, Threaded, or Sanitary Tri-Clamp | — | Customizable per application |
| Surface Roughness (Ra) | 0.5 – 2.0 | μm | Electropolished for hygienic service |
| Manufacturing Standard | ASTM A213 / A269 / ASME B31.3 / EN 10216-5 | — | Multi-standard compliance |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorously controlled process chain that ensures dimensional accuracy, metallurgical integrity, and consistent performance characteristics:
- Raw Material Procurement & Inspection: Stainless steel strip or wire is sourced from certified mills with full chemical composition analysis (spectrometric verification) and mechanical property testing per ASTM standards. Each batch is traceable through heat number documentation.
- Surface Preparation & Cleaning: Incoming material undergoes degreasing, descaling, and pickling to remove mill scale and contaminants. Passivation treatment (citric acid or nitric acid-based) establishes the initial chromium oxide passive layer.
- Precision Coiling (Cold-Formed Spiral Winding): A CNC-controlled coiling machine winds the tube into a precise helical geometry with computerized control of pitch, diameter, and turn count. This process maintains metallurgical integrity without the need for post-forming annealing, preserving the cold-work hardening benefits.
- Support Wire & Spacer Installation: Internal helical support wires or external spacer rings are installed at calculated intervals to prevent coil-to-coil contact, maintain uniform flow distribution, and absorb differential thermal expansion between adjacent turns.
- End Sealing & Connection Fabrication: Tube ends are prepared for the specified connection type — orbital TIG (Tungsten Inert Gas) welding for seamless joints, flange attachment with precision machining, or sanitary tri-clamp fitting installation.
- Post-Weld Heat Treatment (if applicable): For applications requiring stress relief or sensitization avoidance, controlled solution annealing at 1050–1100°C with rapid water quenching may be performed, followed by re-passivation.
- Quality Control & Testing: Comprehensive inspection includes dimensional verification (CMM measurement), hydrostatic pressure testing, visual and penetrant testing of welds (per ASME Section V), and optional eddy current examination for wall thickness uniformity.
- Final Cleaning & Packaging: Completed coils undergo final acid washing and passivation, followed by protective packaging suitable for transport and long-term storage without atmospheric corrosion.
Applications
The intermittent working coil tube heat exchanger finds extensive deployment across multiple industrial sectors where cyclic thermal operation is inherent to the process:
- Food & Beverage Processing: Batch pasteurization systems, milk cooling loops, beer fermentation temperature control, and intermittent heating of viscous food products (honey, syrups, chocolate).
- Pharmaceutical Manufacturing: Batch reactors, sterilization-in-place (SIP) systems, clean steam generation, and process water conditioning under GMP (Good Manufacturing Practice) requirements.
- Chemical Processing: Intermittent reactor cooling, batch distillation condensers, and chemical synthesis temperature regulation where thermal cycling is unavoidable.
- Waste Heat Recovery: Intermittent industrial furnace heat recovery, kiln exhaust gas cooling, and batch-process thermal energy storage systems.
- Biotechnology & Fermentation: Bioreactor jacket cooling, seed tank temperature management, and downstream processing purification circuits.
- Marine & Offshore: Auxiliary engine cooling, ballast water treatment systems, and intermittent marine heating circuits.
- Environmental & Water Treatment: Batch-type wastewater heat recovery, condensate polishing, and thermal disinfection systems.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework ensuring product conformity with international standards:
- ISO 9001:2015 — Quality Management System certification covering all manufacturing, inspection, and documentation processes.
- ISO 14001:2015 — Environmental Management System certification for sustainable manufacturing practices.
- ISO 45001:2018 — Occupational Health and Safety Management System.
- CE Marking (EU) — Conformity with European Pressure Equipment Directive (PED 2014/68/EU) and Machinery Directive.
- ASME "U" Stamp — Authorization for fabrication of pressure-containing components per ASME Boiler and Pressure Vessel Code.
- 3-A Sanitary Standards — Compliance for food and pharmaceutical processing equipment.
- NSF/ANSI 61 — Drinking water system components certification.
- Material Traceability: Full heat-number traceability from mill certificate through final product, with third-party inspection (TPI) available upon request.
Unique Selling Points
Engineered for Intermittent Duty Excellence: Unlike standard continuous-duty coil tubes, this product is specifically parameter-optimized for thermal cycling environments. Advanced fatigue analysis and computational fluid dynamics (CFD) modeling inform the geometric design to minimize thermal stress concentration at coil terminations and support interfaces.
- Zero-Weld Continuous Spiral Construction: The single-piece coiled design eliminates longitudinal weld seams that serve as potential fatigue crack initiation sites, significantly extending service life under cyclic loading.
- Parametric Design Optimization: Each coil tube is engineered based on specific heat duty parameters — including flow rate, inlet/outlet temperatures, allowable pressure drop (ΔP), and cycle frequency — ensuring optimal thermal performance for the exact application.
- Corrosion-Resistant Alloy Flexibility: Material selection from 304 to 316L to duplex grades accommodates aggressive chemical environments, extending applicable service scope beyond conventional stainless steel limitations.
- Hygienic & Cleanability: Electropolished internal surfaces with Ra ≤ 0.5 μm eliminate dead zones and biofilm harborage points, meeting the most stringent pharmaceutical and food-grade requirements.
- Full Traceability & Third-Party Verification: Complete documentation chain from raw material certification through final hydrostatic testing, with optional independent inspection by SGS, BV, or TUV.
- Custom Engineering Support: Dedicated engineering team provides thermal simulation, CFD analysis, and detailed design documentation tailored to customer-specific process requirements.
Technical Notes
Thermal Fatigue Considerations: In intermittent operating modes, the coil tube experiences repeated thermal expansion and contraction. The design incorporates sufficient coil pitch clearance (minimum 1.5× wall thickness) and flexible support structures to accommodate differential movement without inducing plastic deformation at stress concentration points.
Flow Distribution: The helical geometry naturally promotes secondary Dean flow vortices that enhance turbulent mixing, resulting in heat transfer coefficients 20–40% higher than equivalent straight-tube configurations. This advantage is particularly pronounced at the lower Reynolds numbers typical of intermittent batch operations.
Maintenance & Inspection: The modular coil design permits removal for periodic internal inspection, descaling, and hydrostatic retesting without system disassembly, minimizing downtime in production-critical applications.
For detailed engineering specifications, material test certificates, and custom quotation inquiries, contact Wenzhou Jixing Metal Materials Co., Ltd. directly. All products are manufactured to order with lead times commensurate with complexity and material availability.