Stainless Steel Coil Tube (Coiltube) — Reference No. 1703
Product Overview
The Stainless Steel Coil Tube (Coiltube), Reference No. 1703, manufactured by Wenzhou Jixing Metal Materials Co., Ltd, is a precision-engineered tubular component designed primarily for intermittent evaporator systems and related thermal exchange applications. This product represents a specialized form of coiled stainless steel tubing that combines superior corrosion resistance, thermal conductivity, and mechanical durability in a continuous helical geometry. The coil tube is produced in accordance with international metallurgical standards and is engineered to withstand prolonged exposure to aggressive chemical media, elevated temperatures, and cyclic thermal loading conditions inherent in evaporator operations.
Unlike seamless straight tubing, the coil tube undergoes a cold-bending process that introduces controlled residual stresses while maintaining the integrity of the grain structure. This geometric configuration maximizes surface-area-to-volume ratio, thereby enhancing heat transfer efficiency within evaporator vessels and condensers. The product line encompasses a wide range of nominal diameters, wall thicknesses, and coil pitch configurations tailored to specific industrial requirements.
Material & Properties
The coil tubes are fabricated from austenitic and duplex stainless steel grades, selected based on the intended service environment. The primary material grades include:
- 304 (UNS S30408) — General-purpose austenitic stainless steel offering excellent corrosion resistance in non-chloride environments; composition: 18–20% Cr, 8–10.5% Ni, <0.08% C.
- 316 (UNS S31608) — Molybdenum-enhanced austenitic grade providing superior resistance to pitting and crevice corrosion in chloride-containing media; composition: 16–18% Cr, 10–14% Ni, 2–3% Mo.
- 316L (UNS S31603) — Low-carbon variant of 316 with <0.03% C, ideal for welding-intensive applications to prevent intergranular corrosion.
- 321 (UNS S32100) — Titanium-stabilized austenitic grade suitable for high-temperature service up to 870°C.
- 904L (UNS N08904) — High-alloy austenitic grade with 20% Ni, 4.3% Mo, and 1.5% Cu for extreme corrosive environments.
- Duplex 2205 (UNS S31803) — Duplex phase (austenitic-ferritic) stainless steel offering approximately 2× the yield strength of 304/316 with excellent chloride stress corrosion cracking resistance.
Key Mechanical Properties (Typical for Grade 316L Annealed)
- Tensile Strength (Rm): 485–720 MPa (70–104 ksi)
- Yield Strength (Rp0.2): 205 MPa minimum (29.7 ksi)
- Elongation (A50mm): ≥35%
- Hardness (HBW): ≤210
- Density: 8.0 g/cm³
- Thermal Conductivity (20°C): 16.3 W/(m·K)
- Specific Heat (20°C): 500 J/(kg·K)
- Thermal Expansion Coefficient (20–100°C): 16.0 × 10⁻⁶/K
Specifications
| Parameter | Specification / Range | Standard / Reference |
|---|---|---|
| Product Designation | Coiltube (Stainless Steel Coil Tube) | — |
| Reference No. | 1703 | Internal Catalog |
| Nominal Outer Diameter (OD) | 6.0 mm – 108.0 mm (¼" – 4") | ASTM A213 / ASTM A269 |
| Wall Thickness (WT) | 0.5 mm – 6.0 mm (0.020" – 0.236") | ASTM A213 / EN 10216 |
| Coil Diameter (CD) | 100 mm – 2000 mm (4" – 80") | Custom / Customer-Specified |
| Coil Pitch (P) | 15 mm – 150 mm (adjustable) | Custom / Customer-Specified |
| Tube Length (Straight Equivalent) | 3 m – 30 m per coil | — |
| Surface Finish | Mirror Polished (Ra ≤ 0.4 μm), Commercial Pickled (Ra ≤ 1.6 μm), or Brushed | ASTM A478 |
| End Condition | Plain, Beveled, or Threaded (per ASME B1.20.1) | ASME B1.20.1 |
| Manufacturing Method | Cold-Drawn Seamless (CDW) or Welded (ERW/AW) | ASTM A213 / ASTM A269 |
| Maximum Operating Temperature | −196°C to 870°C (Grade-dependent) | — |
| Maximum Operating Pressure | Up to 42 MPa (6000 psi), grade and WT dependent | ASME Section VIII |
| Corrosion Resistance | Equivalent to or exceeding parent material grade | ASTM G48 (Pitting) / ASTM G150 (Crevice) |
| Packaging | Wooden crates with moisture-proof wrapping, or export-standard steel banding | ISO 4180 (Handling) |
Manufacturing Process
The production of the Stainless Steel Coil Tube involves a multi-stage process combining seamless tube fabrication with precision cold-forming techniques:
- Raw Material Preparation: High-purity stainless steel billets or continuous casting slabs are sourced from certified steel mills. Incoming materials undergo strict spectrographic analysis (OES) to verify chemical composition within specified tolerance ranges.
- Seamless Tube Forming (for CDW grade): Billets are heated to 1100–1200°C and pierced through a rotary piercing mill to form hollow tubes. Alternatively, for smaller diameters, the capstan or Mannesmann process may be employed. The resulting tube blank is then cold-drawn through a series of progressively smaller dies to achieve final dimensional tolerances.
- Welded Tube Forming (for ERW/AW grade): Cold-rolled stainless steel strip is slit, edge-trimmed, and fed into a roll-forming station where it is shaped into a tube profile. The longitudinal seam is welded using either Electric Resistance Welding (ERW) or Automatic Welding (AW), followed by internal and external weld bead grinding to achieve a smooth interior surface.
- Solution Annealing: The formed tubes are solution-annealed at 1050–1150°C (grade-dependent) in a protective atmosphere or vacuum to dissolve carbide precipitates, restore full austenitic structure, and achieve the required mechanical and corrosion properties.
- Pickling and Passivation: Post-annealing tubes undergo acid pickling (HNO₃/HF mixture) to remove oxide scale, followed by nitric acid passivation to establish a stable chromium oxide passive film on the surface.
- Cold Coil Bending: The straight tubes are fed into a CNC-controlled coil bending machine equipped with precision mandrels and forming rollers. The bending process is performed at ambient temperature with controlled bend radii (typically R ≥ 3D, where D is the tube OD) to prevent ovalization, wrinkling, or wall thinning. Real-time force monitoring ensures uniform residual stress distribution.
- Post-Bend Stress Relief (Optional): For applications requiring minimal residual stress, the coiled tubes may undergo low-temperature stress relief at 300–400°C.
- Quality Inspection: Each coil undergoes ultrasonic testing (UT) per ASTM E1270, hydrostatic pressure testing per ASTM A213 (minimum 1.5× design pressure), dimensional verification via optical or laser measurement, and visual surface inspection.
- Final Surface Treatment: Tubes requiring mirror finish undergo mechanical polishing followed by electrolytic polishing (EP) to achieve Ra ≤ 0.4 μm surface roughness.
Applications
The Stainless Steel Coil Tube (Ref. No. 1703) is specifically engineered for the following industrial applications:
- Intermittent Evaporators: The primary design application. The helical coil geometry provides efficient heat transfer in batch evaporation processes used in pharmaceutical, food processing, and chemical industries. The coil tube serves as the heating medium channel within evaporator vessels, facilitating uniform heat distribution during intermittent (batch) operation cycles.
- Industrial Heat Exchangers: Spiral coil configurations used in shell-and-coil heat exchangers for process cooling and heating duties.
- Refrigeration and Air Conditioning Systems: Evaporator and condenser coils for commercial refrigeration units, chiller systems, and HVAC applications.
- Chemical Processing: Reactor jacket coils, distillation column internals, and heat transfer elements in corrosive chemical environments.
- Food and Beverage Industry: Pasteurization equipment, sterilization units, and CIP (Clean-In-Place) compatible heat transfer coils in dairy, beverage, and pharmaceutical processing.
- Power Generation: Auxiliary heat recovery coils in boiler systems and waste heat recovery units.
- Marine and Offshore: Seawater-cooled heat exchange coils in marine propulsion systems and offshore platform utilities.
Quality Certifications
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 operations.
- ISO 14001:2015 — Environmental Management System certification.
- ISO 45001:2018 — Occupational Health and Safety Management System certification.
- EN 10204 3.1 Certificate — Full material certification with independent third-party inspection available upon request.
- ASME Stamp (where applicable) — Pressure vessel component certification for ASME Section VIII Div. 1 applications.
- NADCAP (where applicable) — Special process certification for aerospace-grade manufacturing.
- CE Marking — Conformity with European Pressure Equipment Directive (PED 2014/68/EU) and Machinery Directive.
- Material Traceability: Full heat-number traceability from raw steel mill certificates through all manufacturing stages, maintained in a digital quality management system.
Unique Selling Points
1. Precision Coil Geometry: CNC-controlled cold bending ensures dimensional accuracy within ±0.5 mm tolerance on coil diameter and pitch, enabling seamless integration into evaporator vessel designs without secondary machining.
2. Multi-Grade Availability: Sixteen stainless steel grades available, spanning from standard austenitic (304, 316, 316L) to high-performance duplex (2205, 2507) and super-austenitic (904L, AL-6XN) alloys, providing engineering flexibility for any service environment.
3. Superior Surface Quality: Electrolytic polishing capability achieving Ra ≤ 0.2 μm surface roughness, critical for sanitary and pharmaceutical applications where product contact surfaces must be free of contamination-holding crevices.
4. Full Traceability and Certification: Every coil is accompanied by a comprehensive quality dossier including mill test certificates, dimensional reports, NDT records, and chemical analysis, ensuring full regulatory compliance.
5. Custom Engineering Support: Technical design assistance for coil configuration optimization, including heat transfer calculations, pressure rating verification, and vibration analysis for evaporator system integration.
Technical Literature Reference
The development and optimization of this coil tube product line is informed by extensive academic and industry literature, including the "Intermittent Evaporator Coiltube Bibliography" (Reference No. 1703), which compiles critical research on heat transfer performance, corrosion behavior, and mechanical fatigue characteristics of coiled stainless steel tubing in intermittent evaporation service. This bibliographic resource serves as the technical foundation for material selection, geometric optimization, and performance validation of the Coiltube product line.