Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered tubular product formed by continuously winding high-grade stainless steel tubing into a compact helical coil configuration. This product category is designed to deliver superior heat transfer efficiency, fluid distribution uniformity, and mechanical durability in demanding process engineering applications.
The coil tube geometry offers a remarkably high surface-area-to-volume ratio, making it exceptionally well-suited for applications requiring intensive thermal exchange, chemical reaction facilitation, and continuous fluid processing. Notably, coil tube configurations have been extensively validated in environmental biotechnology — particularly in coil-type bioreactors (Coil-Type Bioreactors, CTBRs) — where they demonstrate sustained denitrification performance for low-pollution water treatment and support stable microbial community structures essential for biological nutrient removal processes.
2. Material & Properties
2.1 Available Grades
- AISI 304 (UNS S30400) — General-purpose austenitic stainless steel with excellent corrosion resistance and formability; chromium content 18–20%, nickel content 8–10.5%.
- AISI 316 (UNS S31600) — Enhanced corrosion resistance due to 2–3% molybdenum addition; ideal for chlorinated environments and aggressive chemical media.
- AISI 316L (UNS S31603) — Low-carbon variant of 316 (carbon ≤ 0.03%) providing superior resistance to intergranular corrosion after welding.
- AISI 321 (UNS S32100) — Titanium-stabilized austenitic grade offering excellent resistance to stress corrosion cracking at elevated temperatures.
- AISI 304L (UNS S30403) — Low-carbon variant of 304 with improved weldability and resistance to sensitization.
2.2 Key Mechanical & Physical Properties
- Tensile Strength: 515–720 MPa (depending on grade and cold-work degree)
- Yield Strength: 205–310 MPa
- Elongation: ≥ 40% (as-annealed condition)
- Thermal Conductivity: 14.9–16.3 W/(m·K) at 20 °C
- Thermal Expansion Coefficient: 16–18 × 10⁻⁶ /K (20–100 °C)
- Operating Temperature Range: −196 °C to +870 °C (304); −196 °C to +870 °C (316)
- Corrosion Potential (Ecorr): −0.1 to −0.4 V vs. SCE in neutral aqueous environments
- Surface Finish: 2B (cold-rolled), BA (Bright Annealed), No. 4 Brushed, or custom matte/polished finishes
3. Specifications
| Parameter | Specification Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | Φ3.0 mm – Φ50.8 mm | ASTM A269 / EN 10217 |
| Wall Thickness (WT) | 0.3 mm – 3.0 mm | ASTM A269 / EN 10217 |
| Inner Diameter (ID) | Φ2.0 mm – Φ46.8 mm | — |
| Coil Diameter (CD) | Φ50 mm – Φ600 mm (standard); custom available | — |
| Coil Length | 1 m – 50 m per coil assembly | — |
| Coil Pitch (Turn-to-Turn Spacing) | 0.5 mm – 10 mm (configurable) | — |
| Number of Turns | Up to 5,000+ turns (custom winding) | — |
| Diameter Tolerance | ±0.1 mm (OD); ±0.05 mm (WT for precision grades) | ASTM A269 |
| Straightness | ≤ 0.5 mm/m (pre-coil tube stock) | EN 10217 |
| Surface Roughness (Ra) | 0.4 – 1.6 μm (2B finish); ≤ 0.2 μm (electropolished) | ASTM A269 / ISO 11120 |
| End Preparation | Plain, beveled, threaded, or custom-fitted | ASME B1.20.1 |
| Maximum Working Pressure | Up to 40 bar (depending on OD/WT ratio) | ASME B31.3 |
| Hydrostatic Test Pressure | 1.5× working pressure (minimum) | ASME B31.3 |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Selection & Inspection: Virgin stainless steel strip or seamless tube stock is sourced from certified mills and subjected to incoming quality control including spectral analysis (PMI), tensile testing, and chemical composition verification.
- Tube Forming: For smaller diameters, strip is cold-formed into seamless tubing via roll-forming or capillary drawing processes. For larger diameters, pre-manufactured seamless or welded (weld-seam-removed) tube stock is utilized.
- Heat Treatment (Annealing): Solution annealing at 1010–1150 °C followed by controlled air cooling or water quenching to achieve the desired austenitic microstructure and maximize corrosion resistance.
- Precision Coiling: The annealed tubing is wound onto precision CNC-controlled coiling machines using computerized pitch control systems. The coiling process ensures consistent turn-to-turn spacing, uniform curvature, and minimal mechanical stress introduction. The winding mandrel diameter is carefully selected to prevent ovalization and maintain dimensional accuracy.
- Surface Finishing: Post-coiling surface treatment may include pickling and passivation (acid cleaning to remove oxide scale and establish passive chromium oxide layer), mechanical polishing, or electropolishing for ultra-low surface roughness applications.
- Quality Inspection & Testing: Each coil undergoes dimensional verification (OD, WT, coil diameter, pitch), visual inspection, and pressure testing. Non-destructive testing (NDT) methods such as eddy current testing and ultrasonic testing may be applied to verify wall integrity.
- Packaging & Shipping: Coils are protected with moisture-barrier packaging, wooden crating, or shrink-wrapped on protective reels to prevent mechanical damage and atmospheric exposure during transit.
4.2 Process Advantages
- Computerized CNC coiling ensures repeatable precision with ±0.1 mm dimensional consistency across production batches.
- Continuous coiling eliminates weld joints along the coil body, providing a seamless, leak-free fluid pathway.
- Post-coiling pickling and passivation restores full corrosion resistance regardless of heat input during forming.
5. Applications
5.1 Environmental & Water Treatment Engineering
- Coil-Type Bioreactors (CTBR): Stainless steel coil tubes are employed as reactor vessels for biological nutrient removal processes. Research has demonstrated that coil-type bioreactors utilizing stainless steel coil tubing achieve sustained denitrification performance for low-pollution water, supporting diverse and stable microbial community structures essential for efficient nitrogen cycling (denitrification pathway: NO₃⁻ → NO₂⁻ → NO → N₂O → N₂). The helical geometry promotes optimal gas-liquid mass transfer, enhanced mixing, and biofilm development on the tube inner surface.
- Constructed Wetland Systems: Coil tubes serve as subsurface flow media for constructed wetlands, providing high surface area for biofilm attachment and pollutant degradation.
- Membrane Bioreactors (MBR): Used as sparger tubes and distribution manifolds for aeration and permeate collection.
5.2 Process Heat Transfer
- Heat Exchangers & Coolers: The high surface-area-to-volume ratio of coil geometry maximizes heat transfer coefficients; stainless steel coil tubes are integral components of shell-and-coil heat exchangers, plate-fin heat exchangers, and immersion coolers.
- Refrigeration & HVAC Systems: Evaporator and condenser coils for industrial refrigeration, chiller systems, and heat pump applications.
- Chemical Process Cooling/Heating: Internal coil jackets for reactor temperature control in pharmaceutical and fine chemical manufacturing.
5.3 Chemical & Pharmaceutical Processing
- Reactor Coils: Continuous-flow microreactors and mesoreactors where coil geometry provides uniform residence time distribution and enhanced mass transfer.
- Catalytic Reactors: Packed-bed coil reactors for catalytic hydrogenation, oxidation, and synthesis reactions.
- Pharmaceutical Heat Exchange: GMP-compliant coil heat exchangers for sterile fluid processing, CIP (Clean-in-Place) and SIP (Sterilize-in-Place) applications.
5.4 Energy & Power Generation
- Boiler Tube Coils: Water-wall tubes and superheater coils in utility boilers and industrial steam generators.
- Geothermal Heat Exchangers: Subsurface coil heat exchangers for closed-loop geothermal energy extraction systems.
- Solar Thermal Collectors: Absorber tubes in evacuated tube solar collectors.
5.5 Food & Beverage Processing
- Pasteurization & UHT Systems: Tubular heat exchangers for milk, juice, and beverage pasteurization using 316L stainless steel coil configurations.
- Cooling & Conditioning: Rapid cooling coils for dairy products, sauces, and ready-to-eat food products.
6. Quality Certifications & Compliance
6.1 Product Certifications
- ISO 9001:2015 — Quality Management System certification for manufacturing processes.
- ISO 14001:2015 — Environmental Management System certification.
- ISO 45001:2018 — Occupational Health and Safety Management System.
- EN 10204 3.1 — Material Testing Certificate (third-party inspection).
- EN 10204 3.2 — Material Inspection Certificate (on request).
- ASTM A269 — Compliance for wrought austenitic stainless steel tube.
- EN 10217-7 — European standard for austenitic stainless steel tubes for heat exchangers.
- GB/T 12771 — Chinese national standard for stainless steel seamless tubes for general purposes.
6.2 Industry-Specific Compliance
- ASME BPE (Bioprocessing Equipment) — For pharmaceutical and biotechnology applications requiring sanitary-grade tubing.
- 3-A Sanitary Standards — For food-grade applications.
- NSF/ANSI 61 — Drinking water system components certification.
- PED 2014/68/EU — Pressure Equipment Directive compliance for pressure-vessel applications.
- CE Marking — European conformity marking for applicable product categories.
6.3 Testing & Verification Protocols
- Hydrostatic pressure testing per ASME B31.3 or EN 13480 standards.
- Positive Material Identification (PMI) via optical emission spectrometry (OES) or X-ray fluorescence (XRF).
- Corrosion testing including salt spray testing (ASTM B117), intergranular corrosion testing (ASTM A262 Practice E), and stress corrosion cracking testing.
- Dimensional verification using laser scanning, caliper measurement, and ultrasonic wall thickness gauging.
7. Unique Selling Points
High Surface-Area Efficiency: The helical coil geometry delivers up to 3× greater heat transfer surface area per unit volume compared to straight-tube configurations, enabling compact, high-performance thermal systems.
Seamless Continuous Pathway: Continuous coiling without intermediate welds eliminates potential leak points and contamination vectors — critical for pharmaceutical, food, and water treatment applications requiring high purity and integrity.
Validated Bioreactor Performance: Stainless steel coil tubing configurations have been scientifically validated for sustained biological denitrification in low-pollution water treatment scenarios, supporting robust and diverse microbial community structures essential for long-term bioreactor stability.
Custom Engineering Capability: Wenzhou Jixing Metal Materials Co., Ltd. offers fully customizable coil dimensions — including coil diameter, pitch, number of turns, and tube geometry — to meet project-specific thermal, hydraulic, and spatial requirements.
Multi-Grade Material Availability: Comprehensive grade selection from 304 to 316L and specialty alloys ensures optimal material matching for diverse chemical environments, temperature ranges, and regulatory requirements.
Full Traceability & Certification: Every production batch is accompanied by complete material traceability documentation, third-party test certificates, and compliance with international standards (ASTM, EN, ISO, GB), ensuring seamless integration into global engineering supply chains.