Stainless Steel Coil Tube (Coiltube) — Technical Specification
1. Product Overview
The Stainless Steel Coil Tube (Coiltube) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a continuous-length tubular product formed by cold-drawing or cold-rolling seamless stainless steel tubes into a helical coil configuration. This product is specifically engineered for large-scale industrial applications including ventilation systems, hydronic floor heating (underfloor radiant heating), and HVAC (Heating, Ventilation, and Air Conditioning) networks within high-bay industrial facilities and commercial buildings.
The coil tube format offers significant advantages over traditional straight-length pipe segments, including reduced joint density, enhanced thermal conductivity efficiency, minimized pressure loss in fluid distribution systems, and superior flexibility for complex routing in large architectural structures. The application of Value Engineering (VE) methodology in the selection and optimization of coil tube configurations for ventilation and floor heating systems demonstrates measurable improvements in life-cycle cost performance, thermal efficiency, and structural reliability.
2. Material and Properties
2.1 Base Materials
The coil tubes are fabricated from austenitic stainless steel grades conforming to international standards, with the following primary material specifications:
- AISI 304 (UNS S30400 / 1.4301): The most widely used grade, containing approximately 18% Chromium (Cr) and 8% Nickel (Ni). Offers excellent general corrosion resistance, weldability, and formability. Suitable for non-chloride-containing environments.
- AISI 316 (UNS S31600 / 1.4401): Enhanced corrosion resistance due to the addition of 2–3% Molybdenum (Mo). Recommended for environments with chloride exposure, chemical processing, or coastal atmospheric conditions.
- AISI 321 (UNS S32100 / 1.4541): Stabilized with Titanium (Ti) to prevent intergranular corrosion during welding and high-temperature service (up to 870°C / 1600°F).
- AISI 316L (UNS S31603 / 1.4434): Low-carbon variant of 316 with carbon content ≤ 0.03%, providing superior weldability and resistance to sensitization.
2.2 Mechanical Properties
| Property | AISI 304 | AISI 316 | AISI 321 |
|---|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 515 | ≥ 515 |
| Yield Strength (0.2% Offset, MPa) | ≥ 205 | ≥ 205 | ≥ 205 |
| Elongation (%) | ≥ 40 | ≥ 40 | ≥ 40 |
| Hardness (HB max) | ≤ 217 | ≤ 217 | ≤ 217 |
| Density (g/cm³) | 8.00 | 8.03 | 8.00 |
| Thermal Conductivity at 100°C (W/m·K) | 16.3 | 16.3 | 16.3 |
| Maximum Service Temperature (°C) | 870 | 870 | 900 |
2.3 Surface Finish Options
- 2B Finish: Cold-rolled, annealed, and slightly pickled. Smooth, non-directional matte surface. Suitable for general industrial use.
- No. 4 Brushed Finish: Fine linear grain pattern. Aesthetic appeal for architectural and commercial installations.
- BA (Bright Annealed) Finish: Mirror-like reflective surface achieved through annealing in a controlled atmosphere. Ideal for food processing and pharmaceutical applications.
- Pickled and Passivated: Removal of scale and oxide layers followed by passivation treatment to restore maximum corrosion resistance.
3. Specifications
| Parameter | Specification / Range |
|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd. |
| Product Catalog No. | 1097 |
| Tube Type | Seamless / Welded Coil Tube |
| Outer Diameter (OD) | 6.0 mm – 50.8 mm (¼" – 2") |
| Wall Thickness | 0.5 mm – 3.0 mm |
| Coil Diameter | 300 mm – 1500 mm (adjustable per order) |
| Coil Length | 100 m – 1000 m (continuous) |
| Applicable Standards | ASTM A213 / A269, EN 10216-5, GB/T 12771, GB/T 14976 |
| Tolerance on OD | ± 0.1 mm (standard); ± 0.05 mm (precision) |
| Tolerance on Wall Thickness | ± 10% (standard); ± 5% (precision) |
| Roundness | ≤ 0.1% of OD |
| End Condition | Plain cut / Beveled / Threaded (optional) |
| Packaging | Wooden pallet with moisture-proof wrapping; custom packaging available |
| Minimum Order Quantity | Negotiable based on specification |
4. Manufacturing Process
The production of stainless steel coil tubes at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous multi-stage manufacturing process designed to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection: Hot-rolled stainless steel bars or slabs are procured from certified mills and subjected to incoming inspection including Chemical Composition Analysis (CCA) and mechanical property verification.
- Hot Rolling / Extrusion: Billets are heated to forging temperature (1150°C – 1250°C) and formed into seamless tube blanks via piercing or extrusion methods.
- Cold Drawing / Cold Rolling: Tube blanks are cold-worked to achieve precise dimensional tolerances and enhanced mechanical properties. Multiple passes through calibrated dies ensure consistent wall thickness and roundness.
- Solution Annealing: Tubes are heated to 1050°C – 1150°C and rapidly quenched to dissolve carbides and restore full austenitic microstructure, maximizing corrosion resistance.
- Pickling and Passivation: Acid treatment removes scale and oxide films, followed by passivation to establish a protective chromium oxide layer on the surface.
- Coiling: Continuous-length tubes are wound onto precision mandrels to form coils of specified diameter. Tension control systems ensure uniform coil geometry without deformation or kinking.
- Non-Destructive Testing (NDT): Each coil undergoes ultrasonic testing (UT) for internal defects, eddy current testing (ECT) for surface discontinuities, and hydrostatic pressure testing (typically at 1.5× working pressure) for leak integrity.
- Final Inspection: Dimensional verification, surface finish assessment, and material certification documentation are completed prior to packaging and dispatch.
5. Applications
The stainless steel coil tube is engineered for demanding industrial and commercial applications, particularly in the following domains:
5.1 Large-Scale Industrial Ventilation Systems
Coil tubes serve as heat exchange elements in air handling units (AHUs), cooling coils, and heating coils within high-bay industrial facilities. The continuous coil configuration minimizes connection points, reducing leakage potential and maintenance requirements in large-volume ventilation networks.
5.2 Underfloor Radiant Heating (Floor Heating Coil Systems)
In hydronic underfloor heating systems, stainless steel coil tubes are embedded within concrete slabs or screed layers to provide uniform radiant heat distribution. The high thermal conductivity and corrosion resistance of austenitic stainless steel ensure long-term reliability in wet concrete environments where carbon steel alternatives would suffer from galvanic corrosion.
5.3 Additional Application Areas
- Chemical and Petrochemical Processing: Heat exchangers, condensers, and process piping where resistance to aggressive media is required.
- Food and Beverage Industry: Sanitary piping systems, pasteurization equipment, and dairy processing lines requiring hygienic-grade materials.
- Pharmaceutical Manufacturing: Clean-room piping and heat exchange systems compliant with GMP (Good Manufacturing Practice) standards.
- Power Generation: Boiler tubes, superheaters, and economizers in thermal power plants.
- Architectural and Structural Applications: Decorative railings, handrails, and structural tubing in commercial and residential construction.
- Automotive and Aerospace: Exhaust systems, fuel lines, and hydraulic tubing requiring high-temperature and high-pressure resistance.
6. Quality Certifications and Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure product consistency and traceability:
- ISO 9001:2015 — Quality Management System certification demonstrating adherence to international quality management principles.
- ISO 14001:2015 — Environmental Management System certification confirming responsible environmental practices throughout the production lifecycle.
- EN 10204 3.1 — Third-party inspection certificate for material testing and conformity verification.
- ASTM A213 / A269 — Conformance to American Society for Testing and Materials standards for seamless and welded austenitic stainless steel tubing.
- GB/T 12771 — Chinese national standard for welded stainless steel tubing for fluid transport.
- GB/T 14976 — Chinese national standard for seamless stainless steel tubing for general engineering purposes.
- PED (Pressure Equipment Directive 2014/68/EU) — Conformity assessment for pressure equipment applications where applicable.
- Mill Test Certificates (MTC) — Full chemical composition and mechanical property documentation provided with each shipment.
7. Unique Selling Points
7.1 Value Engineering Integration
The product development and application engineering process incorporates Value Engineering (VE) methodology, which systematically optimizes the function-to-cost ratio of coil tube solutions for specific project requirements. This approach ensures that ventilation and floor heating coil tube configurations deliver maximum performance value, minimizing total cost of ownership (TCO) while maintaining or exceeding functional requirements. VE-driven design considerations include optimal coil pitch selection, material grade rationalization, and system-level thermal performance optimization.
7.2 Superior Corrosion and Thermal Performance
The austenitic stainless steel microstructure provides inherent resistance to pitting, crevice, and intergranular corrosion, significantly extending service life in aggressive environments compared to carbon steel alternatives. The stable thermal conductivity across a wide temperature range ensures consistent heat transfer performance throughout the operational lifecycle of heating and ventilation systems.
7.3 Continuous Coil Configuration Advantages
- Reduction of up to 90% in mechanical joints compared to segmented pipe installations, minimizing potential failure points.
- Streamlined installation with reduced labor hours and lower assembly costs in large-scale projects.
- Enhanced hydraulic efficiency due to fewer connection losses in fluid distribution networks.
- Improved structural integrity and resistance to thermal cycling fatigue.
7.4 Customization and Engineering Support
Wenzhou Jixing Metal Materials Co., Ltd. offers comprehensive customization services including tailored coil dimensions, specialized surface finishes, custom end treatments, and project-specific engineering consultation. Technical support extends to Value Engineering analysis for optimal system design in industrial ventilation and floor heating applications.
7.5 Traceability and Documentation
Each production batch maintains full material traceability from raw material certification through final product dispatch. Comprehensive documentation packages including Mill Test Certificates, dimensional inspection reports, and non-destructive testing results are provided to support client quality assurance and regulatory compliance requirements.
8. Technical Notes
Installation Guidance: When deploying stainless steel coil tubes in underfloor heating systems, maintain a minimum bend radius of 5× the tube OD to prevent kinking or wall thinning. Ensure proper insulation and protection of coil tubes during concrete pouring operations. For ventilation coil applications, verify that coil pitch spacing conforms to manufacturer-recommended heat transfer optimization parameters for the specific air velocity and temperature differential conditions.
Welding Considerations: When field welding coil tube segments, use stainless steel-specific welding consumables (e.g., ER308L for AISI 304, ER316L for AISI 316) with argon gas shielding. Post-weld passivation treatment is recommended to restore corrosion resistance in the heat-affected zone (HAZ).