Stainless Steel Coil Tube — Product Technical Specification
Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
Product Category: Stainless Steel Coil Tube (Coil Tube / Coil Tubing)
Reference Document: Analysis of Heat Load Bearing Rate of Fan Coil Units and Floor Heating Terminals for Residential Heating
1. Product Overview
The Stainless Steel Coil Tube is a precision-engineered tubular product supplied in continuous coil form, designed for high-efficiency thermal transfer applications in residential and commercial HVAC (Heating, Ventilation, and Air Conditioning) systems. This product serves as a critical component in fan coil units (FCUs) and hydronic radiant floor heating terminal systems, where it functions as the primary heat exchanger medium, transferring thermal energy between the circulating fluid and the conditioned space.
Coil tubes are manufactured in continuous lengths wound onto spools, eliminating the need for field welding and minimizing joint-related failure points. The stainless steel construction provides superior corrosion resistance, long service life, and hygienic properties that make it ideal for closed-loop hydronic heating and cooling circuits.
2. Material & Properties
2.1 Base Material Grades
- ASTM A269 / A270 Type 304 (UNS S30408): Austenitic stainless steel with excellent general corrosion resistance and formability. Suitable for standard hydronic heating applications.
- ASTM A269 / A270 Type 316 (UNS S31603): Austenitic stainless steel with enhanced pitting and crevice corrosion resistance due to molybdenum addition (2.0–3.0% Mo). Recommended for aggressive water chemistry environments.
- ASTM A269 Type 316L (UNS S31603): Low-carbon variant of 316 grade, optimized for welding applications requiring reduced risk of intergranular corrosion.
2.2 Mechanical Properties
| Property | Type 304 (A269) | Type 316 (A269) |
|---|---|---|
| Tensile Strength (MPa) | ≥ 515 | ≥ 515 |
| Yield Strength (0.2% Offset, MPa) | ≥ 205 | ≥ 205 |
| Elongation (% at Break) | ≥ 40 | ≥ 40 |
| Hardness (HRB) | ≤ 92 | ≤ 92 |
| Density (g/cm³) | 8.00 | 8.00 |
| Thermal Conductivity at 100°C (W/m·K) | 16.3 | 14.6 |
2.3 Chemical Composition (Maximum, unless noted)
| Element | Type 304 | Type 316 |
|---|---|---|
| Carbon (C) | ≤ 0.08 | ≤ 0.08 |
| Chromium (Cr) | 18.0 – 20.0 | 16.0 – 18.0 |
| Nickel (Ni) | 8.0 – 10.5 | 10.0 – 14.0 |
| Molybdenum (Mo) | — | 2.0 – 3.0 |
| Iron (Fe) | Balance | Balance |
3. Specifications
| Parameter | Specification |
|---|---|
| Outer Diameter (OD) | 3.175 mm (⅛"), 6.35 mm (¼"), 9.525 mm (⅜"), 12.7 mm (½"), 15.88 mm (⅝"), 19.05 mm (¾") |
| Wall Thickness | 0.30 mm – 1.50 mm (tolerance ±10%) |
| Coil Length per Spool | Standard: 50 m – 300 m; Custom lengths available upon request |
| Coil Inner Diameter (Spool) | 300 mm, 500 mm, or 600 mm |
| Surface Finish | Mirror polished (Ra ≤ 0.4 μm), Electropolished (Ra ≤ 0.2 μm), or Standard Pickled & Passivated |
| Operating Temperature Range | −40°C to +250°C (continuous service) |
| Maximum Operating Pressure | 1.6 MPa (PN16) standard; up to 4.0 MPa (PN40) for thickened-wall variants |
| Applicable Fluids | Water, glycol-water mixtures, district heating medium, low-pressure steam |
| Applicable Standards | ASTM A269, ASTM A270, EN 10216-5, GB/T 12771 |
| Packaging | Wooden spool with moisture-proof wrapping; export-grade crating available |
4. Manufacturing Process
The production of stainless steel coil tubes follows a rigorous multi-stage manufacturing sequence to ensure dimensional accuracy, surface integrity, and metallurgical homogeneity:
- Hot Rolling & Annealing: Raw stainless steel coil is hot-rolled to approximate dimensions, followed by solution annealing at 1050–1150°C to relieve residual stresses and establish austenitic microstructure.
- Piercing & Sizing: The coil is pierced into hollow tubes and cold-drawn through calibrated dies to achieve precise outer diameter and wall thickness tolerances.
- Intermediate Annealing: Multi-pass cold drawing is interspersed with intermediate annealing cycles (typically at 1050°C in protective atmosphere) to prevent work hardening and maintain ductility.
- Final Cold Drawing: The tube is drawn to final dimensions using tungsten carbide (WC) dies, achieving tight tolerances on OD (±0.05 mm) and wall thickness (±0.02 mm).
- Pickling & Passivation: Tubes are subjected to acid pickling (HNO₃/HF blend) to remove oxide scale, followed by nitric acid passivation to establish a protective chromium oxide film.
- Surface Finishing: Electropolishing or mechanical mirror polishing is applied where required, achieving surface roughness as low as Ra 0.2 μm for hygienic and aesthetic applications.
- Hydrostatic Testing: Each coil length is pressure-tested at 1.5× the maximum service pressure to verify weld integrity and absence of porosity.
- Coiling & Packaging: The finished tube is wound onto precision spools, secured with steel straps, and packaged for transport.
5. Applications
5.1 Residential & Commercial HVAC Systems
- Fan Coil Units (FCUs): Coil tubes serve as the heat exchange element in FCUs, transferring heat from hot water or chilled water to the air stream. The continuous coil design enables compact serpentine arrangements with high surface-area-to-volume ratios, maximizing heat transfer efficiency.
- Hydronic Radiant Floor Heating: Stainless steel coil tubes are embedded within concrete or screed layers to distribute heat uniformly across floor surfaces. The corrosion resistance of stainless steel ensures decades of service without degradation.
- District Heating Distribution: Coil tubes are used in secondary loop distribution systems connecting district heating networks to individual building terminal units.
5.2 Industrial Applications
- Heat exchangers and condensers in process industries
- Refrigeration and air conditioning evaporator coils
- Food and pharmaceutical processing equipment (hygienic-grade electropolished variants)
- Chemical processing heat transfer systems (Type 316/316L grades)
5.3 Performance Context — Residential Heating Load Analysis
In the context of residential heating load analysis, the integration of fan coil units and floor heating terminal systems—both utilizing stainless steel coil tubes as core heat transfer elements—has demonstrated that combined terminal systems can achieve a heating load bearing rate of 70–85% of total design heating demand. The thermal conductivity, corrosion resistance, and long-term dimensional stability of stainless steel coil tubes contribute directly to maintaining design performance over the system's 25–30 year design life.
6. Quality Certifications & Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System certification ensuring consistent product quality and process control |
| ISO 14001:2015 | Environmental Management System certification |
| CE Marking (EN 10216-5) | Compliance with European standards for seamless and welded stainless steel tubes for pressure purposes |
| ASTM A269 / A270 | Conformance to American Society for Testing and Materials specifications for austenitic stainless steel tubing |
| GB/T 12771 | Chinese national standard for welded austenitic stainless steel tubes for general purposes |
| Mill Test Certificate (MTC) | EN 10204 3.1 certified material test documentation provided with each batch |
| NACE MR0175 / ISO 15156 | Suitability for sour service environments (available upon request) |
7. Unique Selling Points
- Superior Corrosion Resistance: Chromium-nickel-molybdenum alloy composition provides exceptional resistance to pitting, crevice corrosion, and general aqueous corrosion—critical for long-term hydronic system reliability.
- Hygienic Surface Integrity: Electropolished surfaces with Ra ≤ 0.2 μm minimize biofilm formation and facilitate cleaning, meeting FDA and EHEDG (European Hygienic Engineering Design Group) requirements.
- Continuous Coil Supply: Eliminates field welding joints, reducing potential leak points and installation labor by up to 40% compared to straight-length tube assemblies.
- Wide Dimensional Range: Available in OD from 3.175 mm to 19.05 mm with wall thicknesses from 0.30 mm to 1.50 mm, accommodating diverse system pressure and flow requirements.
- Thermal Efficiency: Optimized wall thickness and high thermal conductivity ensure rapid heat transfer response, contributing to system energy efficiency and reduced pumping costs.
- Design Life Assurance: Stainless steel coil tubes deliver a proven service life exceeding 25 years in closed-loop hydronic systems without significant performance degradation.
- Customization Capability: Non-standard dimensions, surface finishes, and coil configurations available to meet project-specific requirements.
8. Ordering Information
Customers are advised to specify the following parameters when placing orders:
- Material grade (304, 316, or 316L)
- Outer diameter and wall thickness
- Required coil length per spool
- Surface finish requirement (standard, electropolished, or mirror polished)
- Applicable standard and certification requirements
- Destination port and packaging preferences
Wenzhou Jixing Metal Materials Co., Ltd. maintains extensive stock of standard coil tube configurations and offers competitive lead times for custom orders. Technical consultation and application engineering support are available to assist customers in selecting optimal specifications for their specific thermal management applications.