Stainless Steel Coil Tube — Product No. 1036
Product Overview
The Stainless Steel Coil Tube (盘管, Coiltube), designated as Product No. 1036 by Wenzhou Jixing Metal Materials Co., Ltd, is a precision-engineered coiled stainless steel tubing product designed for demanding thermal-fluid transfer applications. This product is specifically optimized for integration into fan coil units (FCUs) operating under dry-mode conditions within central air conditioning systems, including innovative river-water cooling (RWC) configurations that leverage ambient water bodies as primary heat sources or sinks.
Unlike conventional copper or aluminum coil tubes, the stainless steel coil tube offers superior corrosion resistance, extended service life, and compatibility with aggressive fluid environments — making it an ideal choice for river-water cooling loops, geothermal heat exchange systems, and industrial process cooling where water quality variability is a persistent challenge.
Material & Properties
The coil tube is manufactured from high-grade austenitic stainless steel, selected for its exceptional combination of mechanical strength, thermal conductivity, and resistance to pitting, crevice, and intergranular corrosion.
- Material Grade: SUS304 (ASTM A213 TP304) or SUS316L (ASTM A213 TP316L) austenitic stainless steel, selected according to application-specific corrosion requirements.
- Chemical Composition (SUS304): Carbon (C) ≤ 0.08%, Chromium (Cr) 18.0–20.0%, Nickel (Ni) 8.0–10.5%, Manganese (Mn) ≤ 2.0%, Silicon (Si) ≤ 0.75%, Phosphorus (P) ≤ 0.045%, Sulfur (S) ≤ 0.030%.
- Chemical Composition (SUS316L): Carbon (C) ≤ 0.03%, Chromium (Cr) 16.0–18.0%, Nickel (Ni) 10.0–14.0%, Molybdenum (Mo) 2.0–3.0%, Manganese (Mn) ≤ 2.0%.
- Density: 7.93 g/cm³ (SUS304); 8.00 g/cm³ (SUS316L).
- Thermal Conductivity: 16.3 W/(m·K) at 20°C (SUS304); 14.6 W/(m·K) at 20°C (SUS316L).
- Specific Heat Capacity: 0.502 kJ/(kg·K) at 20°C.
- Tensile Strength: ≥ 520 MPa (SUS304); ≥ 485 MPa (SUS316L).
- Yield Strength: ≥ 205 MPa (SUS304); ≥ 170 MPa (SUS316L).
- Elongation at Break: ≥ 40% (SUS304); ≥ 45% (SUS316L).
- Operating Temperature Range: −196°C to +870°C (SUS304); −196°C to +870°C (SUS316L).
- Corrosion Resistance: Superior resistance to chlorides, sulfides, and organic acids; Mo addition in SUS316L provides enhanced pitting resistance equivalent to a Pitting Resistance Equivalent Number (PREN) ≥ 24.
- Hygienic Surface Finish: Available in No. 4 brushed finish or electropolished finish with surface roughness Ra ≤ 0.4 μm, ensuring minimal biofilm adhesion and ease of cleaning.
Specifications
| Parameter | Specification |
|---|---|
| Product Designation | Product No. 1036 — Stainless Steel Coil Tube (盘管, Coiltube) |
| Outer Diameter (OD) | 6.35 mm (1/4"), 9.52 mm (3/8"), 12.7 mm (1/2"), 15.88 mm (5/8"), 19.05 mm (3/4") |
| Wall Thickness (WT) | 0.5 mm, 0.8 mm, 1.0 mm, 1.2 mm, 1.5 mm (customizable) |
| Inner Diameter (ID) | Calculated as OD − 2 × WT |
| Coil Pitch (Center-to-Center) | 10 mm to 30 mm (adjustable per heat exchanger design requirements) |
| Coil Length | Standard lengths: 5 m, 10 m, 15 m, 20 m; custom lengths available up to 50 m |
| Coil Diameter | Custom ranging from 100 mm to 600 mm depending on FCU housing dimensions |
| Material Grade | SUS304 / SUS316L austenitic stainless steel (ASTM A213) |
| Surface Finish | No. 4 Brushed (Ra 0.5–1.0 μm) or Electropolished (Ra ≤ 0.4 μm) |
| End Connections | Flared, Grooved, Threaded (BSP/NPT), or Weld-Prep ends (customizable) |
| Maximum Operating Pressure | Up to 1.6 MPa (standard); 2.5 MPa (reinforced wall thickness) |
| Hydrostatic Test Pressure | 2.5 × maximum operating pressure (per ASME B31.3) |
| Heat Transfer Coefficient | 800–1,200 W/(m²·K) (water-to-air, dry-mode FCU conditions) |
| Maximum Fluid Velocity | ≤ 3.0 m/s (to prevent erosion-corrosion and minimize pressure drop) |
| Compliance Standards | ASTM A213, ASME B31.3, EN 10216-5, GB/T 12771 |
Manufacturing Process
The production of the stainless steel coil tube at Wenzhou Jixing Metal Materials Co., Ltd follows a rigorously controlled multi-stage manufacturing sequence to ensure dimensional accuracy, metallurgical integrity, and surface quality:
- Raw Material Selection & Verification: Hot-rolled stainless steel strip is procured from certified mills and subjected to spectroscopic analysis (Optical Emission Spectrometry, OES) to verify chemical composition compliance with ASTM A213 specifications. Certificates of Analysis (CoA) are reviewed for traceability.
- Slitting & Leveling: The strip is slit to the required width using precision slitting lines, then passed through a temper rolling mill to achieve uniform flatness and consistent mechanical properties along the strip length.
- Tube Forming (Seamless or Welded): The leveled strip is fed into a roll-forming machine where progressive tooling rolls incrementally deform the flat strip into a circular cross-section. For welded tubes, a high-frequency induction welding (HF-IW) or TIG (Tungsten Inert Gas) welding process is employed, followed by internal and external weld bead grinding to achieve a smooth, continuous internal surface.
- Heat Treatment & Annealing: Formed tubes undergo solution annealing at 1,050°C ± 10°C followed by controlled water quenching to dissolve carbide precipitates and restore full austenitic microstructure, ensuring maximum corrosion resistance and ductility.
- Coiling (Spiral Winding): The annealed tube is fed through a precision coiling machine equipped with CNC-controlled guide rollers to form the spiral coil geometry. The coil pitch and diameter are controlled within ±0.5 mm tolerance to ensure uniform heat transfer surface area and fit within designated FCU housings.
- Surface Treatment: Depending on application requirements, the coiled tube undergoes either No. 4 brushing (mechanical polishing with 120–150 grit abrasives) or electropolishing (anodic dissolution in H₂SO₄/H₃PO₄ electrolyte at 30–50 V, 10–20 A/dm²) to achieve the specified surface roughness.
- End Processing: Tube ends are cut square to ±0.1 mm, deburred, and finished according to the selected connection type (flared, grooved, threaded, or weld-prep). Threaded connections are machined to ISO 7-1 or ASME B1.20.1 standards.
- Quality Inspection & Testing: Each coil undergoes 100% hydrostatic pressure testing at 2.5 × the maximum operating pressure for a minimum dwell time of 10 seconds. Additional non-destructive testing (NDT) includes:
- Visual inspection for surface defects, weld quality, and coil geometry.
- Eddy current testing (ECT) for internal wall thickness verification and detection of subsurface flaws.
- Dimensional measurement using laser calipers and coordinate measuring machines (CMM).
- Corrosion testing via salt spray (ASTM B117) for a minimum of 1,000 hours with no pitting initiation for SUS316L grade.
- Packaging & Dispatch: Finished coil tubes are individually wrapped in moisture-resistant polyethylene film, placed in corrugated cardboard cartons with desiccant packs, and labeled with product identification tags including batch number, material grade, dimensions, and test results.
Applications
The Stainless Steel Coil Tube (Product No. 1036) is engineered for a diverse range of thermal-fluid transfer applications, with particular optimization for the following domains:
- River-Water Cooling (RWC) Central Air Conditioning Systems: The coil tube serves as the core heat exchange element in fan coil units designed for dry-mode operation using river water as the primary cooling medium. The stainless steel construction provides long-term resistance to the variable water quality (biological growth, mineral deposits, dissolved oxygen) encountered in open water source systems, eliminating the need for aggressive chemical treatment and reducing maintenance intervals.
- Fan Coil Units (FCUs) in Commercial & Industrial HVAC: Installed within air handling units (AHUs) and terminal FCUs for precise temperature and humidity control in office buildings, hospitals, laboratories, and cleanroom environments. The hygienic surface finish minimizes microbial colonization, supporting Indoor Air Quality (IAQ) compliance.
- Geothermal Heat Pump Systems: Used in ground-source heat exchangers where the coil tube interfaces with geothermal fluid loops, benefiting from the stainless steel's resistance to sulfide stress corrosion cracking (SSCC) commonly encountered in geothermal brines.
- Food & Beverage Processing: Deployed in sanitary heat exchangers for pasteurization, sterilization, and cooling circuits in dairy, brewing, and pharmaceutical manufacturing, meeting 3-A Sanitary Standards and FDA compliance.
- Marine & Offshore Applications: Utilized in shipboard cooling systems and offshore platform HVAC units where exposure to seawater and chlorinated environments demands superior corrosion resistance.
- Industrial Process Cooling: Integrated into chiller systems, condensers, and evaporators for chemical processing, power generation, and semiconductor manufacturing where fluid purity and system reliability are critical.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system and product certification framework to ensure international compliance:
- ISO 9001:2015 — Quality Management Systems certification, ensuring consistent product quality and continuous improvement processes throughout the manufacturing lifecycle.
- ISO 14001:2015 — Environmental Management Systems certification, demonstrating responsible environmental practices in raw material sourcing, manufacturing, and waste management.
- CE Marking (EU Conformity) — Product compliance with European Union Directives including the Pressure Equipment Directive (PED 2014/68/EU) for pressure-bearing applications.
- ASME Stamp Certification — Factory inspection and certification for pressure vessel and piping components per ASME Boiler and Pressure Vessel Code, Section VIII, Division 1.
- 3-A Sanitary Standards — Certification for food-grade applications, ensuring the coil tube meets the hygienic design and material requirements of the 3-A Sanitary Foundation.
- NSF/ANSI 61 — Drinking Water System Components certification for potable water applications, verifying that the stainless steel does not leach harmful substances into water.
- GB/T 12771 — Chinese national standard compliance for welded and seamless stainless steel tubes, ensuring adherence to domestic regulatory requirements.
- EN 10216-5 — European standard for welded stainless steel tubes used for pressure purposes, applicable to export markets within the European Economic Area.
- Material Traceability: Every production batch is accompanied by a Mill Test Certificate (MTC) / Certificate of Conformance (CoC) detailing chemical composition, mechanical properties, heat treatment records, and dimensional inspection results, enabling full supply chain traceability from raw material to finished product.
Unique Selling Points
The Stainless Steel Coil Tube (Product No. 1036) from Wenzhou Jixing Metal Materials Co., Ltd distinguishes itself through the following competitive advantages:
- Exceptional Corrosion Durability: The austenitic stainless steel construction provides a service life exceeding 20–25 years in aggressive water environments, compared to 5–8 years for copper alternatives, significantly reducing total cost of ownership (TCO) in river-water and geothermal cooling applications.
- Hygienic Surface Integrity: Electropolished finish with Ra ≤ 0.4 μm creates a smooth, non-porous surface that inhibits biofilm formation and facilitates CIP (Clean-In-Place) procedures, critical for pharmaceutical and food-grade HVAC systems.
- Thermal Performance Optimization: Precision-controlled coil geometry with pitch tolerances of ±0.5 mm ensures uniform heat transfer surface distribution, achieving heat transfer coefficients of 800–1,200 W/(m²·K) in dry-mode FCU operation, outperforming standard copper coil assemblies by 10–15% in equivalent configurations.
- Customization Flexibility: Full customization of OD, wall thickness, coil pitch, coil diameter, length, and end connection types enables seamless integration into proprietary FCU designs and non-standard HVAC architectures.
- Environmental Sustainability: Stainless steel is 100% recyclable without loss of material properties, supporting circular economy principles and reducing lifecycle carbon footprint compared to copper-based alternatives.
- Comprehensive Certification Portfolio: Multi-standard compliance (ASTM, ASME, EN, GB, CE, NSF) eliminates the need for supplementary testing in international markets, accelerating project approval timelines.
- River-Water Cooling Optimization: Specifically engineered for dry-mode operation in RWC systems, where the coil tube's resistance to variable water quality eliminates the need for chemical treatment, reducing operational costs and environmental impact.