Stainless Steel Coil Tube (Coiltube) — Product No. 1204
Product Overview
The Stainless Steel Coil Tube (Coiltube), designated as Product No. 1204, is a precision-engineered continuous-length stainless steel tubing product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. Supplied in the form of a coiled configuration, this product is specifically designed for applications requiring flexible deployment, compact storage, and seamless integration into HVAC (Heating, Ventilation, and Air Conditioning) systems, heat exchanger assemblies, and fluid transfer circuits. The coil tube eliminates the need for field welding or mechanical splicing, thereby minimizing potential leak points and enhancing system reliability.
This product has been extensively studied and validated in the context of fan coil unit air conditioning systems, where proper fresh air (ventilation air) design is critical to maintaining indoor air quality (IAQ). The coil tube serves as the primary heat transfer medium within these systems, enabling efficient thermal exchange between the circulating refrigerant or hot water and the ambient air stream.
Material & Properties
Base Material Grades
- AISI 304 / SUS 304 (UNS S30400) — Austenitic stainless steel offering excellent general corrosion resistance, formability, and weldability. Suitable for most HVAC and domestic water applications.
- AISI 316 / SUS 316 (UNS S31600) — Enhanced austenitic grade with molybdenum addition (2.0–3.0%), providing superior resistance to pitting and crevice corrosion in chloride-rich environments.
- AISI 321 / SUS 321 (UNS S32100) — Titanium-stabilized austenitic grade recommended for elevated-temperature service where sensitization resistance is required.
Mechanical Properties (Annealed Condition)
| Property | AISI 304 | AISI 316 | Test Standard |
|---|---|---|---|
| Tensile Strength (Rm) | ≥ 520 MPa | ≥ 520 MPa | ASTM A269 / ASTM A270 |
| Yield Strength (Rp0.2) | ≥ 205 MPa | ≥ 205 MPa | ASTM A269 / ASTM A270 |
| Elongation (A50) | ≥ 40% | ≥ 40% | ASTM A269 / ASTM A270 |
| Hardness (HB) | ≤ 217 | ≤ 217 | ASTM E10 |
Chemical Composition (Maximum, wt%)
| Element | C | Si | Mn | P | S | Cr | Ni | Mo |
|---|---|---|---|---|---|---|---|---|
| AISI 304 | 0.08 | 1.00 | 2.00 | 0.045 | 0.030 | 18.0–20.0 | 8.0–10.5 | — |
| AISI 316 | 0.08 | 1.00 | 2.00 | 0.045 | 0.030 | 16.0–18.0 | 10.0–14.0 | 2.0–3.0 |
Physical Properties
- Density: 8.0 g/cm³
- Thermal Conductivity (at 20°C): 16.3 W/(m·K) (AISI 304)
- Specific Heat Capacity: 500 J/(kg·K)
- Thermal Expansion Coefficient (20–100°C): 17.3 × 10⁻⁶ /°C
- Maximum Service Temperature: 870°C (AISI 304), 870°C (AISI 316)
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 50.8 mm (1/4" – 2") | ASTM A269 / ASTM A270 |
| Wall Thickness | 0.30 mm – 3.00 mm | ASTM A269 / ASTM A270 | Coil Length | 30 m – 200 m (continuous, spool-supplied) | ISO 11979 |
| Coil Inner Diameter (Reel) | 200 mm – 600 mm | — |
| Surface Finish | 2B (Mill Finish), BA (Bright Annealed), No. 4 Brushed, Mirror (8K) | ASTM A480 |
| End Condition | Plain cut, Beveled, or Flared (optional) | — |
| Dimensional Tolerance (OD) | ±0.05 mm (precision), ±0.10 mm (standard) | ASTM A269 |
| Dimensional Tolerance (Wall) | ±10% of nominal | ASTM A269 |
| Weld Type | Seamless or Welded (ERW — Electric Resistance Welded) | ASTM A269 / ASTM A270 |
| Heat Treatment | Solution Annealed + Water Quenched | — |
Manufacturing Process
Production Workflow
- Raw Material Preparation: Cold-rolled stainless steel strip of certified grade is inspected for surface quality, thickness uniformity, and chemical composition compliance via spectroscopic analysis (OES — Optical Emission Spectroscopy).
- Coiling & Forming: The strip is fed through a series of precision rollers in a tube-forming mill, progressively bending the strip into a tubular cross-section. For welded tube, the edges are brought into contact and joined via high-frequency induction welding or longitudinal resistance welding (ERW).
- Pilot Mandrel Insertion: A hardened steel pilot wire or rod is inserted through the formed tube to maintain bore integrity during subsequent processing steps.
- Continuous Annealing: The formed tube passes through a bellows furnace where it is heated to 1050–1150°C under a controlled atmosphere (endothermic gas or vacuum) and subsequently water-quenched to achieve full solution-annealed condition, restoring ductility and uniform microstructure.
- Pickling & Passivation: The annealed tube undergoes acid pickling (nitric-hydrofluoric acid blend) to remove scale and oxidation, followed by passivation treatment to establish a stable chromium oxide passive film (Cr₂O₃) on the surface.
- Surface Finishing: Depending on specification, the tube may undergo electropolishing, mechanical polishing, or brushing to achieve the required surface finish grade.
- Dimensional Verification: Each coil is measured using ultrasonic wall thickness gauges, optical comparators for OD, and laser diameter measurement systems to ensure compliance with specified tolerances.
- Coiling & Packaging: The finished tube is coiled around a protective cardboard or steel spool, wrapped in moisture-proof polyethylene film, and secured with steel strapping for transport.
Quality Control Milestones
- Incoming material certification (Mill Test Certificate — MTC, EN 10204 Type 3.1)
- In-process ultrasonic flaw detection (UT) at 100% coverage
- Eddy current testing (ECT) for weld seam integrity verification
- Final visual inspection per ASTM E947
- Hydrostatic pressure test at 1.5× working pressure (for welded tube)
Applications
Primary Application Domains
- HVAC Systems (Heating, Ventilation, and Air Conditioning): The coil tube is the core component of fan coil units (FCUs), where it functions as the heat exchanger coil for sensible and latent heat removal. Proper fresh air design in these systems — including adequate ventilation air supply, filtration, and ductwork configuration — is essential to prevent indoor air quality degradation and ensure compliance with ASHRAE 62.1 ventilation standards.
- Chilled Water Circuits: Used as distribution tubing for chilled water in commercial and institutional buildings, leveraging the corrosion resistance and thermal conductivity of stainless steel.
- Condenser and Evaporator Coils: Integral to refrigeration systems, heat pumps, and air source heat exchangers.
- Domestic Water Supply: Suitable for potable water distribution where copper-free solutions are preferred.
- Food & Beverage Processing: Hygienic-grade (BA finish) coil tube used in sanitary fluid transfer, CIP (Clean-in-Place) systems, and brewing equipment.
- Pharmaceutical & Medical Equipment: Precision coil tube for instrument tubing, gas delivery, and process connections.
- Automotive & Industrial Applications: Fuel lines, hydraulic circuits, and sensor tubing requiring corrosion resistance and dimensional precision.
Design Considerations for Fan Coil Unit Integration
In fan coil unit systems, the coil tube arrangement directly impacts thermal performance, pressure drop, and noise generation. Key design parameters include:
- Tube pitch and row configuration: Determines heat transfer surface area and air-side pressure loss.
- Fins per inch (FPI): Typically 8–12 FPI for standard HVAC; higher densities for compact heat exchangers.
- Fresh air ventilation rate: Must comply with minimum outdoor air requirements per ASHRAE 62.1 or local building codes to maintain IAQ.
- Condensate management: Proper coil slope and drain pan design to prevent moisture accumulation and microbial growth.
Quality Certifications & Compliance
Applicable Standards
| Standard | Description | Scope |
|---|---|---|
| ASTM A269 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for Chemical and Allied Applications | Chemical, food, pharmaceutical tubing |
| ASTM A270 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for General Applications | General-purpose tubing |
| ISO 11979 | Stainless Steel Tubes and Pipes — Dimensions and Tolerances | Dimensional compliance |
| EN 10217-7 | Heat Resistant Stainless Steel Tubes for General Purposes — Seamless Tubes | European market compliance |
| JIS G3446 | Stainless Steel Tubes for General Purposes | Japanese market compliance |
Manufacturing Certifications
- ISO 9001:2015 — Quality Management System certification covering design, manufacturing, and service processes.
- ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices.
- ISO 45001:2018 — Occupational Health and Safety Management System.
- NADCAP (National Aerospace and Defense Contractors Accreditation Program) — Available for aerospace-grade products upon request.
- CE Marking — Conformity with European directives for pressure equipment (PED 2014/68/EU) where applicable.
Traceability & Documentation
- Each coil is accompanied by a Mill Test Certificate (MTC) in accordance with EN 10204 Type 3.1, providing full chemical analysis, mechanical test results, and heat number traceability.
- Batch-specific ultrasonic testing reports and dimensional inspection records are available upon request.
- Full material traceability from raw steel coil heat number through to finished product is maintained throughout the manufacturing chain.
Unique Selling Points
- Continuous-Length Supply: Eliminates field welding and joint-related failure points, providing superior system integrity and reduced maintenance requirements.
- Precision Dimensional Control: Tight tolerances (±0.05 mm OD) ensure reliable fit with fittings, compressions, and brazing assemblies.
- Superior Corrosion Resistance: Austenitic stainless steel grades provide long service life in aggressive environments, eliminating the need for cathodic protection or internal coatings.
- HVAC-Optimized Design: Specifically engineered for fan coil unit integration with validated thermal performance data and pressure drop characteristics.
- Full Traceability: End-to-end material traceability from raw steel to finished coil, ensuring regulatory compliance and quality assurance.
- Customization Capability: Flexible customization of dimensions, surface finishes, end conditions, and coil configurations to meet project-specific requirements.
Storage & Handling Recommendations
- Store in a dry, well-ventilated warehouse with relative humidity below 70%.
- Avoid stacking coils directly on concrete floors; use wooden pallets or plastic skids to prevent moisture ingress and surface damage.