Stainless Steel Coil Tube (Coiltube) — Product Technical Specification
Product Overview
The Stainless Steel Coil Tube, catalogued under product code 1358 by Wenzhou Jixing Metal Materials Co., Ltd, is a precision-engineered continuous coil tube designed for demanding fluid transport, heat exchange, and structural applications. Manufactured in a helical coil configuration, this product offers superior thermal conductivity, corrosion resistance, and mechanical integrity compared to conventional straight-tube alternatives. The coil geometry enables compact heat exchanger assemblies with maximized surface-area-to-volume ratios, making it an ideal solution for air conditioning, refrigeration, HVAC, and industrial process systems.
Unlike discrete pipe segments requiring field welding and joint assembly, the coil tube is delivered as a continuous, pre-formed helical coil, eliminating leak-prone connection points and reducing installation labor costs significantly. This product line draws upon best practices established in the ACR (Air Conditioning and Refrigeration) industry, where coil tubes have been proven through extensive field validation in China's mature HVAC market.
Material & Properties
Base Material Composition
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional balance of corrosion resistance, ductility, and thermal performance. The primary alloy grades offered include:
- AISI 304 (UNS S30400 / 1.4301): General-purpose grade with excellent atmospheric and mild chemical corrosion resistance. Contains minimum 18% Chromium (Cr) and 8% Nickel (Ni).
- AISI 316 (UNS S31600 / 1.4401): Enhanced grade with 2–3% Molybdenum (Mo) addition, providing superior resistance to pitting and crevice corrosion in chloride-containing environments.
- AISI 321 (UNS S32100 / 1.4541): Titanium-stabilized grade suitable for elevated-temperature applications up to 870°C, resistant to intergranular corrosion.
Key Physical and Mechanical Properties
- Density: 7.93 g/cm³ (for 304/316 grades)
- Thermal Conductivity: 16.3 W/(m·K) at 20°C (304 grade)
- Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (20–100°C)
- Tensile Strength: ≥ 520 MPa (304), ≥ 515 MPa (316) — annealed condition
- Yield Strength (0.2% offset): ≥ 205 MPa (304), ≥ 170 MPa (316)
- Elongation at Break: ≥ 40% (annealed condition)
- Operating Temperature Range: −196°C to +870°C (321 grade)
Corrosion Resistance Performance
The passive chromium oxide layer (Cr₂O₃) formed on the stainless steel surface self-repairs in the presence of oxygen, providing long-term protection against oxidation, acidic media, and chlorinated solutions. In a 0.5% NaCl solution at 60°C, AISI 316 coil tube demonstrates no measurable weight loss over 30-day exposure periods, consistent with ASTM G48 standardized testing protocols.
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) | — |
| Product Code | 1358 | Internal Catalog |
| Manufacturer | Wenzhou Jixing Metal Materials Co., Ltd | — |
| Outer Diameter (OD) | 3.0 mm – 25.4 mm (1/8" – 1") | ASTM A269 / A213 |
| Wall Thickness | 0.3 mm – 2.0 mm | ASTM A269 / A213 |
| Coil Diameter (CD) | 30 mm – 300 mm | Custom Configurable |
| Coil Length | Up to 500 m per continuous coil | — |
| Surface Finish | 2B (Mill Annealed), BA (Bright Annealed), No.4 Brushed | ASTM A480 |
| Tolerance (OD) | ±0.05 mm (fine tolerance); ±0.10 mm (standard) | ISO 1307 / ASTM A213 |
| Tolerance (Wall Thickness) | ±0.03 mm (fine tolerance); ±0.08 mm (standard) | ISO 1307 / ASTM A213 |
| Helix Pitch | 5 mm – 50 mm (configurable) | — |
| End Condition | Plain cut, Beveled, Flared, or Threaded | ASME B1.20.1 |
| Heat Treatment | Annealed (Solution Annealed + Water Quenched) | ASTM A213 |
| Coating Options | None (Bare), PTFE, Epoxy, PE (Polyethylene) | — |
| Maximum Working Pressure | Up to 16 MPa (160 bar) — dependent on OD and wall thickness | ASME B31.3 |
| Refrigerant Compatibility | R-134a, R-410A, R-32, R-404A, R-407C, R-22, Ammonia (NH₃) | ASHRAE Standard 34 |
| Delivery Form | Continuous helical coil on wooden or steel spool | — |
| Minimum Order Quantity (MOQ) | 50 kg (negotiable for custom configurations) | — |
Manufacturing Process
The production of the stainless steel coil tube follows a rigorously controlled multi-stage manufacturing workflow, adhering to ISO 9001:2015 quality management principles throughout every process step:
- Raw Material Selection and Ingress Inspection: Cold-rolled stainless steel strip is sourced from certified mill suppliers (e.g., POSCO, Outokumpu, Baosteel). Each batch undergoes spectroscopic verification (OES — Optical Emission Spectroscopy) to confirm chemical composition compliance with ASTM A240/A276 specifications. Incoming material is certified with mill test reports (MTRs).
- Strip Cleaning and Surface Preparation: The stainless steel strip is cleaned using alkaline degreasing and acid pickling solutions to remove surface contaminants, scale, and oxidation films. This ensures uniform material behavior during subsequent forming operations.
- Coil Forming (Helical Bending): The flat strip is fed through a precision CNC-controlled coil forming machine equipped with multi-roller bending stations. The strip is progressively formed into a seamless helical coil with controlled coil diameter and pitch. The process employs a continuous bending method, eliminating weld seams along the coil length. Tension and feed rate are dynamically regulated to prevent wall thinning, ovality, or springback.
- Solution Annealing and Pickling: Formed coils are subjected to solution annealing in a continuous annealing furnace at temperatures between 1050°C and 1150°C, followed by controlled water quenching. This relieves internal stresses introduced during forming, restores full annealed mechanical properties, and homogenizes the microstructure. Subsequent pickling removes the heat scale (chromium oxide layer formed during annealing) and restores the passive corrosion-resistant surface.
- Passivation Treatment: After pickling, the coil tube undergoes chemical passivation using a nitric acid or citric acid-based solution. This re-establishes the protective chromium oxide passive film, enhancing long-term corrosion resistance.
- Dimensional Inspection and Quality Control (QC): Each coil undergoes comprehensive dimensional verification using laser micrometers, ultrasonic thickness gauges, and optical comparators. Inspection parameters include outer diameter, wall thickness, coil diameter, pitch uniformity, straightness, and surface finish quality. Sampling is conducted in accordance with ASTM E10 and ASTM E29 statistical methods.
- End Preparation and Finishing: Coil ends are trimmed, beveled, or flared to customer specifications. Surface finishing (BA, brushed, or coated) is applied as required. Final product is coiled onto protective wooden or steel spools with moisture-absorbing desiccant packs for shipment.
- Packaging and Shipping: Each coil is wrapped in polyethylene protective film, secured on a palletized spool, and labeled with product identification, batch number, heat number, and compliance certificates.
Applications
The stainless steel coil tube is engineered for a broad spectrum of industrial and commercial applications where corrosion resistance, thermal efficiency, and mechanical reliability are critical:
Air Conditioning and Refrigeration (ACR)
- Evaporator and Condenser Coils: The helical coil geometry maximizes heat transfer surface area within compact footprint constraints, making it ideal for residential and commercial HVAC units, heat pumps, and refrigeration systems. The seamless coil construction eliminates leak points inherent to brazed or soldered tube-in-tube assemblies.
- Chiller and Cooling Tower Piping: Resistant to the corrosive effects of treated water, glycol-based heat transfer fluids, and ambient atmospheric conditions.
Industrial Process Engineering
- Chemical Processing Piping: Handles aggressive chemical media including acids, alkalis, and halogenated solvents, particularly with AISI 316 grade.
- Food and Beverage Processing: Compliant with FDA (Food and Drug Administration) and 3-A Sanitary Standards for hygienic fluid transport in dairy, brewing, and pharmaceutical applications.
- Pharmaceutical Manufacturing: Suitable for clean-room environments and GMP (Good Manufacturing Practice) compliant systems requiring non-reactive, cleanable piping.
Energy and Power Generation
- Geothermal Heat Exchangers: Resistant to sulfur compounds and high-temperature geothermal fluids.
- Solar Thermal Systems: Withstands thermal cycling and UV degradation in concentrated solar power (CSP) loop systems.
Automotive and Transportation
- Automotive Exhaust and Turbocharger Piping: High-temperature grades (321, 310) suitable for exhaust gas routing and turbocharger hot-side applications.
- Vehicle Cooling System Components: Corrosion-resistant coil tubing for engine coolant loops and aftercooler assemblies.
Marine and Offshore
- Seawater Cooling Systems: AISI 316 and duplex stainless steel coil tubes resist pitting and crevice corrosion in marine environments.
- Ballast Water Piping: Compliant with IMO (International Maritime Organization) ballast water management conventions.
Quality Certifications and Compliance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality assurance framework ensuring that every coil tube product meets or exceeds international standards:
| Certification / Standard | Scope of Compliance |
|---|---|
| ISO 9001:2015 | Quality Management System — covers design, manufacturing, inspection, and delivery processes |
| ISO 14001:2015 | Environmental Management System — sustainable manufacturing practices and waste minimization |
| ISO 45001:2018 | Occupational Health and Safety Management System |
| ASTM A213 | Standard Specification for Seamless Austenitic Stainless Steel Tubing for High Temperature Service |
| ASTM A269 | Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubing for Chemical and Similar Severities |
| EN 10217-7 | European Standard for Heat-Exchanger Tubes and Condenser Tubes — Part 7: Non-ferrous and Non-metallic Tubes (reference methodology) |
| JIS G4315 / G4316 | Japanese Industrial Standard for Stainless Steel Tubes for Heat Exchangers |
| ASME B31.3 | Process Piping — design and pressure rating verification |
| NSF/ANSI 61 | Drinking Water System Components — Health Effects (for potable water applications) |
| CNCA (China Compulsory Certification) | Chinese national certification for market access compliance |
Testing and Verification Protocol
- Hydrostatic Pressure Testing: All coils tested at 1.5× maximum working pressure per ASTM A213 requirements, with zero leakage tolerance.
- Chemical Composition Analysis: OES (Optical Emission Spectroscopy) and wet chemical titration performed per batch to verify alloy grade compliance.
- Hardness Testing: Rockwell B (HRB) or Vickers (HV) hardness measured per ASTM E18 and ASTM E92.
- Tensile Testing: Coupon specimens tested per ASTM E8/E8M to verify yield strength, tensile strength, and elongation.
- Intergranular Corrosion Testing: ASTM A262 Practice No. 1A (acid copper test) for stabilization verification on 321 grade.
- Pitting Corrosion Testing: ASTM G48 Practice A (ferric chloride solution) for 316 grade verification.
- Dimensional Inspection: