Stainless Steel Coil Tube (Coiltube) — Technical Specification
Product Catalogue No.: 592 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.
1. Product Overview
The Stainless Steel Coil Tube (盘管 Coiltube) is a precision-engineered tubular product manufactured by continuously winding stainless steel seamless or welded tubing into a helical coil configuration. This product category serves as a critical component in heat exchange systems, HVAC (Heating, Ventilation, and Air Conditioning) assemblies, refrigeration circuits, chemical processing equipment, and industrial fluid transfer applications. The coil geometry maximizes surface area within a compact volumetric envelope, thereby enhancing thermal transfer efficiency while minimizing pressure drop across the coil assembly.
Wenzhou Jixing Metal Materials Co., Ltd. specializes in producing coil tubes with strict dimensional tolerances, superior surface finish quality, and consistent metallurgical integrity. The company's manufacturing infrastructure integrates advanced coiling technology, automated inspection systems, and rigorous quality control protocols to ensure that every coil tube batch meets or exceeds international industry standards.
2. Material & Properties
2.1 Base Alloy Composition
The stainless steel coil tube is primarily fabricated from austenitic stainless steel grades, with the most common designations including:
- 304 (UNS S30400 / 1.4301): Contains 18% Chromium (Cr) and 8% Nickel (Ni); offers excellent general corrosion resistance, good formability, and weldability. Suitable for food-grade and sanitary applications.
- 316 (UNS S31600 / 1.4401): Contains 16–18% Cr, 10–14% Ni, and 2–3% Molybdenum (Mo); provides enhanced resistance to pitting and crevice corrosion, particularly in chloride-rich environments.
- 316L (UNS S31603 / 1.4434): Low-carbon variant of 316 (C ≤ 0.03%); ideal for welding-intensive applications where sensitization must be avoided.
- 321 (UNS S32100 / 1.4541): Titanium-stabilized grade offering superior resistance to intergranular corrosion at elevated temperatures (up to 870°C).
2.2 Mechanical Properties (Typical Values)
| Property | 304 Grade | 316 Grade | 316L Grade |
|---|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 515 | ≥ 485 |
| Yield Strength (MPa, 0.2% offset) | ≥ 205 | ≥ 205 | ≥ 170 |
| Elongation (% at fracture) | ≥ 40 | ≥ 40 | ≥ 45 |
| Hardness (HB max.) | ≤ 217 | ≤ 217 | ≤ 217 |
| Density (g/cm³) | 8.00 | 8.03 | 8.03 |
2.3 Surface Finish Options
- 2B Finish: Cold-rolled, annealed, and pickled; provides a uniform, semi-reflective matte surface suitable for general industrial use.
- No. 4 Brushed Finish: Directional satin finish achieved through abrasive grinding; aesthetically pleasing for architectural and food-processing applications.
- BA (Bright Annealed) Finish: Annealed in a controlled atmosphere; offers a smooth, reflective surface with superior cleanliness for sanitary and pharmaceutical applications.
- Electropolished Finish: Electrochemical polishing to achieve Ra ≤ 0.4 μm; meets FDA and 3-A sanitary standards for bioprocessing.
3. Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 114.3 mm (¼" – 4") | ASTM A269 / A270 |
| Wall Thickness (WT) | 0.5 mm – 6.0 mm (0.020" – 0.236") | ASTM A269 / A270 |
| Coil Length (per coil) | 5 m – 50 m (customizable up to 200 m) | Manufacturer Specification |
| Coil Inner Diameter (CID) | 50 mm – 500 mm | ASME B31.3 |
| Coil Pitch (turn spacing) | 2 mm – 25 mm (adjustable) | Customer-Specified |
| Number of Turns | 10 – 500 (configurable) | Customer-Specified |
| Dimensional Tolerance (OD) | ± 0.05 mm (± 0.002") | ASTM A213 |
| Dimensional Tolerance (WT) | ± 10% of nominal | ASTM A269 |
| Operating Temperature Range | −196°C to +870°C (grade-dependent) | ASME Section IX |
| Maximum Working Pressure | Up to 40 MPa (design-dependent) | ASME B31.3 / PED 2014/68/EU |
| End Preparation | Plain, Beveled (37°), Threaded (BSPT/NPT), Flanged | ASME B1.20.1 / B16.5 |
| Packaging | Wooden pallet with protective wrap; custom crating available | ISO 11607 / ISTA 3A |
4. Manufacturing Process
4.1 Process Flow
- Raw Material Inspection: Incoming stainless steel tubing is verified for chemical composition (via Optical Emission Spectroscopy — OES), mechanical properties, and dimensional accuracy. Material traceability is maintained through heat number documentation.
- Cutting & Deburring: Tubes are cut to required coil lengths using precision cold-saw or laser-cutting equipment. End faces are deburred to remove burrs and flash, ensuring clean fluid passage.
- End Preparation: Depending on the application, tube ends are beveled, threaded, or prepared for flange attachment per ASME B16.25 or B16.5 standards.
- Coiling / Winding: Tubes are wound into helical coils using CNC-controlled coiling machines. The winding process is programmed to maintain precise pitch, uniform curvature radius, and consistent turn-to-turn spacing. Real-time sensors monitor coil geometry to prevent deviation.
- Stress Relief Annealing: Coiled assemblies undergo controlled thermal treatment (typically 850°C – 1050°C in a protective atmosphere furnace) to relieve residual stresses introduced during forming. This step ensures dimensional stability and restores full mechanical properties.
- Pickling & Passivation: The annealed coils are subjected to pickling (removal of oxide scale) and passivation (formation of a chromium-rich passive film) to achieve optimal corrosion resistance. Passivation solutions conform to ASTM A967.
- Surface Finishing: Final surface treatment (brushing, polishing, or electropolishing) is applied per customer specification.
- Quality Inspection: Each coil undergoes dimensional verification, visual inspection, and non-destructive testing (NDT) including eddy current testing (ASTM E309) or ultrasonic testing (ASTM E213) to detect wall thickness variations, surface defects, and subsurface discontinuities.
- Packaging & Shipping: Inspected coils are wrapped in protective polyethylene film, secured on wooden pallets, and labeled with full traceability documentation including Material Test Reports (MTR) and Certificate of Conformance (CoC).
4.2 Key Manufacturing Advantages
- CNC-automated coiling ensures repeatability and minimizes operator-induced variability.
- In-house stress relief annealing eliminates the need for external heat treatment subcontracting, reducing lead times.
- Integrated NDT capability enables 100% inspection coverage rather than sampling-based verification.
- Full material traceability from mill certificate to finished product supports regulatory compliance in pharmaceutical, food, and aerospace sectors.
5. Applications
5.1 HVAC & Refrigeration Systems
Coil tubes are fundamental to fan coil units (FCUs), air handling units (AHUs), and chiller evaporator/condenser sections. In fan coil unit operation, the coil tube geometry directly influences airflow distribution and heat transfer rates. Proper coil pitch and tube layout are critical to minimizing aerodynamic noise — a key concern addressed in operational analyses of fan coil unit acoustics. Optimally designed coil tubes with uniform pitch and smooth tube surfaces reduce turbulence-induced noise and pressure fluctuations, contributing to quieter system operation and improved occupant comfort.
5.2 Heat Exchangers
Used extensively in shell-and-tube heat exchangers, plate-fin heat exchangers, and air-cooled condensers. The high surface-area-to-volume ratio of coil tubes enhances thermal efficiency in both latent and sensible heat transfer applications.
5.3 Chemical & Petrochemical Processing
316 and 316L grade coil tubes are deployed in reactor cooling systems, distillation columns, heat recovery steam generators (HRSGs), and corrosion-resistant fluid transfer lines. The molybdenum addition provides resistance to sulfuric acid, hydrochloric acid, and chloride ion environments.
5.4 Food & Beverage Processing
BA finish and electropolished coil tubes meet FDA 21 CFR Part 178 and 3-A Sanitary Standards. Applications include pasteurization systems, CIP (Clean-in-Place) circuits, and product transfer lines in dairy, brewing, and pharmaceutical manufacturing.
5.5 Power Generation
321 and 347 (Ni-stabilized) grade coil tubes are used in superheater and reheater sections of boiler systems, as well as in steam turbine exhaust condensers, where resistance to intergranular corrosion at elevated temperatures is paramount.
5.6 Oil & Gas
Coil tubes in duplex stainless steel grades (e.g., 2205 / UNS S32205) are employed in subsea production manifolds, wellhead Christmas trees, and offshore heat exchangers, offering superior chloride stress corrosion cracking (CSCC) resistance.
6. Quality Certifications & Standards Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System — certified for consistent manufacturing quality and continuous improvement. |
| ISO 14001:2015 | Environmental Management System — demonstrates commitment to sustainable manufacturing practices. |
| ISO 45001:2018 | Occupational Health & Safety Management System. |
| EN 10204 3.1 | Inspection Certificate — third-party verified material test reports accompanying each shipment. |
| ASME B31.3 | Process Piping — product suitable for integration into ASME B31.3 governed piping systems. |
| ASTM A269 / A270 | Standard specifications for austenitic stainless steel seamless and welded tubing. |
| PED 2014/68/EU | Pressure Equipment Directive — compliance for EU market entry. |
| CE Marking | European conformity marking for pressure equipment and machinery components. |
| NACE MR0175 / ISO 15156 | Materials for use in H₂S-containing environments in oil and gas service. |
| NSF/ANSI 61 | Drinking water system components — health effects certification (for potable water applications). |
7. Unique Selling Points
- Precision Coiling Technology: CNC-controlled winding delivers dimensional accuracy of ± 0.05 mm on outer diameter and ± 0.5 mm on coil pitch, ensuring consistent performance in heat exchanger and HVAC applications.
- Low-Noise Coil Geometry: Optimized coil pitch and tube surface finish minimize aerodynamic turbulence, directly addressing the noise characteristics identified in fan coil unit operational studies. This results in lower acoustic emissions and improved energy efficiency.
- Multi-Grade Flexibility: Capability to supply coil tubes in 304, 316, 316L, 321, 347, and duplex 2205 grades from a single source, simplifying supply chain management for multi-application projects.
- Full Traceability: Every coil tube is traceable to its original mill heat number, with digital material passports available for digital twin and