Stainless Steel Coil Tube (Coil Tube) — Wenzhou Jixing Metal Materials Co., Ltd

1. Product Overview

The Stainless Steel Coil Tube (Coiltube), product reference No. 416, is a precision-engineered coiled tubing product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is designed for use in thermal management systems, including radiation coil tubes (Radiant Coil Tubes) and fan coil units (Fan Coil Units, FCUs), where efficient heat transfer and long-term corrosion resistance are paramount. The coil tube is supplied in a continuous coiled configuration, enabling flexible installation geometries and minimizing welding joints, thereby reducing potential failure points in closed-loop cooling and heating circuits.

Based on experimental research comparing the cooling performance of radiant coil tubes and fan coil tubes under various operating conditions, this product has been optimized for superior thermal conductivity, structural integrity under cyclic thermal loading, and compatibility with both hydronic and refrigerant-based distribution systems. The coil tube serves as a critical component in modern HVAC (Heating, Ventilation, and Air Conditioning) systems, industrial process cooling, and specialized heat exchange applications.

2. Material & Properties

The coil tube is fabricated from high-grade stainless steel, selected to meet the rigorous demands of thermal cycling and corrosive environments. The material composition and mechanical properties are specified as follows:

• Material Grade: Austenitic stainless steel conforming to ASTM A312 / ASME SA-312 or EN 10217-7 standards. Common grades include 304 (UNS S30408), 316 (UNS S31608), and 321 (UNS S32108), depending on the application-specific corrosion resistance requirements.
• Corrosion Resistance: Excellent resistance to pitting, crevice corrosion, and stress corrosion cracking (SCC) in aqueous environments, including deionized water, glycol-based coolant mixtures, and mildly acidic solutions.
• Thermal Conductivity: Approximately 16.3 W/(m·K) at 20 °C (Grade 304), providing efficient heat transfer performance suitable for radiant cooling and fan coil applications.
• Operating Temperature Range: −196 °C to +870 °C (Grade 304); −196 °C to +925 °C (Grade 316), ensuring reliability across extreme thermal conditions.
• Mechanical Properties: Tensile strength ≥ 515 MPa; Yield strength (0.2% offset) ≥ 205 MPa; Elongation ≥ 40% (for Grade 304, annealed condition).
• Surface Finish: Bright annealed or pickled-and-passivated finish with surface roughness Ra ≤ 0.8 μm, minimizing fluid friction losses and fouling potential.

3. Specifications

Table 1 — Typical Dimensions and Performance Parameters for Stainless Steel Coil Tube

Parameter	Specification	Standard / Tolerance
Outer Diameter (OD)	6.0 mm – 50.8 mm (1/4" – 2")	ASTM A312, ±0.10 mm
Wall Thickness	0.50 mm – 3.00 mm	ASTM A312, ±10%
Coil Diameter	300 mm – 1,500 mm	Custom per customer requirement
Coil Length (per spool)	10 m – 500 m	Continuous coil, no butt welds
Material Grade	304 / 316 / 321 / 316L / 321H	ASTM A312 / EN 10217-7
Surface Treatment	Bright Annealed / Passivated / Electropolished	Internal Ra ≤ 0.8 μm (passivated)
Pressure Rating	Up to 10 MPa (design pressure, dependent on OD/WT)	ASME B31.9 / EN 13480
Operating Temperature	−196 °C to +870 °C	Material-dependent
Heat Transfer Coefficient	1,500 – 4,500 W/(m²·K) (water-based fluids)	Dependent on flow velocity and geometry
End Preparation	Plain cut / Beveled / Threaded / Flanged	Per customer drawing
Coating (optional)	Polyethylene (PE) / PTFE internal lining	Custom specification

4. Manufacturing Process

The production of the stainless steel coil tube at Wenzhou Jixing Metal Materials Co., Ltd follows a tightly controlled, multi-stage manufacturing process to ensure dimensional accuracy, metallurgical integrity, and surface quality:

1. Raw Material Procurement: Selection of certified austenitic stainless steel seamless tubes from approved mills, with full mill test certificates (MTC) conforming to EN 10204 Type 3.1. Incoming material is subjected to spectroscopic verification (OES analysis) to confirm chemical composition.
2. Cold Drawing / Cold Rolling: Seamless tubes undergo precision cold drawing to achieve the target outer diameter and wall thickness within specified tolerances. This process enhances mechanical properties through work hardening while maintaining grain structure integrity.
3. Intermediate Annealing: Where required, the drawn tube is solution annealed at 1,050 °C – 1,150 °C followed by controlled cooling to restore full austenitic microstructure, relieve residual stresses, and achieve the required softness for subsequent coiling.
4. Precision Coiling: The tube is coiled on high-precision CNC-controlled coiling equipment to achieve the specified coil diameter and pitch. The coiling process is monitored to prevent plastic deformation, ovality, or kinking. Coil diameter tolerances are maintained within ±2% of the nominal value.
5. Final Annealing (if applicable): For applications requiring full softness, the coiled tube may undergo a final bright annealing cycle in a controlled-atmosphere furnace (reducing atmosphere, dew point ≤ −40 °C) to achieve a clean, oxide-free surface.
6. Pickling and Passivation: The tube is treated with a citric acid or nitric acid-based pickling solution to remove any residual scale or discoloration, followed by passivation to establish a stable chromium oxide passive film. Passivation is verified per ASTM A967.
7. Quality Inspection: Each coil undergoes 100% visual inspection, dimensional verification (OD, wall thickness, coil diameter), and pressure testing (hydrostatic test at 1.5× design pressure). Random samples are subjected to eddy current testing (ECT) for internal and external defect detection per ASTM E709.
8. Packaging and Dispatch: Coils are wrapped in protective film, crated, and labeled with product identification, heat number, and traceability documentation prior to shipment.

5. Applications

The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd is engineered for a broad spectrum of thermal management and process engineering applications:

• Radiant Cooling Systems (Radiant Coil Tubes): Used as embedded cooling coils in radiant ceiling panels and radiant floor systems. Experimental studies have demonstrated that radiant coil tubes provide uniform surface temperatures and superior thermal comfort compared to conventional convection-based systems, with reduced risk of condensation and improved energy efficiency. The coil tube's high thermal conductivity and corrosion resistance make it ideal for hydronic radiant cooling circuits operating with chilled water at 12 °C – 18 °C.
• Fan Coil Units (FCUs): Employed as heat exchanger tubes in fan coil units for commercial and residential HVAC systems. The coil tube's resistance to scaling and corrosion ensures long-term maintenance-free operation, even in environments with aggressive water chemistry.
• Industrial Process Cooling: Applied in heat exchangers, condensers, and evaporators in chemical processing, pharmaceutical manufacturing, food and beverage production, and semiconductor fabrication facilities where product purity and hygiene are critical.
• Refrigeration and Cryogenic Systems: Suitable for low-temperature applications down to −196 °C, including liquid nitrogen distribution lines and cryogenic heat exchangers.
• Automotive and Marine Engineering: Used in engine cooling loops, hydraulic fluid circuits, and marine propulsion cooling systems where resistance to seawater corrosion (Grade 316/316L) is essential.
• Medical and Laboratory Equipment: Applied in dialysis machines, autoclaves, and analytical instrument cooling circuits where biocompatibility and chemical inertness are required.
• Building Services and District Energy: Integrated into district heating and cooling networks, building energy management systems (BEMS), and geothermal heat exchanger loops.

6. Quality Certifications and Standards Compliance

Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system and holds the following certifications and standard compliances:

• ISO 9001:2015 — Quality Management Systems
• ISO 14001:2015 — Environmental Management Systems
• ISO 45001:2018 — Occupational Health and Safety Management Systems
• ASTM A312 / ASME SA-312 — Standard Specification for Seamless and Welded Austenitic Stainless Steel Tubes for High Temperature Service
• EN 10217-7 — Tubes and Pipes for Mechanical and Thermal Purposes — Non-Alloy, Heat-Resistant and Stainless Steels
• ASME B31.9 — Process Piping (pressure design and testing compliance)
• EN 13480 — Rules for the Construction of Metallic Industrial Piping
• ASTM A967 — Standard Practice for Chemical Cleaning and Passivation of Stainless Steel Parts
• CE Marking — Conformity with EU Pressure Equipment Directive (PED 2014/68/EU) where applicable
• Mill Test Certificates (MTC) — EN 10204 Type 3.1 or 3.2 for all shipped products

7. Unique Selling Points

Several distinguishing characteristics set the Wenzhou Jixing stainless steel coil tube apart from competing products in the global market:

• Superior Thermal Performance: Optimized wall thickness and surface finish yield enhanced heat transfer coefficients, validated through comparative experimental studies on radiant coil tube versus fan coil tube cooling performance. The coil tube delivers uniform temperature distribution and rapid thermal response, reducing energy consumption in radiant cooling applications by up to 20% compared to conventional alternatives.
• Exceptional Corrosion Resistance: Available in multiple grades (304, 316, 316L, 321, 321H), the coil tube provides tailored corrosion protection for diverse chemical environments, including chlorinated water, acidic process streams, and marine atmospheres.
• Continuous Coil Configuration: The seamless, continuously coiled design eliminates butt welds, reducing the risk of leak points and simplifying installation. This is particularly advantageous in long-run radiant cooling circuits and complex heat exchanger assemblies.
• Full Traceability: Every coil is accompanied by complete documentation including mill test certificates, heat numbers, dimensional inspection reports, and pressure test records, ensuring full supply chain traceability and regulatory compliance.
• Customization Capability: Wenzhou Jixing offers flexible customization of outer diameter, wall thickness, coil diameter, coil length, surface finish, end preparation, and optional internal coatings to meet specific project requirements.
• Research-Validated Performance: The product's thermal and hydraulic performance has been validated through rigorous experimental research, including comparative studies on cooling conditions for radiant coil tubes and fan coil tubes, providing customers with empirically supported performance data.

Technical Note: The comparative experimental research on radiant coil tubes and fan coil tubes under cooling conditions has demonstrated that stainless steel coil tubes offer significant advantages in terms of thermal uniformity, energy efficiency, and condensation control in radiant cooling systems. These findings underscore the suitability of the Wenzhou Jixing coil tube product for next-generation sustainable building services and industrial thermal management applications.

8. Ordering Information

Customers are advised to provide the following information when placing an order to ensure optimal product selection and delivery:

• Required material grade (e.g., 304, 316, 316L, 321)
• Target outer diameter and wall thickness
• Required coil diameter and coil length
• Surface finish requirement (bright annealed, passivated, electropolished)
• End preparation type
• Applicable standard or specification reference
• Required certifications and inspection documentation
• Quantity and delivery schedule

Wenzhou Jixing Metal Materials Co., Ltd is committed to delivering premium-quality stainless steel coil tubes that meet the highest international standards for thermal performance, durability, and reliability.