Stainless Steel Coil Tube — Fan Coil Unit (FCU) Series

Product Overview

The Stainless Steel Coil Tube, manufactured by Wenzhou Jixing Metal Materials Co., Ltd., is a precision-engineered tubing product specifically designed for integration into Fan Coil Unit (FCU) systems. This coil tube serves as the core heat exchange element in distributed air conditioning and ventilation systems, where thermal efficiency, corrosion resistance, and long-term structural integrity are paramount. The product is supplied in continuous coil form to facilitate downstream forming, bending, and assembly operations with minimal waste and maximum material utilization.

In the context of distributed Model Predictive Control (MPC) architectures for HVAC systems, the coil tube's predictable thermal performance characteristics enable accurate state-space modeling, facilitating advanced control strategies that optimize energy consumption while maintaining precise temperature and humidity regulation across multi-zone building environments.

Material & Properties

The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional balance of mechanical strength, corrosion resistance, and thermal conductivity — properties critical for HVAC heat exchange applications.

• Base Material: Austenitic Stainless Steel (Type 304 / Type 316L available upon specification)
• Corrosion Resistance: Superior resistance to chloride-induced pitting and general atmospheric corrosion, ensuring long service life in humid indoor environments typical of commercial and residential HVAC installations
• Thermal Conductivity: Adequate thermal transfer capability to support efficient heat exchange between the working fluid (water or refrigerant) and ambient air
• Mechanical Properties: High yield strength and elongation, enabling reliable forming into serpentine, spiral, and multi-row configurations without cracking or thinning beyond tolerance
• Hygienic Surface Finish: Smooth internal and external surfaces minimize fouling, facilitate cleaning, and reduce pressure drop across the coil assembly
• Temperature Range: Suitable for continuous operation from cryogenic temperatures up to 400°C, accommodating both heating and cooling cycle demands

Specifications

Parameter	Specification
Product Category	Stainless Steel Coil Tube (盘管 / Coiltube)
Grade Options	SUS 304 / SUS 304L / SUS 316 / SUS 316L
Outer Diameter (OD)	6 mm – 22 mm (customizable)
Wall Thickness	0.4 mm – 1.5 mm (customizable)
Coil Length	Standard: 50 m – 200 m per coil; bulk orders negotiable
Surface Finish	No. 4 Brushed / Mirror Polish / Matte (upon request)
Forming Tolerance	±0.05 mm on OD; ±0.02 mm on wall thickness
Applicable Standards	ASTM A213, ASTM A269, EN 10217-7, GB/T 12771
Heat Treatment	Solution Annealed and Pickled (SA-P) or Cold Worked and Stress-Relieved
Hydrostatic Testing	100% tested per ASTM A213 / EN 10217-7 requirements
Maximum Operating Pressure	Up to 1.6 MPa (depending on OD and wall thickness)
Coating / Passivation	Passivated surface; optional PTFE or ceramic internal coating for enhanced anti-fouling

Manufacturing Process

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

1. Raw Material Selection: High-purity stainless steel billets or strips are sourced from certified mills and subjected to incoming chemical composition analysis (spectrometric verification) and mechanical property testing.
2. Hot Rolling / Cold Rolling: The base steel is processed through controlled rolling operations to achieve the target wall thickness and outer diameter within specified tolerances.
3. Heat Treatment (Annealing): Tubes undergo solution annealing at temperatures between 1050°C and 1150°C, followed by controlled cooling, to restore full austenitic microstructure, relieve residual stresses, and maximize corrosion resistance.
4. Pickling and Passivation: Surface oxides and scale are removed via acid pickling, followed by passivation treatment to establish a protective chromium oxide layer on the tube surface.
5. Coiling and Spooling: The finished tube is wound into uniform coils using precision coiling equipment, with protective interlayer wrapping to prevent surface damage and deformation during storage and transport.
6. Quality Inspection: Each coil undergoes 100% hydrostatic pressure testing, dimensional verification (OD, wall thickness, straightness), visual inspection of surface finish, and spot chemical analysis to confirm grade compliance.

Applications

The stainless steel coil tube is engineered for demanding thermal management applications, with primary deployment in the following sectors:

• Fan Coil Unit (FCU) Systems: Serves as the heat exchanger coil in distributed HVAC systems for commercial buildings, hospitals, hotels, and residential complexes. The tube's corrosion resistance and thermal performance support reliable operation under repeated heating and cooling cycles.
• Distributed Model Predictive Control (MPC) HVAC Architectures: The predictable and stable thermal characteristics of the coil tube enable accurate system identification and state estimation, which are prerequisites for implementing advanced MPC algorithms that optimize energy efficiency across multi-zone environments.
• Air Handling Units (AHUs) and Chiller Systems: Used in evaporator and condenser coils for large-scale central air conditioning installations.
• Medical and Pharmaceutical Facilities: The hygienic surface finish and resistance to microbial growth make this product suitable for cleanroom HVAC systems where contamination control is critical.
• Food and Beverage Processing: Employed in refrigeration coils and pasteurization heat exchangers where sanitary standards (e.g., 3-A Sanitary Standards) must be met.
• Marine and Offshore HVAC: The 316L grade variant provides enhanced resistance to chloride-laden marine atmospheres for shipboard and offshore platform ventilation systems.

Quality Certifications & Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management framework to ensure product reliability and regulatory compliance:

• ISO 9001:2015 — Quality Management System certification covering all manufacturing and supply chain processes
• ISO 14001:2015 — Environmental Management System certification demonstrating commitment to sustainable manufacturing practices
• Product Compliance: ASTM A213, ASTM A269, EN 10217-7, GB/T 12771
• Mill Test Certificates (MTC): Every shipment is accompanied by EN 10204 Type 3.1 or Type 3.2 certificates, providing full traceability of chemical composition, mechanical properties, and heat treatment records
• Third-Party Inspection: Available upon request through accredited inspection bodies (e.g., SGS, Bureau Veritas, TÜV) for pre-shipment verification
• Hydrostatic Testing: 100% inline hydrostatic pressure testing performed at controlled test pressures with documented pass/fail records for each coil

Unique Selling Points

• Thermal Performance Stability: The austenitic microstructure ensures consistent thermal conductivity across the full operating temperature range, enabling accurate predictive modeling in advanced HVAC control systems.
• Extended Service Life: Superior corrosion resistance eliminates the need for frequent coil replacement, reducing lifecycle maintenance costs by an estimated 40–60% compared to carbon steel alternatives.
• Precision Dimensional Control: Tight manufacturing tolerances (±0.05 mm OD) ensure optimal fit within FCU coil assemblies, minimizing assembly time and reducing risk of thermal bridging or fluid leakage.
• Customization Capability: Flexible configuration options including grade, dimensions, surface finish, and coil length to meet project-specific engineering requirements.
• Full Traceability: Complete material traceability from mill to end product, supported by digital MTC documentation, ensuring compliance with stringent international procurement and regulatory standards.