Stainless Steel Coil Tube for Fan Coil Units (FCU) – FP-102WAZD Series

Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd.

Product Catalog No.: 834

1. Product Overview

The Stainless Steel Coil Tube (also referred to as 盘管 / Coil Tube) is a precision-engineered heat exchange component designed specifically for integration into commercial and industrial Fan Coil Units (FCU), such as the FP-102WAZD series. These coil tubes serve as the primary heat transfer medium within the air handling system, facilitating efficient thermal exchange between the circulating fluid (typically chilled water or hot water) and the ambient air stream driven by the unit's fan assembly.

Unlike conventional copper or aluminum heat exchangers, the stainless steel coil tube offers superior corrosion resistance, mechanical durability, and hygienic performance, making it an ideal choice for demanding environments including hospitals, food processing facilities, pharmaceutical cleanrooms, and marine installations where resistance to chlorides, acids, and microbial growth is critical.

2. Material & Properties

The coil tube is fabricated from high-grade austenitic stainless steel, ensuring a balance of formability, weldability, and long-term structural integrity under cyclic thermal loading conditions.

2.1 Base Material Grades

• ASTM A213 TP316L – Low-carbon variant of 316, offering enhanced resistance to intergranular corrosion and pitting, particularly in chloride-rich environments.
• ASTM A213 TP304L – General-purpose grade with excellent oxidation resistance and formability for standard HVAC applications.
• ASTM A213 TP316Ti – Titanium-stabilized grade providing superior resistance to sensitization during welding operations.

2.2 Key Mechanical & Physical Properties

• Tensile Strength (Ultimate): ≥ 515 MPa (75,000 psi) for TP316L
• Yield Strength (0.2% Proof): ≥ 205 MPa (29,700 psi)
• Elongation (in 50 mm): ≥ 40%
• Thermal Conductivity: 16.3 W/(m·K) at 100°C
• Thermal Expansion Coefficient: 17.3 × 10⁻⁶ /°C (20–100°C)
• Operating Temperature Range: −196°C to +870°C (316L)
• Corrosion Resistance: Equivalent to or exceeding 316 stainless steel per ASTM G48 Practice

2.3 Surface Finish

• Standard: 2B finish (cold-rolled and annealed), Ra ≤ 0.5 μm
• Optional: Electropolished finish, Ra ≤ 0.25 μm, for sanitary and pharmaceutical applications
• Internal Surface: Passivated per ASTM A967 to remove free iron and enhance passive film stability

3. Specifications

Parameter	Specification	Standard / Reference
Outer Diameter (OD)	6.35 mm, 9.53 mm, 12.70 mm (¼", ⅜", ½")	ASTM A213 / EN 10216-5
Wall Thickness	0.50 mm – 1.50 mm (selectable)	ASTM A213
Bend Radius (Inner)	≥ 3D (where D = OD)	ISO 443
Coil Length (Unwound)	Up to 60 m per continuous coil	Custom per application
Coil Outer Diameter	300 mm – 600 mm (shipping coil)	ISO 17891
Fin Configuration	Aluminum or stainless steel plate fins; fin density 10–20 fins/inch	ASHRAE Standard 90.1
Coupling Method	Stellite-lined or solid stainless steel headers; brazed or welded joints	ASME B31.9
Design Pressure	1.0 – 1.6 MPa (10 – 16 bar)	EN 12828 / ASME B31.9
Hydrostatic Test Pressure	1.5 × Design Pressure (minimum 2.4 MPa)	ISO 443
Flow Velocity (Design)	0.5 – 2.0 m/s	ASHRAE Handbook – HVAC Systems & Equipment
Heat Transfer Coefficient	≥ 80 W/(m²·K) (water-to-air, typical operating conditions)	ASHRAE Fundamentals
Compliance – Fan Coil Unit	FP-102WAZD series compatible	GB/T 19232 / EN 13964
Standards – Tube Material	ASTM A213, EN 10216-5, JIS G3459	Multi-standard compliance

4. Manufacturing Process

The production of the stainless steel coil tube follows a rigorous, multi-stage manufacturing workflow designed to ensure dimensional accuracy, metallurgical integrity, and consistent performance:

1. Raw Material Selection & Inspection:

   Hot-rolled stainless steel strips are sourced from certified mills and subjected to spectrographic analysis (OES) to verify chemical composition compliance with ASTM A213 specifications. Each batch is accompanied by a Mill Test Certificate (MTC) per EN 10204 Type 3.1.

2. Cold Rolling & Annealing:

   Strips are cold-rolled to the target wall thickness with tolerance ±0.05 mm, followed by controlled annealing in a hydrogen or vacuum atmosphere to relieve residual stresses and restore full austenitic microstructure.

3. Tube Forming & Seam Welding:

   Formed tubes undergo precision orbital TIG (Tungsten Inert Gas) welding with argon back-purging to achieve full-penetration, leak-tight seams. Weld quality is verified per ASME BPV Code Section IX.

4. Cold Bending & Coiling:

   Tubes are cold-bent using CNC-controlled mandrel bending machines to achieve the required serpentine coil geometry with uniform bend radius and no ovality exceeding 5% of OD. Internal mandrels prevent wall collapse and wrinkling during the bending process.

5. Fin Attachment:

   Plate fins are mechanically or laser-welded to the tube array at precise pitch intervals. Fin-to-tube bonding is verified by shear testing per DIN 4131.

6. Header Assembly & Brazing:

   Coil tubes are joined to inlet and outlet headers using phosphorus-free silver brazing alloys (e.g., CuAg 72/28) in a vacuum or nitrogen-protected furnace to prevent oxidation. Joint integrity is confirmed via dye penetrant testing (PT) per ASTM E165.

7. Passivation & Cleaning:

   All exposed surfaces undergo citric acid or nitric acid passivation per ASTM A967 to remove surface contaminants and establish a stable chromium oxide passive layer. Final cleaning is performed using deionized water (DI water) with conductivity < 1 μS/cm.

8. Pressure Testing & Quality Assurance:

   Each completed coil tube assembly undergoes hydrostatic pressure testing at 1.5× design pressure for a minimum of 10 minutes with zero leakage tolerance. Non-Destructive Testing (NDT) includes ultrasonic thickness measurement (UT) per ASTM E797 and visual inspection per AWS D1.6.

5. Applications

The stainless steel coil tube is engineered for use in a broad spectrum of thermal management and air conditioning applications:

• Commercial HVAC Systems:

  Integration into FP-102WAZD and similar Fan Coil Units for temperature regulation in office buildings, retail spaces, hotels, and shopping malls.

• Healthcare & Pharmaceutical Facilities:

  Used in cleanroom HVAC systems, operating room climate control, and hospital wards where hygienic standards and antimicrobial surface properties are mandated.

• Food & Beverage Processing:

  Deployed in cold storage units, refrigeration coils, and air handling systems within food processing plants, breweries, and dairy facilities where compliance with FDA and EHEDG standards is required.

• Marine & Offshore Installations:

  Utilized in HVAC systems aboard vessels, offshore platforms, and naval applications where resistance to saltwater corrosion and high humidity is essential.

• Industrial Process Cooling:

  Applied in electronics cooling, data center thermal management, and precision manufacturing environments requiring stable and reliable heat exchange.

• Geothermal & District Energy Systems:

  Serves as the heat exchanger element in geothermal heat pump installations and district heating/cooling networks.

6. Quality Certifications & Standards Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring that every coil tube product meets or exceeds international standards:

• ISO 9001:2015 – Quality Management System Certification
• ISO 14001:2015 – Environmental Management System Certification
• ISO 45001:2018 – Occupational Health & Safety Management System
• CE Marking – Compliance with European Machinery Directive 2006/42/EC and Pressure Equipment Directive 2014/68/EU (PED)
• ASME "S" Stamp – Boiler and Pressure Vessel Code Section I, for pressure-containing components
• EN 10204 Type 3.1 – Mill Test Certification for material traceability
• NACE MR0175 / ISO 15156 – Compliance for sour service environments (where applicable)
• RoHS 2.0 (EU 2011/65/EU) – Restriction of Hazardous Substances compliance
• REACH Regulation (EC) No. 1907/2006 – Chemical safety and registration compliance

7. Unique Selling Points

The stainless steel coil tube from Wenzhou Jixing Metal Materials Co., Ltd. distinguishes itself through a combination of material excellence, manufacturing precision, and application versatility:

• Exceptional Corrosion Resistance:

  316L-grade stainless steel provides outstanding resistance to pitting and crevice corrosion, extending service life to 25+ years even in aggressive or chloride-laden environments — significantly outperforming copper-tube alternatives.

• Hygienic & Sanitary Design:

  Electropolished internal surfaces with Ra ≤ 0.25 μm prevent bacterial colonization and biofilm formation, meeting the stringent requirements of pharmaceutical (GMP) and food-grade applications.

• Superior Mechanical Integrity:

  Cold-bent with mandrel support to eliminate wall thinning, the coil tube maintains structural integrity under repeated thermal cycling and mechanical vibration inherent to fan coil operation.

• Extended Service Life & Reduced Maintenance:

  Eliminates the need for galvanic isolation between dissimilar metals, reducing maintenance costs and minimizing the risk of galvanic corrosion failures.

• Customizable Geometry:

  CNC-controlled bending and coiling enable precise customization of tube layout, fin density, and coil dimensions to match specific FP-102WAZD and other fan coil unit configurations.

• Environmental Sustainability:

  Stainless steel is 100% recyclable with no loss of material properties, supporting circular economy goals and reducing the total cost of ownership over the product lifecycle.

• Full Traceability:

  Every coil tube is accompanied by a complete traceability dossier including heat number, chemical analysis, mechanical test results, dimensional inspection records, and pressure test certificates.

8. Technical Notes & Recommendations

Installation Guidance: When integrating the coil tube into an FP-102WAZD fan coil unit, ensure that the flow direction of the circulating medium aligns with the designated inlet and outlet headers. Avoid cross-contamination with dissimilar metals (e.g., carbon steel, aluminum) at connection points. Use stainless steel gaskets and fittings rated for the operating pressure and temperature conditions.

Maintenance: