Stainless Steel Coil Tube — Fan Coil Unit Condensate Drainage System

Product Overview

The Stainless Steel Coil Tube (Model No. 1458) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered coiled piping solution designed specifically for condensate drainage systems within fan coil unit (FCU) installations. This product addresses the critical hydraulic requirements of horizontal condensate dry piping in HVAC (Heating, Ventilation, and Air Conditioning) applications, where reliable fluid transport, corrosion resistance, and thermal stability are paramount.

Coil tubes of this designation are coiled at the manufacturing stage and delivered in continuous lengths, enabling efficient on-site installation with minimal jointing, reduced labor costs, and enhanced system integrity. The product is particularly suited for applications requiring the hydraulic management of condensate water generated by evaporator coils in commercial and industrial fan coil units.

Material & Properties

The coil tube is fabricated from high-grade austenitic stainless steel, selected for its exceptional resistance to corrosion, mechanical strength, and long-term durability in demanding HVAC environments. Key material characteristics include:

• Base Material: Austenitic stainless steel (Grade 304 / 316L), conforming to ASTM A213/A269 standards
• Corrosion Resistance: Superior resistance to chlorides, condensate water, and atmospheric pollutants
• Thermal Conductivity: Low thermal conductivity minimizes heat gain or loss in condensate lines
• Mechanical Strength: High tensile strength ensures resistance to pressure fluctuations and mechanical stress
• Hygienic Surface: Smooth internal finish (Ra ≤ 0.4 μm) prevents scale buildup and biofilm formation
• Temperature Range: Operational range from −40 °C to +400 °C
• Recyclability: 100% recyclable, supporting sustainable construction practices

Technical Specifications

Parameter	Specification	Standard / Reference
Product Designation	Coil Tube — Series 1458	Wenzhou Jixing Internal Classification
Material Grade	ASTM A213 TP304 / TP316L	ASTM A213, ASTM A269
Outer Diameter (OD)	6.35 mm – 50.8 mm (1/4" – 2")	ASTM B537
Wall Thickness	0.5 mm – 3.0 mm	ASTM B537
Coil Inner Diameter (CID)	150 mm – 600 mm (configurable)	Manufacturer Specification
Maximum Coil Length	Up to 3,000 m per coil	Wenzhou Jixing Production Standard
Surface Finish	Mirror polished / Electropolished (Ra ≤ 0.4 μm)	ASTM A478
Maximum Operating Pressure	1.6 MPa – 4.0 MPa (dependent on OD and wall thickness)	ASME B31.9
Hydraulic Gradient	Designed for self-draining slope of 1:100 to 1:50	ASHRAE Handbook — HVAC Applications
Tolerance (OD)	±0.1 mm (tight tolerance)	ASTM A213
Tolerance (Wall Thickness)	±10% of nominal	ASTM A213
Delivery Form	Coiled (in-situ bendable) / Straight cut lengths	—
Welding Compatibility	TIG (GTAW), Orbital, Push-type welding	ASME B31.9, AWS D10.9

Hydraulic Design Considerations

The design of horizontal condensate dry piping for fan coil units requires careful hydraulic calculation to ensure adequate drainage and prevent water accumulation, which can lead to mold growth, structural damage, and system inefficiency. The following principles govern the hydraulic performance of this coil tube system:

1. Velocity Criteria: Condensate flow velocity in horizontal dry pipes must be maintained between 0.5 m/s and 1.5 m/s to ensure self-draining capability without excessive erosion.
2. Slope Requirement: A minimum longitudinal slope of 1:100 (1%) is recommended for horizontal condensate runs; steeper slopes of 1:50 (2%) are advised for runs exceeding 10 meters.
3. Friction Loss: Darcy-Weisbach equation is applied to calculate frictional head loss, with the stainless steel surface roughness (ε = 0.015 mm) yielding a favorable friction factor.
4. Minor Losses: Fittings, bends, and transitions introduce additional head losses, calculated using the Hazen-Williams method or equivalent length approach.
5. Trap Height: A P-trap or siphon trap is installed at each FCU connection to maintain a water seal (minimum 25 mm) that prevents air infiltration and odor migration.

Manufacturing Process

The production of the Stainless Steel Coil Tube — Series 1458 follows a rigorous multi-stage manufacturing process to ensure dimensional accuracy, metallurgical integrity, and surface quality:

1. Coil Unwinding & Straightening: Raw stainless steel coil is unwound and passed through a multi-roller straightening line to achieve the desired tube geometry.
2. Piercing & Forming: Hot-rolled or cold-drawn blanks are pierced and formed into seamless tube sections using rotary piercing mills or capstan drawing processes.
3. Cold Drawing & Sizing: Tubes are cold-drawn through calibrated dies to achieve precise outer diameter and wall thickness tolerances.
4. Heat Treatment (Solution Annealing): Tubes are solution-annealed at 1050 °C – 1150 °C followed by rapid water quenching to restore full austenitic microstructure and maximize corrosion resistance.
5. Pickling & Passivation: Surface oxide scale is removed via acid pickling (HNO₃/HF blend), followed by passivation treatment to restore the protective chromium oxide layer.
6. Mechanical Polishing / Electropolishing: Internal and external surfaces are polished to achieve the required surface roughness (Ra ≤ 0.4 μm), critical for hygienic condensate flow.
7. Coiling: Finished tubes are coiled at controlled tensions to maintain dimensional stability and prevent deformation during storage and transport.
8. Non-Destructive Testing (NDT): 100% eddy current testing and hydrostatic pressure testing are performed to detect surface and volumetric defects.
9. Final Inspection & Packaging: Each coil is inspected, tagged with material traceability information, and packaged for shipment.

Applications

The Stainless Steel Coil Tube — Series 1458 is deployed across a broad spectrum of HVAC and industrial applications:

• Commercial HVAC Systems: Condensate drainage piping for fan coil units in office buildings, shopping malls, hotels, and hospitals.
• Industrial Process Cooling: Condensate collection and transport in manufacturing facilities requiring hygienic fluid handling.
• Food & Pharmaceutical Processing: Clean-in-place (CIP) compatible condensate lines in food-grade and pharmaceutical-grade production environments.
• Chilled Water Distribution: Secondary loop piping in large-scale air conditioning systems where corrosion resistance is essential.
• Marine & Coastal Applications: HVAC condensate systems in marine vessels and coastal facilities exposed to high-chloride environments.
• Renewable Energy Systems: Condensate management in solar thermal collectors and geothermal heat exchange systems.

Quality Certifications & Compliance

Wenzhou Jixing Metal Materials Co., Ltd. maintains an extensive portfolio of international certifications and standards compliance, ensuring that every coil tube meets the highest global quality benchmarks:

• ISO 9001:2015 — Quality Management System Certification
• ISO 14001:2015 — Environmental Management System Certification
• ISO 45001:2018 — Occupational Health and Safety Management System
• EN 10204 3.1 — Material Test Certificate (MTC) per European standard
• ASTM A213 / A269 — Material conformity for stainless steel tubing
• ASME B31.9 — Compliance for pressure piping systems
• CE Marking — Conformity with European regulatory requirements
• NORSOK M-650 — Materials for offshore applications (where applicable)
• Mill Test Reports (MTR) — Provided with every shipment for full material traceability

Unique Selling Points

"Engineering Precision Meets Hydraulic Intelligence"

• Hydraulic Optimization: This product line is uniquely informed by advanced hydraulic calculation methodologies for fan coil unit condensate systems, ensuring that every coil tube is engineered for optimal flow performance, minimal pressure drop, and reliable self-draining capability.
• Seamless Coiled Delivery: Continuous-length coiled delivery eliminates field welding joints, reducing potential leak points by up to 80% compared to traditional cut-and-weld installation methods.
• Precision Tolerances: Tight dimensional tolerances (±0.1 mm OD) ensure compatibility with standard HVAC fittings, traps, and connection hardware without adapter requirements.
• Hygienic Surface Integrity: Electropolished internal surfaces (Ra ≤ 0.4 μm) prevent biofilm colonization and scale adhesion, critical for maintaining water quality in condensate systems.
• Full Traceability: Every coil is accompanied by a complete Mill Test Report (MTR) with chemical composition, mechanical properties, and heat number, enabling end-to-end quality traceability.
• Customization Capability: Flexible manufacturing parameters allow customization of coil diameter, tube dimensions, surface finish, and packaging configuration to meet project-specific requirements.
• Sustainability: 100% recyclable stainless steel construction, combined with reduced waste from coil-based installation, supports green building certifications (LEED, BREEAM).

Installation Recommendations

To maximize the performance and service life of the Stainless Steel Coil Tube — Series 1458 in condensate drainage applications, the following installation guidelines are recommended:

• Maintain a minimum slope of 1:100 along all horizontal runs to ensure positive drainage flow.
• Install cleanout access points at intervals not exceeding 15 meters and at all changes in direction.
• Use compatible stainless steel or PTFE-lined fittings to avoid galvanic corrosion at joints.
• Employ TIG welding (GTAW) with argon shielding for all welded connections to maintain metallurgical integrity.
• Perform a hydrostatic pressure test at 1.5× the maximum operating pressure prior to system commissioning.
• Install P-traps at each fan coil unit connection point with a minimum water seal depth of 25 mm.

Wenzhou Jixing Metal Materials Co., Ltd. is committed to delivering premium-quality stainless steel coil tube solutions that meet the rigorous demands of modern HVAC engineering, backed by decades of manufacturing expertise, comprehensive quality assurance, and dedicated technical support.