Stainless Steel Coil Tube (Coiltube) — HVAC Fan Coil Unit Series
Product Overview
The Stainless Steel Coil Tube (Product No. 1451) is a precision-engineered coiled piping product manufactured by Wenzhou Jixing Metal Materials Co., Ltd. This product is specifically designed for use in Fan Coil Unit (FCU) systems and hydronic air conditioning applications. The coil tube serves as the primary heat exchange medium, facilitating efficient thermal transfer between the circulating refrigerant/water and the ambient air within the fan coil unit assembly.
This product addresses critical engineering challenges identified in the "Analysis of Ceiling Water Leakage in Fan Coil Unit Systems" (风机盘管系统吊顶渗水问题分析), including condensate drainage management, corrosion resistance under prolonged moisture exposure, and structural integrity under cyclic thermal loading conditions.
Material & Properties
The coil tube is fabricated from high-grade austenitic stainless steel, selected for its superior resistance to corrosion, thermal cycling fatigue, and mechanical deformation under operational stress.
- Base Material: Austenitic Stainless Steel (e.g., SUS304 / SUS316 / Grade 304/316 per ASTM A269)
- Corrosion Resistance: Excellent resistance to pitting and crevice corrosion in humid HVAC environments, particularly critical for condensate drainage zones where water accumulation occurs beneath ceiling panels
- Thermal Conductivity: Optimized for efficient heat exchange between the working fluid (water or refrigerant) and the surrounding air stream
- Mechanical Strength: Maintains dimensional stability under repeated thermal expansion and contraction cycles typical of HVAC operational duty cycles
- Weldability: Suitable for TIG (Tungsten Inert Gas) welding and brazing connections at coil joints and manifold interfaces
- Surface Finish: Smooth inner bore surface minimizes flow resistance and prevents sediment accumulation that could lead to blockage and subsequent water leakage
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Product Name | Stainless Steel Coil Tube (Coiltube) | — |
| Product Number | 1451 | — |
| Material Grade | SUS304 / SUS316 (Austenitic Stainless Steel) | ASTM A269 / GB/T 12771 |
| Outer Diameter (OD) | 9.52 mm / 12.7 mm / 15.88 mm (standard HVAC sizes) | ASTM B88 / JIS G3447 |
| Wall Thickness | 0.8 mm – 1.5 mm (configurable per application) | ISO 1127 |
| Coil Diameter | 150 mm – 350 mm (typical for FCU integration) | Manufacturer specification |
| Operating Temperature Range | −20 °C to +120 °C | — |
| Maximum Working Pressure | 1.6 MPa – 2.5 MPa (depending on wall thickness) | GB/T 12771 / EN 10217 |
| Surface Treatment | Pickled and passivated; optional polished finish | ASTM A380 |
| Connection Type | Flared / Brazed / Threaded (G1/4" to G3/8") | BSPP / JIC |
| Applicable Working Fluids | Water, Glycol solutions, Refrigerant (R-410A, R-32, R-22) | — |
| Manufacturing Standard | GB/T 12771, ASTM A269/A270, EN 10217-7 | — |
Manufacturing Process
The coil tube is produced through a rigorous multi-stage manufacturing process designed to ensure dimensional accuracy, metallurgical integrity, and resistance to the failure modes associated with ceiling water leakage in fan coil unit systems:
- Raw Material Inspection: Incoming stainless steel seamless tubes are verified for chemical composition (spectroscopic analysis), mechanical properties (tensile testing per ASTM A370), and surface quality.
- Cold Drawing: Tubes are cold-drawn to achieve precise outer diameter and wall thickness tolerances (±0.05 mm), ensuring uniform heat transfer performance across the coil.
- Pickling & Passivation: Tubes undergo chemical pickling (HNO₃/HF blend) followed by passivation to remove surface scale and form a protective chromium oxide layer, critical for long-term corrosion resistance in wet HVAC environments.
- Coil Forming: Precision coiling equipment shapes the tube into the designated spiral geometry with controlled coil diameter, pitch, and number of turns. Uniform bending radius prevents localized stress concentrations that could lead to fatigue cracking.
- Welding & Brazing: Manifold connections and inlet/outlet ports are fabricated using TIG welding or silver brazing, followed by full-penetration weld inspection.
- Hydrostatic Pressure Testing: Each coil assembly undergoes hydrostatic testing at 1.5× the maximum working pressure to verify leak-tightness and structural integrity.
- Dimensional & Non-Destructive Testing (NDT): Final inspection includes dimensional verification, visual examination, and optional eddy current testing to detect subsurface defects.
- Protective Packaging: Coils are packaged with moisture-absorbing desiccants and protective wrapping to prevent condensation-related degradation during storage and transportation.
Applications
The stainless steel coil tube is integral to the following applications, with particular emphasis on resolving ceiling water leakage issues in fan coil unit installations:
- Fan Coil Units (FCUs): Primary heat exchanger coil for commercial and residential HVAC systems, providing sensible and latent heat removal from indoor air streams.
- Air Handling Units (AHUs): Chilled water and hot water coils for large-capacity air conditioning and heating systems.
- Condensate Drainage Systems: The corrosion-resistant properties of stainless steel prevent degradation at condensate drain pans and connection points, directly addressing the root causes of ceiling water leakage identified in technical analyses.
- Refrigeration Coils: Evaporator and condenser coils in commercial refrigeration and cold storage applications.
- Industrial Heat Exchangers: Custom coil configurations for process heating, cooling, and temperature control in manufacturing environments.
- Medical & Laboratory HVAC: High-purity air systems requiring corrosion-free, contaminant-free heat exchange surfaces.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains adherence to international quality management and product standards:
- ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control
- ISO 14001 — Environmental Management System certification
- GB/T 12771 — Chinese national standard for welded stainless steel tubes (seamless equivalent specifications applied)
- ASTM A269 / A270 — American standards for austenitic stainless steel seamless, welded, and heavily cold-worked tubes
- EN 10217-7 — European standard for pressure equipment — austenitic stainless steel tubes
- CE Marking — Conformity with European Pressure Equipment Directive (PED 2014/68/EU)
- Material Test Reports (MTR): Full chemical and mechanical property documentation provided with each batch
Unique Selling Points
1. Targeted Anti-Leakage Engineering: This coil tube product is specifically engineered to address the failure mechanisms identified in the "Analysis of Ceiling Water Leakage in Fan Coil Unit Systems", including enhanced condensate management design, superior corrosion resistance at drain interfaces, and improved structural rigidity to prevent coil sagging that causes water pooling.
2. Superior Corrosion Resistance: The austenitic stainless steel construction provides exceptional resistance to the humid, condensate-laden environments of ceiling-mounted HVAC systems, significantly extending service life compared to carbon steel or copper alternatives.
3. Precision Manufacturing Tolerances: Tight dimensional control (±0.05 mm) ensures optimal airflow distribution across the coil face, maximizing heat transfer efficiency and preventing localized condensate formation.
4. Comprehensive Quality Assurance: Every unit undergoes hydrostatic pressure testing and non-destructive examination, providing verifiable assurance against leakage failures that compromise ceiling integrity.
5. Customizable Configurations: Coil diameter, pitch, tube count, and connection types can be tailored to specific FCU models and installation constraints, ensuring optimal thermal performance for each application.
Technical Reference
Related Technical Literature: 《风机盘管系统吊顶渗水问题分析》 (Analysis of Ceiling Water Leakage in Fan Coil Unit Systems) — Technical Learning Document, Category: Literature Study (文献学习), Document No. 1451.
This product specification is intended for engineering professionals, HVAC system designers, procurement specialists, and facility maintenance managers evaluating coil tube solutions for fan coil unit applications where ceiling water leakage prevention is a critical design requirement.