Stainless Steel Coil Tube (Coiltube) — HVAC Bypass Regulation System Component
Product Overview
The Stainless Steel Coil Tube (hereinafter referred to as "Coiltube") is a precision-engineered tubing product manufactured by Wenzhou Jixing Metal Materials Co., Ltd, specifically designed for integration into air conditioning (HVAC — Heating, Ventilation, and Air Conditioning) bypass regulation systems. This product plays a critical role in modulating the relative humidity within air-conditioned zones by enabling controlled fluid circulation through bypass channels. The coil tube geometry allows for compact heat exchange surface area within confined installation spaces, making it an essential component in precision climate control applications.
The Coiltube product line is engineered to address the challenges of maintaining stable indoor air quality (IAQ — Indoor Air Quality) parameters, particularly relative humidity (RH — Relative Humidity), in environments where strict humidity control is mandated — including pharmaceutical cleanrooms, semiconductor fabrication facilities, data centers, and high-end commercial buildings.
Material & Properties
The Coiltube is fabricated from high-grade austenitic stainless steel, selected for its superior corrosion resistance, mechanical integrity, and thermal conductivity characteristics.
- Primary Material Grades: SUS 304 (AISI 304), SUS 316 (AISI 316), and SUS 316L (AISI 316L) — with the option for duplex stainless steel grades (e.g., 2205) for high-pressure applications.
- Corrosion Resistance: Excellent resistance to chloride-induced pitting corrosion and general atmospheric corrosion, ensuring long-term service life in humid environments.
- Mechanical Properties: Tensile strength ranging from 515–730 MPa (depending on grade and temper condition); elongation ≥ 35–40%.
- Thermal Conductivity: Approximately 14.6–16.3 W/(m·K) at 20°C, providing efficient heat transfer performance in HVAC fluid circuits.
- Operating Temperature Range: −196°C to +450°C (depending on grade), suitable for both chilled water and hot water applications.
- Surface Finish: Electropolished or passivated inner surface with Ra ≤ 0.4 μm for hygienic and low-flow-resistance applications.
Specifications
| Parameter | Specification | Standard / Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 25.4 mm (custom sizes available) | ASTM A213 / GB/T 14976 |
| Wall Thickness (WT) | 0.5 mm – 2.0 mm | ISO 13906 |
| Coil Diameter | 100 mm – 500 mm (customizable) | Manufacturer specification |
| Coil Length | Up to 200 m per coil (continuous) | — |
| Pressure Rating | Up to 1.6 MPa (standard); up to 4.0 MPa (heavy-wall) | ASME B31.9 |
| Surface Treatment | Electropolished / Passivated / Matte | ASTM A967 |
| Forming Condition | Full Annealed (A) / Half Hard (H) | ASTM A269 |
| Connection Method | Welded (TIG/Orbital) / Flanged / Threaded / Compression Fitting | ASME B31.9 / EN 12164 |
| Fluid Compatibility | Chilled water, glycol-water mixtures, steam, refrigerant (R-134a, R-410A) | — |
| Dimensional Tolerance | OD: ±0.05 mm; WT: ±0.02 mm | ISO 4629 |
| Material Certification | Mill Test Certificate (MTC) per EN 10204 Type 3.1 | EN 10204 |
Manufacturing Process
The production of the Stainless Steel Coiltube at Wenzhou Jixing Metal Materials Co., Ltd follows a rigorous multi-stage manufacturing workflow to ensure dimensional accuracy, metallurgical integrity, and functional reliability:
- Raw Material Selection & Inspection: Certified stainless steel seamless or welded tube blanks are sourced from approved mills. Incoming inspection includes spectroscopic chemical analysis, mechanical testing, and visual surface examination in accordance with ASTM E415 and ISO 17638.
- Precision Cutting & Deburring: Tubes are cut to specified lengths using automated laser or plasma cutting systems, followed by mechanical and/or chemical deburring to ensure smooth internal bore surfaces.
- Coil Forming (Cold Bending): The tube is cold-formed into the desired coil geometry using CNC-controlled bending equipment. The bending radius is carefully controlled to prevent ovality exceeding 1.5% of nominal OD and to avoid surface cracking. Inter-bend annealing may be applied for tight-radius configurations.
- Heat Treatment & Stress Relief: Where required, the formed coil undergoes solution annealing (1050–1150°C) with rapid water quenching to restore full austenitic structure and eliminate residual bending stresses.
- Surface Treatment: Electropolishing (EP) is performed using a controlled electrolytic process to achieve a mirror-like internal surface finish, enhancing flow characteristics and reducing fouling potential. Alternative passivation treatment per ASTM A967 is available for standard applications.
- Final Inspection & Testing: Each coil undergoes hydrostatic pressure testing (typically 1.5× working pressure), dimensional verification (OD, WT, coil diameter, and pitch), and visual inspection. Radiographic testing (RT) or dye penetrant inspection (DPI) is performed on welded joints where applicable.
- Packaging & Shipping: Coils are protected with moisture-absorbing desiccant packaging and wooden crates to prevent corrosion and mechanical damage during transit.
Applications
The Stainless Steel Coiltube is specifically engineered for the following application domains:
- HVAC Bypass Regulation Systems: Serves as the primary heat exchange and fluid distribution component in bypass loops, enabling precise modulation of cooling/heating capacity to maintain target relative humidity levels in conditioned spaces.
- Pharmaceutical & Biotechnology Facilities: Used in cleanroom HVAC systems where stringent humidity control (typically 40–60% RH) is required for product stability and regulatory compliance (GMP — Good Manufacturing Practice).
- Semiconductor Manufacturing: Critical for ultra-cleanroom environments requiring RH control within ±2% for process-sensitive fabrication steps.
- Commercial & Institutional Buildings: Integrated into variable air volume (VAV) and constant volume (CV) air handling units for humidity regulation in offices, hospitals, and laboratories.
- Industrial Process Cooling: Utilized in glycol-water chiller loops and evaporative cooling systems where corrosion resistance is paramount.
- Refrigeration Systems: Employed as evaporator and condenser coils in medium- and large-capacity refrigeration installations.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd maintains comprehensive quality management and product certification credentials:
- ISO 9001:2015 — Quality Management System certification
- ISO 14001:2015 — Environmental Management System certification
- EN 10204 Type 3.1 — Material Test Certification for each production batch
- ASTM A213 / ASTM A269 — Compliance with American standards for stainless steel tubing
- GB/T 14976 — Compliance with Chinese national standards for seamless stainless steel tubes
- CE Marking — Conformity with European directives for products used in HVAC applications
- ASME B31.9 — Compliance for refrigeration and air-conditioning piping systems
Unique Selling Points
1. Precision Humidity Control Capability: The Coiltube's optimized geometry and high thermal conductivity enable rapid response to bypass regulation signals, achieving RH stability within ±1% in demanding environments.
2. Superior Corrosion & Hygiene Performance: Electropolished 316L stainless steel construction eliminates dead zones for microbial growth, meeting FDA and pharmaceutical-grade sanitation requirements.
3. Customizable Coil Geometry: Flexible manufacturing capabilities allow tailored coil diameters, pitch spacing, and total surface area to match specific HVAC system design parameters.
4. Extended Service Life: Resistance to pitting, crevice corrosion, and galvanic degradation ensures a design life exceeding 25 years under continuous HVAC operating conditions.
5. Low Flow Resistance Design: Smooth internal surfaces and optimized bend radii minimize pressure drop across the coil assembly, reducing pumping energy consumption by up to 15% compared to standard configurations.
Product Reference: Catalog No. 1614 | Manufacturer: Wenzhou Jixing Metal Materials Co., Ltd | Product Category: Coil Tube (Coiltube) for HVAC Bypass Regulation Systems